General information
An isolate is confirmed as Salmonella when the specific O serogroup has been determined and biochemical identification has been completed

Taxonomy
Family: Enterobacteriaceae

Natural habitats
Most cases of salmonellosis are caused by food infected with Salmonella enterica, with often infects cattle and poultry, though also other animals such as domestic cats and hamsters have also been shown to be sources of infection to humans.

Raw chicken eggs and goose eggs can harbor S. enterica, initially in the egg whites, although most eggs are not infected. As the egg ages at room temperature, the yolk membrane begins to braek down and S. enterica can spread into the yolk. Refrigeration and freezing do not kill all the bacteria, but substantially slow or halt their growth.
Pasteurizing and foods irradiation are used to kill Salmonella for commercially produced foodstuffs containind raw eggs such aas ice cream.

Clinical significance
Strains of Salmonella are categorized as typhoidal and nontyphoidal.

Nontyphoidal infection
Usually cause an intestinal infection (accompanied by diarrhea, fever and abdominal cramps) that often lasts one week or longer.
They can also cause extra intestinal infections, e.g., bacteremia, urinary tract infection, or osteomyelitis, especially in immunocompromised persons.

Taxonomy
Family: Pasteurellaceae

Natural habitats
Colonization of the cervix with H. ducreyi has been documented following sexual intercourse.

Clinical significance
Chancroid is a sexual transmitted disease caused by H. ducreyi which is usually characterized by the development of a single painful genital ulcer, with associated inquinal lymphadenopathy occyring 2 to 7 days following exposure.
Chancroid occurs most often in developing countries, including much of Asia, Africa, and Latin Aerica.

Epidemics of disease are associated with low socioeconomic status, poor hygiene, prostitution, and drug abuse, and commercial sex workers are believed to serve as reservoirs for H. ducreyi.

Taxonomy
Family: Enterobacteriaceae, genus: Escherichia coli, E. coli O157.H7
E. albertii, E. fergusonii, E. hermannii, E. vulneris

Origin
E. coli O157:H7 is so-named because it expresses the 157th somatic (O) antigen identified and the 7th flagellar (H) antigen.

Natural habitats
E. coli O157 is found regularly in the faeces of healthy cattle, and is transmitted to humans through contaminated food, water, and direct contact with infected people or animals.

Transmission
E. coli O157 is transmitted by food and water, directly from one person to another, and occasionally through occupational exposure.
Most foodbourne outbreaks have been traced to foods derived from cattle, especially ground beef an raw milk.

Clinical significance
Human infection is associated with a wide range of clinical illness, including asymtomatic shedding, non-bloody diarroea, haemorrhagic colitis, haemolytic uraemic syndrome, and death.

Taxonomy
Family: Mycoplasmataceae
Genus: Metamycoplasma hominis
Formely: Mycoplasma hominis

Natural habitats
M. hominis lives parasitically and saphrophytically with hosts.
M. hominis plays a significant role in the microflora of men and women.

Vector and mode of transmission.
M. hominis infection is spread through vaginal intercourse, oral-to-genital contact, and vertically from mother to her infant in utero or by the colonization by the bacteria as the baby descends through the birth canal or by nosocomial acquisition through transplanted tissues

Clinical significance
M. hominis is a pathogen in humans commenly found as part of urogenital tract flora especially of women and sexually active adult males.
This bacteria cause a variety of infections which may lead to pelvic inflammatory disease, post-abortal fever, post partum fever and extragenital infections for immunodepressed humans.
It also can cause meningitis, pneumonia and abcesseses in newborn children.

It can be present in bacterial vaginosis.

Neonatal infection
Neonates, especially if preterm, are susceptible to Mycoplasma infections organisms through vertical transmission or colonization through passing the birth canal or in utero.
If the bacteria is present in the bloodstream it can access the central nervous system.
If Mycoplasma hominis and ureoplasma organisms are specifically sampled and cultured, they are of etiollogic significans in neonatal lung disease, bacteremia, and meningitis.
There are no characteristic signs and symptoms that can determine the type of pathogen present
Clinicians can consider Mycoplasma species if signs and symptoms of infections are present and if the infant does not improve with administration of beta-lactam medications.
Deaths have occurred in neonates with septicemia and meningitis caused by M. hominis.

Important
This bacteria is important due to the infections it can cause and is growing resistance to treatment, including erythromycin.

Cell wall
Mycoplasmas have a triple-layered membrane and lack a cell wall.

L-forms
The permanent lack of a cell wall barrier makes the Mycoplasma (class: Mollicutes) unique among prokaryotes and differentiates from bacterial L-forms for wich the cell wall is but a temporary reflection of enviromental conditions.

Taxonomy
Family: Enterobacteriaceae

Natural habitats
Klebsiella variicola is known to associate with different plants.
Some strains have been associated with disease in humans, suggesting they may be able to serve as opportunistic pathogens of humans.

The majority of isolation of Klebsiella variicola are from sterile sites, mainly blood and urine.

Clinical significance
Proper identification of K. variicola will be critical in the further evaluation of its clinical significance as an underreported infectious agent and in the development of more tailored.

All Vibrionaceae require Na• for growth

Taxonomy
Family: Vibrionaceae

Natural habitats
V. alginolyticus is very common in the marine ecosystem.

Clinical significance
It is most frequently isolated from ear and wound infections following seawater exposure.

V. alginolyticus has also been isolated from ocular infections.

It is occasionally isolated from diarrheal stool, but there is no evidence that it actually causes diarrhea.

The significance of the recovery of Aeromonas from stool specimens should be interpreted cautiously and must rely on both laboratory information and clinical interpretation.

Taxonomy
Family: Aeromonadaceae

Natural habitats
Aeromonas are inhabitants of aquatic ecosystems worldwide.

They don’t like saltwater.

They are also found in a wide variety of fresh produced meat (beef, poultry and pork), and dairy products (raw milk and ice cream)
And found in the gut of medical leeches and in the mouth of snakes

Clinical significance

Clinical strains formely referred to as A. sobria are in fact, A. veronii bv sobria.
This is especially important because of A. veronii bv. sobria's association with more severe, extraintestinal infections, such as septicemia and meningitis.

They are capable of causing gastroenteritis and wound infections in humans, especially those individuals with liver disease.

Aeromonas gastroenteritis ranges from an acute watery diarrhea (most common form) to dysenteric illness or chronic illness.

Stools from acute watery diarrhea are loose and erythrocytes and fecal leukocytes are absent.

Symptoms
Abdominal pain, fever, vomiting, and nausea.
Infections are usually self-limiting, but children may require hospitalization due to dehydration.

Aeromonads can also be isolated, on other sites, although blood and wounds are the most common sources

Taxonomy
Family: Pasteurellaceae

Natural habitats
H. haemolyticus is a human commensal bacterium that colonizes the nasopharynx.

Clinical significance They are closely related to the human patogen H. influenzae but has rarely been reported to cause invasive disease. They may cause disease more as a oppertunistic pathogen

The significance of the recovery of Aeromonas from stool specimens should be interpreted cautiously and must rely on both laboratory information and clinical interpretation.

Taxonomy
Family: Aeromonadaceae

Natural habitats
Aeromonas are inhabitants of aquatic ecosystems worldwide.

They don’t like saltwater.

They are also found in a wide variety of fresh produced meat (beef, poultry and pork), and dairy products (raw milk and ice cream)
And found in the gut of medical leeches and in the mouth of snakes

Clinical significance
They are capable of causing gastroenteritis and wound infections in humans, especially those individuals with liver disease.

Aeromonas gastroenteritis ranges from an acute watery diarrhea (most common form) to dysenteric illness or chronic illness.

Stools from acute watery diarrhea are loose and erythrocytes and fecal leukocytes are absent.

Symptoms
Abdominal pain, fever, vomiting, and nausea.
Infections are usually self-limiting, but children may require hospitalization due to dehydration.

A. caviae infection can even mimicinflammatory bowel disease in children.

Aeromonads can also be isolated, on other sites, although blood and wounds are the most common sources

Taxonomy
Family: Flavobacteriaceae, genus: C. canimorsus, C. cynodegmi

Natural habitats
It is a commensal bacteria in the normal gingival flora of canine and feline species.
Transmission may occur through bites, licks or even close proximity with animals.

Clinical significance
A wound infection (dog bite) with these bacteria may cause serious local problems.

Moreover, there is a high probability of a running fulminant sepsis, in wich multi-organ failure (MOF) may occur.

An isolate is confirmed as Salmonella when the specific O serogroup has been determined and biochemical identification has been completed

Taxonomy
Family: Enterobacteriaceae

Natural habitats
Humans are the only reservoir for Salmonella typhi, indicating that they are adapted to the human host; healthy carriers have been noted.

Clinical significance
Strains of Salmonella are categorized as typhoidal and nontyphoidal.

S. typhi ► typhoidal infection

Typhoid fever
Caused by Salmonella typhi, is a serious bloodstream infection, common in the developing world. Typhoid fever typically presents which a sustained debilitating high fever and headache.

Adults characteristically present without diarrhea. Illness is milder in young children, where it may manifest as nonspecific fever.

This fever has a low infectious dose (<103), and a long high variable incubation period (1 to 6 weeks)

It is transmitted through person-to-person contact or fecally contaminated food or water.

Fatal complications of typhoid most commonly occur in the second or third week of the illness.

General information
An isolate is confirmed as Salmonella when the specific O serogroup has been determined and biochemical identification has been completed

Taxonomy
Family: Enterobacteriaceae

Natural habitats
Salmonella is ubiquitous in animal populations, and human illness is usually linked to foods of animal origin.

Salmonellosis also is transmitted by direct contact with animals, by nonanimal foods, by water, and occasionally, by human contact.

Clinical significance
Strains of Salmonella are categorized as typhoidal and nontyphoidal.

Nontyphoidal infection
Usually cause an intestinal infection (accompanied by diarrhea, fever and abdominal cramps) that often lasts one week or longer.
They can also cause extra intestinal infections, e.g., bacteremia, urinary tract infection, or osteomyelitis, especially in immunocompromised persons.

Taxonomy
Family: Enterobacteriaceae

There are 4 subgroups of Shigella
- S. dysenteriaea
- S. flexneri
- S. boydii
- S. sonnei

The primary difference between E. coli and Shigella is the ability of Shigella to invade the intestinal epithelium.

Natural habitats
Humans and other large primates are the only natural reservoirs of Shigella bacteria.

Most transmission is by person-to-person spread, but infection is also caused by ingestion of contaminated food or water.

Shigellosis is most common in situations in which hygiene is compromised (e.g., child care centers, and other institutional settings).

In developing populations without running water and indoor plumbing, shigellosis can become endemic.

Sexual transmission of Shigella among men who have sex with men also occurs.

Clinical significance
They are the causative agents of bacillary dysentery.

Shigella causes bloody diarrhea (dysentery) and non-bloody diarrhea.

Shigellosis often begins with watery diarrhea accompanied by fever and abdominal cramps but may progress to classic dysentery with scant stool containing blood, mucus and pus.

Ulceration, which are restricted to the large intestine and rectum, typically do not penetrate beyond the lamina propria.
Bloodstream infections can occur but are rare.

All 4 subgroups of Shigella are capable of causing dysentery.
S. dysenteriae serotype 1, is associated with the most severe form of dysentery.

Taxonomy
Family: Pasteurellaceae
3 subspecies
- P. multocida subsp. multocida
- P. multocida subsp. septica
- P. multocida subsp. gallicida

History
Is named after Louis Pasteur (1822-1895), chemist and bacteriologist in Paris

Natural habitats
They are part of the normal flora of the respiratory tract of animals.
Through contact with these animals (licking, biting and scratching), humans can be infected, often by cats and dogs.

Clinical significance
Through contact with animals or bites especially cats or dogs the bacterium is transmitted to humans.
Arise within 48 hours painful infections erythema and swelling, the presence of pus is rare.
Infection can also occur through inhalation of the micro-organism.

Respiratory infections and urogenital infections also occur.
Complications can arise due to sepsis, meningitis, septic arthritis, peritonitis, and osteomyelitis.

Virulence
Due to the polysaccharide capsule is the Pasteurella resistant to phagocytosis.
Although some strains produce a cytotoxin its role in the pathogenesis of the disease is not clear.

Of all the P. species is P. multocida the most virulent.

There are five serogroups (A, B, D, E and F) based on the capsular antigen

H.influenzae was first described in 1892 by Richard Pfeiffer during an influenza pandemic.

The bacterium was mistakenly considered to be the cause of influenza until 1933 when the viral etiology of influenza became apparent.

Taxonomy
Family: Pasteurellaceae
H.influenzae 2 types
- unencapsulated
- encapsulated ► capsular antigens type (a-f)

The most virulent strain is H. influenzae type b (Hib)

Their capsule allows them to resist phagocytosis.

The unencapsulated strains are almost always less invasive; they can, however, produce an inflammatory response in humans, which can lead to many symptoms.

Natural habitats
H. influenzae belongs to the normal flora of the nasopharynx, but rarely in the oral cavity.

They may be present in the vaginal flora.

It is usually the non-encapsulated strains that are harbored as normal flora, but a minority of healthy individuals harbor H. influenzae type b (Hib) encapsulated strains in the upper respiratory tract.

These strains are opportunistic pathogens; that is, they usually live in their host without causing disease, but cause problems only when other factors (such as a viral infection, reduced immune function or chronically inflamed tissues, e.g. from allergies) create an opportunity.

Clinical significance
Naturally acquired disease caused by H. influenzae seems to occur in humans only.

In infants and young children.

H. influenzae type b (Hib) causes bacteremia, pneumonia, epiglottitis and acute bacterial meningitis.

On occasion, it causes cellulites, osteomyelitis, and infectious arthritis.

Vaccination
with Hib conjugate vaccine is effective in preventing Hib infection, but does not prevent infection with unencapsulated strains

All Vibrionaceae require Na+ for growth

Taxonomy
Family: Vibrionaceae

Natural habitats
Marine environments

Clinical significance
V. vulnificus causes primary cellulites, septicemia, foodborne disease and wound infections.

Patients usually have predisposing conditions such as liver disease, immunosuppression, or other chronic diseases.

Patients typically present with a sudden onset of fever and chills, vomiting, diarrhea, and abdominal pain.

Secondary skin lesions
often appear, progressing to bulla formation and necrosis.

Endotoxic shock
often occurs and can rapidly lead to death.

They also cause severe wound infections, usually after trauma and exposure to marine animals or the marine environment.

All Vibrionaceae require Na• for growth

Taxonomy
Family: Vibrionaceae

Natural habitats
Marine environments

Clinical significance
V. parahaemolyticus are the leading course of foodborne intestinal infections, almost always associated with the consumption of oysters, raw fish or shellfish.

They are primarily associated with diarrhea, but it had occasionally isolated from extraintestinal sites. They causes gastroenteritis with nausea, vomiting, abdominal cramps, lowgrade fever and chills.

The diarrhea is usually watery, but can on rare occasions be bloody.

Rehydration is usually the only treatment needed, but in some severe cases the patient requires hospital admission. Antimicrobial therapy may be beneficial.

All Vibrionaceae require Na+ for growth

Taxonomy
Family: Vibrionaceae

It is divided into 3 major subgroups
1 V. cholerae-O1
⇒ 3 serovars: Inaba, Ogawa, Hikojima
⇒ 2 biotypes: El Tor and Classical
2 V. cholerae-O139
3 V. cholerae non O1

Natural habitats
Marine environments and people.
Cholera infections are most commonly acquired from drinking water in which V. cholerae is found naturally or into which the water has been polluted from the feces of an infected person.

Transmission from person to person, is rarely documented.

Clinical significance
Vibrio cholera is the only species that causes endemic, epidemic, and pandemic cholera.

They secretes cholera toxin, that causes watery diarrhea.
They ranging from asymptomatic to cholera gravis.
Symptoms include abrupt onset of watery diarrhea (a grey and cloudy liquid / rice water stools), or occasionally vomiting and abdominal cramps.

Dehydration with symptoms and signs such as thirst, dry mucous membranes, decreased skin turgor, sunken eyes, hypotension, tachycardia, renal failure, seizures, somnolence, coma and death.
The disease typically lasts from 4-6 days.

Worldwide cholera is the second leading cause of death for children under the age of 5 and at least 120.000 death are estimated to be caused by cholera each year. (source: wikipedia)

Taxonomy
Family: Neisseriaceae

Natural habitats
Inhabits soil and water in tropical and subtropical climates.

Clinical significance
Causes rarely infections in humans

Localized infections usually arise from contaminated wounds, and septicemia with multiple organ abscesses may follow.

Taxonomy
Family: Enterobacteriaceae genus: S. rubidaea

Natural habitats
They are widely distributed in nature.

Clinical significance
Rarely from clinical material

Have been isolated from humans and are usually transients or cause of opportunistic infections.

Taxonomy
Family: Morganellaceae

P. alcalifaciens
- P. rustigianii (P. alcalifaciens biogroep 3)
P. rettgeri
P. stuartii

apathogeen P. heimbachae, P. vermicola

Natural habitats
They are ubiquitous in the environment, especially water and clinical samples, such as; urine, feces, blood, wounds and throat. Also occur in animals, mammals, birds, reptiles and insects.

Clinical significance
Patients with burns are at a higher risk of Providencia wound infection, like P. stuartii and P. rettgeri
Patients who develop Providencia urinary tract infections often have long-standing dependence on an indwelling urinary catheter.

Both species (P. rettgeri more commonly than P. stuartii) have recently been implicated as etiologic agents in traveler's diarrhea, making travel history important in patients with acute-onset diarrhea.

Vomiting is common in P. rettgeri gastrointestinal infection.

Taxonomy
Family: Morganellaceae

P. alcalifaciens
- P. rustigianii (P. alcalifaciens biogroep 3)
P. rettgeri
P. stuartii

apathogeen P. heimbachae, P. vermicola

Natural habitats
They are ubiquitous in the environment, especially water and clinical samples, such as; urine, feces, blood, wounds and throat. Also occur in animals, mammals, birds, reptiles and insects.

Clinical significance
Patients who develop Providencia urinary tract infections often have long-standing dependence on an indwelling urinary catheter.

P. alcalifaciens, P. rustigianii, and P. heimbachae

Infections with these Providencia species are most likely to elicit gastrointestinal symptoms.

P. alcalifaciens infection is also associated with overseas travel.

Taxonomy
Family: Moraxellaceae
P. vulgaris
- P. penneri (= P. vulgaris genomosp 1)
- P. hauseri (= P. vulgaris genomosp 3)

Natural habitats
Proteae occur in humans, animals and the environment, especially in locations where animal protein decomposes.

Clinical significance
They were isolated from wounds, soft tissue and urine

P. vulgaris and P. penneri are easily isolated from individuals in long term care facilities and hospitals and from patients with underlying diseases or compromised immune systems.

In people with congenital or anatomic abnormality of the urinary tract or a stone in the urinary tract, are predominantly Proteus (mostly P. mirabilis) infections.
They quickly put this urea into ammonia, which creates an alkaline environment.

This can be harmful to the kidney and promotes the formation of stones materials consist of a biochemical complex, which is called struvite.

In the stone Proteus bacteria can survive despite therapy, leading to chronic UTI.

Taxonomy
Family: Enterobacteriaceae
K. pneumoniae subsp pneumoniae
K. pneumoniae subsp. ozaenae
K. pneumoniae subsp. rhinoscleromatis
K.oxytoca

Natural habitats
They are widely distributed in nature and can be found in water, soil, on plants and have been isolated from clinical samples of humans and animals.

They are part of the normal intestinal flora of humans and animals.

Clinical significance
K. pneumoniae & K. oxytoca
They are important causes of nosocomial (hospital-acquired) and community-acquired infections in humans.

They can cause a variety of infections of the urinary and respiratory tract (pneumonia).

This species can cause septicemia, peritonitis, meningitis, infections of wounds and burns.

Taxonomy
Family: Enterobacteriaceae
E. aerogenes
E. cloacae complex
- E. cloacae, E. asburiae, E. hormaechei, E. kobei, E. ludwigii
E. amnigenus I
E. cancerogenus
E. gergoviae
E. intermedium

Pathogenic to plants: E. amnigenusII, E. cowanii, E. pyrinus, E. radicincitans

Natural habitats
Can be found in soil, water, sewage, food and also on the human skin and in the intestinal tract.

Clinical significance
Enterobacter species cause a wide variety of nosocomial infections, including respiratory- and urinary tract infections, wound infections, osteomyelitis, meningitis and bacteremia.

Especially patients which are hospitalized for more than 72 hours and immunocompromised patients are at risk for an infection caused by Enterobacter.

Taxonomy
Family: Enterobacteriaceae

C. freundii complex
-- C. freundii, C. braakii, C. gilleni, C. murlinae, C. sedlakii, C. werkmanii, C. youngae
C. koseri (C. diversus)
C. amalonaticus
C. farmeri

Natural habitats
Isolated from soil, water, food, feces, urine of humans and animals.
They are commensals of the intestine.

The natural habitat of some Citrobacter species is unknown.

Clinical significance
Citrobacter species cause a wide variety of nosocomial infections, including infections of the respiratory- and urinary tract, blood, wounds, bone, meninges and other normally sterile tissues.

Especially patients which are hospitalized for more than 72 hours and neonates and immunocompromised patients are at risk for an infection caused by Citrobacter.

In many cases the infection arises from the gastrointestinal or genitourinary tract.

Taxonomy
Family: Flavobacteriaceae,
genus: C.ochracea, C.gingivalis, C.sputigena, C.haemolytica and C.granulosa

Natural Habitat
They are normal inhabitants of the human mouth

Clinical Significance
The first three are also associated with juvenile and adult periodontitis, whereas the latter two been isolated from supragingival plaque of healthy adults as well as from subgingival plaque in adult periodontitis.

All five species may cause septicemia and other infections in immunosuppressed (mainly neutrpenic) patients.

Taxonomy
Family: Enterobacteriaceae

Yersinia has 3 species of which are pathogenic for humans, namely

Y. enterocolitia, Y. pseudotuberculosis and Y. pestis

Natural habitats
Comes in all animal species, but has also been isolated from (drinking) water, soil and vegetables, also from animal products such as raw milk, cream, ice cream, beef, pigs oysters, lamb and chicken.

Clinical significance
They can cause yersiniosis in human and animals and they are a significant food-borne pathogen.

Infection usually lead to mild self-limiting enterocolitis, terminal ileitis and adenitis in humans.

Symptoms may include watery or bloody diarrhea and fever.

The infections are sometimes followed by chronic inflammatory diseases such as arthritis and erythema nodosum

Sepsis may occur with a high mortality in debilitated patients with severe underlying diseases.

Yersinia can also occur in pus of deep abscesses.

Taxonomy
Family: Enterobacteriaceae
(Plesiomonas is Greek for neighbors)

Natural habitats
Is isolated from a wide range of mammals, birds, fish, water-dwelling, reptiles and amphibians.

Clinical significance
Human P. shigelloides infections are associated with living in or travel to tropical countries and / or a history of seafood consumption; both acute diarrhea and chronic diarrhea episodes of > 2 weeks have been reported.

Most of the infections are self-limited.

General Information
Yersinia pestis was discovered in Hong Kong in 1894 by a Swiss physician Alexandre Yersin.

He linked Y. pestis to the bubonic plague, an epidemic that ravaged Europe during the 1300s.

The organism was isolated during a outbreak in Hong Kong

Taxonomy
Family: Enterobacteriaceae
It was formerly known as Pasteurella pestis.

The closest relative is the gastrointestinalpathogen Y. pseudotuberculosis and more distantly Y. enterocolytica

Natural habitats
Yersinia pestis interacts mainly with rodents such as rats and fleas (Xenopsylla cheopsis)

Through these carriers, Yersinia pestis is able to invade human cells and create diseases.

Clinical significance
Human Y. pestis infection takes three main forms, pneumonic, septicemic and bubonic plagues.

All three forms were responsible for a number of high-mortality epidemics troughout human history, including: the sixth century's Plague of Justinian, the Black Death, which accounted for the death of at least one-third of the European population between 1347 and 1353; and the 19th century's Third Pandemic

It has now been shown that these plagues probably originated in rodent populations in China.

Yersinia pestis infections must be diagnosed quickly due to the high virulence of these organisms.
Death from pneumonic plague can occur in as little as 24 hours after the first appearance of symptoms.

Taxonomy
Family: Enterobacteriaceae genus: S. marcescens
2 subsp.- S. marcescens ssp marcescens
- S. marcescens ssp sakuensis
S. odorifera
S. liquefaciens group
- S. liquefaciens
- S. grimesii

S. plymuthica and S. rubidiaea (red pigment, rarely from clinical material)

Not pathogenic
S. entomophila, S. ficaria, S. fonticola, S. proteamaculans, S. quinivorans, S.ureilytica

Natural habitats
They are widely distributed in nature. Isolated from water, soil, foods.

Clinical significance
Serratia ssp are notorious health care-associated pathogens and colonizers

Transmission is predomiately from person to person, but medical apparatuses, intravenous fluid, and other solutions are often implicated as well.

In children, the gastrointestinal tract is a common source of infections.

Pigment
Production in S. marcescens appears to be a marker that the strain is environmental in origin and of low virulence.

Taxonomy
Family: Enterobacteriaceae
(formerly designated : Klebsiella)

R. terrigena & R. planticola (plant pathogen)

Natural habitats
They are found in water, fish, insects, nature and land.

They are commensals in the gut of humans and animals.

Clinical significance
R. ornithinolytica has the ability to convert histidine to histamine in scombroid fish.

Infection causes redness of the skin.

Scombroid food poisoning
Is a foodborne illness from eating spoiled fish.
It is often missed because it resembles an allergic reaction

The generic name Rahnella was given to honor the German-American bacteriologist Otto Rahn, and the species name aquatilis was selected because the organism is usually isolated from water.

Taxonomy
Family: Enterobacteriaceae

Natural habitats
As the name implies, they are ubiquitous in the environment, especially water, it is a water-dweller. Is also on food (meat, fresh water, fish and dairy products) plants, human and animal feces.

Clinical significance
Isolated from immunocompromised human patients, blood, sputum, wound, burn infections and bacteremia.

General information
Organisms belonging to the genus Providencia have undergone many taxonomic changes since their first description, with frequent confusion and overlap between organisms of the closely related genera Providencia, Proteus and Morganella

Taxonomy
Family: Morganellaceae

P. alcalifaciens
- P. rustigianii (P.alcalifaciens biogroep 3)
P. rettgeri
P. stuartii

apathogeen P. heimbachae, P. vermicola

Natural habitats
They are ubiquitous in the environment, especially water and clinical samples, such as; urine, feces, blood, wounds and throat.
Also occur in animals, mammals, birds, reptiles and insects.

Clinical significance
Patients with burns are at a higher risk of Providencia wound infection, like P. stuartii and P. rettgeri
Patients who develop Providencia urinary tract infections often have long-standing dependence on an indwelling urinary catheter.

Both species (P. rettgeri more commonly than P. stuartii) have recently been implicated as etiologic agents in traveler's diarrhea, making travel history important in patients with acute-onset diarrhea.

Taxonomy
Family: Enterobacteriaceae
P.vulgaris
- P.penneri (= P.vulgaris genomosp 1)
- P.hauseri (= P.vulgaris genomosp 3)

Natural habitats
Proteae occur in humans, animals and the environment, especially in locations where animal protein decomposes.

Clinical significance
They were isolated from wounds, soft tissue and urine

P. vulgaris and P. penneri are easily isolated from individuals in long term care facilities and hospitals and from patients with underlying diseases or compromised immune systems.

P. vulgaris is more susceptible to cause nosocomial infections

In people with congenital or anatomic abnormality of the urinary tract or a stone in the urinary tract, are predominantly Proteus (mostly P. mirabilis) infections.
They quickly put this urea into ammonia, which creates an alkaline environment. This can be harmful to the kidney and promotes the formation of stones materials consist of a biochemical complex, which is called struvite. In the stone Proteus bacteria can survive despite therapy, leading to chronic UTI.

Taxonomy
Family: Morganellaceae
genus Proteus mirabilis

Natural habitats
Proteae occur in humans, animals and the environment, especially in locations where animal protein decomposes.

Clinical significance
They are found in urinary tract infections and wounds.
Very often these infections are caused by their own fecal flora. P.mirabilis occurs in patients with chronic wounds, leg ulcers and decubitis. In people with congenital or anatomic abnormality of the urinary tract or a stone in the urinary tract, are predominantly Proteus infections.
They quickly put this urea into ammonia, which creates an alkaline environment.
This can be harmful to the kidney and promotes the formation of stones materials consist of a biochemical complex, which is called struvite.

In the stone Proteus bacteria can survive despite therapy, leading to chronic UTI.

was: Enterobacter agglomerans

P. agglomerans
P. dispersa (rarely)

Pathogeen voor planten
P. ananatis, P. stewartii ssp indologenes, P. stewartii ssp stewartii, P. terrae

Natural habitats
Widely distributed in nature. Isolated from human and animals stools

Clinical significance P. agglomerans can cause opportunistic infections in immune compromised patients.

General information
morganii from: Harry de Riemer Morgan (1863-1931), physician te London

Taxonomy
Family: Morganellaceae
M. morganii
- M. morganii ssp morganii
- M. morganii ssp sibonii

Natural habitats
Widely distributed in nature are normal inhabitants of the gut.

Clinical significance
Is most frequently considered a health care-associated pathogen, primarily causing urinary tract infections, though wound infections and bacteremias are also commonly encountered.
Respiratory infections are rare.

Taxonomy
Family: Enterobacteriaceae

Natural habitats
Widely distributed in nature.

Clinical significance
Pathogenicity undetermined (opportunistic pathogen).

Rarely isolated from clinical samples.

Kluyvera is a newly described genus in the family Enterobacteriaceae

Taxonomy
Family: Enterobacteriaceae
K. cryocrescens, K. ascorbata, K. georgiana, K. intermedia

Natural habitats
They are widely distributed in nature.

Clinical significance
They are infrequent opportunistic pathogens.

K. ozaenae and K. rhinoscleromais are associated with chronic diseases of the upper airways: ozena and rhinoscleroma.

Taxonomy
Family: Enterobacteriaceae
K. pneumoniae subsp pneumoniae
K. pneumoniae subsp. ozaenae
K. pneumoniae subsp. rhinoscleromatis

Clinical significance
- K. ozaenae
Occurs in ozena (a chronic disease of the nose characterized by foul smelling nasal discharge and atrophy of nasal structures) and other chronic diseases of the respiratory tract

- K. rhinoscleromatis
Causes a slowly progressing granulomatous disease of the nasal mucous membrane (rhinoscleroma)

Taxonomy
Family: Enterobacteriaceae
K. pneumoniae subsp pneumoniae
K. pneumoniae subsp. ozaenae
K. pneumoniae subsp.rhinoscleromatis
K. oxytoca

Natural habitats
They are widely distributed in nature and can be found in water, soil, on plants and have been isolated from clinical samples of humans and animals.

They are part of the normal intestinal flora of humans and animals.

Clinical significance
K. pneumoniae & K. oxytoca
They are important causes of nosocomial (hospital-acquired) and community-acquired infections in humans.

They can cause a variety of infections of the urinary and respiratory tract (pneumonia). This species can cause septicemia, peritonitis, meningitis, infections of wounds and burns.

Taxonomy
Family: Enterobacteriaceae

Natural habitats
Widely distributed in nature, water, soil, dairy products and rarely from clinical samples (feces) from humans and animals

Clinical significance
H. alvei seem to be opportunistic pathogens which produce infections in patients with underlying illness or predisposing factors.

May cause nosocomial infections associated with other bacteria, like septicemia, enteritis, urinary tract infections, pneumonia and abscesses.

Taxonomy
Family: Enterobacteriaceae,
Genus: Atlantibacter hermannii
Formely: Escherichia hermannii

Natural habitats
Widely distributed in nature, water, soil, foods and clinical samples.

Clinical significance
Most have been isolated from feces and wounds

Taxonomy
Family: Enterobacteriaceae, genus: Escherichia coli
E. albertii, E. fergusonii, E. hermannii, E. vulneris

Natural habitats
Widely distributed in nature, water, soil, foods and clinical samples.

The genus Escherichia will occupy the last part of the small intestine and the large intestine in humans and warm-blooded animals. In more than 99% of the isolates, it is a Escherichia coli.

E. coli is a good indicator of the water it is clean. (fecal contamination)

Clinical significance
They are generally located in the intestinal lumen (colon), but some strains can cause a variety of infections, enteritis, septicemia, peritonitis, urinary infections, meningitis (neonatal) etc, in humans and animals.

Taxonomy
Family: Enterobacteriaceae
E. aerogenes
E. cloacae complex
- E. cloacae, E. asburiae, E. hormaechei, E. kobei, E. ludwigii
E. amnigenus I
E. cancerogenus
E. gergoviae
E. intermedium

Pathogenic to plants: E. amnigenusII, E. cowanii, E. pyrinus, E. radicincitans

Natural habitats
Can be found in soil, water, sewage, food and also on the human skin and in the intestinal tract.

Clinical significance
Enterobacter species cause a wide variety of nosocomial infections, including respiratory- and urinary tract infections, wound infections, osteomyelitis, meningitis and bacteremia.

Especially patients which are hospitalized for more than 72 hours and immunocompromised patients are at risk for an infection caused by Enterobacter.

Taxonomy
Family: Enterobacteriaceae
Formerly known as Enterobacter sakazakii

Natural habitats
Can be found in soil, water, sewage, food, some dairy products and also on the human skin and in the intestinal tract.

Cronobacter sakazakii have also been found in powdered baby food.
The bacterium can grow at a low temperature, growth at 8 ° C has been documented.

Clinical significance
May cause significant infections in various anatomical sites.

Meningitis, necrotizing enterocolitis and sepsis associated with high mortality have been documented in especially neonates.

Taxonomy
Family: Enterobacteriaceae

C.freundii complex
-- C. freundii, C. braakii, C. gilleni, C. murlinae, C. sedlakii, C. werkmanii, C. youngae

C. koseri (C. diversus)
C. amalonaticus
C. farmeri

Natural habitats
Isolated from soil, water, food, feces, urine of humans and animals.
They are commensals of the intestine.

The natural habitat of some Citrobacter species is unknown.

Clinical significance
Citrobacter species cause a wide variety of nosocomial infections, including infections of the respiratory- and urinary tract, blood, wounds, bone, meninges and other normally sterile tissues.

Especially patients which are hospitalized for more than 72 hours and neonates andimmunocompromised patients are at risk for an infection caused by Citrobacter.

In many cases the infection arises from the gastrointestinal or genitourinary tract.

Taxonomy
Family: Pasteurellaceae, previously: Haemophilus
Genus: Aggregatibacter aphrophilus
Formerly: Haemophilus aphrophilus

Natural habitats
Occur in the mouth and oropharynx of healthy individuals.

It is a frequent member of the microflora of human dental plaque, particularly between the teeth and in the gingival pockets

Clinical significance
Has been isolated from blood, spinal fluid, peritoneum, pleura, wounds and jaw infections.

Opportunistic pathogen occasionally implicated in subacute endocarditis, brain abscesses, sinusitis, arthritis and osteomyelitis often caused by dental treatments that cause a break of the oral mucosal barrier and a temporary bactereamia.

The significance of the recovery of Aeromonas from stool specimens should be interpreted cautiously and must rely on both laboratory information and clinical interpretation.

Taxonomy
Family: Aeromonadaceae

Natural habitats
Aeromonas are inhabitants of aquatic ecosystems worldwide.

They don’t like saltwater.

They are also found in a wide variety of fresh produced meat (beef, poultry and pork), and dairy products (raw milk and ice cream)
And found in the gut of medical leeches and in the mouth of snakes

Clinical significance
They are capable of causing gastroenteritis and wound infections in humans, especially those individuals with liver disease.

Aeromonas gastroenteritis ranges from an acute watery diarrhea (most common form) to dysenteric illness or chronic illness.

Stools from acute watery diarrhea are loose and erythrocytes and fecal leukocytes are absent.

Symptoms
Abdominal pain, fever, vomiting, and nausea.

Infections are usually self-limiting, but children may require hospitalization due to dehydration.

Aeromonads can also be isolated, on other sites, although blood and wounds are the most common sources

Taxonomy
Family: Pasteurellaceae, formerly: Pasteurella ureae
Genus: Actinobacillus ureae and A. hominis

Natural habitats
A. ureae is usually a commensal in the human respiratory tract, particularly in patients with lower respiratory tract disease.

Clinical significance
They may be involved in the pathogenesis of sinusitis, bronchopneumonia, meningitis, and other infections in immunocompromised patients.

Cases are rare.

Taxonomy Family: Flavobacteriaceae, genus: C.ochracea, C.gingivalis, C.sputigena, C.haemolytica and C.granulosa

Natural Habitat They are normal inhabitants of the human mouth

Clinical Significance The first three are also associated with juvenile and adult periodontitis, whereas the latter two been isolated from supragingival plaque of healthy adults as well as from subgingival plaque in adult periodontitis.

All five species may cause septicemia and other infections in immunosuppressed (mainly neutrpenic) patients.