Tribe Klebsielleae1. Klebsiella2. Enterobacter3. Serratia4. Pantoea5. Cronobacter6. Hafnia

Habitat:

1. Intestinal tract of humans2. Free-living in soil, water and on plants

Common characteristics:• Simmons citrate, potassium cyanide broth• None produce hydrogen sulfide• A few hydrolyze urea slowly• (-) methyl red test• (+) Voges Proskauer test• With few exceptions, indole is not produced from

tryptophan• Motility is variable

Klebsiella

diseases: pneumoniabacteremiathrombophlebitisUTIcholecystitisdiarrheaupper respiratory tract infectionwound infectionosteomyelitismeningitisrhinoscleromaozena

Antibiogram:Aminoglycozidesamykacine, TobramycineImipenemaztreoname

K. pneumoniae

• Most commonly isolated species• Polysaccharide capsule • Lower respiratory tract infections• Wound infections, UTIs, bacteremia• Nosocomial outbreaks: plasmid transfer of

antimicrobial resistance

K. ozaenae

• Nasal secretions and cerebral abscesses• Plasmid-mediated ESBLs

K. rhinoscleromatis• Patients with rhinoscleroma

Both were true species but reclassified based on nucleic acid studies

K. onrithinolyticaK. planticola

• Urine• Respiratory tracts• Human blood

Klebsiella oxytoca

• Identical to Klebsiella pneumoniae except:– Production of indole– Ornithine positive

Enterobacterinfections:Bacteremialower respiratory tract infectionsskin and soft tissue infectionsurinary tract infections (UTIs)endocarditisIntra-abdominal infectionsseptic arthritisosteomyelitisophthalmic infections

• 12 species (1 with 2 biotypes)– E. cloacae– E. aerogenes– E. gergoviae– E. hormaechei

• Motile• Simmons citrate medium, potassium cyanide broth• (-) methyl red test• (+) Voges-Proskauer test• Produce ornithine decarboxylase• Produce lysine decarboxylase

(except E. gergoviae & E. cloacae)

E. gergoviae & E. cloacae

• 2 most common isolates• Wounds, urine, blood, csf

Pantoea (Enterobacter) agglomerans

• Nationwide outbreak of septicemia• E. Agglomerans complex• Triple decarboxylases negative :

(-) lysine, ornithine, arginine• >13 hybridization groups:

P. Agglomerans HG XIII

E. gergoviae

• Respiratory samples• Rarely isolated from blood cultures

Cronobacter (Enterobacter) sakazaki

• Produces yellow pigment• Pathogen in neonates• Meningitis and bacteremia• Powdered infant formula• Brain abscesses, respiratory & wound infections

E. hormaechei -Blood, wounds, sputum

-biochemically similar to E.cloacae- blood, urine, feces, sputum,

wounds

- Traumatic wounds, osteomyelitis- Formerly E. taylorae

- Newly recognized

E. Asburiae

E. Dissolvents,E. nimipressuralis

E. cancerogenus

Serratia• Opportunistic pathogens• Nosocomial outbreaks• Ferment lactose slowly (except S. fonticola)• (+) ortho-nitrophenyl galactoside• Produces extracellular DNase• Resistance to a wide range of antimicrobials

Prodigiosin- pink to red pigment (esp. If incubated at room temp)

• s. marcescens– most clinically significant– Nosocomial infections of urinary/respratory tract– Bactermic outbreaks in nurseries, cardiac surgery & burn units– Septic arthritis

• s. plymuthica- osteomyelitis (motorcycle accident)

• s. rubidaea- human sources (s. liquefaciens, s. fonticola)

S. odorifera

• Dirty, musty odor (potato-like)• 2 biogroups:– Biogroup 1

respiratory tract (+) sucrose, raffinose, ornithine, (60%) indole

– Biogroup 2 blood, CSF(-) sucrose, raffinose, ornithine (50%) indole (+)

• S. ficaria• S. entomophila

Hafnia

• Human anatomic sites and environment• Stool cultures (occasionally)• Delayed (+) citrate reaction• 1 species with 2 biotypes H. alvei

H. alvei biotype 1– Beer wort of breweries– Has not been isolated clinically

Tribe Proteeae

1. Proteus2. Morganella3. Providencia

Proteus• Normal intestinal microbiota• Opportunistic pathogens• Deaminate phenylalanine• Non lactose fermenting• 3% of all nosocomial infection in US (esp UTIs)• Infects upper & lower urinary tract and proximal

tubules• Glomerulonephritis

(urinary tract defects and catheterization

P. mirabilis, P. vulgaris• Widely recognized human pathogens• Produce H2S and hydrolize urea• Urine, wounds, ear, bacteremic infections• Swarming colonies– on nonselective media– Produce “burnt chocolate” odor– Ascending nature of Proteus-associated UTIs– Tightly regulated cycle of differentiation swimmers (standard vegetative cells)

Swarmers (hyperflaggellated, elongated, polyploid cells)

indole and ornithine decarboxylase testP. mirabilis• Does not produce indole from tryptophan• (+) ornithine

P. vulgaris• produces indole from tryptophan• (-) ornithine• Acid/acid reaction in TSI agar

P. penneri

• Swarm colonies• Patients with diarrhea

• Gypsy moths• Large amount of slime

P. myxofaciens

Morganella

• Documented cause of UTI• Has been isolated from other body sites• 1 species: P. morganii

2subspieces: morganii sibonii

Providencia

• 5 species• Documented pathogen of urinary tract• Occasional nosomial outbreaks• Diarrheal disease among travelers

• Burn units• Urine cultures• P. stuartii, P. rettgeri infections:

difficult to treat

P. stuartii

P. alcalifaciens

• Feces of children with diarrhea

• Formerly strain of P. Alcalifaciens• Rarely isolated• Unproven pathogenecity

• Yet to be isolated from clinical specimens

P. rustigianii

P. heimobachae

Edwardsiella

• (-) urea• (+) lysine carboxylase, hydrogen sulfide, indole• Do not grow on Simmons citrate

E. tarda• the only recognized human pathogen• Opportunist• Causes bacteremia & wound infections

E. hoshinae• Snakes, birds, water

E. ictaluri• Fish: enteric septicemia

Plant pathogens

Erwinia• Poor growth at 37o• Fail to grow on selective media & other media

typically used for enteric isolations

Pectobacterium

Citrobacter

• 11 species• Hydrolyze urea slowly• MAC: resembles those of E. coli• Grow on Simmons citrate medium• (+) methyl red test

C. freundii

• Diarrheal stool cultures• Nosocomial diseases• UTI, pneumonia, intra-abdominal abscesses• Intravenous drug abusers: endocarditis• (80%) (+) hydrogen sulfide• (50%) (-) lactose

• C. freundii• C. koseri

(C. diversus)• C. amalonaticus• C.farmeri• C. braaki

• C. gillenii• C. murliniae• C. rodentium• C. sedlakii• C. werkmanii• C. youngae

BiochemicalTests

C. freundii Salmonella

Hydrolize urea +(70%)

-

Decarboxylate lysine

- +

C. koseri

• Nursery outbreaks of neonatal mening• Brain abscesses

C. almalonaticus• Feces• Sites of extraintestinal infections

(blood, wounds)

Sites of infection

Proteus mirabilis with peritrichous flagella

Swarming colony of Proteus mirabilis