Enterobacteriaceae II: Shigella, Salmonella, Edwardsiella, Klebsiella, Yersinia, Proteus, Serratia, Enterobacter, Citrobacter Flashcards by Dan Kim

What tribe is the genus shigella?

Tribe I: Escherichieae

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What are the key ID features of Shigella?

MacConkey: Flat-dry, Lactose NEGATIVE, Nonmotile, CO2 neg

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How is shigella transmitted?

Person to perosn via fecal oral

Contaminated food, water, flies, feces, etc

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Who are at most risk for Shigella infections?

Young children and their siblings/parents

Male Homosexuals

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What is the pathogenesis of shigella?

Virulent strains with plasmid -> can attach and enter cells via phagocytic vacuole -> intracellular replicaiton in cytoplasm -> cna transfer to adjacent cells

Can kill phagocytic macrophages
Some produce shiga toxin

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What are hte clinical presentations of Shigella?

Bacillary Dysentery

Abd cramps, tenesmus (urge to defecate but nothing there), pus and blood in stool

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How is shigella treated?

Self limiting, resolves on its own

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Does shigella need a high innoculum to cause disease?

No, very low innoculum -> easily spread for this reason

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What species is in Edwardsielleae?

E.Tarda

Found in cold blood vertebrates, fresh water, catfish

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What are the clinical sx of E.Tarda infection?

Gastroenteritis (selfe limitng) with watery diarrhea

Mistaken for salmonellosis and IBD (Chron’s Disease)

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What is Tribe III?

Salmonelleae: Salmonella

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Where is salmonella found?

Animals for nontyhpoid strains

Humans for S.typhi

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Characteristics of Salmonella

Non-lactose fermenter
Produce H2S
Transmission via improper food handling and person to person
High innoculation to cause sx unlike shigella

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Salmonella Clinical Sx

Asymptomatic: Carrier state with non-S.typhi

Febrile Gastroenteritis: most common; self limiting; don’t need to treat unless severe

Enteric Fever: Typhoid Fever; Caused by S.Typhi and S.Paratyphi A and B

Septicemia: without major GI involvement; underlying disease of reticuloendothelial sx patients

Focal Infections: Osteomyelitis, Meningitis, Brain Abscess, Endocarditis

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What is the only reservoir for S.Typhi?

Humans

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What is the pathogenesis of gastroenteritis in Salmonella infection?

Salmonells produces adhesins -> rearrange plasma membrane -> ruffles -> enter via pinocytosis -> large inflammatory response induced in bowels

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What is the pathogenesis of enteric fever in salmonella infections?

Bacteria binds to M cells -> infection kills cell -> go to Peyer’s Patch -> invade macrophages-> multiply and inhibit oxidative metabolic burst=> survive intracellularly

LPS: virulence factor causing septic shock

Common with disesaed RE system

What are the clinical presentations of a pt with salmonella enteric fever?

Fever: temperature-pulse dissociation (bradycadia with pulse rate less than waht is expected for body temp)
HA
Rose Spots: Pink macules or prupuric lesions
Constipation
Neuropsychiatric

What are some complications associated with salmonella enteric fever?

GI bleed
Perforation of ileal ulcers
Circulatory collapse
Relapse
Long term carriage

What are the clinical presentations of salmonella bacteremia?

Increased risk in pediatric, geriatric, AIDS patients
Similar to other gram neg bacteremia
Dx: psoitive blood cultures

How is salmonella bacteremia treated?

3rd gen Cephalosporin

A 50 year old female returned to Chicago from a 3 week trip to Jakarta (Indonesia) and about 5 days later started having flu like symptoms and a low grade fever. On the day prior to admission she had spiking fevers followed by profuse sweating. Stool cultures, ova and parasite exams and urine cultures were all negative. The
blood culture collected after a spiking fever episode grew a glucose-fermenting, gram-negative rod that was oxidase negative. Additional testing showed the organism was lactose-negative and
H2S positive. What is the likely etiologic agent of this patient’s
symptoms?
A. Shigella
B. E. coli O157
C. Malaria (Plasmodium falciparum)
D. Salmonella typhi
E. Vibrio cholera

What are the Tribe IV Enterobactericeae?

Citrobactereae: C.Freundii and C.Koseri

Found in intestinal tracts of humans and animals

What are the clinical presentations of Citrobacter?

Nosocomial infections: urinary and resp tracts of hospitalized patients; endocarditis, hospital acquired bacteremias

C.Freundii: rare cause of diarrhea
C.Koseri: rare cause of meningitis and brain abscess in neonates

What is Tribe V Enterobactericeae genus?

Klebsiella: K.Pneumoniae, K.Oxytoca, K.ozaenae, K.rhinoscleromatis Found in intestines and upper resp tract of humans and animals

What are the clinical presentations of K.Pneumoniae/K.Oxytoca?

K.Pneumoniae/K.Oxytoca: primary lobar pneumonia with destructive changes, necrosis, and hemorrhage (CURRANT JELLY SPUTUM). Bronchopneumonia, Bronchitis, UTI, bacteremias

What are the clinical presentations of K.Ozaenae?

Atrophic Rhinitis, Destruction of mucosa and mucopurulent discharge

What are the clinical presentations of K.Rhinoscleromatis?

Rhinoscleroma, chronic granulomatous disease of upper resp tract

What tribe does the genus Enterobacter belong to? What species are important?

Tribe V: Klebsielleae Species: E.Aerogenes, E.Cloacae In environment and GI tract of humans

What are the clinical presentaitons of Enterobacter?

Opportunistic infections of hospital patients -> UTI, resp tract, cutaneous wounds Septicemia Meningitis Reisstant to multiple abx -> difficult to treat

What tribe is the genus Serratia belong to?

Tribe V: Klebsielleae Species: S.Marcescens Found in environment

What are the characteristics of Serratia Marcescens on MacConkey agar?

Red colonies | NOT lactose fermenting

What are the clinical presentations of Serratia?

``` Nosocomial Infections Pneumoniae Septicemia UTI Surgical wound and cutaneous infections ```

What is Tribe VI and what genus is in it?

Proteeae Genus: Proteus Species: P.Mirabilis, P.Vulgaris

What is the key ID features of Proteus?

Swarming on blood agar and interval growth Lactose Neg on MacConkey Strongly urease positive

Where is proteus found?

Soil, water, intestinal tract of humans and animals

What are the clinical presentations of Proteus?

Commonly seen in clinical lab P.Mirabilis most frequently isolated -> UTI and wound infections Strong Urease Positive -> highly alkaline urea -> RENAL CALCULI of STRUVITE P.Vulgaris: common in infected sites in IC patients

What are the key identifying features of Yersinia Enterocolitica?

Pinpoint colonies on MacConkey Agar Urease Positive Gram Neg baccilus lactose Negative

What are hte major reservoir for Yersinia infections?

Pigs

What are the clinical presentations of Yersinia Enterocolitica?

Mimics appendicitis;Common in Children Enterocolitis most common: fever, abd pain, Blood contamination from asymptomatic Y.Enterocolitica bacteremia on blood donation

What is the pathogenesis of Yersinia?

Bacteria adheres to and penetrates ileum -> terminal ileitis, lymphadenitis, acute enterocolitis

A 1-year-old African-American patient was brought into the emergency room of an intercity hospital suffering from diarrhea and subsequent dehydration. The family reports that the illness began a couple of days after Christmas. In questioning the parents about food-born source of the infection the parents reported serving chitterlings to the adults but not the children. A stool specimen sent to the laboratory grew a lactose-negative gram-negative bacillus that gave biochemical reactions typical of E. coli except that the organism was urease positive. What is the most likely identity of the bacterium? A. E. coli 0157:H7 B. Salmonella serotype arizonae C. Yersinia enterocolitica D. Vibrio cholerae E. Edwardsiella tarda