Enterobacteriaceae II: Shigella, Salmonella, Edwardsiella, Klebsiella, Yersinia, Proteus, Serratia, Enterobacter, Citrobacter Flashcards
What tribe is the genus shigella?
Tribe I: Escherichieae
What are the key ID features of Shigella?
MacConkey: Flat-dry, Lactose NEGATIVE, Nonmotile, CO2 neg
How is shigella transmitted?
Person to perosn via fecal oral
Contaminated food, water, flies, feces, etc
Who are at most risk for Shigella infections?
Young children and their siblings/parents
Male Homosexuals
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
What are hte clinical presentations of Shigella?
Bacillary Dysentery
Abd cramps, tenesmus (urge to defecate but nothing there), pus and blood in stool
How is shigella treated?
Self limiting, resolves on its own
Does shigella need a high innoculum to cause disease?
No, very low innoculum -> easily spread for this reason
What species is in Edwardsielleae?
E.Tarda
Found in cold blood vertebrates, fresh water, catfish
What are the clinical sx of E.Tarda infection?
Gastroenteritis (selfe limitng) with watery diarrhea
Mistaken for salmonellosis and IBD (Chron’s Disease)
What is Tribe III?
Salmonelleae: Salmonella
Where is salmonella found?
Animals for nontyhpoid strains
Humans for S.typhi
Characteristics of Salmonella
Non-lactose fermenter
Produce H2S
Transmission via improper food handling and person to person
High innoculation to cause sx unlike shigella
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
What is the only reservoir for S.Typhi?
Humans
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
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
D
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
C
