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Flashcards in Enterobacteria II Deck (43)

What are the features of Shigella?

Biochemically and antigenically similar to E. coli but has some DIFFERENCES:

􏰉 Non-lactose fermenter
􏰉 Non gas producer
􏰉 Nonmotile


What is the main transmission of Shigella?

Fecal-oral route


What is the pathogenesis of Shigella?

􏰀Virulent strains carry plasmid for attachment and entry
􏰀Enters cells by phagocytic vacuole 􏰀
Organism escapes in cytoplasm
􏰀Intracellular replication
􏰀Actin “tail” drives organism in cytoplasm
􏰀Organisms enter adjacent cells


What diseases does Shigella cause?

Bacillary Dysentery


What are the main symptoms of Shigella infection?

Abdominal cramps, tenesmus, pus and blood in stool


What does E. tarda cause?



What are the symptoms of E. tarda infection?

􏰉Acute, self-limiting gastroenteritis with watery diarrhea 􏰉

Typhoid-like illness with bloody diarrhea and possible
fever, nausea, vomiting, colonic ulcerations and terminal ileum nodularity


What is the reservoir of Salmonella?

Poultry, cows, pigs, pets for nontyphoid strains
Humans for S. typhi


What is the reservoir of Salmonella?

Poultry, cows, pigs, pets for nontyphoid strains
Humans for S. typhi


What are the characteristics of Salmonella?

Gram Negative
􏰀Non-lactose fermenter
􏰀Produces hydrogen sulfide (black)


What are the routes of transmission of Salmonella?

Contaminated poultry and poultry products
􏰀Also associated with reptiles


What are the 5 Salmonella clinical syndromes?

1. Asymptomatic Carrier
2. Febrile Gastroenteritis
3. Enteric Fever (as in Typhoid Fever)
4. Septicemia
5. Focal Infections


What is the only reservoir of S. typhi?



What is the pathogenesis of Salmonella?

􏰀Bacteria bind to M cells
􏰀Infection kills cell, bacteria go to Peyer’s
􏰀Organisms invade macrophages where they multiply
􏰀Inhibition of oxidative metabolic burst allows organisms to survive intracellularly


What are the clinical manifestations of Salmonella enteric fever?

Presents with fever, headache, rose spots, constipation


What is the treatment for Salmonella bacteremia?

3rd Generation 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. Salmonella typhi


What is the reservoir of Citrobacter?

GI tract of humans and animals


What does C. freundii cause?

Rare cause of diarrhea


What does C. koseri cause?

Rare cause of meningitis and brain abscess in neonates


What is the reservoir of Klebsiellae?

Intestines and upper respiratory tract of humans and animals


What do K. pneumoniae and oxytoca cause?

Primary lobar pneumonia characterized by destructive changes, necrosis, and hemorrhage


What does K. ozaenae cause?

Atrophic rhinitis (ozena), destruction of mucosa and fetid mucopurulent discharge


What does K. rhinoscleromatis cause?

Rhinoscleroma, a chronic granulomatous disease involving mucosa of upper respiratory tract


What tribe is Enterobacter a part of?



What is the reservoir of Enterobacter?

Widely distributed in the environment and GI tract of humans


What is a major problem with the treatment of Enterobacter infections?

Many are multi-antibiotic resistant


What infections does Enterobacter cause?

Opportunistic infections involving urinary tract, respiratory tract, cutaneous wounds, occasional cause of septicemia and meningitis


What are the most important Enterobacter species?

E. aerogenes
E. cloacae


What is the reservoir of Serratia (Tribe Klebsiellae)?

Widely found in the environment


What does Serratia marcescens stain on MacConkey?

Red - it is the only organism to do this


What are the main Serratia infections?

Nosocomial infections, pneumoniae, septicemia, UTI, surgical wound and cutaneous infections


What is the reservoir of Proteeae?

Soil, water and intestinal tract of humans and animals.


What are key features in the identification of Proteeae?

Swarming observed on blood agar
Lactose Neg on MacConkey
Strongly Urease Positive


What are the main Proteeae species?

P. vulgaris
P. mirabilis


How can P. mirabilis and vulgaris be identified?

Indole positive is P. vulgaris
Indole negative is P. mirabilis


What can Proteeae cause in the kidney?

Strongly urease positive produces highly alkaline urea which can lead to renal calculi composed of struvite due to conversion of urea to HCO3-


What temperature does Yersinia grow best at?

Around 25 ˚C


What is the reservoir for Yersinia?

Widely distributed in lakes and reservoirs


What is the reservoir for Yersinia infection in humans?

Pigs are a major reservoir for infection in humans


What is a main route of infection for Yersinia in humans?

Ingestion via chitterlings (pig intestine)


How is Yersinia related to blood transfusion?

Blood contamination occurs do to asymptomatic Y. enterocolitica bacteremia at time of blood donation

􏰀Y. enterocolitica can proliferate in blood stored at 4˚ C after 2-3 weeks


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. Yersinia enterocolitica

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