Enterobacteria II Flashcards
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?
Gastroenteritis
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?
- Asymptomatic Carrier
- Febrile Gastroenteritis
- Enteric Fever (as in Typhoid Fever)
- Septicemia
- Focal Infections
What is the only reservoir of S. typhi?
Humans
What is the pathogenesis of Salmonella?
Bacteria bind to M cells
Infection kills cell, bacteria go to Peyer’s
patches
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?
Klebsiellae
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
