Minor Enterobacteriaceae Pathogens Yersinia enterocolitica and Yersinia pseudotuberculosis @ Y. enterocolitica & Y. pseudotuberculosis are gram-negative rods. Transmitted to humans by contamination of food with excreta of domestic animals, e.g. dogs, cats, and cattle. @ Y. enterocolitica causes enterocolitis that is not distinguished clinically from that caused by Salmonella or Shigella.
@ Y. enterocolitica & Y. pseudotuberculosis cause mesenteric adenitis that resemble acute appendicitis. @ These organisms are involved in bacteremia or liver abscess & spleen, in persons with underlying diseases. @ Y. enterocolitica is isolated from stool and forms a lactose-negative colonies on Mac Conkey agar. @ It grows better at 25°C. Biochemical tests are positive at 25°C & negative at 37°C
@ Incubation of stool at 4°C for 1 week (cold enrichment) increases frequency of recovery of the organism. @ Y. enterocolitica & Y. pseudotuberculosis are distinguished by biochemical tests. @ Cultures are rarely made to diagnose Y. pseudotuberculosis. Serology not done @ Enterocolitis and mesenteric adenitis do not require treatment. @ For bacteremia or abscess, give co- trimoxazole or ciprofloxacin.
Citrobacter @ Citrobacter species are gram-negative, motile rods, and related to Salmonella & Arizona. @ They occur in the environment and in the human colon @ They are opportunistic, and can cause sepsis in immunocompromised patients @ C. freundii is the most species isolated.
@ May be isolated from urine, blood and pus specimens. @ Because Citrobacter species can be late or non-lactose fermenters, they require differentiation from salmonellae. @ Many strains of C. freundii ferment sucrose whereas Salmonella species are non-sucrose fermenters.
Arizona @ Arizona species are gram-negative rods, ferment lactose slowly. @ Arizona hinshawii is found in the feces of chickens and other domestic animals @ In Man it causes diseases similar to those caused by Salmonella, such as enterocolitis and enteric fevers. @ The organism is usually transmitted by contaminated food, eg, dried eggs.
Edwardsiella @ Edwardsiella species are gram-negative rods, resembling Salmonella. @ Edwardsiella tarda causes enterocolitis, sepsis, and wound infections. Erwinia @ Erwinia species are gram-negative rods, found in soil and water. @ Erwinia herbicola rarely involved in human disease.
Hafnia @ Hafnia species are gram-negative rods, found in soil and water @ Hafnia alvei is an opportunistic bacteria, & may be cultured on Mac Conkey agar Pectobacterium @ Pectobacterium is gram negative rods. @ Plant pathogens of potato and carrot. @ They are opportunistic and may cause human infections.