Shigella n others

• Divide large amounts of leftovers

  Into shallow containers for quick cooking in the refrigerator
• Typhoid fever vaccines

  • Ty21a vaccine
  • Vi capsular polysaccharide vaccine
• Ty21a vaccine

  • Live attenuated oral vaccine in capsule formulation
  • Given in 4-dose schedule taken every other day over a one-week period to people at least 6 years of age
  • Protection should last about 5 years, at which time a booster dose would be needed
• Vi capsular polysaccharide vaccine

  • Consists of purified capsular antigen
  • Injected intramuscularly in a single dose for people over 2 years of age
  • Booster dose is given every 2 years
• The Ewing's classification of shigellae is based on their O antigens
• Shigella serogroups

  • A
  • B
  • C
  • D
• Biochemical differentiation of shigellae

  • Mannitol fermentation with acid production
  • ONPG based on their ability to produce β-galactosidase
• The habitat of shigellae is limited to the colon of man, and only associate with man in disease
• Shigellae can also infect large primates, such as apes and monkeys, which also serve as reservoir of shigella infections to man
• Shigella species

  • S. dysenteriae
  • S. flexneri
  • S. boydii
  • S. sonnei
• S. dysenteriae

  Shiga's bacillus, Japanese dysentery bacillus
• S. flexneri

  Flexner's bacillus, Strong's bacillus, Philippine dysentery bacillus
• S. boydii

  Boyd's bacillus, British dysentery bacillus
• S. sonnei

  Sonne-Duval's bacillus, US dysentery bacillus
• The genus Shigella is named after the Japanese microbiologist Kiyoshi Shiga, who first isolated the organism in 1896
• Transmission from person-to-person is via fecal-oral route
• Principal factors for transmission

  • Flies
  • Fingers
  • Food or water contaminated by infected persons
• Infection can be initiated with low infective dose (approximately <100 bacilli), thus is highly communicable
• Shigellosis

  Also known as bacillary dysentery
• Most severe infections are caused by S. dysenteriae
• Pathogenicity of Shigella species

  • Invasion of the mucosal epithelial cells (M cells) of the terminal ileum and large intestine is the key
• Signs and symptoms of shigellosis

  1. Initial symptoms appear approximately 24 to 48 hours after ingestion of the organisms and are marked by high fever, chills, abdominal cramps and pain, accompanied by tenesmus (rectal spasms)

  2. Watery diarrhea progresses to bloody stools containing mucus and numerous leukocytes (dysenteric diarrhea) as the organisms invade the colonic tissues and cause an inflammatory reaction
• Virulence factors of Shigella

  • OMPs (outer membrane proteins) mediate attachment to the epithelial cell and break down the membrane of the vacuole, allowing bacteria to multiply within the cytoplasm, and induce actin polymerization within the cytoplasm providing a motive force for bacterial movement and cell-to-cell spread
  • Endotoxin (LPS) probably contributes to the irritation of the bowel wall
  • Shiga toxin produced by S. dysenteriae type I acts as an enterotoxin, neurotoxin, and cytotoxin
• The term "dysentery" was used by Hippocrates to indicate a condition characterized by frequent passage of stool containing blood and mucus accompanied by straining and painful defecation
• Prevention and control measures for shigellosis

  • Sanitary control of water, food, and milk; sewage disposal and fly control
  • Isolation of patients and disinfection of excreta
  • Detection of subclinical cases and carriers, particularly food handlers
  • Antibiotic treatment of infected individuals
• Klebsiella pneumoniae

  Also known as Friedlander's bacillus, the most commonly isolated Klebsiella species
• Klebsiella pneumoniae

  • Gram-negative, nonmotile bacilli with large polysacchride capsules; produce mucoid colonies on culture
  • Normal inhabits the intestines of humans and animals; it can also be found in the respiratory tract of about 5% of normal individual
  • Causes a small proportion (~1%) of bacterial pneumonias characterized as extensive hemorrhagic necrotizing consolidation of the lung resulting in the production of sputum that may be thick, mucoid, and brick red, or thin and "currant jelly-like" in appearance
  • Also associated with urinary tract infection, wound infections, meningitis, bacteremia with focal lesions (e.g., lives abscesses) in debilitated patients
  • Pathology has been associated with a large polysaccharide capsule that confers protection against phagocytosis and antimicrobial absorption
• Klebsiella oxytoca


  Produces infections similar to those caused by K. pneumoniae, and has also been linked to antibiotic/antimicrobial-associated hemorrhagic colitis (AAHC)
• Klebsiella-Enterobacter-Serratia species

  • Klebsiella aerogenes (Formerly Enterobacter aerogenes)
  • Enterobacter cloacae
  • Pantoea agglomerans (Formerly Enterobacter agglomerans)
  • Serratia marcescens
• Klebsiella-Enterobacter-Serratia species

  • Resemble Klebsiella in terms of growth and most biochemical characteristics except that they motile
  • Cause of many nosocomial infections: bacteremia, LRTIs, UTIs, surgical site infections, and intravascular device-associated infections; less commonly occurring infections are nosocomial meningitis, sinusitis, osteomyelitis
  • Cause less commonly community-acquired infections
• Serratia marcescens


  • The most important member of the genus Serratia; and is a common opportunistic pathogen causing pneumonia, bacteremia and endocarditis especially in narcotics addicts and hospitalized patients
  • Unique among the enterobacteria in producing three hydrolytic enzymes: lipase, gelatinase, and DNase
  • Exhibit chromogenicity producing red pigments which are easily seen when grown on blood-free media such as nutrient agar especially when the cultures are incubated at room temperature
• Proteus species

  • P. mirabilis
  • P. vulgaris
• Proteus species

  • Widely recognized human pathogens associated primarily with UTIs, and also cause septicemia, and pneumonia
  • In UTI, they produce urease that hydrolyzes urea in urine to ammonia and ammonium carbonate making the urine alkaline, thus favoring bacterial growth; and, because acidification is virtually impossible, this results in the formation struvite kidney stones (or calculi) that can cause an obstruction and leads to kidney failure
  • Highly motile and give rise to a very thin film of bacteria on the surface of the agar, but interrupted with periods when the cells stop and undergo a cycle of growth so that colonies have a distinct zonation; cultures usually give off a "burnt gun powder" odor
• Morganella morganii


  The only species of the genus Morganella; previously designated as Proteus morganii
• Morganella morganii

  • Cause of UTI and wound infections and has also been identified as a cause of neonatal sepsis
  • Also produces urease and is motile but unlike Proteus species, it does not swarm
• The Dienes phenomenon is of value in differentiating the two strains of Proteus for epidemiological purposes
• Providencia species

  • P. rettgeri
  • P. stuartii
  • P. alcalifaciens
• Providencia species

  • P. rettgeri and P. stuartii have been associated with human infections, particularly difficult to treat because of their resistance to antimicrobials
  • P. rettgeri is a documented pathogen of the urinary tract and has caused occasional outbreaks in health care settings and also been implicated in diarrheal disease among travelers
  • P. stuartii has been implicated in outbreaks in burn units and has been isolated from urine cultures
  • P. alcalifaciens is most commonly found in the feces of children with diarrhea; however, its role as a cause of diarrhea has not been proven
• Citrobacter species

  • C. freundii
  • C. koseri (Formerly C. diversus)
• Citrobacter species

  • C. freundii is biochemically and antigenically related to most Salmonella serotypes, other than S. typhi, thus must be distinguished from Salmonella
  • Associated with UTIs, respiratory tract infections and sepsis