Transcript H. pylori
THE GENUS HELICOBACTER Gram –ve rod, curved oxidase + microaerophilic strong urease activity At least 22 species included in this genus Majority colonize mammalian stomach or intestine Human pathogens : H. pylori, H. cinaedi, H. fennelliae H. pylori : * Mode of transmission is unclear oral- oral, fecal-oral houseflies, ingestion * Cultured from feces and dental plaque * 50% of adults older than age 60 are infected * Highest rates of initial infection occur by age 10 especially between ages 4-5 year Pathogenesis & Pathogenicity colonizes the mucous layer of the antrum and fundus of stomach does not invade the epithelium ability to colonize the gastric mucosa genome is the most variable sequence, changing the expression of OMP persist host immune defense cause host tissue damage Gastritis, peptic ulcer, gastric cancer Duodenal peptic ulcer Virulence factor : surface is covered with urease enzyme produce ammonia (base) from urea in the host, help to protect from acid adhesins for colonization of mucosal surfaces stimulate cell to initiate mediators of inflammation cytotoxin causes damage to gastric epithelial cells H. cinaedi and H. fennelliae * cause proctitis, enteritis, sepsis in homosexual men * septicemia, cellulitis and meningitis in immunocompromised patients H. pylori in cats : * has been cultured from feces, salivary secretion, gastric fluid and dental plaque of naturally-infected cats * infected cats had moderate to severe lymphofollicular gastritis * clinical sign : vomiting, weight loss possibly diarrhea (subclinical sign) Feline isolates shown to be genetically similar to human isolate (99.7% identity in 16s rRNA) Human to cats to human transmission of H. pylori as a reverse zoonosis? * Epidemiologic studies H. pylori infection and animal contact are conflicing * Overall rate of colonization of stray cats much lower than that of humans * Humans may the 1ry reservoir of the organism human cat Dogs and cats H. felis H. bizzozeronii H. salomonis (naturally infected dog) asymptomatic, some show intermittent vomiting, weight loss and emaciation possibility of zoonotic infection has been considered H. heilmannii associated highest infection rates in dogs and cats (group confinement) 0.2-0.4% human gastric cases species resembling H. heilmannii isolated from cats and dogs H. bizzozeronii swine, dog, and cat, human) * found in gastric mucosa * pig contact is an important risk for humans * infection of humans: milder from of chronic gastritis than H. pylori and may be self-limiting Other Helicobacter : H. mustelae - hypergastrinemia in ferret H. acinomyx - gastritis in cheetah H. cinaedi - part of flora of hamster H. suis - swine, gastric ulcer There has been no report pointing to a direct relationship of human infection by animal helicobacter spp. and gastric disorder in human caused by H. pylori Direct Detection : * Warthin-Starry stain, silver stain, Giemsa biopsy specimens * placing crush tissue biopsy in urea broth * Urea breath test * H. pylori stool antigen tests Isolation & Identification * Demonstration of histologic evidence of inflammatory changes accompanied by spiral organism in mucosa Biopsy speciman : Gastric mucosa e.g. chocolate agar, brucella agar + 5% sheep blood 4-7 days of incubation Biochemical test typical cellular morphology Positive results for : Oxidase Catalase Rapid urease test etc. (from table)