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GI pathogens
Microbiology
| Question | Answer |
|---|---|
| Stomach normal flora include: | Lactobacilli, Streptococci |
| Small bowel/colon contain ____ bac/gram; mostly ____ | 10(11); anaerobes |
| Small bowel/colon normal flora include: | Peptostreptococci, Bacteroides, Enterobacteriaceae |
| Normal GI flora: Viruses/Fungi | Adenovirus, Enterovirus; Candida |
| Normal GI flora: Parasites | Mostly amoebae; Blastocystis hominis; Entamoeba coli; Endolimax nana; Trichomonas hominis |
| Etiologic agent of gastroenteritis is related to: | Age |
| Most important agent of gastroenteritis in infants | Rotavirus A |
| Other agents of gastroenteritis in infants | Adenovirus (serotypes #40/41); Coxsackie Virus |
| Most important viral agent of gastroenteritis in children/adults | Calicivirus |
| Other viral agents of gastroenteritis in children/adults | Norwalk virus; Astrovirus; Reovirus |
| What age group more affected by viral GI syndromes? | Infants |
| Viral GI syndromes are usually ____ and require _____ | mild; only symptomatic tx |
| Bac agents of cholecystitis/biliary disease: | Enterobacteriaceae, Enterococcus, Bacteroides Clostridium spp. |
| Bacterial agents of gastritis/PUD: | Helicobacter pylori |
| Bile stimulates growth of ___ | Bacteroides |
| traveler’s diarrhea | Escherichia coli (ETEC) |
| food intoxication | S. aureus, C. botulinum, B. cereus |
| food infection: “Big Three” | Campylobacter jejuni; Salmonella spp.; Shigella spp. |
| Other poss bacterial agents of gastroenteritis | C. difficile, C. perfringens, C. botulinum, Vibrio cholerae, Listeria monocytogenes, Yersinia species |
| Causes of primary (spontaneous) peritonitis | Enterobacteriaceae (70%), S. pneumoniae, Enterococcus, anaerobes |
| Causes of secondary peritonitis | (Secondary: poss from trauma); Enterobacteriaceae, Bacteroides, P. aeruginosa |
| Agents of peritonitis from continuous ambulatory peritoneal dialysis (CAPD) | S. aureus (mostly), S. epidermidis, sterile (20%) |
| Diverticulitis | Enterobacteriaceae; Enterococcus; Bacteroides |
| AIDS-associated diarrhea | Mycobacterium avium-intracellulare (MAI) |
| When to suspect bacterial gastroenteritis | Severe abd pain; large #’s of stools; bloody stools; fever (≥ 101°F); fecal leukocytes; tenesmus |
| Often considered the hallmark of bacterial gastroenteritis | Bloody stools |
| Bloody diarrhea+ fever+ tenesmus = ? | dysentery |
| GI syndromes: exceptions to 3-day rule | travelers diarrhea; dysentery s/s |
| 5 major groups of E. coli | Enterotoxigenic; enteropathogenic; enteroaggregative; enterohemorrhagic; enteroinvasive |
| E. coli groups = small bowel processes | Enterotoxigenic; enteropathogenic; enteroaggregative |
| E. coli groups = colon processes (bloody diarrhea) | enterohemorrhagic; enteroinvasive |
| E coli group = in developed countries | Enterohemorrhagic |
| E coli group = more common in pediatric populations (usu developing countries) | Enteropath & enteroaggregative |
| E coli group = most common in developing countries | Enteroinvasive |
| E coli group = travelers diarrhea | Enterotoxigenic E coli |
| ETEC | Enterotoxigenic E coli: profuse, watery diarrhea; mild: supportive tx only |
| Severe cases of ETEC can be treated with: | SMZ/TMP or quinolone; prophylaxis not recommended |
| Enteropathogenic E. coli (EPEC) | AKA enteroadherent E. coli; can be part of normal human flora; childhood diarrhea associated with daycare outbreaks (infection rarely seen in older children or adults); mild self limiting disease; non invasive |
| Enteraggregative E. coli (EAggEC) | Similar to EPEC in dz; self limiting diarrhea in children (rarely seen in older children and adults except travelers to endemic areas); difference is vigorous adherence to mucosal cells (facilitated by fimbriae); may be part of normal human flora |
| E coli group characterized by vigorous adherence to mucosal cells (facilitated by fimbriae) | Enteraggregative E. coli (EAggEC) |
| Like EHEC, disease can be mild to severe hemorrhagic colitis | Enteroinvasive E. coli (EIEC) |
| Most common strain of E coli seen in developed countries | Enterohemorrhagic E. coli (EHEC)[mediated by Shiga toxins (STEC)] |
| E coli group: small inoculum size (<100 bacteria) can cause infection | Enterohemorrhagic E. coli (EHEC) |
| >50 serotypes; 0157 most common in US | Enterohemorrhagic E. coli (EHEC) |
| HUS (hemolytic uremic syndrome) dreaded complication (ARF, thrombocytopenia, hemolytic anemia) | Enterohemorrhagic E. coli (EHEC) |
| E coli group that is mild & self limiting & noninvasive | Enteropathic |
| E coli group that may be normal flora | Enteraggregative E. coli (EAggEC) |
| most common cause of BACTERIAL gastroenteritis | C. jejuni |
| Risk factors of C. jejuni gastroenteritis | ages < 5yrs and 20-30 years; males; raw/ undercooked poultry etc; unpasteurized milk & dairy prods; consumption of untreated water; contact with pets and farm animals |
| Most common clinical presentation of non-typhoidal salmonella | Gastroenteritis |
| transmission risk increased with foods of animal origin | salmonella |
| Risk factors = consumption of contaminated water, exposure to infected reptiles, and person-person transmission | salmonella |
| incidence of severe disease greater in infants, elderly, and those with immunosuppressive conditions | salmonella |
| Fecal shedding serves as reservoir for new infections (children < 5 yrs made shed bacteria for months) | Salmonella |
| Mostly a pediatric disease; transmission almost exclusively fecal-oral; travelers at risk | Shigella |
| As few as 10 bacilli = infective dose | Shigella |
| Prolonged fecal carriage in Shigella… | …is rare |
| Tx for Shigella | Antimicrobial therapy, even for mild disease, helps with complete eradication |
| Etiologic Agents of Food Intoxication | S. aureus; Clostridium botulinum; Bacillus cereus; C. difficile |
| enterotoxin A is preformed in food | S. aureus |
| ingestion disrupts intestinal mucosa | S. aureus |
| Vomiting & diarrhea; onset within 2-4 hrs after digestion | S. aureus |
| Organism can colonize colon in neonates; avoid honey | Clostridium botulinum |
| neurotoxin; types A, B, and E | Clostridium botulinum |
| spore formation enables survival in extreme conditions | Clostridium botulinum |
| home canning is risky | Clostridium botulinum |
| What type of C. botulinum infxn rare in USA? | Wound botulism |
| Can cause upper or lower food infection; both self limiting | Bacillus cereus |
| Upper food infection: emetic symptoms; spores in fried rice, onset of symptoms 2-6 hrs | Bacillus cereus |
| S/S of B. cereus upper food infection | Emetic symptoms; spores in fried rice, onset of symptoms 2-6 hrs |
| Lower food infxn: diarrheal symptoms; spores in reheated meats and vegetables (microwave); onset is 24 hours | B. cereus |
| S/S of B. cereus lower food infection | Diarrheal symptoms; spores in reheated meats and vegetables (microwave); onset is 24 hours |
| agent of antibiotic associated colitis (AAC) | C. diff |
| enterotoxin mediated | C. diff |
| antibiotic resistence | C. diff |
| explosive bloody diarrhea | C. diff |
| S/S include many stools (double digits) | C. diff |
| 20-30% may need retreatment due to relapse | C. diff |
| Toxin A = enterotoxin; Toxin B = cytotoxin | C. diff |
| Normal GI flora in some; disrupted by antibiotics; metronidazole, vancomycin | C. diff |
| C. diff toxin types | Toxin A = enterotoxin; Toxin B = cytotoxin (Both can cause S/S = high # bloody stools, explos. Diarrhea) |
| Parasitic GI Syndromes in AIDS patients/protracted diarrhea: | MAI, Giardia lamblia, Cryptosporidium parvum, Isospora belli |
| Parasitic GI causes of diarrheal disease | G. lamblia, C. parvum, B. hominis |
| Intestinal amoebiasis | Entamoeba histolytica |
| Common cause of acute self-limiting diarrhea in immunocompetent hosts | Cryptosporidium |
| Worldwide distribution; more common in summer; seroprevalence in US ~30% | Cryptosporidium |
| Cryptosporidium sources | Contaminated water (drinking & recreational), apple cider, raw produce; daycare settings |
| Most common cause of parasitic diarrhea in US | Giardia |
| Giardia infxn most common when? | Late summer, fall |
| ~5% of patients with diarrhea >1 week | Giardia |
| Low infective dose (10-20 cysts) | Giardia |
| Antigenic variation important in pathogenesis | Giardia |
| Giardia infection can result in: | Asymptomatic carriage; acute self-limiting diarrhea; chronic diarrhea; chronic diarrhea + malabsorption |
| Cyst form swallowed, gets decysted; troph form seen in sm bowel | Giardia |
| Has an on/off clinical presentation (s/s come & go; pt may have it for a long time before coming for tx) | Giardia |
| Antigenic variation | Important in pathogenesis; not unique to giardia; way to rearrange cell surface pro’s, hide from body’s immune system; all RNA-interference-based |
| GI parasites only affects brush border cells (aot isospora belli which it may resemble clinically) | Cryptosporidium |
| GI parasite that tends to appear in “showers” | Giardia |
Created by:
Abarnard
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