GI Infections Flashcards
Anaerobic GI organism
Clostridia
Canned/vacuum packed foods: Honey (kids), beans (students). Ingestion of preformed toxin (inactivated by cooking)
Blocks Ach release from peripheral nerves - descending paralysis (different from GBS)
Clostridia Botulinum
Tx - antitoxin
Reheated meats, superantigen enterotoxin (bind directly to TCR + MHC outside peptide binding site - massive cytokine production by CD4 ie systemic toxicity
+ supression of adaptive response
Acts on small bowel 8-16 hours incubation
Watery diarrhoea + cramps, lasts 24 hours
Causes gas gangrene
Clostridia Perfringens
2 exotoxins (A,B) Get pseudomembranous colitis (ie an inflamed bowel) Caused by Abx usually cephalosporins/fluorquinolones
C Difficile
Tx - Metronidazole
Vancomycin PO
Aerobic GI oraganisms
Bacillus Cereus
Staph Aureus
Reheated rice (spores germinate) and sudden vomiting Super antigen - short incubation (4hrs) increased cAMP - L:ong incubation 18 hrs Watery non-bloody diarrhoea
Bacillus Cereus
Self limiting
Main virulence factor Protein A
Catalase, coagulase +ve
Appears in tetrads - clusters on gram stain
Beta hemolytic on blood agar
Produces enterotoxin (exotoxin that acts as superantigen, releasing IL1 and 2 - prominent vomiting and watery non-bloody diarrhoea
Staph Aureus
Don’t treat
Self limiting
Gram -ve lactose fermentor
Enterobacteriacae Coli
Toxigenic, Travellers Diarrhoea
Heat labile LT stimulates adenyl cyclase and cAMP
Heat stable ST stimulates guanylate cyclase
Act on the jejeunum, ileum not on colon
Enterotoxigenic E Coli
ETEC
Invasive Dysentery
Enteroinvasive E Coli
EIEC
Haemorrhagic, caused by verotoxin
Enterohaemorrhagic E Coli
EHEC
Anaemia, thrombocytopaenia, renal failure (0157:H7 toxin)
Haemolytic Uraemic Syndrome
HUS
Infantile Diarrhoea (Paeds)
Enteropathogenic E Coli
EPEC
Tx for E Coli
Self limiting
Can treat with cipro (avoid Abx)
Source - human faeces - contaminated food/water
Non-lactose fermentors
Salmonella, Shigella, Yersinia enterocolitis
Only transmitted by humans Multplies in peyers patches 3% carriers in gallbladder Slow onset fever + constipation Relative bradycardia SPlenomegaly and rose spots, anaemia and leukopenia
Salmonella typhi/paratyphi (enteric fever)
Tx Ceftriaxone or Ciprofloxacin
Poultry, eggs and meat, invasion of small and large bowel Bacteraemia is infrequent
Self limiting non-bloody diarrhoea
Salmonella Enteritides
Tx Ceftriaxone or Ciprofloxacin (if required)
Salmonella
O, H, Vi antigens, H2S producers, TSI agar, XLD agar, Selenite F broth
Mainly affects distal ileum + colon -> mucosal inflammation, fever, pain, bloody diarrhoea,. Shiga enterotoxin
Shigella Avoid Abx (Cipro if required)
Enterocolitis, mesenteric adenitis w/ necrotising granulomas, associated reactive arthritis and erythema nodosum
Transmitted via food contaminated with domestic animals excreta
Prefers 4 degress cold enrichment
Yersinia
COmma shaped
Late lactose fermentors
Oxidase +ve
Vibriosis
comma shaped
Rice water stool
Human faeces (in shellfish)
Increase cAMP opens Cl channel at apical membrane of enterocytes - efflux of CL to lumen (loss of H2O and electrolytes)
Massive diarrhoea without inflammation
Vibrio Cholera
Tx Supportive
Ingestion of raw undercooked seafood (common in japan)
3/7 of diarrhoea often self-limiting
Vibrio Parahaemolyticus
Tx Doxycycline
Cellulitis in shellfish handlers
Fatal septicaemia with D+V in HIV patients
Vibrio Vulnificus
Tx Doxycycline
Curved, comma or S shaped Misc Gi organism
Campylobacter
Drinking unpasteurised milk, food eg poultry
Prodrome of headache and fever, abdo cramps, bloody foul-smelling diarhhoea
Curved, S-shaped, microaerophillic, oxidase +ve, motile, sensitive to malidixic acid (first quinolone)
ASsoc with Guillain-Barre and reactive arthritis
Campylobacter Jejuni
Erythromycin or Cipro if first 4-5 days
V or L shaped protozoa
Beta Haemolytic
Aesculin +ve
Tumbling motility
Listeria Monocytogenes
GI Watery diarrhoea, cramps, headache, fever, little vomiting
Perinatal infection, immunocompromised patients
Outbreaks of febrile gastroenteritis
Refrigerated food - unpasteurised dairy, vegetables
Listeria monocytogenes
Tx - Ampicilliin, Ceftriaxone, Cotrimoxazole
Motile trophozoite in diarrhoea
Non-motile cyst in non-diarrhoea
4 nuclei and no animal reservoir. Colonise colon
Makes flask shaped ulcer (histology)
Sx: Dysentery, wind, tenesmus,
Chronic weight loss and RUQ pain (liver abscess)
Entamoeba Histolytica Associated with MSM ALso food, water, soil Stool Microscopy Tx - Metronidazole + Paromomycin if luminal
Pear shaped trophozoite
2 nuclei trophozoites/cysts found in stool
Get it by ingesting cysts from faecally contaminated H2P
Malabsorption of protein and fat - foul semlling non-bloody diarrhoea
Giardia Lamblia
EMQ: Travellers/Hikers/MSM/Mental hospitals
Dx: ELISA string test
Tx: Metronidazole
Infects the jejunum
Severe diarrhoea in immunocompromised
Oocytes seen in stool by modified Kinyoun acid fast stain
Cryptosporidium Parvum
Tx: Paromomycin, Nitazoxanide in kids
Mycobacterium - M Tb, MAI
Always a possibility
Assoc with HIV
Viruses that cause GI problems
Rotavirus
No/Low grade fever
No white blood cells in stool
Secretory Diarrhoea V Cholera ETEC EAggEC EPEC EHEC
Fever
White blood cells in stool (Neutrophils)
Inflammatory DIarrhoea Camylobacter jejuni Shigella spp Non-typhoidal Salmonella serotypes EIEC
Fever
White blood cells in stool (Mononuclear cells)
Enteric Fever
Typhoidal salmonella
Enteropathogenic Yersinia Spp
Brucella spp
