Acute infectious diarrheal disease

다양한 임상적 증상이 있으며 virus, bacteria, parasite를 포함한 다양한 감염인자들이

관여한다.

1. Pathogenic mechanism

1) inoculum size

Salmonella, Vibrio cholera : 105-108개

Shigella, Giardia lamblia, Entamoeba : 10-100개 정도로도 infection을 일으킨다.

* transmission

Shigella, Entamoeba, Giardia : person to person

Salmonella : food

2) Adherence

균들은 병을 일으키기 위해 정상 위점막에 부착해야 하는데 이때 normal flora와 경쟁하며

증식한다. 세균은 장내세포에 부착하는 specific cell-surface protein을 분비한다.

예> V. cholera : specific surface adhesin(toxin-coregulated pilus, 다른 accessory

colonization factors)으로 소장세포의 brush border에 부착한다.

ETEC : adherence protein(colonization factor Ag) 분비

EPEC, EHEC : 장내 정막세포의 brush border에 부착하는 virulence determinant생산

3) toxin production

① enterotoxin : secretory mx을 통하여 watery diarrhea유발

* prototype : cholera toxin

(A subunit : toxin의 enzymatic activity, B subunit : enterocyte surface receptor에

결합)

ETEC : heat-labile enterotoxin(LT)생산-> secretory diarrhea유발

② cytotoxin : mucosal cell파괴

-> inflammatory diarrhea, bloody diarrhea(dysentery유발)

S. dysentery(shiga toxin), V. parahemolyticus, C. difficile, EHEC(O157:H7)(shiga-like

toxin)

③ neurotoxin : CNS, PNS에 작용

Staphylococcal, Bacillus cereus toxin -> CNS에 작용하여 vomiting유발

④ exotoxin : Shigella dysenteriae type 1 -> exotoxin생산 -> enterotoxin, cytotoxic

activity

4) Invasion

Shigella, EIEC -> mucosal epithelial cell invasion

-> intraepithelial multiplication

subsequent spread to adjacent cell

Salmonella : bowel mucosa invasion하지만 enterocyte를 파괴하거나 dysentery를

일으키지 않는다.

S. typhi, Y. enterocolitica -> intestinal mucosa penetration

-> Peyer's patch, lymph node에서 증식

-> 혈액을 타고 퍼짐

-> enteric fever, headahce, relative bradycardia, abd pain, splenomegaly,

leucopenia

2. Host defenses

1) Normal flora : 99%이상이 anaerobic bacteria

acidic pH, volatile fatty acid생성하여 colonization을 못하도록 한다.

2) Gastric acid : acidic pH of stomach = important barrier

gastric surgery후 Salmonella, shigella, G. lamblia, 많은 helminths등의 감염이

증가한다.

antacid, H2 blocker로 neuralization -> enteric colonization risk↑

rotavirus : acidity에도 생존

3) intestinal motility : major mx

4) immunity : cell-mediated immunity, humoral immunity 모두 중요

3. Lab

pathogenic E. coli : routine culture로 normal fecal와 구별×

LT, ST의 special test : 대부분의 lab에서 유용×

cholera : TCBS agar

salmonella & shigella : MacConkey's agar

Tab 128-1 Acute diarrhea를 일으키는 pathogen

1) Noninflammatory(Enterotoxin) - proximal small bowel

- watery diarrhea

- stool WBC(-)

V. cholerae, ETEC, C. perfringens, Bacillus cereus, S. aureus

Aeromonas hydrophila, Plesiomona shigellosis, Rotavirus등,

Giardia lamblia, Cryptosporidium

2) Inflammatory(Invasion or cytotoxin) - colon or distal small bowel

- dysentery or inflammatory diarrhea

- stool neutrophil(+)

Shigella, Salmonella, C. jejuni, EHEC, EIEC, Y. enterocolitica,

V. parahemolyticus, C. difficile, E. histolytica

3) Penetrating - distal small bowel

- enteric fever

- stool monocyte(+)

S. typhi, Y. enterocolitica

Tab 128-2 Bacterial food poisoning

1-6 hr incubation : S. aureus, B. cereus

8-16hr : C. perfringens, B. cererus

> 16hr : V. cholerae, ETEC, Salmonella, Shigella, V. parahemolyticus