Agents of digestive system infections (I. & II. completed in 1 lecture) MUDr. Lenka Černohorská, Ph.D. 5.10.2012 , based upon slides of M. Votava and V. Woznicová Institute of Microbiology, Medical Faculty of Masaryk University & St. Anne`s Faculty Hospital in Brno D:\Documents and Settings\lenka\My Documents\My Pictures\stolice.gif Digestive system •in the colon is approx. 1012 bacteria/g •normal intestinal flora: 99 % anaerobes •(Bacteroides, Fusobacterium, Clostridium, Peptostreptococcus), only 1 % Enterobacteriaceae (mainly E. coli) & enterococci Mouth cavity I •Normal flora: •viridans (α-haemolytic) streptococci (e.g. Streptococcus salivarius) •oral neisseriae (e.g. Neisseria subflava) •haemophili of very low pathogenicity (e.g. Haemophilus parainfluenzae) •Dental plaque is adherent microbial layer at the tooth surface consisting of living and dead bacteria and their products together with components from the saliva. Dental plaque= biofilm - cannot be washed off, only mechanically removed zubní kámen 2 Mouth cavity II •Dental caries: chronic infection caused by normal oral flora → localized destruction of tooth tissue •Etiology: mouth microbes (mostly Strept. mutans) making acids from sucrose in food •Thrush (in Latin soor): Candida albicans - occurs mostly in newborns •Herpetic stomatitis: primary infection with HSV 1 •Ludwig´s angina: polymicrobial anaerobic infection of sublingual and submandibular spaces (Porphyromonas, Prevotella etc.) Stomach •The microbes are killed by means of HCl except Helicobacter pylori. It produces an urease and hydrolyzes urea, it increases pH around itself • (1 urea NH2-CO-NH2 + H2O → 1 CO2 + 2 molecules of NH3) •H. pylori causes chronic gastritis, peptic ulcus • • Oesophagus •Oesophagitis usually in immunocompromised persons (AIDS, after a chemotherapy) due to: Candida albicans, Cytomegalovirus (CMV) • 39 helicobacter%20pylori Biliary tree & the liver I •Acute cholecystitis (colic, jaundice, fever): obstruction due to gallstones •Etiology: intestinal bacteria (E. coli etc.) •Complication: ascending cholangitis •Chronic cholecystitis: the most dangerous agent is Salmonella Typhi (carriers of typhoid fever) •Granulomatous hepatitis: Q fever, tbc, brucellosis • Biliary tree & the liver II •Parasitic infections of the liver: •Amoebiasis (Entamoeba histolytica: liver abscess) •Malaria (the 1st, clinically silent part of the life cycle of malaric plasmodia) •Leishmaniasis (Leishmania donovani: kala-azar, L. infantum) • •Schistosomiasis (eggs of Schistosoma japonicum, less often S. mansoni) • C:\Documents and Settings\muprac\Dokumenty\Černohorská\LF MUas\podzimní semestr\leishmania1.jpg Entamoeba Leishmania Infections which start in the digestive tract •Enteric fever (typhoid fever and paratyphoid fever): Salmonella Typhi, Salmonella Paratyphi A, B and C •Listeriosis: Listeria monocytogenes (dangerous for the fetus) •Peritonitis (after appendicitis or an injury): colonic flora (Bacteroides fragilis + other anaerobes + mixture of facultative anaerobes) •Viral hepatitis: HAV, HEV • Small and large intestine •Diarrhoea: increase amount of stool water – common intestinal response to many agents •Dysentery: acute inflammation of the colon → abdominal pain & small-volume stools with blood, pus and mucus D:\Documents and Settings\lenka\My Documents\My Pictures\prujmy.jpg Etiology of diarrhoea •Infectious etiology: •Bacterial (the most frequent) •Viral •Parasitic •Mycotic •Non-infectious etiology: •Food poisoning • Bacterial agents of diarrhoea and dysentery •Escherichia coli - important component (approx. 1 %) of normal intestinal flora, non-pathogenic in the intestine. Only some strains are pathogenic even in the intestine: • Strains causing diarrhoea: •ETEC (enterotoxic E. coli): children in developing countries, traveller´s diarrhea; 2 enterotoxins (heat-labile and heat-stable) •EPEC (enteropathogenic E. coli): O55, O111; small infants; disruption of microvillus structure •EIEC (enteroinvasive E. coli): similar to shigellae → dysentery-like disease ; invasion of colonic cells •EHEC (enterohaemorrhagic E. coli): O157:H7; 2 cytotoxic shigatoxins, destruction of microvilli; hemorrhagic colitis & hemolytic-uremic syndrome (HUS); in 2011 strain O104:H4 Bacterial agents of diarrhoea and dysentery – II •Salmonella •Taxonomical remarks: There are >4.000 salmonella serotypes •Official names of them are very inconvenient: 1.The most frequent salmonella: Salmonella enterica subspecies enterica serotype enteritidis 2.The most important salmonella: Salmonella enterica subspecies enterica serotype typhi •Instead of them we can use more useful names: 1.Salmonella Enteritidis 2.Salmonella Typhi Bacterial agents of diarrhoea and dysentery – III •2 types of salmonella infections: •1) Systemic infections (enteric fever = typhoid fever): S. Typhi, S. Paratyphi A – C •Pathogenesis starts with the invasion of intestinal epithelia. Invasion continues and infection becomes generalized → little or no diarrhoea, but pronounced fever & other general symptoms •2) Gastroenteritis ( = salmonellosis): remaining >4.000 serotypes •Pathogenesis starts with the invasion of intestinal epithelia. Infection is localized to ileocaecal region → diarrhoea, nausea & vomiting, abdominal pain, temperature may be elevated • Bacterial agents of diarrhoea and dysentery – IV •Diagnosis & treatment of salmonella infections: 1)Enteric fever (reservoir: human beings only): • Detection of salmonellae in blood, urine and stool (on special media), later detection of antibodies (Widal reaction), in suspected carriers examination of duodenal fluid • Treatment: antibiotics (chloramphenicol, fluoroquinolones, ampicillin, cotrimoxazol) •2) Gastroenteritis (reservoir: poultry & animals): • Examination of stool only • Treatment: symptomatic only, no antibiotics • Bacterial agents of diarrhoea and dysentery – V •Campylobacter jejuni •As common as salmonella (or even more); invades jejunal epithelium; reservoir: poultry •Cultured on a special medium, in an atmosphere of reduced oxygen, at 42 °C • •Shigella sonnei, S.flexneri, S.boydii, S.dysenteriae •Very low infectious dose → epidemic outbreaks, it is •transmitted only among human beings. Invasion of cells of colon and rectum •The disease is called bacterial dysentery D:\Documents and Settings\lenka\My Documents\My Pictures\caje.jpg Bacterial agents of diarrhoea and dysentery – VI •Yersinia enterocolitica • gastroenteritis, in children also mesenterial lymphadenitis (mimicking acute appendicitis) • vector: contaminated food • the microbe multiplies in refrigerator even at 4 °C •Vibrio cholerae •Cholera toxin activates adenylate cyclase → hypersecretion of water & electrolytes → death by dehydration and electrolyte abnormalities •V. cholerae flourishes in water & causes epidemics •Vibrio parahaemolyticus: from raw fish & shell-fish Diarrhoea due to antibiotic therapy •Common after tetracyclines; from multiplied Staphylococcus aureus, Pseudomonas aeruginosa or Candida albicans (diarrhoea of mycotic origin) •After lincomycin/clindamycin (+ other ATB) → dangerous pseudomembranous colitis caused by Clostridium difficile • Patients contaminate the hospital environment with resistant spores • Treatment: metronidazol, vankomycin Viral agents of diarrhoea •Generally: small, acid- and bile-resistant non-enveloped viruses •Rotaviruses (Reoviridae family) • serious diarrhoea of young children, epidemics in winter •Noroviruses and sapoviruses (formerly agents Norwalk and Sapporo, Caliciviridae family) epidemics in children and adults •Astroviruses (star-shaped virions) •Adenoviruses type 40 and 41 •Small, round gastroenteritis viruses D:\Documents and Settings\lenka\My Documents\My Pictures\rotavirus.jpg D:\Documents and Settings\lenka\My Documents\My Pictures\norwalk.bmp rotavirus Norwalk Parasitic agents of diarrhoea •In previously healthy individuals: • Entamoeba histolytica: amoebic dysentery • Giardia lamblia: giardiasis • Cryptosporidium parvum: cryptosporidiosis • Cyclospora cayetanensis • •In AIDS also: • Isospora belli (coccidium) • Enterocytozoon bieneusi (microsporidium) • Strongyloides stercoralis hyperinfection (helminth) D:\Documents and Settings\lenka\My Documents\My Pictures\giardia.jpg D:\Documents and Settings\lenka\My Documents\My Pictures\cyclospora.jpg Giardia Isospora Other intestinal parasites not causing diarrhoea (helminths) •Small intestine: • Ascaris lumbricoides (human roundworm) • Ancylostoma duodenale (Old World hookworm) • Necator americanus (New World hookworm) • Strongyloides stercoralis (threadworm) • Fasciolopsis buski (giant intestinal fluke) • Taenia saginata (beef tapeworm) • Taenia solium (pork tapeworm) • Hymenolepis nana (dwarf tapeworm) • Diphyllobothrium latum (fish tapeworm) •Large intestine: • Enterobius vermicularis (pinworm) • Trichuris trichiura (whipworm) C:\Documents and Settings\muprac\Dokumenty\Černohorská\LF MUas\pinworm1.jpg Enterobius - eggs Food poisoning •Intoxication due to a toxin preformed in the food: • Bacillus cereus: heat-stable enterotoxin and vomiting toxin (mostly in rice). Heat-labile diarrhoea toxin (cold sauce) • Clostridium perfringens: heat-labile enterotoxin • Clostridium botulinum: heat-labile neurotoxin • • • • • • D:\Documents and Settings\lenka\My Documents\My Pictures\ryze.jpg D:\Documents and Settings\lenka\My Documents\My Pictures\s958_pap009-copy-copygif.gif