Enterobacteriaceae Vibrio د. حامد الزعبي
Enterobacteriaceae Escherichia coli, proteus and klebsiella... Shigella Salmonella
Members of the Enterobacteriaceae are: small Gram negative straight rods. Some genera are motile by means of peritrichous flagella except Shigella and Klebsiella species which are non-motile. They are facultatively anaerobic and most species grow well at 37 C Divided into Lactose -fermenters and Lactose non-fermenters Catalase +ve & Oxidase ve Many are normal flora
E. Coli 1 Escherichia coli: Gram negative motile rods (peritrichous flagella) Lactose fermenting A normal flora of human and animal intestines: Antigenic and serological characters: Somatic O, and capsular (K) flagellar (H)antigen Approx. 100 K, 150 O, 50 H antigens
E. Coli Virulence: Pili: colonising factors Polysaccharides Capsule: inhibits phagocytosis LPS endotoxin Some produce enterotoxins: heat labile and stable plasmid coded toxins Infections: 80% of UTI s cases Others (GIT, Respiratory, urinary, meningitis, sepsis)
E. Coli 1. Enterotoxigenic E. Coli Traveller s diarrhoea and infantile Diarrhoea Usually self limiting watery diarrhoea but be careful of dehydration Pathogenesis: Adhesion to small intestine via pili > 2 toxins released : Antigenic heat labile and non antigenic heat stable secretion of water and chloride & decreased sodium absorption > watery diarrhoea
2. Enteropathogenic E. Coli: Infantile enteritis and diarrhoea No toxin production Adhesion and effacement to small intestinal epithelium >microvilli damage impaired absorption and secretion 3. Enteroinvasive E. Coli: The only non-motile and non-lactose fermenting (Shigella like) 2 types of toxins: Invasion toxin (plasmid coded) LPS and aerobactin (chromosomal mediated) > Bloody diarrhoea similar to Shigella
E. Coli 4. Verotoxigenic E. Coli: Verotoxin 1 (immunogenic) and verotoxin 2 (non immunogenic) Transmitted via contaminated food, water and person to person E. coli O157 is commonly transmitted from beef Clinically: Bloody diarrhoea and haemolytic uremic syndrome. Special media: Cefixime tellurite sorbitol MacConkey s medium (CTSMAC) > colourless colonies due to absence of sorbitol fermentation in almost all cases (other E. Coli do ferment sorbitol resulting in pink colonies)
E. Coli Dx: Culture, gram stain and biochemical reactions Serotyping and toxin detection Rx and prevention:
2. Klebsiella Lactose fermenters UTI, Septicemia, Wounds.. Rare Meningitis.. Common Hospitalized patients. Encapsulated K. pneumoniae more pathogenic & Multidrug-resistant than other coliforms.. causes fatal pneumonia.. Common Outbreak Nosocomial infection
3. Proteus and Morganella species: Lactose -ve Low incidence in human & animal intestine.. cause about 3% of all UTIs, Less incidence Septicemia, Wounds, Nosocomial infection. Proteus & Morgenella spp. causes renal stones. All Urease positive..providencia spp. 50%.
Shigella 1. Shigella dysenteriae - serogroup A 2. Sh. flexneri - serogroup B 3. Sh. boydii - serogroup C 4. Sh. sonnei - serogroup D Non motile (No H antigen)and non lactose fermenter (sh. Sonnei is a late lactose fermenter) Grows at 37 C under aerobic and facultative anaerobic conditions We use MacConkey s and Deoxycholate citrate agar (DCA)
Shigella
Shigella Pathogenesis: Infects humans large intestine but not animals necrosis of intestinal mucosa are then sloughed and ulcers form. Low infectious dose of 10 organisms is enough Toxins: Endotoxin (LPS) Shiga toxin : It is an enterotoxin / neurotoxin and is thought to cause the HUS
Shigella Clinically (bacillary dysentery, shigellosis): Faecal oral route of transmission (10-100 organism is enough) The incubation period is usually between 2 and 3 days, but may be as long as 8 days. The onset of symptoms is usually sudden, and frequently the initial symptom is abdominal colic. diarrhoea, fever, tenesmus and the frequent passage of small volumes of stool, predominantly consisting of bloody mucus.
Shigella Complications such as : Strains of Sh. dysenteriae may cause haemolytic uraemic syndrome, HUS, ( haemolytic anaemia, thrombocytopenia and acute renal failure). Diagnosis: Stool sample Culture Antiserum on colonies (agglutination) Treatment : supportive +- ampicillin or co -trimoxazole
Salmonella Salmonella: more than 2000 serotypes but Major pathogens are: 1. Salmonella enteritidis (S. Enteritidis) 2. Salmonella Typhimurium 3. Salmonella typhi and paratyphyi (A, B, C) Habitat: S. Enteritidis and Typhimurium: Gut of domestic animals, especially cattle and poultry S. typhi and Paratyphi: humans and primates
Salmonella Characteristics: Motile, flagellated S. Typhi > capsulated Non-lactose fermenting Virulence factors: LPS Somatic antigen (O) Flagella (H) Antigen Vi antigen that codes for a polysaccharides capsule (only S. typhi)
Salmonella Clinically: 1. Gastroenteritis or food poisoning: (diarrhea and vomiting) mainly S. Enteritidis and typhimurium, sometimes paratyphi faecal oral transmission via contaminated food (poultry, eggs, meat)
Salmonella 2. Enteric (typhoid) fever: S. Typhi and paratyphi: Human reservoir, person to person transmission through contaminated food or water Incubation period 7-21 days Picture: Fever+Nonspecific symptoms (FUO) Rose spots (transient mac.papular lesions on the trunk) Splenomegally and diarrhoea (late manifestation)
Salmonella Course: 4 days if treated If untreated 3-4 weeks but might get complicated Complications: Relapse, GIT haemorrhages and perforations Sepsis > meningitis, osteomyelitis or pneumonia of recovered Chronic carrier state in 5% (stool secretion of organism for > 1 year, carried in the Gallblader) Blood, Stool and urine sample
Salmonella Laboratory Diagnosis: The appropriate sample is plated on selentine broth and special media (MacConkey s o,xld media) at 37 C (XLD = Xylose lysine deoxycholate agar ) On XLD: Salmonellae metabolise thiosulfate to produce hydrogen sulfide, which leads to the formation of colonies with black centers and allows them to be differentiated from the similarly coloured Shigella colonies Latex agglutination on colonies to detect O and H reactivity
Salmonella / XLD
Salmonella Rx: Food poisoning Supportive, Antibiotics if extreme ages, sickle cell or immunosuppressed Enteric fever: You must treat: ciprofloxacin, Azithromycin is an alternative Ceftriaxone for intravenous Prevention: hygiene, vaccine, chronic carriers?
Vibrio Characteristics: Gram negative rods or comma shaped Motile by a flagellum Optimum growth at alkaline ph (8-8.5) Virulence: LPS, Pili and cholera toxin (exotoxin) The cholera toxin: Decreased NACL and water absorption Increased Cl and bicarbonates and water excretion
Vibrio Classification: Non-Halophilic: V. Cholera Halophilic: V. Parahaemolyticus, V. Vulnificus V. Cholera has 2 classification systems: 1. Serology (based on O1 antigen) A. V. Cholera O1 antigen (3 isolates) B. Non O1 antigen: Types 2-139 2. Biotyping (phage typing): Classical V. Cholera El Tor
Vibrio Clinically: Faecal oral (contaminated water mainly) IP : 6hrs 5 days Multiplies in small intestinal epithelium Profuse diarrhoea with flecks of mucosa (rice diarrhoea fish odour ) Abdominal pain Effortless vomiting Fatal in 12 24 hrs N.B asymptomatic carriers 1:100
Vibrio
Vibrio Diagnosis: Stool sample: 1. In peptone alkaline water (PAW) for 6 hrs 2. Take a loop from the PAW and grow on Thiosulphate Citrate Bile Sucrose (TCBS) which is green in colour V. Cholera turns the green media into yellow as it ferments sucrose 3. Take a colonie and gram stain it: GNR comma shape, oxidase positive 4. Toxin can be detected by immunoassay
Vibrio Treatment: 1. Fluids : 2.9gm Na Citrate, 2.6gm NaCl, 1.5 gmkcl and 13.5 gm glucose 2. Antibiotics to decrease the execretion of cholera into environment Use Tetracycline Alternatives: erythromycin, Ciprofloxacin, ceftriaxone 3. No antitoxin Prevention: Hygiene and clean water Vaccine: Oral killed vaccine for O1 Ag type
Vibrio
Vibrio cholera / TCBS
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