Salmonella. Serological. Salmonella. food poisoning. Use of pasteurized milk and milk products Improvement of hygiene. Proper storage of foods

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1 Character Habitat Serological Pathogenicity Salmonella food poisoning Salmonella Gram ve facultative anaerobes, non lactose fermenter bacilli Intestinal tracts of humans and animals Salmonella: >1000 species à according to different antigen (somatic, flagellar, surface) Somatic (O) or cell wall antigens: are heat stable and alcohol resistant Surface antigen: may be found in some salmonella serovar. One specific surface antigen is Vi antigen which occurs in S typhoid and Paratyphi C Flagella (H) antigen: flagellar antigens are heat labile proteins 1. Enteric fever( Typhoid fever, Paratyphoid fever) S. typhi, S. paratyphi A,B,C No animal reservoir 2. Food poisoning (gastroenteritis) S. typhimurium, S. enteritidis No systemic infection Zoonotic infection 3. Septicemia May be caused by any species but S. cholerae- suis is common In this case, antibiotic therapy is required Epidemiology It is the most common salmonella infection CA S.typhimurium and S. enteritidis Pathogenesis The organism invade the epithelium and do not produce systemic infection Reservoir Animal reservoir is very important ; no human reservoir MOT From contaminated food ( poultry, meat, dairy products ) IP hours Symptoms Diarrhea, vomiting, fever that last 2 5 days Prevention Avoiding contamination of food Use of pasteurized milk and milk products Improvement of hygiene Proper storage of foods Brucella Main difference between members of the genus Brucella Organism Inhibition of growth by CO2 required H2S production Basic fuchsin 1/25000 Thionine 1/30000 Br. Melitensis Br. Abotus Br. Suis

2 Typhoid and paratyphoid fever CA S. typhi (typhoid fever) S. paratyphi A/B/C (paratyhoid fever) Info It is strictly a human disease MOT Contaminated water or food Source of infection Case or carrier. A carrier state is common; thus a food handler can cause a lot of spread Pathogenesis 1. The bacteria enter human digestive tract, penetrate intestinal mucosa and multiply in mesenteric LN, passes into blood à bacteremia usually within the 1 st week 2. The bacteremia is temporary and the organism finally lodging the gall bladder 3. Organisms are shed into the intestine for some weeks Virulence factors Release of endotoxin and exotoxins Salmonella strains may produce a thermolabile enterotoxin The Vi(capsular) antigen plays a role in the pathogenesis of typhoid Salmonella carriage Salmonella excretion by human patients may continue long after clinical cure Asymptomatic carrier are potentially dangerous About 5% of patients clinically cured from typhoid remain carrier for months or even years Antibiotics are usually ineffective on Salmonella carriage because the site of carriage in gall bladder may not allow penetration by the antibiotic C/P Step ladder fever How to diagnose enteric fever? 1. Isolation of the organism a. 1 st week: blood b. 2 nd week: stool Lab diagnosis c. 3 rd week: stool, urine 2. Culture of feces: in at least 50% of the cases culture of feces is positive in 1 st week. The isolation of S. typhi greatly increases in the 2 nd or 3 rd week 3. Urine culture: is positive in 1/3 of cases and in great majority of cases, it will be free from organisms weeks before the feces become negative Culture characters O2: facultative anaerobes Temperature: 37C CO2: no need Media Media Example Results Enrichment Selenite broth Maximal recovery of Tetrathionate salmonella Selective SS HE XLD Indicator MacKonkey agar Pale colonies (NLF) DCA Nutrient Nutrient agar Identification of colonies Film stained by Gram Biochemical reaction Slide agglutination Serodiagnosis Nb Gram negative bacilli Motile Non capsulated Non sporulated Widal test (tube agglutination test) Ferment: glucose, mannitol, maltose, sortbitol with acid (S.typhi) and gas S.paratyphi) Lactose is not fermented Negatve: indole, Voges Prosk, Urease test H2S produced from thiosulfate Diagnosis is based on prolonged presence of undulating fever (at least a week) By using o and H antisera against salmonellae to confirm the diagnosis

3 Widal test Dx thyphoid carrier Vaccine Use Diagnostic titer Widal test is an agglutination test for detection of antibodies against S.typhi and S.paratyphi, the common causal agents of enteric fevers When serum sample containing ab against S.typhi and S.paratyphi A,B or C are mixed with respective antigens, agglutination take place 2. In S.typhi and S.paratyphi 2 types of antinges are recognized as diagnostically important: O antigen, H antigen Principle 3. O antigen of various species have components in common and hence only one O antignet; non species specific 4. H antigens of Salmonella sp. are species specific, and hense the H antigens of all S.typhi and S.paratyphi A, S. paratyphi B and S.paratyphi C are employed in the test 5. Seum ab against H and O antigens of salmonella usually appear by 7 th 10 th days of infection and the titer reaches maximum during the 4 th week Result O Ab H Ab typhi H Ab paratyphi H Ab H Ab Result A paratyphi B paratyphi C S. typhi inf S. p.typhi A S. p.typhi B Recent vacc Old vaccine 5% are cured Asymptomatic à transmission Difficult treatment In order to label a person as a typhoid carrier, the isolation of the organism should be done from urine or faeces If these are repeatedly negative, bile or duodenal aspirate can be used Vi antibodies present in titre of more than 1:10 is also suggestive of chronic typhoid carrier 1. Live oral vaccine Using living avirulent bacteria It is given in 4 doses, 2 days apart as need for protection A booster dose is needed every 5 years for people who remain at risk Should not be given to children younger than 6 years of age 2. Parenteral heal phenol inactivated vaccine (TAB) Has been widely used for many years Given in 2 doses Efficacy over 2 3 year after vaccination ranges from 50% to 77% A booster dose is needed every 2 years for people who remain at risk 3. Newly licensed parenteral vaccine. Vi capsular polysaccharide (ViCPS) Composed of purified Vi (Virulence) antigen, elaborated by S.typhi 4. Acetone inactivated parenteral vaccine Currently available only to the armed forces in America Efficacy for this vaccine, ranges from 75% to 94% *no typhoid vaccine is 100% effective and is not a suitable for being careful about what you eat or drink

4 Brucella Species B. abortus affects cows B. melitensis affects goats and sheep B. suis affects pigs Species are differentiated by production of urease, H2S, dye sensitivity, cell wall antigens, and phage sensitivity Morph Gram negative cocco bacilli Non spore forming Non motile Non capsulated Disease Brucellosis Brucellosis Is a severe acute febrile disease caused by Brucella species Human infections are acquired from handling of infected animals Consuming contaminated milk or milk products (zoonosis) No human to human transmission Acquired exposure is frequently occupational. Thus veterinarians, meat workers and animal handlers are at great risk In animals, brucellae affect the reproductive organs causing abortion and sterility In contrast to animals, abortion is not a feature of brucellosis in pregnant woman 1) Portal of entry are the mouth, conjunctivae, respiratory tract and skin abrasion 2) Brucellae are facultative intracellular parasites, multiply in monocyte macrophage cells to RES (spleen, liver, Pathogenesis BM, LN, kidneys) where they live and multiply forming granulomas in these organs 3) Release of brucella from granulomas causes recurrent bacteremia and recurrence of fever and chills 4) These may produce an undulant fever in which intensity of fever and symptoms recur and reced at about 10 days intervals 1. Isolation a. Specimens : blood,biopsy of (LN,spleen,liver,BM); samples are highly infectious (hazard group 3) should be handled in a safety cabinet b. Blood culture: method of choice; early in the disease O2: strictly anaerobes CO2: 5-10% B. abortus Tempt: 37C Duration: 3 4 weeks c. Media Enriched media is need to support adequate Brucella growth Tryptone soya castenada diphasic medium are used for brucellae isolation form blood Diagnosis Identify growth: - Morphology: G ve, non motile, cocco bacilli - BR: catalase +ve, oxidase +ve, H2S production +ve for B. abortous, B. suis - Slide agglutination: with specific antiserum and growth inhibition by dyes - Molecular technique: for tying are being developed 2. Serodiagnosis a. Rapid slide agglutination : rapid screening, undiluted an diluted serum used to avoid prozone phenomenon (*def:a falsely negative test due to very high titers of antibody) b. Tube agglutination test: Wide range of dilution of the patient serum ( up to 1/1280 ) to avoid prozone phenomenon A titer of 1/100 to 1/200 is diagnostic Interpretation depends on patient occupation and disease endemicity Rising titer is diagnostic c. EIA: enzyme immunoassay test à to detects specific IgM and IgG 3. PCR: direct detection of brucella in clinical samples 4. Brucellin test: Principle: intradermal allergic test similar to tuberculin Method: using heat killed brucella suspension for intradermal injection Pasteurizing milk Minimize occupational exposure by observing safety precautions (protective clothing and laboratory containment) Control Eradication of infected animals and vaccination of animals by live attenuated vaccines to reduces the reservoir Vaccines for humans have been developed Vaccination for persons at high risk is possible but not widely accepted Treatment Tetracycline Or tetracyclin/streptomycin + generally curative

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