Bacteriology Finals PDF 2024

acteriolog b y fin als Prepared by: Rana Mae A. Santiago, RMT Non-Enteric Gastrointestinal Pathogens Vibrio spp. All are oxidase positive except V. metschnikovii Gas from glucose: all negative except V. fumissii causes voluminous “rice water” diarrh...

acteriolog b y fin als Prepared by: Rana Mae A. Santiago, RMT Non-Enteric Gastrointestinal Pathogens Vibrio spp. All are oxidase positive except V. metschnikovii Gas from glucose: all negative except V. fumissii causes voluminous “rice water” diarrhea Culture: best isolated in alkaline (pH 8.4) peptone broth Best agar medium: Thiosulfate citrate bile salts (TCBS) agar Gram negative (-) comma shaped, curved, straight bacilli Facultative anaerobe Catalase negative, oxidase positive, able to reduce nitrate to nitrite except V. metschnikovii Vibrio spp. Other reactions of V. cholerae MR (-) VP (+/-) Citrate (+) Urease (-) TSI - A/A, Gas (-), H2S (-) Laboratory Diagnosis: String Test: emulsify organism in 0.5% sodium deoxycholate on a slide Cholera red reaction: add a few drops of concentrated sulphuric acid to 24hrs peptone water culture with V. cholerae = positive pink color is formed Vibrio spp. Salt Concentration (0.5%) \ most commonly used laboratory media, such as nutrient agar or sheep blood agar (SBA) SBA or Chocolate (CHOC) Agar Medium to large colonies that appear smooth, opaque and iridescent with a greenish hue Selective Differential Media MAC Cefsulodin-Irgasan-Novobiocin (CIN) agar Vibrio spp. Summary for Vibrio spp. Vibrio alginolyticus: Positive Oxidase, Sucrose, Lysine Decarboxylase, 6%NaCl, Yellow TCBS, Nitrate to Nitrite Vibrio cholerae: Positive Oxidase, Indole, Sucrose, Lysine Decarboxylase, Ornithine Decarboxylase, 0% NaCl, Yellow TCBS Vibrio cincinnatiensis: Positive Oxidase, Sucrose, 6% NaCl, Yellow TCBS, Nitrate to Nitrite Grimontii hollisae: Positive Oxidase, Indole, 6% NaCl, Green TCBS, Nitrate to Nitrite Photobacterium damsela: Positive Oxidase, Arginine Dihydrolase, 6% NaCl, Green TCBS, Nitrate to Nitrite Vibrio fluvialis: Positive Oxidase, Sucrose, Arginine Dihydrolase, 6% NaCl, Yellow TCBS, Nitrate to Nitrite Summary for Vibrio spp. Vibrio fumissii: Positive Oxidase, Gas Glucose, Sucrose, Arginine Dihydrolase, 6% NaCl, Yellow TCBS Vibrio harveyi: Positive Oxidase, Indole, Lysine Decarboxylase, 6% NaCl, Yellow TCBS, Nitrate to Nitrite Vibrio metschnikovii: Positive Sucrose, Yellow TCBS Vibrio mimicus: Positive Oxidase, Indole, Lysine Decarboxylase, Ornithine Decarboxylase, 0% NaCl, Green TCBS Vibrio parahaemolyticus: Positive Oxidase, Indole, Lysine Decarboxylase, Ornithine Decarboxylase, 6% NaCl, Green TCBS, Nitrate to Nitrite Vibrio vulnificus: Positive Oxidase, Indole, Lactose, Lysine Decarboxylase, Ornithine Decarboxylase, 6% NaCl, Green TCBS, Nitrate to Nitrite Summary for Vibrio spp. Indole Positive Negative Variable Grimontii hollisae V. alginolyticus V. cholerae V. cincinnatiensis V. harveyi Photobacterium damsela V. fluvialis V. mimicus V. fumissii V. parahaemolyticus V. metschnikovii V. vulnificus Glucose Positive Negative Variable Grimontii hollisae V. alginolyticus V. cincinnatiensis V. cholerae P. damsela V. vulnificus V. metschnikovii V. fluvialis V. mimicus V. fumissii V. harveyi V. parahaemolyticus Summary for Vibrio spp. Sucrose Positive Negative Variable V. alginolyticus Grimontii hollisae V. cholerae Photobacterium damsela V. cincinnatiensis V. mimicus V. harveyi V. fluvialis V. parahaemolyticus V. fumissii V. vulnificus V. metschnikovii Lysine Decarboxylase Positive Negative Variable V. alginolyticus V. cholerae G. hollisae V. cincinnatiensis V. harveyi V. fluvialis P. damsela V. mimicus V. fumissii V. metschnikovii V. parahaemolyticus V. vulnificus Summary for Vibrio spp. Arginine Dihydrolase Positive Negative Variable G. hollisae V. alginolyticus V. cholerae P. damsela V. cincinnatiensis V. fluvialis V. metschnikovii V. harveyi V. fumissii V. mimicus V. parahaemolyticus V. vulnificus Ornithine Decarboxylase Positive Negative Variable G. hollisae V. cincinnatiensis V. cholerae P. damsela V. mimicus V. fluvialis V. alginolyticus V. parahaemolyticus V. fumissii V. vulnificus V. harveyi V. metschnikovii Summary for Vibrio spp. Growth in 0% NaCl Positive Negative Variable G. hollisae V. alginolyticus V. cincinnatiensis P. damsela V. cholerae V. fluvialis V. mimicus V. fumissii V. harveyi V. metschnikovii V. parahaemolyticus V. vulnificus Summary for Vibrio spp. Growth in 6% NaCl Positive Negative Variable G. hollisae V. alginolyticus V. cincinnatiensis P. damsela V. cholerae V. fluvialis V. metschnikovii V. fumissii V. mimicus V. harveyi V. parahaemolyticus V. vulnificus Colony on TCBS GREEN YELLOW V. alginolyticus G. hollisae V. cholerae P. damsela V. cincinnatiensis V. mimicus V. fluvialis V. parahaemolyticus V. fumissii V. vulnificus V. harveyi V. metschnikovii Aeromonas spp. Key Characteristics Gram negative straight bacilli Facultative anaerobe Fermentative Indole positive Oxidase positive Motile Resistant to vibriostatic agent O/129 (2,4 diamino-6,7- diisopropylpteridine) Non-Inositol Fermenter A. hydrophila most common human isolate Aeromonas spp. Selective Culture Media MAC Agar Ferment lactose (A. caviae) A. trota: Unusual universal susceptibility to ampicillin CIN Medium Pink-centered colonies from the fermentation of mannitol, with an uneven, clear apron resembling Yersinia enterocolitica Alkaline peptone water Aeromonas spp. Presumptive Identification Oxidase Test (Aeromonas = positive) Spot indole test on suspicious colonies on SBA, especially Bhemolytic colonies Ability to grow in the presence of NaCl Campylobacter spp. Key Characteristics Gram negative comma, curved, S-shaped, seagull wing shaped bacilli Microaerophilic (5% O2) Capnophilic Motile (one polar flagellum) Oxidase positive Non-fermentative Sodium Hippurate Hydrolysis positive Urease negative Exhibit a characteristic Motility on hanging drop preparations or when visualized under phase contrast microscopy Campylobacter spp. A. Campylobacter jejuni and Campylobacter coli causes enteritis (especially in children) leading cause of acute diarrhea worldwide Sometimes responsible for bacteremia or endocarditis Culture: Incubate for 48hrs in an atmosphere containing 5% O2, 10% CO2, and nitrogen (campy gas mixture) Isolation media: “Campo-thio” or “Campy-blood” agar Media made selective with antibiotics Campylobacter spp. Biochemical reactions of C. jejuni Non-fermentative Oxidase (+), Catalase (+), Nitrate (+), H2S (-) Grows in 1% glycine Hippurate (+) (C. coli is negative) Colony Morphology C. jejuni and other enteric Campylobacters Moist, runny looking and spreading, usually nonhemolytic; some are round and raised and others may be flat C. fetus subsp. fetus Produces smooth, convex, translucent colonies C. mucosalis and C. hyointestinalis Can produce a dirty yellow pigment Helicobacter pylori Curved, flagellated, motile gram-negative rod “Triple positive”: catalase (+), oxidase (+), urease (+) Diagnosis: Biopsy Urea breath test Stool antigen Aerobic Gram-Positive Bacilli Corynebacterium non-spore forming, nonbranching, catalase-poisitive bacilli aka Kleb Loeffler’s bacillus Microscopy: Highly pleomorphic gram-positive bacillus Club-shaped swellings and beaded forms are common The metachromatic areas of the cell, which stain more intensely than other parts, are called Babes-Ernst granules Culture characteristics: facultative anaerobe grows best under aerobic conditions and has an optimal growth temperature of 37C, although multiplication occurs within the range of 15C to 40C Grows on nutrient agar, better growth is usually obtained on a medium containing blood or serum, such as Loeffler Serum or Pai Agars Corynebacterium Cystine-tellurite Blood Agar (CTBA) a modification of Tinsdale medium, contains sheep red blood cells, bovine serum, cystine and potassium tellurite (inhibits many noncoryneform bacteria). Key Characteristics of C. diphtheriae non-motile nitrate reduction (+) except that C. diphtheria var. mitis is variable Urease (-) Catalase (+) Glucose and maltose fermented Sucrose not fermented Corynebacterium Culture from throat, nasopharynx, and skin wounds Special culture media is required Loeffler’s or Tinsdale Black colonies on Tinsdale media Metachromatic (blue/red) granules on Loeffler’s media Media to enhance pleomorphism and granule production Loeffler seru agar + poached egg colonies Pai coagulated egg medium Listeria monocytogenes Key characteristics Facultative intracellular catalase positive tumbling motility on hanging drop technique (at room temperature) but usually non-motile @ 35-37C Hippurate hydrolysis positive Esculin positive; salicin (+) CAMP positive (hemolysis looks like shovel, not arrowhead) Grows from 0.5 - 45C Cold enrichment may be used. Listeria monocytogenes Culture: Sheep blood agar to detect beta hemolysis; or Trypticase agar to see blue-green colonies; or McBride Listeria medium with sheep blood For contaminated specimens, use phenylethylalcohol agar (inhibits gram negative organisms) Suspect cultures and tissues - hold at 4C up tp 6 months; subculture weekly for 1 month, and monthly thereafter Umbrella shaped pattern Erysipelothrix rhusiopathiae slender, pleomorphic gram positive rods that form filaments may be alpha hemolytic on blood agar decolorizes easily on gram stain thus may appear as gram negative catalase, oxidase and indole negative Produces H2S, differentiating it from L. monocytogenes test tube brush growth Mycobacterium obligate aerobes slender, nonspore-forming, acid fast, gram-positive rods (do not gram stain well) Culture media - incubate in 5-10% CO2 Lowenstein-Jensen (L-J) (green color and opaque) contains egg glycerol more species grow, less drying out, good for niacin test difficult to prepare Middlebrook 7H10 or 7H11 agar Clear agar see colony early good for antimicrobial susceptibility test Fewer contaminants grow Both L-J and Middlebrook media contain glycerol - enhances human strain of M. tuberculosis Mycobacterium Identification of mycobacteria - based on pigment production, growth rate and biochemical reactions Niacin Test - best test for M. tuberculosis (+) Enzymatic hydrolysis of Tween 80 hydrolysis releases oleic acid, which turns neutral red (indicator) from amber to pink Runyon groups I and III are positive in 5 days M. tuberculosis is positive in 5 days Nitrate reduction M. tuberculosis is positive, M. bovis negative M. kansasii is positive control Catalase reaction Almost all mycobacteria are catalase positive After incubation at 69C for 30mins, M. tuberculosis and M. bovis are catalase negative Mycobacterium Mycobacterium tu b i s e r c ulo s rough, wrinkled, dry, elevated, buff-colored (“cauliflower-like”) at 35-37C slow growth - 2-3 weeks or longer innoculate in 2 L-J slants wrap in aluminum foil incubate at 35C until visible growth occurs in unshielded tube expose covered tube to light for 1 hour, cover again and reincubate overnight Mycobacterium tu b i s e r c ulo s Biochemical characteristics Niacin positive (yellow color) Tween 80 hydrolyzedd in 10-20days (pink color) Nitrate positive Catalase at 68C: negative No growth in MacConkey Medium Arylsulfatase negative Mycobacterium ulcerans associated with skin lesions in tropical and subtropical areas (Buruli ulcers in Africa) requires several weeks incubation at 32C (6- 9 weeks for growth to become visible) (-) for niacin, nitrate reduction, Tween 80 Mycobacterium avium complex most common non-TB mycobacterial infection includes several bacteria:. avium, M, intracellulare slow growing, acid-fast organisms causes disseminated disease in HIV/AIDS with low CD4 count (