Clostridioides spp Flashcards
Culture conditions
Anaerobic 37C blood agar
Anaerobic bacteria
Clostridioides
Bacteroides
Anaerobic Gram positive bacillus
Clostridioides
Colonial morphology
Large convex irregular edge double B-haemolysis.
Gram stain
Gram positive bacilli
Single endospores
C. perfringens = short fat rods + central spore
C. tetani = drumstick appearance + terminal spore
C. difficile = large spores
Endospores location Clostridium spp.
C. perfringens = central spore
C. tetani = terminal spores
Biochemical tests
KOH = negative
Catalase = negative
Oxidase = negative
Presumptive clostridium spp tests
- Anaerobic growth tests
- Metronidazole susceptibility test
- Lactose gelatin medium
- Egg yolk agar = Nagler reaction
Anaerobic growth test + metronidazole susceptibility test procedure
- Lawn inoculate blood agar purity plate with test organism + PC ( P. aeruginosa) + NC (C. perfringens) and incubate AEROBICALLY overnight at 37C
- Lawn inoculate blood agar purity plate with test + controls (PC = C. perfringens, NC = P. aeruginosa).
- Place metronidazole disc on secondary inoculum of test organism.
- Incubate ANAEROBICALLY for 48hrs using anaerobic jar and AnaeroGen sachet.
Lactose Gelatin media test procedure
- Using straight wire loop stab - inoculate selected colony into tube
- Inoculate control strains C.perfringens, C. sporogenes, E.coli
- Incubate 35C anaerobically for 24-48hrs.
- Following incubation examine for lactose fermentation
- Refrigerate tubes until well chilled (1hr) and examine for gelatin liquification.
Lactose Gelatin medium test results
Lactose fermentation= presence of bubble + colour change red to yellow
Gelatinase positive = gel is now liquid.
C. perfringens = yellow + liquid (= ferments lactose + gelatinase positive).
C. sporogenes = red + liquid
C. difficile = yellow + liquid
C. tetani = red + gel
C. botulinum = red + liquid.
Nagler reaction - egg yolk agar test procedure
- Divide egg yolk into 2 halves
- Label one with Cperfringens type A antitoxin A.
- Wear disposable gloves + safety glasses and swab half plate with antitoxin A
- Inoculate test + control (C.perfringens) onto half without antitoxin and move across to antitoxin side.
- Incubate anaerobically at 37C for 48hrs.
Nagler reaction principle
Detects lecithinase (phospholipiase) activity + lipase activity
Lecithinase positive -> opaque, diffuse zone around colonies.
Disappearance of opacity on antitoxin hald of plate (= neutralization of lecithinase)
Lipase positive -> iridescent sheen.
Nagler reaction test results
C. perfringens = opaque diffuse zone + no sheen
C. sporogenes = no zones + iridescent sheen
C. difficile = no zones + no sheen
C. tetani = no zones + no sheen
C. botulinum = variable zones + iridescent sheen
C perfringens diseases
Gas gangrene
Myonecrosis
Food poisoning - diarrhoea (6-18hrs after food consumption + resolves within 1-2 days)
C. difficile infection + treatment
Antibiotic associated diarrhoea
Pseudomembrane colitis
Cephalosporins, clindamycin, fluoroquinlones
C. botulinum disease
Botulism = flaccid paralysis
C. tetani disease
Tetanus = severe prolonged muscle spasms
C. perfringens Food Poisoning + Gas gangrene/myonecrosis treatment
Rehydration
IV fluid
Penicillin G
Specimens
Would/soft tissue = pus , tissue sample, muscle biopsy
Foodborne infections = faeces, food, gastric contents
Pseudomembrane colitis = faecal specimen.
