Manual of Clinical Microbiology

• What is the role of blood agar?

  Detects haemolytic activity
• Which organisms are found by blood agar?

  Streptococci & other fastidious organisms
• Which organisms are picked up by cooked meat medium?

  Anaerobes, especially pathogenic clostridia
• What is grown on chocolate agar?

  Nutritionally fastidious organisms, e.g. Haemophilus influenzae and Neisseria meningitidis
• What does blood agar contain which bacteria like H. influenzae need to grow?

  Blood growth factors like nicotinamide adenine dinucleotide (NAD or factor V) and haemin (factor X)
• Which organisms are picked up by buffered charcoal yeast extract?

  Legionella (including Legionella pneumoniae)
• Why is charcoal useful for growing Legionella?

  Charcoal removes toxic metabolites
• Which organism is detected by CIN (cefsulodin- irgasan- novobiotin) agar?

  Yersinia entercolitica
• Which factors enable CIN to grow Yersinia enterocolitica?

  Mannitol fermentation
• How does Yersinia enterocolitica appear on CIN agar?

  'Bull's eye' with deep red centre surrounded by transparent periphery
• How does chromogenic culture media work?

  A substrate is targeted by a specific enzyme produced by the target organism, which cleaves the colourless chromogenic conjugate resulting ain a chromophore being released (which is a distinctive colour)
• What colour are Gram negatives with chromagar ESBL?

  Pink to red
• Which organisms are metallic blue on ESBL chromagar?

  Klebsiella, Enterobacter and Citrobacter
• What colour is Proteus on ESBL chromagar?

  Brownish halo
• What colour is VRE on Chromagar VRE?

  Red to mauve
• Which bacteria are detected by Colistin- Nalidixic Acid (CNA) agar?

  Gram positive cocci
• Which organism is targeted by Hoyle medium (Tellurite)?

  Corynebacterium diphtheriae
• Which organisms are grown on MacConkey agar?

  Coliforms and enteric pathogens
• Which substrate is fermented in MacConkey agar?

  Lactose
• What is the appearance of lactose fermenting organisms on MacConkey agar?

  Pink
• What is the appearance of non- lactose fermenting organisms on MacConkey agar?

  Colourless/ transparent
• Which organisms are designed to be targeted by MacConkey agar Fluorocult?

  Salmonella, Shigella and coliform bacteria, especially E. coli
• Which organism is cultured on MacConkey agar with sorbitol?

  E. coli producing O157:H7
• Which organism is grown on OFPBL?

  Burkholderia cepacia
• What is the appearance of Burkholderia cepacia on OFPBL?

  Colonies change from green to yellow
• Which organisms are detected by TCBS?

  Vibrio cholerae and Vibrio parahaemolyticus
• Which organisms are detected by Thayer- Martin agar?

  Fastidious organisms, especially Neisseria
• Which types of organisms are grown on VK/KH?

  Obligate anaerobe Gram negative bacilli
• Which examples of obligate anaerobic Gram negative bacilli are grown on VK/KH?

  Prevotella melaningenica and Bacteroides fragilis
• Which organisms are grown on XLD (xylose- lysine- deoxycholate) agar?

  Eneteric pathogens especially Shigella and Providentia
• What is the function of Sabouraud dextrose agar ('Sabdex')?

  Cultivates dermatophytes (fungi)