To be Edited

• What are the major nutritional needs for microbial growth?

  Carbon, nitrogen, and an energy source
• Why do non-fastidious organisms require basic nutrients for growth?

  Because they can synthesize all necessary cellular components from simple nutrients
• What distinguishes fastidious organisms from non-fastidious organisms?

  Fastidious organisms need additional nutrients and specific growth conditions
• What are examples of fastidious organisms and their requirements?

  • Blood: X and V factors
  • Mucobacterium: heat labile proteins
  • Salt: tolerance to increased concentrations
  • Nutritionally Variant Streptococci: require Vitamin B6
• What is the role of X factor and V factor in bacterial growth?

  X factor is hemin and V factor is NAD
• What is the significance of salt concentration for certain bacteria?

  Some bacteria can tolerate high salt concentrations for growth
• Which bacteria can tolerate 7.5% salt concentration?


  Staphylococcus aureus
• What are the oxygen requirements for strict aerobes?

  They require oxygen for growth
• What is the difference between obligate anaerobes and facultative anaerobes?

  Obligate anaerobes cannot survive in the presence of oxygen, while facultative anaerobes can grow with or without it
• What are the categories of oxygen requirements for bacteria?

  • Strict aerobes: require oxygen
  • Obligate anaerobes: cannot tolerate oxygen
  • Facultative anaerobes: can grow with or without oxygen
  • Microaerophiles: require low levels of oxygen
• What is the gas composition in a Gas Pak jar for anaerobic culture?

  5% CO2, 10% H2, 85% N2
• What is the purpose of using indicators like Methylene Blue and Resazurin in anaerobic culture?

  To indicate the presence or absence of oxygen
• What color does Methylene Blue turn in the presence of oxygen?


  Blue
• What color does Resazurin turn in the absence of oxygen?


  Colorless
• What are the temperature categories for bacterial growth?

  • Psychrophilic: <10 °C
  • Mesophilic: 20-40 °C
  • Thermophilic: 50-55 °C
  • Thermoduric: can withstand high temperatures but do not grow well
• Which bacteria are known to contaminate blood bags at 4 °C?


  Yersinia enterocolitica and Listeria monocytogenes
• What is the significance of pH for bacterial growth?

  Most bacteria grow optimally at pH 7-7.5
• What are the categories of bacteria based on pH requirements?

  • Acidophiles: require acidic conditions
  • Alkaliphiles: require basic conditions
  • Neutrophiles: prefer neutral pH
• What is the purpose of antimicrobial susceptibility testing?

  To determine the resistance or susceptibility of an organism to antimicrobial agents
• What are the methods of antimicrobial susceptibility testing?


  1. Dilution method
  2. Disk diffusion method (Kirby-Bauer technique)
  3. Agar dilution
• What does the dilution method determine in antimicrobial susceptibility testing?


  It determines the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)
• What is the standard inoculum size for the broth dilution method?


  5 × 10^5 CFU/mL
• What is the significance of McFarland standards in antimicrobial testing?


  To standardize the inoculum size for accurate results
• What are the common errors in antimicrobial susceptibility testing?

  • Improper storage of disks
  • Reading and clerical errors
  • Deterioration of turbidity standards
• What type of agar is used for MRSA testing?


  MHA with 2% NaCl
• What is the role of beta-lactam antibiotics?


  They inhibit cell wall synthesis in bacteria
• What are the classes of antibiotics and their targets?

  • Beta Lactam: cell wall inhibitors
  • Glycopeptide: cell wall inhibitors
  • Aminoglycosides: protein synthesis inhibitors
  • Fluoroquinolones: nucleic acid synthesis inhibitors
• What is the function of polymyxins?


  They disrupt cell membrane function
• What are the automated systems used for bacterial identification?

  • Vitek System
  • Phoenix System
  • MALDI-TOF
• What is the purpose of the D-test in antimicrobial susceptibility testing?


  To detect inducible clindamycin resistance among strains of Staphylococcus aureus
• What does a positive D-test result indicate?


  Blunting of the Clindamycin zone producing a D pattern
• What is the significance of using a strip with single antibiotic concentrations in the E-test?


  It measures the activity of antibiotics against the pathogen
• What is the purpose of the serum bactericidal test?


  To detect if the patient is receiving effective antibiotic treatment
• What does the Index-API use for its tests?


  Plastic strips and microtubes with biochemical substrates
• How are the biochemical substrates prepared in the Index-API?


  They are inoculated with pure culture suspension
• What is the VITEK SYSTEM used for?


  It is a system for automated microbial identification and susceptibility testing
• What does MALDI-TOF stand for?


  Matrix Assisted Laser Desorption Ionization - Time of Flight
• What are the miscellaneous tests mentioned in the study material?

  • D-test: Detects inducible clindamycin resistance in S. aureus
  • E-test: Determines antibiotic susceptibility using strips
  • Serum Bactericidal Test: Measures antibiotic activity in patient's serum
• What is the purpose of the D-test?


  To detect inducible clindamycin resistance among strains of S. aureus
• What antibiotics are used in the D-test?

  15 µg Erythromycin and 2 µg Clindamycin