Bacterial infection

• What are the microbiological hazard categories?

  • Hazard Group 1: Unlikely to cause human disease (e.g., Pseudomonas fluorescens)
  • Hazard Group 2: Can cause human disease, unlikely to spread (e.g., Vibrio cholerae)
  • Hazard Group 3: Can cause severe disease, may spread (e.g., Yersinia pestis)
  • Hazard Group 4: Causes severe disease, likely to spread (No bacteria in this group)
• What percentage of bacterial species are human pathogens?

  Less than 0.0001%
• Why do bacteria cause infections in humans?

  The human body provides a favorable niche for bacteria to reproduce.
• Why don’t all bacteria cause infections?

  Not all bacteria find a favorable environment to thrive in the human body.
• Where can bacteria cause infections in the human body?

  Bacteria can infect the gastrointestinal tract, central nervous system, respiratory tract, urogenital tract, and skin/muscle.
• Which bacteria are associated with gastrointestinal infections?

  • Escherichia coli
  • Shigella
  • Salmonella
  • Campylobacter jejuni
  • Vibrio cholerae
  • Clostridium difficile
• Which bacteria are associated with central nervous system infections?

  • Neisseria meningitidis
  • Haemophilus influenzae
  • Streptococcus pneumoniae
  • Clostridium tetani
  • Clostridium botulinum
• Which bacteria are associated with respiratory tract infections?

  • Streptococcus pyogenes
  • Streptococcus pneumoniae
  • Bordetella pertussis
  • Mycobacterium tuberculosis
  • Legionella pneumophila
  • Pseudomonas aeruginosa
  • Haemophilus influenzae
  • Corynebacterium diphtheriae
• Which bacteria are associated with urogenital tract infections?

  • Escherichia coli
  • Proteus mirabilis
  • Chlamydia trachomatis
  • Treponema pallidum
  • Neisseria gonorrhoeae
• Which bacteria are associated with skin and muscle infections?

  • Staphylococcus aureus
  • Streptococcus pyogenes
  • Rickettsia prowazekii
• Which bacteria are associated with multisystem infections?

  • Borrelia burgdorferi
  • Yersinia pestis
  • Franciscella tularensis
  • Coxiella burnetii
  • Leptospira spp.
• How are bacterial infections transmitted?

  • Airborne: aerosolized droplets and fomites
  • Ingestion (faecal-oral): infection and intoxication
  • Vector-borne: ticks, lice, fleas
  • Direct contact: skin wounds, scratches, nasal secretions, sexual intercourse
• What is the role of airborne transmission in bacterial infections?

  Airborne transmission spreads bacteria through aerosolized droplets and fomites.
• What is the difference between infection and intoxication in the context of ingestion transmission?

  Infection involves bacteria multiplying in the gastrointestinal tract, while intoxication involves ingestion of toxins produced by bacteria.
• What are some examples of vector-borne bacterial infections?

  • Ehrlichiosis (Ehrlichia chaffeensis)
  • Lyme disease (Borrelia burgdorferi)
  • Q fever (Coxiella burnetii)
  • Rocky Mountain Spotted Fever (Rickettsia rickettsii)
  • Epidemic typhus (Rickettsia prowazekii)
  • Endemic typhus (Rickettsia typhi)
  • Bubonic plague (Yersinia pestis)
• How can direct contact lead to bacterial infections?

  Direct contact can occur through skin wounds, scratches, nasal secretions, and sexual intercourse.
• What is the significance of the Ziehl-Neelsen stain in detecting Mycobacterium leprae?

  The Ziehl-Neelsen stain reveals Mycobacterium leprae as red/pink due to its high concentration of mycolic acids in the cell wall.
• What are the virulence factors of pathogenic bacteria?

  • Adhesins and fimbriae
  • Capsule
  • Exoenzymes
  • Toxins
• How do bacterial infections cause damage to the host?

  • Direct damage from bacterial toxins
  • Damage from immune responses to the pathogen
• What are the methods for preventing bacterial infections?

  • Hygiene and sanitation
  • Vaccines (inactivated, attenuated, subunit, toxoid)
  • Prophylaxis (antibiotics, immunotherapy)
  • Antimicrobial coatings on medical devices
  • Safe sex practices
  • Vector control (insecticides)
  • Quarantine and contact tracing
• How are bacterial infections diagnosed?

  • Patient presentation (signs and symptoms)
  • Samples from sputum, blood, urine, stools
  • Urine dip-stick test
  • Microbial culture
  • Microscopy
  • Biochemical tests
  • Molecular diagnostics (e.g., PCR)
  • Serological diagnostics (e.g., ELISA)
• What are the treatment options for bacterial infections?

  • Topical disinfectants (e.g., Chlorhexidine)
  • Surgery / Debridement
  • Antimicrobial coatings
  • Antibiotics (bacteriostatic and bactericidal)
• How do antibiotics work against bacterial infections?

  Antibiotics target specific components of bacterial cellular machinery to inhibit growth or cause bacterial death.
• What is the concern regarding antibiotic resistance?

  There is an alarming increase in rifampicin resistant and multi-drug resistant strains of bacteria.
• What is the causative agent of Tuberculosis?

  Mycobacterium tuberculosis
• Who discovered Mycobacterium tuberculosis as the causative agent of tuberculosis?

  Robert Koch
• What is the generation time of Mycobacterium tuberculosis?

  Approximately 16 hours
• What is the distinction between tuberculosis infection and disease?

  • Only 5% of infections lead to active disease
  • 95% of infections are latent
  • Untreated active infections have a 50% fatality rate
• What happens during a latent tuberculosis infection?

  • Immune response forms granulomas (tubercles)
  • Mycobacterium tuberculosis can survive and become dormant
  • Can reactivate to cause active infection if untreated
• What are the symptoms of active tuberculosis disease?

  • Fever
  • Night sweats
  • Weight loss
  • Cough
  • Cavities in the lung
• How is tuberculosis detected?

  • Ziehl-Neelsen stain for acid-fast bacteria
  • Mantoux test for hypersensitivity
  • X-Ray test for cavities in the lung
• What is the treatment regimen for tuberculosis?

  • Triple therapy over 6 months:
  • Isoniazid
  • Pyrazinamide
  • Rifampicin/Rifampin
• What is the efficacy of the BCG vaccine for tuberculosis?

  20-80% efficacy
• What is the global significance of tuberculosis?

  TB is one of the top 10 leading causes of death globally.
• What is the characteristic of non-acid fast bacteria when treated with alcohol?

  They are decolourised due to lower lipid concentration in their cell wall.
• What does a positive Mantoux test indicate?

  It indicates hypersensitivity and suggests infection or previous vaccination.
• How much PPD is injected in the Mantoux test?

  0.1 ml of PPD.
• What is observed in an X-Ray test for tuberculosis?

  Cavities appear as radio-opaque patches in the lower parts of the lung.
• What are the components of the triple therapy for tuberculosis treatment?

  • Isoniazid: interferes with mycolic acid cell wall synthesis
  • Pyrazinamide: action unknown, converted to pyrazinoic acid in the liver
  • Rifampicin/Rifampin: inhibits transcription by binding to β-subunit of RNA polymerase
• What is the significance of the alarming increase in rifampicin resistant strains?

  It indicates a growing challenge in treating tuberculosis effectively.