Microbiology Class: Normal Flora Quiz

Bacteria Important in Human Health

• Bacteria play a significant role in human health, both positively and negatively.
• They can be protective, causing disease, or opportunistic.

Role of Bacteria in Human Health

• Protective: Microbiota (normal flora) protects the body.
• Disease-causing: Pathogenic bacteria cause disease.
• Opportunistic: These bacteria cause disease only when the host's immune system is compromised.

Microbiota (Normal Flora of Human Body)

• Microorganisms colonize the body's surfaces soon after birth.
• Permanent microbiota are microorganisms that create permanent colonies without causing disease.
• Transient microbiota are microbes present for varying periods before disappearing.
• The relationship between the normal microbiota and the host is symbiotic (mutualism).
• Beneficial microorganisms derive nutrients and protection from the host, while the host receives protection from pathogens.

Parts of the Human Body Containing Normal Flora

• Skin
• Eyes (conjunctiva)
• Nose and throat (upper respiratory system)
• Mouth
• Gastrointestinal tract
• Genitourinary tract

Normal Flora

• Consists of many microorganisms.
• Key members are summarized in the following sections.

Skin Microbiota

• Staphylococcus epidermidis is a common species.
• Staphylococcus epidermidis is gram-positive cocci.
• Staphylococcus epidermidis is facultative anaerobic.

Mouth Microbiota

• Streptococcus mutans is a common species.
• Streptococcus mutans is gram-positive cocci.
• Streptococcus mutans are facultative anaerobic.
• Streptococcus mutans contribute to tooth decay.

Gastrointestinal Tract Microbiota

• Enterobacteriaceae (enteric bacteria like Escherichia coli) are common.
• Enterobacteriaceae are gram-negative bacilli.
• Enterobacteriaceae are facultative anaerobic.

Genitourinary Tract Microbiota

• Lactobacillus in the vagina is a key species.
• Lactobacillus is gram-positive bacilli.
• Lactobacillus is facultative or strictly anaerobic.
• The acidic pH of the vagina creates an inhibiting environment for pathogens.

Disease-Causing Bacteria

• Pathogenic bacteria: Can cause disease directly.
• Opportunistic bacteria: Cause disease only when the host's immune system is compromised.
• Examples can include bacteria introduced through medical procedures like catheters.

Infection and Infectious Disease

• Infection: The multiplication of an infectious agent within the body.
• Infectious disease: A clinically evident illness with characteristic signs and/or symptoms resulting from the infection.

Transmission of Pathogenic Bacteria

• Portals of entry: Respiratory, gastrointestinal, genital, urinary, capillary, skin, eyes, and ears.
• Routes of entry: Ingestion, inhalation, trauma, needlestick, arthropod bites, and sexual transmission.

Bacterial Diseases (Specific Examples)

• Staphylococcus aureus:
  • Gram-positive cocci
  • Forms grape-like clusters
  • Facultative anaerobic
  • Beta-hemolytic
  • Toxin production (positive)
  • Important clinical diseases: skin and soft tissue infections, gastroenteritis, toxic shock syndrome
• Staphylococcus epidermidis:
  • Gram positive cocci
  • Forms grape-like clusters
  • Facultative anaerobic
  • Non-hemolytic
  • Normal skin flora
  • Important clinical diseases: Wound infections and infections related to implants/catheters
• Streptococcus pyogenes:
  • Gram-positive cocci
  • Forms chains
  • Group A Beta-hemolytic streptococci (GABHS)
  • Facultative anaerobic
  • Beta-hemolytic
  • Toxin production (positive)
  • Important clinical diseases: skin and soft tissue infections, streptococcal sore throat (pharyngitis), scarlet fever
• Streptococcus pneumoniae:
  • Gram-positive diplococci
  • Alpha-hemolytic
  • Polysaccharide capsule (positive)
  • Important clinical diseases: pneumonia, sinusitis, otitis media, meningitis
• Corynebacterium diphtheriae:
  • Gram-positive bacilli
  • Metachromatic granules (positive)
  • Toxin production (positive)
  • Important clinical disease: Diphtheria
• Bacillus anthracis:
  • Gram-positive bacilli
  • Centrally located spores (+)
  • Capsule (+)
  • Polypeptide (poly-D-glutamic acid)
  • Toxin production (+)
  • Important clinical disease: Anthrax
• Mycobacterium tuberculosis:
  • Gram-positive cell wall
  • Aerobic rods
  • Cannot be stained with Gram stain
  • Lipid-rich cell wall
  • Contain mycolic acids
  • Intracellular
  • Important clinical diseases: Tuberculosis (TB)
• Legionella pneumophila:
  • Pleomorphic
  • Gram-negative, aerobic rods
  • Intracellular
  • Important clinical diseases: Pontiac fever, Legionnaires' disease
• Clostridium tetani:
  • Gram-positive rods
  • Anaerobic
  • Terminal spores (+)
  • Toxin production (+)
  • Important clinical disease: Tetanus
• Clostridium botulinum:
  • Gram-positive rods
  • Anaerobic
  • Subterminal spores (+)
  • Toxin production (+)
  • Important clinical disease: Botulism
• Pseudomonas aeruginosa:
  • Gram-negative bacilli
  • Aerobic
  • Toxin production (+)
  • Diffusible pigments (+)
  • Important clinical diseases: pulmonary infections, infections of burn wounds
• Bordetella pertussis:
  • Gram-negative coccobacilli
  • Aerobic
  • Toxin production (+)
  • Important clinical disease: Pertussis (whooping cough)
• Neisseria species:
  • Gram-negative diplococci
  • Aerobic
  • Intracellular
  • Important clinical diseases: Neisseria meningitidis: meningitis
• Neisseria gonorrhoeae*: urogenital infections
• Treponema pallidum:
  • Gram-negative spiral bacilli
  • Spirochetes
  • Cannot be stained with Gram stain
  • Dark-field microscopy is needed
  • Cannot be cultured
  • Important clinical disease: Syphilis
• Chlamydia trachomatis:
  • Gram-negative bacteria
  • Lack rigid peptidoglycan
  • Cannot be stained with Gram stain
  • Cultivated only in cell cultures
  • Important clinical diseases: ocular infections, urogenital infections
• Rickettsia species:
  • Gram-negative rods
  • Aerobic
  • Intracellular
  • Cannot be stained with Gram stain
  • Cultivated only in cell cultures
  • Transmitted by arthropod vectors
  • Important clinical diseases: spotted fever, typhus
• Enterobacteriaceae:
  • Gram-negative bacilli
  • Facultative anaerobic
    • Some are normal flora, but some cause disease
    • Some produce toxins (exotoxins)
    • Endotoxin is an important virulence factor
    • Identification requires special growth media & biochemical tests
• Vibrio cholerae:
  • Gram negative curved rods
  • Vibrio shaped bacilli
  • Halotolerant
  • Can grow at high pH
  • Toxin production (+)
  • Important clinical disease: Cholera
• Helicobacter pylori:
  • Gram-negative spiral rods
  • Multiple flagella at one pole
  • Microaerophilic
  • Urease (+)
  • Important clinical diseases: gastritis, ulcers, stomach cancers
• Brucella species:
  • Gram-negative coccobacilli
  • Aerobic
  • Intracellular
  • Important clinical disease: Brucellosis.