Gram-Positive Bacteria Overview

Gram-Positive Bacteria

• Streptococci:
  • Streptococcus pyogenes: Gram-positive, b-hemolytic, causes skin infections, strep throat, rheumatic fever, glomerulonephritis. Group A bacteria invades skin and mucous membranes.
  • Streptococcus agalactiae: Gram positive, found in women's vaginal cervical tract and men's urethral mucous membranes and GI tract. Can be transmitted to baby from mother in birth.
  • Streptococcus pneumoniae: Gram-positive, non-motile, encapsulated. Can cause pneumonia, otitis media, meningitis, and bacteremia/sepsis.

Enterococci

• Associated with intestines
• Important species: E. faecalis, E. faecium
• Can be b, α, or γ hemolytic
• Viridans streptococci:
  • Normal oral flora
  • Streptococcus mutans and other viridans species cause dental caries.
  • Can cause subacute bacterial endocarditis in people with damaged or abnormal heart valves.

Staphylococcus

• Staphylococcus aureus: Causes skin infections (furuncle, carbuncle, scalded skin syndrome), toxic shock syndrome (TSS), and food poisoning.
• Staphylococcus epidermidis: Part of normal skin flora and causes prosthetic implant infections
• Staphylococcus saprophyticus: Causes urinary tract infections, especially cystitis in women.
  • Coagulase-negative: S. epidermidis, S. saprophyticus. Can cause hospital-acquired infections.

Bacilli (Rods)

• Corynebacterium diphtheriae: Causes diphtheria, a cutaneous and respiratory disease, which can be life-threatening. Preventable with vaccination. Corynebacteria species are non-motile and unencapsulated, most are facultative anaerobes.
• Listeria species: Slender, short gram-positive rods. Don't form spores. L. monocytogenes can grow at 4°C, transmitted from dairy products (ice cream, cheese, etc.), causes septicemia (blood poisoning) and meningitis (listeriosis).

Spore-Forming Rods

• Bacillus anthracis: Develops a papule, causes cutaneous and pulmonary anthrax. (95% of cases are cutaneous). Papule can be black, painless and severely swollen pustule. Can cause fatal septicemia. Pulmonary anthrax is caused by inhalation of spores (mortality ~100% if not treated). Facultative or strict aerobic, non-motile, culture on blood agar.
• Clostridium perfringens: Anaerobic and gram-positive rods, spore-forming. Causes gas gangrene. Large, rod-shaped, non-motile, unencapsulated. Part of normal GI tract flora and vagina. Some cause food poisoning.
• Clostridium botulinum: Causes botulism from the action of neurotoxin, causing flaccid paralysis. Transmitted by feeding infants honey (≤2 days). Category A agent with Yersinia pestis and Bacillus anthracis. Used in Botox injections.
• Clostridium tetani: Causes tetanus. Spores even in small wounds, rare in developed countries. Produces neurotoxin that sends to CNS and causes spastic paralysis.
• Clostridium difficile: Causes pseudomembranous colitis (from diarrhea). Spore-forming. Can be effective because of excessive antibiotic use.

Filamentous

• Actinomyces
• Nocardia

This quiz covers important types of gram-positive bacteria, including Streptococci, Enterococci, and Staphylococcus. Learn about their characteristics, associated diseases, and significance in human health. This comprehensive overview is essential for understanding microbiology concepts related to bacterial infections.