Streptococcus Bacteria Overview

Study Notes

Streptococcus

Streptococcus pyogenes: Opportunistic pathogen found in the upper respiratory tract, spread through respiratory droplets.
- Causes: Strep throat (sore throat, enlarged tonsils, exudates, lymph node tenderness, mild fever), otitis media, mastitis, impetigo.
- Additional complications: Rheumatic fever (linked to untreated strep throat), scarlet fever (pink-red rashes, blood vessel damage, fever), necrotizing fasciitis (rare, exotoxins A and B, superantigen M-protein), streptococcal toxic shock-like syndrome (fever, rash, vomiting, diarrhea, respiratory distress, bacteremia, necrotizing fasciitis).
Streptococcus pneumoniae: Found in upper respiratory tract, frequently causes secondary lung infections.
- Causes: Meningitis (rare), pneumonia.
- Additional information: Some strains act as superantigens.
Streptococcus agalactiae: Normal flora in the female genital tract and lower gastrointestinal tract.
- Causes: Infections in neonates and pregnant women, septic arthritis (rare).
- Additional information: Occasionally colonizes the upper respiratory tract (more prevalent in babies).
- Pregnant woman infections: Postpartum infections like endometritis, leading to pelvic abscesses and septic shock.
- Neonatal infections (early-onset first 5 days, late-onset 7 days to 3 months):
  - Transmission: Mother to baby (in utero or during delivery), nosocomially (from mother, healthcare worker, or family member).
  - Symptoms: Sepsis, fever, meningitis, respiratory distress, lethargy, hypotension.
Streptococcus bovis: Veterinary pathogen causing mastitis, rare in humans.
Streptococcus salivarius and Streptococcus mitis: Non-pathogenic normal flora of the mouth.
- Additional information: Obligate fermenters, associated with dental caries (tooth decay).
Enterococcus faecalis: Non-pathogenic normal flora of the intestinal tract, isolated from fecal samples.

Neisseria gonorrhoeae

Primary pathogen causing gonorrhea, a sexually transmitted infection.
Infections primarily occur in: Urethra, endocervix, anal canal, pharynx, conjunctiva.
Most common sexually transmitted bacterial infection in the U.S.
Asymptomatic carriers are common.
Incubation period: 2-7 days.
Disease in males: 3%-5% asymptomatic, 95%-97% develop symptoms.
- Symptoms: Acute urethritis (inflammation of urethra), purulent discharge, dysuria.
- Complications: Ascending infections including prostatitis and epididymitis.
Disease in females: Up to 50% asymptomatic.
- Symptoms: Endocervix infections (site of infection), vaginal discharge, dysuria, lower abdominal pain, vaginal bleeding.
- Complications: Pelvic inflammatory disease (inflammation of female reproductive organs), leading to sterility or ectopic pregnancy (fertilized egg fails to drop).
Disease in neonates:
- Ophthalmia neonatorum: Gonococcal eye infection, occurs during vaginal delivery from infected birth canal, may result in blindness. All neonates receive antibiotics to prevent this.