Podcast
Questions and Answers
Which of the following bacteria is a common inhabitant of the throat and nasopharynx of healthy people?
Which of the following bacteria is a common inhabitant of the throat and nasopharynx of healthy people?
What percentage of patients with pneumococcal pneumonia have bacteremia?
What percentage of patients with pneumococcal pneumonia have bacteremia?
Which vaccine is effective for 5 years in older adults and other high-risk individuals?
Which vaccine is effective for 5 years in older adults and other high-risk individuals?
Which of the following is NOT a disease caused by S. pneumoniae?
Which of the following is NOT a disease caused by S. pneumoniae?
Signup and view all the answers
What is the name of the bacteria that was previously classified as group D streptococcus?
What is the name of the bacteria that was previously classified as group D streptococcus?
Signup and view all the answers
Which of the following bacteria is associated with urinary tract infections?
Which of the following bacteria is associated with urinary tract infections?
Signup and view all the answers
What is the treatment of choice for Group A and B streptococci?
What is the treatment of choice for Group A and B streptococci?
Signup and view all the answers
Which of the following bacteria is a normal flora of the oral and nasopharyngeal flora?
Which of the following bacteria is a normal flora of the oral and nasopharyngeal flora?
Signup and view all the answers
What is the name of the vaccine used for children aged 2 to 23 months?
What is the name of the vaccine used for children aged 2 to 23 months?
Signup and view all the answers
Which of the following diseases is associated with high mortality?
Which of the following diseases is associated with high mortality?
Signup and view all the answers
Study Notes
Gram-PoBacteria
- Genera: Staphylococcus, Streptococcus, Enterococcus, Corynebacterium, Listeria
Staphylococcus
- Gram-positive cocci, arranged in grape-like clusters, facultative anaerobic and non-fascidious bacteria
- Classification:
- Coagulase positive: S. aureus
- Coagulase negative: S. epidermidis, S. saprophyticus
- Pathogenicity: S. aureus (common pathogen), S. epidermidis, S. saprophyticus (opportunistic pathogens)
Staphylococcus aureus
- Most virulent and well-known member of the genus
- Virulence factors:
- Cell wall-associated structures
- Extracellular toxins
- Enzymes for invasion
- Protein A, TSST, coagulase, capsule, exfoliative toxin, hyaluronidase, clumping factor, enterotoxin, lipase, leukocidin, protease, haemolysin, DNAse
Epidemiology of S. aureus Infections
- Infection sources: human carriers (10-30% carry S. aureus in their nose), infected animals
- Transmission: direct contact (person-to-person), fomites, dust, airborne droplets, or food
- Nosocomial cross-infection is important
Hemolysis on Agar Plates
- Types of hemolysis:
- γ (gamma) complete (beta) hemolysis
- α (alpha) incomplete hemolysis
- No (gamma) hemolysis
- α-hemolysis is characterized by a greenish zone around the bacterial colony
Enterococcus
- Classification: non-hemolytic
- Normal flora: colonize the gastrointestinal and genitourinary tracts
- Pathogens: β-hemolytic streptococci (S. pyogenes, S. agalactiae), Streptococcus pneumoniae
Streptococcus pyogenes
- β-hemolytic, group A
- Normal flora: 5-15% of individuals harbor the bacterium in the respiratory tract without signs of disease
- Most serious streptococcal pathogen
- Infections:
- Suppurative: pharyngitis, pyoderma (impetigo), erysipelas, necrotizing fasciitis
- Nonsuppurative: streptococcal toxic shock syndrome, bacteremia, pneumonia
Streptococcusal Infections
- Pharyngitis:
- Highest incidence in ages 5-15
- Person-to-person transmission via droplets or secretions
- Impetigo:
- Superficial lesions that break and form highly contagious crust
- Often occurs in epidemics in school children
- Associated with insect bites, poor hygiene, and crowded living conditions
- Erysipelas:
- Acute infection of the skin
- Pathogen enters through a break in the skin and spreads to the dermis and subcutaneous tissues
Streptococcus pneumoniae
- Normal inhabitant (5-50%) of the throat and nasopharynx of healthy people
- Diseases:
- Pneumonia (bacteria multiply in alveolar spaces)
- Meningitis (high mortality)
- Bacteremia (25-30% of patients with pneumococcal pneumonia, >80% of patients with meningitis)
- Sinusitis
- Otitis media (middle ear infection)
Treatment and Prevention of S. pneumoniae
- Traditionally treated with penicillin G or V
- Increased drug resistance (PRSP)
- Two vaccines available for high-risk individuals:
- Capsular antigen vaccine for older adults and other high-risk individuals (effective for 5 years)
- Conjugate vaccine for children 2 to 23 months
Viridans Streptococci
- α-hemolytic streptococci
- Members of the normal oral and nasopharyngeal flora
- Large complex group: Streptococcus mitis, Streptococcus mutans, Streptococcus oralis, Streptococcus sanguis, Streptococcus salivarius (K)
- Diseases:
- Dental caries
- Subacute endocarditis
Enterococcus
- Previously classified as group D streptococcus
- Most commonly isolated and clinically important: Enterococcus faecalis, Enterococcus faecium
- Colonize the gastrointestinal tract
- Associated infections:
- Bacteremia
- Urinary tract infections
- Wound infections
- Endocarditissitive
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz covers the characteristics and classification of Gram-positive bacteria, including Staphylococcus, Streptococcus, and more.
