Gram Positive Cocci PDF

Gram Positive cocci Microbiology Department Dr. Mohamed Elmutasim 8th Feb.2023 Objective: - To study: Diseases caused by Gram positive cocci: diagnosis and management Gram-positive cocci The following types are gram-positive cocci: Staphylococcus: Staphylococcus grows in grape-like...

Gram Positive cocci Microbiology Department Dr. Mohamed Elmutasim 8th Feb.2023 Objective: - To study: Diseases caused by Gram positive cocci: diagnosis and management Gram-positive cocci The following types are gram-positive cocci: Staphylococcus: Staphylococcus grows in grape-like clusters. Normally, they exist on our skin and mucous membranes without causing problems. But if staphylococci enter the body, they can cause serious infections. Staphylococcus species: -Staphylococcus aureus -Staphylococcus epidermidis -Staphylococcus saprophyticus  Staphylococcus aureus Diseases S. aureus is the most pathogenic staphylococci bacteria. It’s responsible for most staphylococci infections, including: -Toxic shock syndrome -Abscesses of many organs -Endocarditis -Gastroenteritis (food poisoning) -Hospital-acquired pneumonia -Surgical wound infections -Sepsis  Staphylococcus aureus Main habitat is human nose & skin. Transmission is via the hands. Diagnosis: Gram-positive cocci in clusters. Coagulase-positive. Catalase-positive. Most isolates produce β-lactamase  Staphylococcus aureus : Predisposing factors to infection: - Breaks in the skin - Foreign bodies such as sutures - Neutrophil levels below 500/ml - Intravenous drug use right-sided endocarditis - Tampon use toxic shock syndrome  Staphylococcus epidermidis Diseases: -Endocarditis on prosthetic heart valves -Prosthetic hip infection -Intravascular catheter infection -Cerebrospinal fluid shunt infection -Neonatal sepsis  S. epidermidis Habitat: Normal flora of human skin & mucous membranes. Transmission: -Patient's own strains cause infection -from person to person via hands Diagnosis: Gram-positive cocci in clusters. Coagulase-negative. Catalase-positive  Staphylococcus saprophyticus Gram-positive cocci in clusters. Coagulase-negative. Resistant to novobiocin (S. epidermidis is sensitive). Community-acquired urinary tract infections in young women.  Streptococcus Streptococci are divided into the following categories: S. pyogenes (Group A) S. agalactiae (Group B) Enterococci (Group D) S. Viridans S. pneumoniae  Streptococcus pyogenes Diseases: Suppurative (pus-producing) diseases: - Pharyngitis - Cellulitis Nonsuppurative (immunologic) diseases: - Rheumatic fever - Acute glomerulonephritis.  Streptococcus pyogenes Habitat is the human throat & skin. Transmission is via respiratory droplets. Diagnosis: Gram-positive cocci in chains β-hemolytic Catalase-negative. Bacitracin-sensitive Streptococci are subdivided into group A, B, etc., by differences in the antigenicity of their cell wall carbohydrate.  Streptococcus agalactiae Disease: Neonatal meningitis & sepsis. Main habitat is the human vagina. Transmission occurs during birth. Diagnosis: Gram-positive cocci in chains. β hemolytic. Catalase-negative. Bacitracin-resistant.  Streptococcus pneumoniae Diseases: Pneumonia & meningitis in adults Otitis media & sinusitis in children. Habitat is the human upper respiratory tract. Transmission is via respiratory droplets.  Streptococcus pneumoniae Diagnosis: Gram-positive "lancet-shaped" cocci in pairs (diplococci) β –hemolytic under anaerobic condition. Catalase-negative. Sensitive to bile & optochin Prominent polysaccharide capsule. One of three classical encapsulated pyogenic bacteria (Neisseria meningitidis & Haemophilus influenzae are the other two). Viridans Group Streptococci (e.g., S. sanguis, S. mutans) Diseases: Endocarditis. Brain abscess (in mixed infections with mouth anaerobes). S. mutans implicated in dental caries. Habitat: is human oropharynx. Transmission: Organism enters bloodstream during dental procedures.  Viridans Group Streptococci Diagnosis: Gram-positive cocci in chains. α-hemolytic. Catalase-negative. Resistant to bile & optochin  Enterococcus faecalis Diagnosis: Urinary tract & biliary tract infections Endocarditis rare but life-threatening. Habitat is human colon; urethra & female genital tract can be colonized. Transmission: May enter bloodstream during gastrointestinal (GI) or genitourinary tract procedures. May infect other sites, e.g., endocarditis. Diagnosis: Gram-positive cocci in chains. Catalase-negative. Thank You