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ch 14
gram pos cocci
| Question | Answer |
|---|---|
| structure of pathogenic streptococcus | cocci growing in chains and sometimes pairs |
| physiology of pathogenic streptococcus | aerotolerant anaerobes, nonmotile, catalase negative, characterized by Lancefield classification |
| Lancefield classification | Divided into serotypes based on bacteria’s antigens Lancefield groups A and B include the significant human pathogens: Group A (Streptococcus pyogenes) Group B (Streptococcus agalactiae) |
| species of pathogenic streptococcus | S. pyrogens, S. agalactiae, S. pneumoniae |
| What bacteria can be found in pairs, diplococcus | S. pneumoniae |
| how are the streptococcus species differentiated | patterns of hemolysis, sensitivity to bacitracin, group-specific cell wall antigens |
| patterns of hemolysis for S. pyogenes | beta |
| pattern of hemolysis of S. agalactiae | beta |
| pattern of hemolysis of S. pneumonia | alpha |
| What streptococcus species is sensitive to antibiotic bacitracin and which is resistant | S. pyogenes is sensitive and S. agalactiae is resistent |
| What is the group-specific cell wall antigen for S. pyogenes | A antigen |
| What is the group-specific cell wall antigen for S. agalactiae | B antigen |
| What is the group-specific cell wall antigen for S. pneumoniae | no antigen |
| What is another name for S. pyogenes | Group A strep |
| What is the epidemiology of S. pyogenes | infects the pharynx or skin, opportunistic when normal microbiota are depleted, spreads via respiratory droplets |
| What is the pathogenesis of S. pyogenes | has structural components to evade phagocytosis, extracellular enzymes, toxins, |
| What S. pyogenes structural components help it evade phagocytosis | M protein destabilizes complement, hyaluronic acid capsule hides bacteria from leukocytes |
| What extracellular enzymes contribute to S. pyogenes pathogenesis | streptokinase, DNases, C5a peptidase, Hyaluronidase |
| Streptokinase | helps S. pyogenes breakdown blood clots, enables bacteria to spread |
| DNases | help S. pyogenes reduce the firmness of pus to facilitate the spread of the bacteria |
| C5a peptidase | helps S. pyogenes break down complement protein C5a which decreases movement of white blood cells to infection site |
| Hyaluronidase | facilitates the spread of streptococcus through tissues |
| What toxins help the pathogenesis of S. pyogenes | pyrogenic toxins, toxic shock syndrome toxins and streptolysins |
| How do pyrogenic toxins help S. pyogenes | can stimulate fever, rash, and shock |
| How do streptolysins help s. pyogenes | lyse red blood cells, white blood cells and platelets |
| What diseases are caused by S. pyogenes | Pharyngitis, rheumatic fever, scarlet fever, (pyoderma, erysipelas, and cellulitis), streptococcal toxic shock syndrome (STSS), necrotizing fasciitis, glomerulonephritis |
| Pharyngitis | caused by S. pyogenes, inflammation of the pharynx, also called strep throat |
| Rheumatic fever | caused by S. pyogenes, complication of untreated strep throat, inflammation damages heart valves and muscle, autoimmune response against heart antigens |
| Scarlet fever | caused by S. pyogenes, may occur after strep throat infections, chest rash that spreads across body |
| Pyoderma, erysipelas, cellulitis | caused by S. pyogenes, pyoderma pus producing lesion occur on exposed skin, erysipelas infection of lymph nodes surrounding streptococcal infection , cellulitis inflammation of deeper skin layers |
| Streptococcus toxic shock syndrome (STSS) | bacteremia that causes severe multisystem infections, can cause organ failure, shock, and death, caused by S. pyogenes |
| Necrotizing Fasciitis | Streptococci enter body and spread along the fascia, caused by S. Pyogenes, secrete toxins and enzymes that destroy tissue |
| Glomerulonephritis | a S. pyrogens disease, caused by antibody bound streptococcal antigens that accumulate in the glomeruli of the kidneys, inflammation causes hypertension and low urine output, adults may suffer irreversible kidney damage |
| how are S. pyogenes diagnosed | positive rapid group A antigen test or presence of beta hemolytic cocci growing in chains that are susceptible to bacitracin |
| How are S. pyogenes treated | with penicillin |
| How are S. Pyogenes diseases prevented | by avoiding contact with infected individuals |
| What is the epidemiology of S. agalactiae | colonizes the GI, GU tracts, wound infections and childbrith cause most adult infections, newborns inoculated at birth |
| What is teh pathogenesis of S. agalactiae | often infects newborns without specific antibodies, produces enzymes whose roles are not yet understood |
| What is synonymous with S. agalactiae | Group B strep |
| What diseases are caused by S. agalactiae bacteria | Associated with neonatal bacteremia, meningitis, an pneumonia, older immunocompromised pt's are also at risk |
| How are S. agalactiae disease diagnosed | enzyme linked immunosorbent assay (ELISA) test used to identify group B strep |
| How are S. agalactiae diseases treated | with penicillin or ampicillin, |
| How are S. agalactiae diseases prevented | prophylactic use of penicillin during childbirth reduces newborn infections, immunization of women can protect future children |
| What is the epidemiology of streptococcus pneumoniae | present in the mouth and pharynges of most humans, causes disease when it travel to the lungs, infections occur most often in children and the elderly |
| what are the pathogenesis factors of S. pneumoniae | Virulence factors, extracellular factors, |
| What are the virulence factors for S. pneumoniae | Antiphagocytic factors such as the polysaccharide capsule (required for virulence), and phosphorylcholine |
| Phosphorylcholine | stimulated body cell to phagocytize the bacteria to allow bacteria to live intracellularly by preventing destruction by lysosomes |
| What extracellular enzymes does S. pneumoniae secrete | IgA protease, which destroys IgA |
| What diseases are caused by S. pneumoniae | Pneumococcal pneumonia, sinusitis and otitis media, Bacteremia and endocarditis, pneumococcal meningitis |
| How is S. pneumoniae diagnosed | Gram stain of sputum smears and confirmed with quellung reaction |
| How are S. pneumoniae diseases treated | with penicillin, although some resistant strains have emerged |
| How are S. Pneumoniae diseases prevented | by vaccines made from purified capsular material |
| Pathogenic enterococcus | was previously classified with group D streptococci, all enterococci live in the intestinal tracts of animals |
| What is the structure of enterococcus | form short chains and pairs depending on species |
| What is the physiology of enterococcus | facultative anaerobes |
| What are the pathogenic species of enterococcus | E. faecalis, and E. faecium |
| Where are E. faecalis and E. faecium found | in the human colon, and are rarely pathogenic here although can cause disease any other part of the body |
| How are E. faecalis and E. faecium diseases diagnosed | distinguished from streptococcus pneumoniae by its sensitivity to bile |
| How are E. faecalis and E. faecium diseases treated | Difficult to treat enterococcal infections Enterococci often resistant to antimicrobials |
| How are E. faecalis and E. faecium diseases prevented | Prevention is difficult in health care setting Patients often have weakened immune systems Good hygiene and aseptic techniques minimize transmission |
Created by:
Acrob89
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