click below
click below
Normal Size Small Size show me how
Group A Strep
Group A Strep seen in Clinical Micro
| Question | Answer |
|---|---|
| What the main pathogenic bacteria in Group A Strep? | Streptococcus pyogenes |
| What test is most often used to identify the presence of GAS and how does it look on Blood Agar? What other test can be used? | The main test used to identify GAS is the Bacitracin or 'A' Disk test. 95% of GAS are susceptible to bacitracin and present a zone of inhibition around the disk on BAP. Another test that can be used is PYR. |
| What type of hemolysis does GAS present? What does it look like on a BAP? | GAS presents INTENSE beta hemolysis. On BAP, it appears as small pinpoint colonies with a large, clear zone of hemolysis surrounding it. |
| What severe inflammatory disease can arise following a pharyngeal or skin infection with GAS? | Acute Glomerular Nephritis. This is an inflammatory disease of the glomerulus in the kidney, causing increased protein and blood to be excreted in the urine. This condition most often leads to kidney failure. |
| What is Rheumatic Fever and what is its main characteristic? | Rheumatic fever is a multi-system collagen-vascular disease that causes cardiac inflammation and thickening of the heart valves. The main characteristic is the presence of perivascular granulomas called "Aschoff" bodies. |
| What is the main virulence factor for GAS? | M Protein. This is a cell surface antigen that prevents phagocytosis of the organism by immune cells. |
| What is the antibiotic of choice when treating a Strep throat (Pharyngitis)? What if the patient has an allergic reaction? | Penicillin is the preferred treatment but if the patient is allergic, they can be given erythromycin instead. |
| What disease does a patient most likley have if the GAS produces the enzyme, hyaluronidase? | The patient most likely has Necrotizing fasciitis or "Flesh-Easting Disease". The bacteria produce hyaluronidase which breaks down host connective tissue. |
| What causes Scarlet Fever and what are the symptoms? | Scarlet Fever is caused if pharyngitis (S. pyogenes) goes untreated for a long period of time. Symptoms include a characteristic rash and "Strawberry Tongue" due to the erythrogenic toxin the bacteria produces. |
| What two tests are used if the patient is suspected of having Scarlet Fever? | Dick and Schultz-Carlton Tests. The Dick test is used to determine the degree of which the patient formed antibodies towards the erythrogenic toxin of S. pyogenes. The Schultz-Carlton test uses an antitoxin in the skin rash to form a blanching response. |