Medical Microbiology Exam 1
Terms
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- -no nuclear membrane
- Prokaryotes
-
-true cell structure
-fungi, parasites - Eukaryotes
-
-smallest of infectious agents
-consists of either RNA or DNA
-absolute parasites - Virus
- Key Events in the Viral process
-
Attachment and Penetration
Uncoating
Viral mRNA synthesis
Viral protein synthesis
Progeny Virion Assembly
Virion Release from Cell - Surface antigen that binds to the Fc region of IgG and makes it unavailable to the receptor site on the phagocyte
- Protein A
- Surface antigen that promotes adherence to tissues, catheters, etc.
- Clumping Factor
- Surface antigen that mediates adhesion by binding to tissue fibronectin
- Teichoic Acid
- Extracellular Enzyme that prevents opsonization and phagocytosis
- Coagulase
- Extracellular Enzyme that plays a role in pathogenesis of boils and acne
- Lipase
- Extracellular Enzyme that hydrolyses hyaluronic acid
- Hyaluronidase
- Extracellular Enzyme that cleave DNA and RNA
- Nucleases
- Toxin that penetrates blood vessels either causing leaky or broken cells
- Hemolysin
- Toxin that when released into the intestines causes cramps and diarrhea and/or vomitting
- Enterotoxin
- Toxin that causes the skin to shed
- Epidermolytic / Exfoliative Toxin (ET)
- Toxin cause when a bacteria infects locally then breaks through to the blood stream
-
TSST-1
Toxic Shock Syndrome Toxin - Antigens, mostly from bacterial toxins, that interact with a set of T-lymphocytes bearing a set of products of the V_T receptor genes. As a consequence these activate large numbers of T cells and result in SHOCK
- Superantigens
-
Gram +
-transmitted via direct contact or by contaminated linens and clothing.
-ingestion of contaminated food resulting in food poisoning
-Aspiration of nasopharyngeal secreations resulting in pneumonia - Stahpylococcus Aureus
-
Causes: Inflammatory Diseases
Folliculitus
Furunculosis and Carbunculosis (BOIls)
Imptigo
Osteomyelitis
Arthritis
Pneumonia
Endocarditis - Stahpylococcus Aureus
- This toxin mediated illness results in skin exfoliation
- SSSS- Staphylococcal Scalded Skin Syndrome
- This in food causes food poisoning after an incubation period of 2-6 hours. Toxin is ingested where it interacts with mucosa resulting in vomiting and diarrhea
- Staphylococcal Aureus
- This infection (a) is caused by what microbe (b) growing on a tampon causing TSST-1 to enter the bloodstream resulting in fever, rash, and shock (death occurs in about 3% of cases)
-
a: Toxic Shock Syndrome (TSS)
b: Stahpylococcus Aureus - Stahpylococcus Aureus presents this way in a colony morphology
- large, creamy, opaque colonies, usually Beta hemolytic
- Stahpylococcus Aureus presents this way in Biochemical testing
-
catalase +
mannitol/salt +
Coagulase + - Stahpylococcus Aureus treatment
-
Beta lactase resistant penicillans such as Methicillan, nafcillon, cloxacillon etc.
and if MRSA (contracted in healthcare setting or found resistant to penicillans) treated with Vancomycin - Stahpylococcus Aureus prevention
- WASH YOUR HANDS!
- -colonizes prosthetic (plastic) devices
- Stahpylococcus Epidermidis
- produces biofilm
- Stahpylococcus Epidermidis
- Stahpylococcus Epidermidis sources
- patient skin or hands of hospital staff
- Stahpylococcus Epidermidis effect on plastic
- biofilm errodes the plastic surface and/or breaks off and disseminates
- Stahpylococcus Epidermidis treatment
- removal of plastic device
- Why is vancomycin the antibiotic choice when treating Stahpylococcus Epidermidis?
- 40% of coagulase-negative staphylococci are resistant to Beta-lactamase resistant antibiotics
- Antibiotics used to treat Stahpylococcus Epidermidis
- vancomycin, Rifampin, gentamicin
- Why is Staphylococcus Saprophyticus generally overlooked in urinary tract infections and why is this important?
- Only 30% of cases are caused by S. Saprophyticus which is gram positive. Most cases are caused by E. coli which is gram negative. If treated with gram negative antibiotics, the infection will not go away.
-
Group characteristics:
-Gram + cocci in chains
-Catalase negative
-Nutritionally fastidious
-Hemolysis: alpha, beta, or none
Metabolism: aetolerant anaerobes - Streptococci
- Streptococci Group Characteristics
-
-Gram positive cocci in chains
-Catalase negative
-Nutritionally fastidious
-Hemolysis: alpha, beta, or none
-Metabolism: aerotolerant anaerobes - This presents a surface antigen hyaluronic acid capsule as an immunological disguise and to inhibit phagocytosis
- Streptococcus Pyogenes
- This presents a surface antigen of M Protein which makes it 'fuzzy looking' to antibodies and inhibits phagocytosis
- Streptococcus Pyogenes
- This a) bacteria secretes streptolysin O (SLO), which is a b)toxin
-
a)Streptococcus Pyogenes
b) oxygen sensitive - This a) bacteria secretes streptolysin S (SLS), which is a toxin that does what in blood agar? b)
-
a) Streptococcus Pyogenes
b) it creates a zone of beta hemolysis surrounding GAS colonies - This enzyme is produced by Streptococcus Pyogenes and digests blood clots which aids in what?
- streptokinase digests blood clots which aids in he invasion of wounds