bacterial iddentificaton Flashcards
draw the diagram fo all the gram positive bacteria
what does a double zone of hemolysis n blood agar denote ?
clostridium pefergenines
What is the first step in identifying streptococci in the lab?
Determine if the bacterium is Gram-positive cocci and catalase-negative.
What test differentiates Streptococcus from Staphylococcus?
The catalase test. Streptococcus is catalase-negative, while Staphylococcus is catalase-positive.
How do you differentiate Viridans streptococci from Streptococcus pneumoniae
Viridans streptococci: Optochin-resistant, bile-insoluble.
Streptococcus pneumoniae: Optochin-sensitive, bile-soluble.
What infections are caused by Viridans streptococci?
Dental caries and subacute endocarditis.
What infections are caused by Streptococcus pneumoniae?
Meningitis, otitis media, pneumonia, and sinusitis.
MOPS
How do you differentiate Group A Streptococcus (GAS) from Group B Streptococcus (GBS)?
GAS (Streptococcus pyogenes): PYR-positive, bacitracin-sensitive
GBS (Streptococcus agalactiae): PYR-negative, CAMP-positive
What diseases are caused by Streptococcus pyogenes (GAS)?
Scarlet fever, rheumatic fever, PSGN (post-streptococcal glomerulonephritis)
What diseases are caused by Streptococcus agalactiae (GBS)?
Neonatal sepsis & meningitis, UTI.
How do you differentiate Enterococcus from Streptococcus gallolyticus
Enterococcus: Grows in bile & 6.5% NaCl, PYR-positive.
Streptococcus gallolyticus: Grows in bile but NOT 6.5% NaCl, PYR-negative.
What infections are associated with Enterococcus?
UTI, cholecystitis, and subacute endocarditis.
What infections are caused by Staphylococcus aureus?
Inflammatory diseases: Skin infections, organ abscesses, pneumonia, infective endocarditis, septic arthritis, osteomyelitis.
Toxin-mediated diseases: Toxic shock syndrome (TSST-1), scalded skin syndrome (exfoliative toxin), rapid-onset food poisoning (enterotoxins).
What is MRSA, and why is it important?
Methicillin-resistant Staphylococcus aureus (MRSA) is a serious cause of hospital- and community-acquired infections.
Resistance is due to altered penicillin-binding proteins (mecA gene).
Some strains release Panton-Valentine leukocidin (PVL), which kills leukocytes and causes tissue necrosis.
What is Staphylococcal Toxic Shock Syndrome (TSS)?
Caused by TSST-1 superantigen
Binds MHC II and T-cell receptor, leading to cytokine storm
Symptoms: Fever, vomiting, diarrhea, rash, desquamation, shock, multi-organ failure
Risk factors: Prolonged tampon use, nasal packing
How does Staphylococcus aureus cause food poisoning?
Enterotoxin-mediated (not the bacteria itself)
Short incubation (2–6 hrs)
Symptoms: Non-bloody diarrhea & vomiting
Heat-stable toxin → Not destroyed by cooking
What are the key features of Staphylococcus epidermidis?
Gram-positive, catalase-positive, coagulase-negative
Novobiocin-sensitive
Normal skin flora, contaminates blood cultures
Infects prosthetic devices (e.g., hip implants, heart valves) & IV catheters by producing adherent biofilms
What are the key features of Staphylococcus saprophyticus?
Gram-positive, catalase-positive, coagulase-negative
Novobiocin-resistant
Normal microbiota of female genital tract & perineum
Second most common cause of uncomplicated UTI in young females (after E. coli)
what are thee fatures of scalded skin. syndrome ?
damage only happens to thee keratinocytes in the stratum granulosum
what finding is positive in association with h staph scalded skin syndrome ?
nikolsky sign positive
What is Streptococcus gallolyticus associated with?
Bacteremia and colorectal cancer (CRC).
