ID Flashcards
Mechanism of Action of Bactrim:
Sulfamethoxazole interferes with bacterial folic acid synthesis and growth via inhibition of dihydrofolic acid formation from para-aminobenzoic acid;
trimethoprim inhibits dihydrofolic acid reduction to tetrahydrofolate resulting in sequential inhibition of enzymes of the folic acid pathway
Weight-based dosing recommendations are based on the trimethoprim (TMP) component.
Typical biochemical identification tests include of staph.Aureus:
catalase positive (all pathogenic Staphylococcus species).
coagulase positive (to distinguish Staph.aureus from other Staphylococcus species),
novobiocin sensitive (to distinguish from Staph.saprophyticus)
mannitol fermentation positive (to distinguish from Staph.epidermidis).
Difference between Azithromycin vs. Erythromycin in bone infections;
Erythromycin has low bone penetration. It poorly penetrates biofilms produced by MRSA while azithromycin has a long half-life in serum and tissues, and its bone concentrations are HIGHER than its serum concentrations
Mechanisms for evasion of the host immune response include
- production of an antiphagocytic capsule.
- sequestering of host antibodies or antigen masking by Protein A.
- biofilm formation.
- intracellular survival.
- blocking chemotaxis of leukocytes
Linezolid has antibiotic activity against
a wide spectrum of Gram-positive organisms. It does not cause cross-resistance to antibiotic agents of other classes, and it does not require its dose to be adjusted according to renal and hepatic function.
Fosfomycin has excellent ……………… activity against …………….
Fosfomycin has excellent in vitro activity against many Gram-positive and Gram-negative organisms, including methicillin-resistant staphylococci.
S. aureus are one the most common bacterial infections in humans and are the causative agents of multiple human infections, including
infective endocarditis,
skin and soft tissue infections (e.g., impetigo, folliculitis, furuncles, carbuncles, cellulitis, scalded skin syndrome, and others),
osteomyelitis, septic arthritis, prosthetic device infections,
pulmonary infections (e.g., pneumonia and empyema), gastroenteritis, meningitis, toxic shock syndrome
PBP-2a is a:
a penicillin-binding protein (PBP),
it is an essential bacterial cell wall enzyme that catalyzes the production of the peptidoglycan in the bacterial cell wall.
MRSA carries the ………… gene which encodes the protein ………………………..?
mec gene which encodes PBP-2a (penicillin-binding protein 2a)
Macrolides should NOT be used as monotherapy in staphylococcal bone and joint infections due to:
azithromycin was ineffective as a single drug against experimental staphylococcal osteomyelitis despite concentrations in bone that markedly exceeded the MIC
β-Lactams, which inhibit cell wall synthesis, are inactive against …………………….but are ……….. when combined with …………. in bone infections.
β-Lactams, which inhibit cell wall synthesis, are inactive against biofilm-associated staphylococci, but are active when combined with rifampicin in bone infections.
Fusidic acid is a
bacterial protein synthesis inhibitor with antibiotic activity against staphylococci, including methicillin-resistant organisms.
Staphylococcus aureus is:
a gram-positive bacteria meaning it stains purple by Gram stain.
Cocci-shaped and tend to be arranged in clusters that are described as “grape-like.”
Colonies are often golden or yellow (aureus means golden or yellow).
Grow with and without oxygen
aerotolerant anaerobic
Tx of group B streptococcus infections in pregnant women w/penicillin allregy:
Vancomycin is recommended as an alternative option to prevent the transmission of group B streptococcal (GBS) disease from mothers to newborns.
