Antibiotics Flashcards
Name 4 antibiotics that cover MRSA
MRSA is covered by
- vancomycin
- linezolid
- daptomycin
- ceftaroline
Exceptions:
- Daptomycin is inactivated by lung surfactant – don’t use in pneumonia
- Linezolid is bacteriostatic (mainly)– don’t use in bloodstream infections (although it can be used for VRE bacteremia)
- Ceftaroline is vancomycin and ceftriaxone rolled into one loveable fuzzball
Ref: https://www.pharmacyjoe.com/tips-for-memorizing-antibiotic-spectrum-of-activity/
Piperacillin-tazobactam and the carbapenems ertapenem, meropenem, doripenem, and imipenem provides which coverage?
Piperacillin-tazobactam and the carbapenems ertapenem, meropenem, doripenem, and imipenem cover gram positives, gram negatives, and anaerobes
Exceptions:
- Ertapenem doesn’t cover pseudomonas
- Piperacillin-tazobactam doesn’t cover ESBL well enough to be used in severe infections (although it probably works for UTI)
Quinolones ciprofloxacin, levofloxacin, and moxifloxacin cover gram positives and gram negatives (double check your local resistance patterns!!!).
Quinolones ciprofloxacin, levofloxacin, and moxifloxacin cover gram positives and gram negatives (double check your local resistance patterns!!!).
Exceptions:
- Ciprofloxacin is weak against strep pneumoniae, but causes the least QTC prolongation and probably doesn’t cause torsades
- Moxifloxacin is best against anaerobes but has no pseudomonas coverage
- Moxifloxacin is hepatically metabolized – this is a double-edged sword as it has no dose adjustment in renal failure but can’t be used for a UTI
Cephalosporins for empiric use in the ICU are cefepime, ceftriaxone, ceftazidime, and ceftaroline. They cover what organisms?
Cephalosporins for empiric use in the ICU are cefepime, ceftriaxone, ceftazidime, and ceftaroline. They cover gram positives and gram negatives.
Exceptions:
- Only cefepime and ceftazidime for pseudomonas
- None cover enterococcus (remember – this shows up on the gram stain as “gram-positive cocci resembling strep!”)
Which class of antibiotics are derived from cultures of streptomyces? Name 3 drugs in this ckass
Class: Aminoglycosides. Drugs: Gentamicin, Tobramycin, and amikacin
1)Name gram-positive aerobic cocci -in clusters -in pair/chains 2)Name gram-positive anaerobic cocci
1) Name species of Gram-negative aerobic cocci
2) Name species Gram-negative anaerobic cocci
What is the MoA of β-lactam antibiotics? Cephalosporins? Differences between the two?
Cephalosporins are bactericidal and have the same mode of action as other β-lactam antibiotics (such as penicillins), but are less susceptible to β-lactamases. Cephalosporins disrupt the synthesis of the peptidoglycan layer forming the bacterial cell wall. -The peptidoglycan layer is important for cell wall structural integrity. The final transpeptidation step in the synthesis of the peptidoglycan is facilitated by penicillin-binding proteins (PBPs). -PBPs bind to the D-Ala-D-Ala at the end of muropeptides (peptidoglycan precursors) to crosslink the peptidoglycan. -Beta-lactam antibiotics mimic the D-Ala-D-Ala site, thereby irreversibly inhibiting PBP crosslinking of peptidoglycan.
1)Name species of gram-positive aerobic rods 2)Name species of gram-positive anaerobic rods
1)Name species of gram-negative aerobic rods -lactose fermenting -non-lactose fermenting 2)Name species of gram-negative anaerobic rods
*Serratia and Citrobacter spp can appear initially as non-lactose fermenting due to slow fermentation.
Interpretations of Key Phrases
- “Gram positive cocci in clusters” may suggest ____________
- “Gram positive cocci in pairs and chains” may suggest _____
- “Gram negative coccobacilli” may suggest ______
- “Lactose-positive gram negative rods” may suggest _____
- “Lactose-negative gram negative rods” may suggest _____
- “Branching Gram positive rods, modified acid fast stain positive” may suggest _____
- “Acid fast bacilli” may suggest _____
- “Yeast” suggests ______spp. “Round Yeast” suggests _____ “Fungal elements or hyphal elements” suggest ______
. 7) . 8). 9)
- “Gram positive cocci in clusters” may suggest Staphyloccocus species
- “Gram positive cocci in pairs and chains” may suggest Streptococcus species or Enterococcus species
- “Gram negative coccobacilli” may suggest Haemophilus species
- “Lactose-positive gram negative rods” may suggest Enterobacteriaceae, such as E. coli, Klebsiella, or Enterobacter spp.
- “Lactose-negative gram negative rods” may suggest Pseudomonas
- “Branching Gram positive rods, modified acid fast stain positive” may suggest Nocardia or Streptomyces species
- “Acid fast bacilli” may suggest Mycobacterium species
- “Yeast” suggests Candida spp. “Round Yeast” suggests Cryptococcus spp. “Fungal elements or hyphal elements” suggest filamentous fungi (moulds).
- What are pathogens in blood cultures?
- What are likely contaminants/normal flora in blood cultures
- What’s the significance of multiple positive blood cultures from a single venipuncture or a line?
- Pathogen: Any organism isolated
- Likely contaminants/normal flora
- Coagulase-negative staphylococci
- Alpha-hemolytic (viridans) streptococci
- Bacillus spp.
- Corynebacterium spp. (Except C. jeikeium)
- Propionibacteirum acnes
- Micrococcus
- Multiple positive bottle drawn from a single venipuncture (or sequentially through one line) are not considered separately when evaluating the potential significance of a likely contaminant
- What are pathogens in urine cultures?
- Which organisms are involved in contamination?
- Pathogens
- Enterobacteriaceae
- Enterococcus spp
- Pseudomonas spp
- Group B streptococci (in pregnancy)
- S. aureus
- S. saprophyticus
- Yeast
- Significance determined by colony count e.g. contamination usually in small numbers
- Corynebacterium
- Coagulase-negative staphylcocci
- Alpha-hemolytic streptococci
- Lactobacillus spp
- Gram-negative rods
- Bacillus spp
urine from stomas and conduits are not sterile
- What are pathogens in tissue/body fluid cultures?
- What are likely contaminants/normal flora in tissue/body fluid cultures?
- Pathogens Any organism isolated; use judgment to evaluate the possibility of normal flora being present in relation to the source of the specimen.
- Contaminants/normal flora in tissue/body fluids
- Eye/Ear
- Coagulase-negative staphylococci
- Non-hemolytic streptococci
- Alpha-hemolytic streptococci
- Corynebacterium
- Skin
- Coagulase-negative staphylococci
- P. acnes
- Corynebacterium
- Alpha-hemolytic streptococci
- Bacillus spp.
- Eye/Ear
- What are pathogens in the GI tract?
- What are likely contaminants/normal flora in the GI tract?
- Pathogens
- Salmonella spp
- Shigella spp
- Campylobacter jejuni
- Aeromonas/Plesiomonas
- Yersinia enterocolitica
- Vibrio spp
- Likely contaminants/normal flora
- Enterobacteriaceae
- Staphylococcus spp
- Streptococcus spp
- Enterococcus spp
- Pseudomonas spp
- Anaerobes
- Yeast
- What are pathogens in the respiratory tract?
- What are likely contaminants/normal flora in the respiratory tract?
- Pathogens
- Group A streptococci
- Streptococcus pneumoniae*
- S. aureus (many)
- H. influenzae*
- Neisseria meningitidis
- Enterobacteriaceae (many)
- Pseudomonas (many)
- Nocardia spp
- Moraxella catarrhalis* (many)
*S. pneumoniae, H. influenze, and M. catarrhalis are all members of the normal respiratory flora and the presence of these organisms in a respiratory culture alone does not necessarily indicate infection.
- Likely contaminants/normal flora
- Staphylcoccus spp
- Alpha-hemolytic streptococci
- Gram-negative rods
- Beta-hemolytic streptococci other than Group A
- Saprophytic Neisseria spp
- Enterococcus spp
- Corynebacterium spp
- Bacillus spp
- Yeast
- Anaerobes
- Haemophilus spp
- Micrococcus spp
- Stomatococcus spp (Rothia)
- Which bacteria do stool cultures typically test for?
- If you want to look for other bacteria, what cultures should you look for?
- A total of ___ samples of consecutive days will increase probability of isolating etiologic agent in > 95% of cases
- When is it inappropriate to order a stool culture for a hospitalized patient?
- Salmonella, Shigella spp, Campylobacter spp.
- If Yersinia enterocolitica or Vibrio sp are suspected, alert the laboratory as specialized media are required to optimize recovery of these organisms.
- 3
- It is inappropriate to order a stool culture on patients who develop diarrhea after >3 days in the hospital given most likely will be C.difficile
- How is C.diff testing performed?
- If C.diff testing is negative, does testing need to be done? Should you do empiric therapy?
- Should test of cure be done?
- The C. difficile testing is performed by nucleic acid amplification test (NAAT).
- This test is >99% sensitive and specific, therefore empiric therapy for patients with negative C. difficile NAAT should be avoided. Due to the high sensitivity and specificity, repeat testing is unnecessary.
- This test is not indicated for test of cure, as patients may remain positive for 30 days following clinical cure. Many patients will continue to carry the organism without any clinical manifestations of colitis and need no further treatment.
- Minimum amount blood to be drawn?
- Should you delay antibiotics to obtain cultures?
- What happens if the patient is persistently febrile without a source of infection?
- A minimum of two sets (one set = one anaerobic and one aerobic bottle) should always be obtained. The minimum volume of blood needed per bottle for adults is 10 ml. Thus, the minimum volume of blood per set is 20 ml.
- Ideally, blood cultures should be drawn before the first dose of antibiotics, but antibiotics should not be withheld because of a delay in getting blood drawn.
- If a patient is persistently febrile without a defined source of infection, obtain two sets of cultures per day for 48-72 hours. Do not continue drawing daily blood cultures beyond 72 hours.
- If a vascular catheter is thought to be a potential site of infection, blood should be drawn from the catheter and the periphery.
Lower respiratory tract
- Appropriate specimens to identify pathogens causing disease of the lower respiratory tract (tracheitis, bronchitis, pneumonia, lung abscess, and empyema) include samples from?
Upper respiratory tract:
- Appropriate specimens to identify pathogens causing respiratory tract infections include samples from?
Lower respiratory tract
- expectorated and induced sputum, endotracheal tube aspirations, bronchial brushings, washes, or alveolar lavages collected during bronchoscopy and pleural fluid.
- Lower respiratory tract specimens (particularly sputum) are assessed for quality (lack of contaminating oral respiratory tract flora and epithelial cells) through a Gram stain. If the specimen shows a lack of PMNs but many epithelial cells and oropharyngeal flora, the specimen will be rejected by the laboratory and another specimen must be collected for culture.
Upper respiratory tract
- samples from the nasopharynx, throat, oral ulcerations
- Nares swabs and nasopharyngeal swabs and washes are not acceptable for routine bacterial culture. If Bordatella pertussis or B. parapertussis is suspected, a nasopharyngeal specimen should be submitted for B. pertussis/parapertussis PCR
See UCLA website: https://res.mednet.ucla.edu/AntibioticsGuide
Differences between Pharmacodynamics and Pharmacokinetics?
Pharmacokinetics versus pharmacodynamics
- Pharmacokinetics mathematically describe the relationship of antibiotic concentration to time. Terminology that is typically associated with pharmacokinetics includes: absorption, distribution, metabolism, elimination, half-life, volume of distribution, and area under the concentration-time curve (AUC).
- Pharmacodynamics describe the relationship of antibiotic concentration to pharmacologic effect or microorganism death. The three main pharmacodynamic parameters that are used are the peak to minimal inhibitory concentration ratio (peak/MIC), the AUC to MIC ratio (AUC/MIC), and the time the drug concentration remains above the MIC (T>MIC).
Give examples of gram-negative enterobacteriacae
Give examples of gram-negative non-lactose fermenters
Give examples of anti-pseudomonal beta-lactams
Give the drawbacks of each.
- cefepime
- piperacillin-tazobactam
- ceftazidine
- meropenem
