Prior to me employed by a non-academic teaching hospital I spent 11 years teaching Infectious Disease to medical students, Internal Medicine residents and ID fellows at 3 different academic teaching hospitals. I had a vast array of clinical pearls that I would share on teaching rounds. In my last 5 years in a non-teaching setting I am often amazed that no one ever taught physicians who are Board Certified in Internal Medicine these important teaching points. I thought it might be useful to share some of my favorite ID teaching points or "pearls" in this blog.
1) oral Beta lactam agents are not adequate treatment of bacteremia
2) Beta-lactam- beta lactamase drugs (Unasyn, Zosyn) and Carbapenems (Ertapenem and Meropenem) have perfectly adequate anaerobic coverage and do not require the addition of Metronidazole
3) Oral vancomycin has no bioavailability
4) Vancomycin is inferior to Beta lactam drugs for the treatment of serious MSSA infections
5) When awaiting sensitivities of a serious Staph aureus infection give Vancomycin and Cefazolin and then drop one agent when the sensitivities are known
6) In patients with a significant Penicillin allergy who need empiric therapy for Gram negative infections Aztreonam, a monobactam, is a good choice
7) For patients with active C diff colitis who need coverage for a concomitant intra-abdominal infection consider using Tigecycline which actually has activity against C diff
8) For patients with Severe Babesiosis I give triple therapy with Clindamycin, Azithromycin and Atovaquone as Clindamycin has the most rapid killing based upon time-kill curves
9) A patient is unlikely to have Human Granulocytic Anaplasmosis with normal transaminases
10) A patient is unlikely to have Babesiosis with a normal LDH
11) The best target for MRSA killing is achieving a Vancomycin AUC:MIC ratio of at least 400. For an MRSA isolate with a VANCO MIC of 1, I arrive at an empiric dose by multiplying 400 X estimated Vancomycin clearance . Estimated Vancomycin clearance is calculated the following way:
Creatinine clearance X 0.79 + 15.4 X 0.06.
12) I do not use Vancomycin for MRSA infections where the Vancomycin MIC is 2 or greater
13) The key determinant to microbial killing by Beta- lactams and Carbapenems is time above the MIC. To maximize this I dose the following drugs as follows:
Zosyn 3.375gms IV q 8 hours with each dose administered over 4 hours
Cefepime 1 gm IV q 6 hours
Meropenem 500mg IV q 6 hours
14) If you considering a systemic infection with a Herpes family virus such as CMV or EBV, check a PT-INR and D-dimer as these viruses cause endothelial damage and a microvascular coagulopathy
15) If Staph aureus grows in a blood culture within 14 hours of the time it was collected (time to positivity < or =14 hours) then an endovascular infection is likely
16) For patients with pneumonia, order an MRSA screen of the nares and throat, if these are both negative and you do not have a sputum culture with MRSA you can stop Vancomycin
17) In patients with Diabetic Foot Ulcers, if you can touch bone with a blunt forceps (probe to bone test) you have made the diagnosis of osteomyelitis and do not need to order an MRI
18) In Diabetic foot ulcers the following are highly suggestive of osteomyelitis: an ESR> 70, an ulcer depth > 3mm, and ulcer size > 2 cm squared
19) Eosinopenia - an absolute eosinophil count < 50 cells/mm3 is good marker of infection
20) In a patient with infection, an ANC:ALC ratio> 10 and/or an absolute lymphocyte count < 1000 cells/mm3 are suggestive of concomitant bacteremia
21) In patients with non-purulent cellulitis who have venous insufficiency, lymph node resection or irradiation or lymphedema think Group A Strep. If they are diabetic also consider Group B Strep
1) oral Beta lactam agents are not adequate treatment of bacteremia
2) Beta-lactam- beta lactamase drugs (Unasyn, Zosyn) and Carbapenems (Ertapenem and Meropenem) have perfectly adequate anaerobic coverage and do not require the addition of Metronidazole
3) Oral vancomycin has no bioavailability
4) Vancomycin is inferior to Beta lactam drugs for the treatment of serious MSSA infections
5) When awaiting sensitivities of a serious Staph aureus infection give Vancomycin and Cefazolin and then drop one agent when the sensitivities are known
6) In patients with a significant Penicillin allergy who need empiric therapy for Gram negative infections Aztreonam, a monobactam, is a good choice
7) For patients with active C diff colitis who need coverage for a concomitant intra-abdominal infection consider using Tigecycline which actually has activity against C diff
8) For patients with Severe Babesiosis I give triple therapy with Clindamycin, Azithromycin and Atovaquone as Clindamycin has the most rapid killing based upon time-kill curves
9) A patient is unlikely to have Human Granulocytic Anaplasmosis with normal transaminases
10) A patient is unlikely to have Babesiosis with a normal LDH
11) The best target for MRSA killing is achieving a Vancomycin AUC:MIC ratio of at least 400. For an MRSA isolate with a VANCO MIC of 1, I arrive at an empiric dose by multiplying 400 X estimated Vancomycin clearance . Estimated Vancomycin clearance is calculated the following way:
Creatinine clearance X 0.79 + 15.4 X 0.06.
12) I do not use Vancomycin for MRSA infections where the Vancomycin MIC is 2 or greater
13) The key determinant to microbial killing by Beta- lactams and Carbapenems is time above the MIC. To maximize this I dose the following drugs as follows:
Zosyn 3.375gms IV q 8 hours with each dose administered over 4 hours
Cefepime 1 gm IV q 6 hours
Meropenem 500mg IV q 6 hours
14) If you considering a systemic infection with a Herpes family virus such as CMV or EBV, check a PT-INR and D-dimer as these viruses cause endothelial damage and a microvascular coagulopathy
15) If Staph aureus grows in a blood culture within 14 hours of the time it was collected (time to positivity < or =14 hours) then an endovascular infection is likely
16) For patients with pneumonia, order an MRSA screen of the nares and throat, if these are both negative and you do not have a sputum culture with MRSA you can stop Vancomycin
17) In patients with Diabetic Foot Ulcers, if you can touch bone with a blunt forceps (probe to bone test) you have made the diagnosis of osteomyelitis and do not need to order an MRI
18) In Diabetic foot ulcers the following are highly suggestive of osteomyelitis: an ESR> 70, an ulcer depth > 3mm, and ulcer size > 2 cm squared
19) Eosinopenia - an absolute eosinophil count < 50 cells/mm3 is good marker of infection
20) In a patient with infection, an ANC:ALC ratio> 10 and/or an absolute lymphocyte count < 1000 cells/mm3 are suggestive of concomitant bacteremia
21) In patients with non-purulent cellulitis who have venous insufficiency, lymph node resection or irradiation or lymphedema think Group A Strep. If they are diabetic also consider Group B Strep
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