“Drugs for Bugs 2011”in Diabetic Foot Infections Warren S. Joseph, DPM, FIDSA Roxborough Memorial Hospital, Phila., PA www.leinfections.com
Discharge 2/9/11 Deep soft tissue & Bone cultures grew MSSA & Group B Streptococcus Patient initially on Vanco + pip/tazo Given these bugs…what drug do you choose? Cephalexin
What’s New for 2011 A marked decrease in patients presenting with MRSA An increase in ESBL/KPC caused DFI The approval and release of ceftaroline The revised IDSA DFI Guidelines
IDSA Diabetic Foot Infection Guidelines – Exec Sum point 4 “Aerobic gram-positive cocci (especially Staphylococcus aureus) are the predominant pathogens in diabetic foot infections. Patients who have chronic wounds or who have recently received antibiotic therapy may also be infected with gram-negative rods, and those with ischemia or gangrene may have obligate anaerobes.” CID Oct 1, 2004
Anti-Staph and Strep antibiotic Staphylococcus aureus Beta-haemolytic Strep Enterobacteriaceae Anaerobes Commensal gram-positive cocci Antibiotics and the head of the snake Slide Courtesy of A. Berendt, MD May be true in mild infection but no definitive data Polymicrobial flora may worsen prognosis Caution in severe infection and in osteomyelitis
Methicillin Susceptible S. aureus (MSSA) IDSA Mild (po) • ASOC • Amoxicillin/clavulanic acid • Clindamycin • Oral PRP Moderate/Severe • Β-lactam/β-lactamase inhibitor compound • Ertapenem • Cefazolin • Clindamycin (IV/PO) • Vancomycin
NEJM Jan 2009 Methicillin Resistant S. aureus (MRSA) THE ROLE OF HANDWASHING IN THE SPREAD of MRSA
Methicillin Resistant Staph aureus (MRSA) Mild • Later generation tetracycline (PO) • Minocycline • Doxycycline • TMP/SMX • Clindamycin (+/-) Moderate/Severe • Linezolid (IV/PO) • Vancomycin (IV) • Daptomycin (IV) • Tigecycline (IV) • Ceftaroline (IV)
MIC Creep • An increasing clinical problem • “Staph aureus with reduced susceptibility to vancomycin” • aka “MIC Creep” • Difficult to detect • MIC on the rise from 0.5 » 1.0 » 2.0 µg • Have been associated with Tx failures • PLEASE – Look at your vancomycin MIC if considering its use against MRSA!
Vancomycin MIC on the Move 80.9 79.9 70.4 64.6 60.1 % of Isolates 39.7 35.1 28.8 19.9 18.9 0.8 0.2 0.3 0.2 0.2 MIC=minimum inhibitory concentration. Wang G et al. J Clin Microbiol. 2006;44:3883-3886.
MIC Creep & the use ofvancomycin “If you show a vancomycin MIC against MRSA of >1µg/ml you can not achieve a level of vancomycin that is high enough to be both safe and effective. You should use an alternative agent” paraphrasing Robert Moellering, MD, ICAAC 2009
Group B Streptococcus This one is easy…pretty much anything you use for Staphylococcus will be active against Group B Streptococcus
Multi-drug Resistant Gram negs (MDR GNR) • Extended Spectrum β-lactamases (ESBL) • Increasing in E. coli, Proteus mirablis& Klebpneumoalong with other gnr • Resistant to most penicillins, cephalosporins and βlactamase inhibitor compounds • Still susceptible to most carbapenems and tigecycline • Carbapenemase producing gnr (KPC) • Not yet as common as ESBL • As name implies, resistant to carbapenems • NDM-1 • Do we need to concern ourselves??
Pseudomonas aeruginosa • Do we really need to treat it? Options • Ciprofloxacin (PO/IV) • Ceftazidime (IV) • Cefepime (IV) • Aztreonam (IV) +/- Aminoglycoside • Other quinolone • Piperacillin/tazobactam *
Conclusions “Head of the Snake” principle Consider empiric “De-escalation” therapy depending on local MRSA prevalence Watch your vancomycin MICs for “creep” Be aware of ESBLs and KPCs in your hospital (speak with your IC specialist) Be alert for “Pseudomonophobia”