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Antibiotics: Novel and Rediscovered Stephen Swanson, MD, DTM&H Pediatric Infectious Diseases, Travel Medicine Department of Pediatrics Hennepin County Medical Center Antibiotic Groups • • • • • • • • • • • • • PENICILLINS CEPHALOSPORINS Monobactams, Carbapenems Vancomycin (Glycopeptide) Linezolid (Oxazolidinone) Aminoglycosides Macrolides Clindamycin Tetracyclines Sulfonamides plus trimethoprim Rifamycins Quinolones Metronidazole β – lactams Truth in Advertising Objectives • MRSA Epi Trends • Old Antibiotics used for Gram-positive Infections • Newer Antibiotics: on Horizon and Approved Evolution of Drug Resistance in S. aureus Penicillin Methicillin Penicillin-resistant MethicillinS. aureus resistant [1950s] S. aureus [1960s] S. aureus (MRSA) [ 1998 ] [ 1981 ] [ 1999 ] 4 Pediatric Deaths in MN and ND - MMWR “Community Acquired MRSA in Children With No Identified Predisposing Risk” -JAMA CA-MRSA among IV Drug Users) Minnesota Population Distribution and Sentinel Hospital Laboratories . . . . . ..... . CA-MRSA in MN: a shift from USA400 to USA300 lineage CA-MRSA in MN: a shift from USA400 to USA300 lineage USA300 MRSA (predominant lineage) is more susceptible to clindamycin CA-MRSA Antibiotic Susceptibilities in MN, 2006 (N=492) Antibiotic % Susceptible Erythromycin 17 % Clindamycin 95 % Ciprofloxacin 72 % Tetracycline 96 % TMP/SMX 100 % Gentamicin 100 % Vancomycin 100 % Linezolid 100 % Rifampin 99 % Mupirocin 97 % Source: MDH CA-MRSA Antibiotic Susceptibilities in MN, 2006 (N=492) Antibiotic % Susceptible Erythromycin 17 % Clindamycin 95 % Ciprofloxacin 72 % Tetracycline 96 % TMP/SMX 100 % Gentamicin 100 % Vancomycin 100 % Linezolid 100 % Rifampin 99 % Mupirocin 97 % Source: MDH Epidemiologic Trends of MRSA: USA300 and USA100 • USA300 strain more common among: – Patients < 20 years – ~92% susceptible to clindamycin – Wound/abscess • USA100 – Blood, lower respiratory tract – Elderly (age > 65) – 95% resistance to clindamycin Activity of Ceftaroline and Epidemiologic Trends of Staphlyococcus aureus collected from 43 Medical Center in the United States in 2009; Richter et al., Antimicrob Agents Chemother. 2011 CA-MRSA Antibiotic Susceptibilities in MN, 2006 (N=492) Antibiotic % Susceptible Erythromycin 17 % Clindamycin 95 % Ciprofloxacin 72 % Tetracycline 96 % TMP/SMX 100 % Gentamicin 100 % Vancomycin 100 % Linezolid 100 % Rifampin 99 % Mupirocin 97 % Source: MDH CA-MRSA Antibiotic Susceptibilities in MN, 2006 (N=492) Antibiotic % Susceptible Erythromycin 17 % Clindamycin 95 % What about rifampin and 72 % Tetracycline 96 % gentamicin? Ciprofloxacin TMP/SMX 100 % Gentamicin 100 % Vancomycin 100 % Linezolid 100 % Rifampin 99 % Mupirocin 97 % Source: MDH Clinical Practice Guidelines by IDSA for MRSA - 2011 • Addition of gentamicin or rifampin for bacteremia or native valve infective endocarditis not recommended in adults (A-II, A-1 evidence) • Data in children insufficient to support routine use of combination therapy. • Osteomyelitis – maybe helpful • Pneumonia – not likely helpful • Eradication – never rifampin monotherapy BACTRIM: Why Bactrim Might Fail with ca-MRSA infections… Why Bactrim Might Fail with MRSA infections… Why Bactrim Might Fail with MRSA infections… Take-home: Avoid TMP-SMX monotherapy if significant amount of tissue damage/necrosis MRSA necrotizing pneumonia following influenza Vancomycin Limitations: Newer Gram-positive Antibiotics Needed • Burden of MRSA increasing • USA300 entering hospital system • Treatment failures and poor outcomes with Vancomycin – Variable dosing/levels – Limited penetration of bone, lung epithelial fluid, CSF – Slow killing time, especially higher inocula • MIC creep (> 2 μg/mL) requires higher dosing Linezolid • Oxazolidinone-class antibiotic – Inhibits protein synthesis – Excellent bioavailability – Excellent CSF penetration • Covers GAS, S. pneumoniae, MSSA/MRSA, enterococcus, Listeria, oral anaerobes – Uses: • Pneumonia • Complicated SSTI • Osteomyelitis • Meningitis* – Failures: endocarditis (static) • Major side effect: reversible myelosuppression – Follow weekly CBC if using > 2 weeks Minocycline – the forgotten child • • • • Oral and IV Can be used in MRSA SSTI Data lacking for more invasive infections Very active against MRSA and CONS embedded in biofilms on catheters Raad I., et al. Antimicrob. Agents Chemother, May 2007 Ceftaroline fosamil (Teflaro) • • • • 5th generation cephalosporin Low propensity for inducing resistance Excellent safety profile Gram-positive bacteria (CONS, MRSA, VISA, VRSA, resistant pneumococcus, resp gram negs) – 4-fold greater activity against MRSA than Vanc – 16-fold greater activity against MSSA than Ceftr – Active against daptomycin- and linezolidresistant staph • Avoid in ESBLs, Pseudomonas, Acinetobacter • FDA approved in 2010 for CAP and cSSTI (adults) Ceftobiprole - another 5th gen ceph • Active against MRSA • Approved in Canada • FDA approval pending further evaluation The newer antibiotics… never to be approved for children? Daptomycin Activity of Nafcillin, Vancomycin and Daptomycin Rapid killing of almost all clinically relevant gram-positive bacteria Effective all stages of bacterial growth 10 Log10 CFU S aureus per thigh An old drug, that did not receive FDA approval until 2003 Vanco Nafcillin Dapto 1 0 6 12 18 24 48 Time (hours) T. Greenhow, MD Daptomycin Clinical trials in complicated SSTIs showed it was equivalent to nafcillin / vancomycin Cure rate >96% Currently indicated for complicated SSTIs (adult) Drug was found to be less effective than ceftriaxone in treating community-acquired pneumonia – Binds to surfactant which reduces its activity in the alveolar spaces of the lung Carpenter, CF and HF Chambers CID 2004 Hancock, RE Lancet 2005 Daptomycin Approved for right-sided endocarditis, S. aureus bacteremia (6mg/kg) Prolonged half-life (once daily dosing) Monitor weekly CPK levels (dose-dependent, reversible) Not FDA approved in 2 – 17 year olds, but literature increasingly supportive Pregnancy B category Carpenter, CF and HF Chambers CID 2004 Hancock, RE Lancet 2005 N Engl J Med 2006; 355:653-665 Adura M, et. al. “Daptomycin therapy for invasive Gram-positive bacterial infections in children.” PIDJ 2007: 1128-1132 Daptomycin Pediatric Dosing Dosing under study. Recommended starting doses: Complicated SSTI 9 mg/k IV QD (ages 2-6) 7 mg/kg IV QD (ages 7-11) 5 mg/kg IV QD (ages 12-17) Osteomyelitis, Septic Arthritis, Bacteremia 6-10 mg/kg IV daily Failures more likely in patients with prior vancomycin exposure or elevated vancomycin MICs (adult data) Final notes • Azithromycin resistance rates – >20% for S. pneumoniae – 5-10+% for GAS • Clindamycin – S. pneumoniae (~88% susceptible) – Group A streptococcus (~10% inducible resistance) – Group B streptococcus (~70% susceptible) Thank you.