Carbapenem Resistance in Enterobacteriaceae Jean B. Patel, PhD, (D)ABMM Leader, Antimicrobial Resistance Team Division of Healthcare Quality Promotion

Carbapenems Drug Route of Administration FDA Status Imipenem IV Cleared Meropenem Ertapenem IM, IV Doripenem Application Submitted

Spectrum of Activity + Drug Strep spp. & MSSA Entero-bacteriaeae Non-fermentors Anaerobes Imipenem + Meropenem Ertapenem Limited activity Doripenem

How are Carbapenems Used? Uses by Clinical Syndrome Bacterial meningitis Hospital-associated sinusitis Sepsis of unknown origin Hospital-associated pneumonia Use by Clinical Isolate Acinetobacter spp. Pseudomonas aeruginosa Alcaligenes spp. Enterobacteriaceae Mogenella spp. Serratia spp. Enterobacter spp. Citrobacter spp. ESBL or AmpC + E. coli and Klebsiella spp. Reference: Sanford Guide

Emerging Carbapenem Resistance in Gram-Negative Bacilli Significantly limits treatment options for life-threatening infections No new drugs for gram-negative bacilli Emerging resistance mechanisms, carbapenemases are mobile, Detection of carbapenemases and implementation of infection control practices are necessary to limit spread

Carbapenem Resistance: Mechanisms Enterobacteriaceae Cephalosporinase + porin loss Carbapenemase P. aeruginosa Porin loss Up-regulated efflux Acinetobacter spp.

Carbapenemases Classification Enzyme Most Common Bacteria Class A KPC, SME, IMI, NMC, GES Enterobacteriaceae (rare reports in P. aeruginosa) Class B (metallo-b-lactamse) IMP, VIM, GIM, SPM P. aeruginosa Enterobacteriacea Acinetobacter spp. Class D OXA

Carbapenemases in the U.S. Enzyme Bacteria KPC Enterobacteriaceae Metallo-b-lactamase P. aeruginosa OXA Acinetobacter spp. SME Serratia marcesens

Klebsiella Pneumoniae Carbapenemase KPC is a class A b-lactamase Confers resistance to all b-lactams including extended-spectrum cephalosporins and carbapenems Occurs in Enterobacteriaceae Most commonly in Klebsiella pneumoniae Also reported in: K. oxytoca, Citrobacter freundii, Enterobacter spp., Escherichia coli, Salmonella spp., Serratia spp., Also reported in Pseudomonas aeruginosa (Columbia)

Susceptibility Profile of KPC-Producing K. pneumoniae Antimicrobial Interpretation Amikacin I Chloramphenicol R Amox/clav Ciprofloxacin Ampicillin Ertapenem Aztreonam Gentamicin Cefazolin Imipenem Cefpodoxime Meropenem Cefotaxime Pipercillin/Tazo Cetotetan Tobramycin Cefoxitin Trimeth/Sulfa Ceftazidime Polymyxin B MIC >4mg/ml Ceftriaxone Colistin Cefepime Tigecycline S

KPC Enzymes Located on plasmids; conjugative and nonconjugative blaKPC is usually flanked by transposon sequences blaKPC reported on plasmids with: Normal spectrum b-lactamases Extended spectrum b-lactamases Aminoglycoside resistance

KPC’s in Enterobacteriaceae Species Comments Klebsiella spp. K. pneumoniae-cause of outbreaks K. oxytoca-sporadic occurrence Enterobacter spp. Sporadic occurrence Escherichia coli Salmonella spp. Citrobacter freundii Serratia spp. Pseudomonas aeruginosa – Columbia & Puerto Rico

Geographical Distribution of KPC-Producers Mixed; 29 reported Yes, they conducted some surveillance activity for MRSA; 23 had MRSA reportable in some form and all or selected area. Frequent Occurrence Sporadic Isolate(s)

Geographical Distribution of KPC-Producers in New Jersey

KPC Outside of United States France (Nass et al. 2005. AAC 49:4423-4424) Singapore (report from survey) Puerto Rico (ICAAC 2007) Columbia (Villegas et al. 2006. AAC 50:2880-2882 & ICAAC 07) Brazil (ICAAC 2007) Israel (Navon-Venezia et al. 2006. AAC 50:3098-3101) China (Wei Z, et al. 2007. AAC 51: 763-765)

Inter-Institutional & Inter-State Spread of KPC-Producing K. pneumoniae

Intra-institution, Interspecies KPC Plasmid Transfer Cf Ko Cf Ko

Laboratory Detection of KPC-Producers Problems: 1) Some isolates demonstrate low-level carbapenem resistance 2) Some automated systems fail to detect low-level resistance

Susceptibility of KPC-Producers to Imipenem *12% of isolates test susceptible to imipenem

Susceptibility of KPC-Producers to Meropenem *9% of isolates test susceptible to meropenem

Susceptibility of KPC-Producers to Ertapenem None of the isolates test susceptible to ertapenem

Can Carbapenem Susceptibility of I or R Detect KPC-Producers? Method Sens/Spec (%) for Detection of KPC-mediated R* Imipenem Meropenem Ertapenem Ref BMD 94/93 94/98 97/89 Disk Diffusion 42/96 71/96 97/82 Etest 55/96 58/96 90/84 Vitek Legacy 52/98 N/A Vitek 2 71/98 48/96 MicroScan 74/96 84/98 100/89 Phoenix 81/96 61/98 *N = 76 K. pneum, K. oxy, E. coli; 31 KPC-producers & 45 non-KPC producers

CAP Results (D-05) KPC-producing Klebsiella pneumoniae Susceptible Results MIC Method Disk Method Imipenem 63 57 Meropenem 18 Ertapenem

Carbapenem MIC ≥ 2 mg/ml to Detect KPC-producers Method Sens/Spec (%) for Detection of KPC-mediated R* Imipenem Meropenem Ertapenem Ref BMD 100/93 100/89 Etest 84/89 90/87 100/82 Vitek Legacy NA Vitek 2 71/91 93/89 MicroScan Phoenix 74/96 87/93 *N = 76 K. pneum, K. oxy, E. coli; 31 KPC-producers & 45 non-KPC producers

When to Suspect a KPC-Producer Enterobacteriaceae – especially Klebsiella pneumoniae that are resistant to extended-spectrum cephalosporins: MIC range for 151 KPC-producing isolates Ceftazidime 32 to >64 mg/ml Ceftriaxone ≥ 64 mg/ml Cefotaxime ≥ 64 mg/ml Variable susceptibility to cefoxitin and cefepime

Reading Disk Diffusion & Etest

Phenotypic Tests for Carbapenemase Activity Modified Hodge Test 100% sensitivity in detecting KPC; also positive when other carbapenemases are present 100% specificity Procedure described by Lee et al. CMI, 7, 88-102. 2001.

Modified Hodge Test Test isolates Imipenem disk Lawn of E. coli ATCC 25922 1:10 dilution of a 0.5 McFarland suspension Test isolates Imipenem disk Described by Lee et al. CMI, 7, 88-102. 2001.

Modified Hodge Test Preliminary results suggest that any of the three carbapenem disks work in the Modified Hodge Test

What Labs Should Do Now Look for isolates of Enterobacteriaceae (especially K. pneumoniae), with carbapenem MIC ≥ 2 mg/ml or nonsusceptible to ertapenem by disk diffusion Consider confirmation by Modified Hodge Test Can submit initial isolate to CDC via NJ State Lab for confirmation by blaKPC PCR if KPC-producers not previously identified in hospital’s isolate population Alert clinician and infection control practitioner to possibility of mobile carbapenemase in isolate

KPC – Questions If I have detect KPC-production, should I change susceptible carbapenem results to resistant? Not enough data to make a clear recommendation Clinical outcomes data will be necessary

Testing Other Drugs Tigecycline: Test by Etest if possible – disk diffusion tends to overcall resistance No CLSI breakpoint, but there are FDA breakpoint Susceptible ≤ 2 mg/ml Intermediate = 4 mg/ml Resistant ≥ 8 mg/ml

Testing Other Drugs Polymixin B or Colistin Could test either, but colistin used clinically Disk diffusion test does not work – don’t use! Etest – works well, but not FDA cleared Broth microdilution – reference labs Breakpoints - none MIC ≤ 2 mg/ml, normal MIC range MIC ≥ 4 mg/ml indicates increased resistance

Acknowledgements Fred Tenover Roberta Carey Kamile Rasheed Kitty Anderson Brandon Kitchel Linda McDougal David Lonsway Jana Swenson Arjun Srinivasan Susan Mikorski