Nebraska Public Health Laboratory 2008 CLSI M100-S18 update Paul D. Fey, Ph.D. Associate Professor/Associate Director Josh Rowland, M.T. (ASCP) State Training Coordinator
Agenda Discuss 2008 M100- S18 major changes Organism specific changes KPC carbapenemase Other AST issues and questions from discussion group
Issue 1-New Appendices Appendix A -ESBL screening Appendix B -Staphylococcus aureus susceptibility testing issues Appendix C -Coagulase-negative Staphylococcus susceptibility testing issues Appendix D -Screening for high-level Aminoglycoside resistance within the enterococci.
Tables 1 and 1A-Antibiotic reporting tables Starting pages 24 (Disk diffusion) and 86 (MIC). Tables 1 and 1A. Changes Table 1: Tobramycin moved from group B (selective reporting) to group A (primary) in Enterobacteriaceae and Pseudomonas aeruginosa. Ticarcillin moved from group A to group B in Enterobacteriaceae and Pseudomonas aeruginosa. Macrolides, Clindamycin, Trimethoprim/sulfa. moved to group A under Staphylococcus. Note that t Daptomycin is MIC only-do not use disk diffusion i disks Acinetobacter spp. Ampicillin-sulbactam, ciprofloxacin, levofloxacin and gentamicin, tobramycin moved to group A.
Tables 1 and 1A-Antibiotic reporting tables Starting pages 24 (Disk diffusion) and 86 (MIC). Tables 1 and 1A. Changes table 1A Note that Streptococcus spp. other than Streptococcus pneumoniae column has been split into two columns: 1) Streptococcus spp. Beta-hemolytic group (Groups A, B, C, and G) and 2) Streptococcus spp. Viridans group (Small colony forming β-hemolytic colonies [ S. anginosus] are included in this group).
Haze in zone of inhibition New comments on M2-disk diffusion tables about appropriate methods to read zones of inhibition to certain antibiotics i.e. Proteus mirabilis and swarming, trimethoprim-sulfamethoxazole testing, etc. Please read all comments if disk diffusion is common in your laboratory. Page 52 Organisms that show hazy growth throughout the zone of inhibition around the clindamycin disk should be reported as clindamycin resistant, whether or not they show a D-zone. To detect t any type of colonies that t may show resistance-page 52- When testing linezolid, disk diffusion zones should be examined using transmitted light. Organisms with non-susceptible results should be confirmed using an MIC method.
Streptococcus pneumoniae If you are performing disk diffusion to detect resistance in Streptococcus pneumoniae, read page 66. Penicillin MICs should be determined for those isolates with oxacillin zone diamters < 19 mm, because zones of < 19 mm occur with penicillin- resistant, intermediate, or certain susceptible strains based upon the meningitis and oral penicillin V interpretive criteria given in M7, Table 2G. Isolates should not be reported as penicillin-resistant or intermediate based solely on an oxacillin-zone < 19 mm.
Streptococcus pneumoniae Significant reporting changes regarding penicillin Interpretive standards for parenteral penicillin nonmeningitis, meningitis, and oral penicillin non- meningitis. On meningitis isolates, only report meningitis interpretive standards. On non-meningitis isolates (e.g. pneumonia or blood), report both meningitis and non-meningitis interpretive standards. d
Streptococcus pneumoniae isolated from blood-penicillin MIC of 1 Ceftriaxone (meningitis)- <0.5 S Ceftriaxone (non-meningitis)- <0.5 S Erythromycin->1 R Levofloxacin- <0.5 S Penicillin (meningitis)-1 R Penicillin (non-meningitis)-1 S Penicillin oral (non-meningitis)-1 I Vancomycin-0 0.5S Based on therapy category, different interpretive standards. Multiple comment suggestions in the CLSI These changes must reflected in your antibiogram.
Staphylococcus aureus changes Page 111. Cefoxitin MIC test to detect methicillin resistance only reliable for S. aureus and S. lugdunensis. The results of cefoxitin MIC tests t can be used to predict the presence of meca-mediated resistance in S. aureus and S. lugdunensis. Isolates for which cefoxitin MICs are > 8 μg/ml should be reported as resistant. Isolates for which the cefoxitin MICs are < 4 μg/ml should be reported as oxacillin susceptible.
Staphylococcus aureus changes Page 114-Erythromycin-resistant and clidamycinsusceptible isolates. New approved way to detect inducible resistance to clindamycin. Well containing 4 μg/ml erythromycin and 0.5 μg/ml clindamycin growth in the well indicates resistance to clindamycin.
KPC carbapenemase Enzyme capable of hydrolyzing carbapenems (imipenem, ertapenem, meropenem, doripenem). Isolated primarily on the east coast of US in ICUs. Klebsiella pneumoniae and other Enterobacteriaceae. KPC not easily detected using commercial susceptibility systems some isolates have an MIC of 2 to the carbapenems (still susceptible) KPC enzymes hydrolyze expanded-spectrum cephalosporins as well therefore, all Enterobacteriaceae t isolates that have an ESBL phenotype should be screened for a carbapenemase.
KPC carbapenemase Ertapenem most useful carbapenem to detect KPC. If ertapenem is not on your panel, suggest that all ESBL/AmpC-like Enterobacteriaceae (i.e. expanded- spectrum cephalosporin resistant) be tested with ertapenem (and other carbapenems) by disk diffusion or MIC method (E-test). If isolate has MIC of > 2 μg/ml (susceptible isolates should have an MIC of < 0.5 μg/ml), contact physician and send isolate to reference laboratory. Modified Hodge test PCR for KPC