Table 2C Table 2C. and s for Product Name: Infobase 2010 - Release Date: February 2010 60 Clinical and Laboratory Standards Institute. All rights reserved. Testing Conditions Medium: diffusion: MHA Broth dilution: CAMHB; CAMHB + 2% NaCl for oxacillin, methicillin, and nafcillin; CAMHB supplemented to 50 µg/ml calcium for daptomycin Agar dilution: MHA; MHA + 2% NaCl for oxacillin, methicillin, and nafcillin. Agar dilution has not been validated for daptomycin. Inoculum: Direct colony suspension, equivalent to a 0.5 McFarland standard Incubation: 35 ± 2 C; ambient air; diffusion: 16 to 18 hours; 24 hours (coagulase-negative staphylococci and cefoxitin); Dilution methods: 16 to 20 hours; All methods: 24 hours for oxacillin, methicillin, nafcillin, and vancomycin. Testing at temperatures above 35 C may not detect MRS. Refer to Supplemental Tables 2C-S3 and 2C-S4 at the end of Table 2C for additional recommendations for testing conditions, reporting suggestions, and QC. General Minimal QC Recommendations (See Tables 3 and 4 for acceptable QC ranges.) Staphylococcus aureus ATCC 25923 ( diffusion) Staphylococcus aureus ATCC 29213 (MIC) Escherichia coli ATCC 35218 (for β-lactam/β-lactamase inhibitor combinations) (1) For disk diffusion, measure the diameter of the zones of complete inhibition (as judged by the unaided eye), including the diameter of the disk. Hold the Petri plate a few inches above a black, nonreflecting background illuminated with reflected light, except for linezolid, oxacillin, and vancomycin, which should be read with transmitted light (plate held up to light source). The zone margin should be considered the area showing no obvious, visible growth that can be detected with the unaided eye. Ignore faint growth of tiny colonies that can be detected only with a magnifying lens at the edge of the zone of inhibited growth. With trimethoprim and the sulfonamides, antagonists in the medium may allow some slight growth; therefore, disregard slight growth (20% or less of the lawn of growth) and measure the more obvious margin to determine the zone diameter. Any discernable growth within the zone of inhibition is indicative of oxacillin, linezolid, or vancomycin resistance. (2) Historically, resistance to the penicillinase-stable penicillins (see Glossary I) has been referred to as methicillin resistance or oxacillin resistance. MRSAs are those strains of that express meca or another mechanism of methicillin resistance, such as changes in affinity of penicillin binding proteins for oxacillin (modified [MOD-SA] strains). (3) For oxacillin-susceptible and coagulase-negative staphylococci, results for parenteral and oral cephems, β-lactam/β-lactamase inhibitor combinations, and carbapenems, if tested, should be reported according to the results generated using routine interpretive criteria. See comment (4) for reporting β-lactam results on oxacillin-resistant strains. (4) WARNING: For oxacillin-resistant and coagulase-negative staphylococci (MRS), other β-lactam agents, ie, penicillins, β-lactam/β-lactamase inhibitor combinations, cephems (with the exception of the newer cephalosporins with anti-mrsa activity ), and carbapenems, may appear active in vitro but are not effective clinically. Results for β-lactam agents other than the cephalosporins with anti-mrsa activity should be reported as resistant or should not be reported. This is because most cases of documented MRS infections have responded poorly to β-lactam therapy, or because convincing clinical data have yet to be presented that document clinical efficacy for those agents.
Clinical and Laboratory Standards Institute. All rights reserved. 61 (5) Detection of oxacillin resistance: Tests for meca or for the protein expressed by meca, the penicillin-binding protein 2a (PBP 2a, also called PBP2'), are the most accurate methods for prediction of resistance to oxacillin and can be used to confirm results for isolates of staphylococci from serious infections. Isolates of staphylococci that carry the meca gene, or that produce PBP 2a (the meca gene product), should be reported as oxacillin resistant. Isolates that do not carry meca or do not produce PBP 2a should be reported as oxacillin susceptible. Because of the rare occurrence of resistance mechanisms other than meca, if MIC tests are performed in addition to disk diffusion, isolates for which oxacillin MICs are 4 μg/ml and are meca negative or PBP 2a negative should be reported as oxacillin resistant. These isolates may test as susceptible to cefoxitin by disk diffusion. (6) Routine testing of urine isolates of S. saprophyticus is not advised, because infections respond to concentrations achieved in urine of antimicrobial agents commonly used to treat acute, uncomplicated urinary tract infections (eg, nitrofurantoin, trimethoprim ± sulfamethoxazole, or a fluoroquinolone). (7) For some organism/antimicrobial agent combinations, the absence or rare occurrence of resistant strains precludes defining any results categories other than susceptible. For strains yielding results suggestive of a nonsusceptible category, organism identification and antimicrobial susceptibility test results should be confirmed. (See Appendix A.) (8) For screening tests for β-lactamase production, oxacillin resistance, meca-mediated oxacillin resistance using cefoxitin, reduced susceptibility to vancomycin, and inducible clindamycin resistance, refer to Supplemental Table 2C-S3 at the end of Table 2C for group and Supplemental Table 2C-S4 for coagulase-negative staphylococci at the end of Table 2C. In addition, further explanation on the use of cefoxitin for prediction of mecamediated oxacillin resistance can be found in Section 12 of M07-A8 and Section 11 of M02-A10. NOTE: Information in boldface type is considered tentative for one year. For Use With M02-A10 and M07-A8 M100-S20 Table 2C
Table 2C Product Name: Infobase 2010 - Release Date: February 2010 62 Clinical and Laboratory Standards Institute. All rights reserved. Test/Report PENICILLINS Antimicrobial Content S I R S I R (9) Penicillin-susceptible staphylococci are also susceptible to other penicillins, β-lactam/β-lactamase inhibitor combinations, cephems, and carbapenems approved for use by the FDA for staphylococcal infections. Penicillin-resistant, oxacillin-susceptible strains are resistant to penicillinase-labile penicillins but susceptible to other penicillinase-stable penicillins, β- lactam/β-lactamase inhibitor combinations, relevant cephems, and carbapenems. Oxacillin-resistant staphylococci are resistant to all currently available β-lactam antimicrobial agents with the exception of the newer cephalosporins with anti-mrsa activity. Thus, susceptibility or resistance to a wide array of β-lactam antimicrobial agents may be deduced from testing only penicillin and either cefoxitin or oxacillin. Routine testing of other penicillins, β-lactam/β-lactamase inhibitor combinations, cephems, or carbapenems is not advised. (10) If a penicillinase-stable penicillin is tested, oxacillin is the preferred agent and results can be applied to the other penicillinase-stable penicillins, cloxacillin, dicloxacillin, flucloxacillin, methicillin, and nafcillin. See comment (4). A Penicillin 10 units 29 28 0.12 0.25 (11) Penicillin-resistant strains of staphylococci produce β-lactamase, and the testing of penicillin instead of ampicillin is preferred. Penicillin should be used to test the susceptibility of all staphylococci to all penicillinase-labile penicillins, such as ampicillin, amoxicillin, azlocillin, carbenicillin, mezlocillin, piperacillin, and ticarcillin. An induced β-lactamase test should be performed on staphylococcal isolates with penicillin MICs 0.12 µg/ml or zone diameters 29 mm before reporting the isolate as penicillin susceptible. However, the prevalence of penicillinsusceptible strains is low. Isolates that test as susceptible to penicillin may still produce β-lactamase, which is usually detected by an induced β-lactamase test. Occasional isolates are not detected by induced β-lactamase testing. Thus, for serious infections, laboratories should consider performing MIC tests for penicillin and testing for induced β-lactamase production on subsequent isolates from the same patient. A positive β- lactamase test predicts resistance to penicillin, ampicillin, amoxicillin, carbenicillin, ticarcillin, mezlocillin, and piperacillin. For oxacillin-resistant staphylococci, report penicillin as resistant or do not report. See Supplemental Table 2C-S3 and Table 2C- S4 at the end of Table 2C. A Oxacillin For and S. lugdunensis. 1 μg oxacillin 13 11-12 10 2 (oxacillin 1 μg oxacillin 2 (oxacillin) 30 µg cefoxitin 22 21 4 (cefoxitin) 4 (oxacillin) 4 (oxacillin) 8 (cefoxitin) For. For S. lugdunensis. For and S. lugdunensis. (12) Cefoxitin is used as a surrogate for oxacillin resistance; report oxacillin susceptible or resistant based on the cefoxitin result. If both cefoxitin and oxacillin are tested against or S. lugdunensis and either result is resistant, the organism should be reported as oxacillin resistant. See comment (9).
Clinical and Laboratory Standards Institute. All rights reserved. 63 Test/Report A Antimicrobial Oxacillin For coagulasenegative staphylococci except S. lugdunensis. Content 1 μg oxacillin 0.25 (oxacillin) 30 μg cefoxitin S I R S I R 0.5 (oxacillin) 25 24 See comment (12). See comment (9). For coagulase-negative staphylococci except S. lugdunensis. (13) Oxacillin interpretive criteria may overcall resistance for some coagulase-negative staphylococci because some non S. epidermidis strains for which the oxacillin MICs are 0.5 to 2 µg/ml lack meca. For serious infections with coagulase-negative staphylococci other than S. epidermidis, testing for meca or for PBP 2a or with cefoxitin disk diffusion may be appropriate for strains for which the oxacillin MICs are 0.5 to 2 µg/ml. For Use With M02-A10 and M07-A8 M100-S20 Table 2C
Table 2C Product Name: Infobase 2010 - Release Date: February 2010 64 Clinical and Laboratory Standards Institute. All rights reserved. Test/Report Antimicrobial PENICILLINS (Continued) Content S I R S I R O Ampicillin 10 μg 29 28 0.25 0.5 (14) Class representative for ampicillin and amoxicillin. (15) For oxacillin-resistant staphylococci, report ampicillin as resistant or do not report. O Methicillin 5 μg 14 10 13 9 8 16 (16) For use with only. O Nafcillin 1 μg 13 11 12 10 2 4 See comment (16). β-lactam/β-lactamase INHIBITOR COMBINATIONS (17) For oxacillin-resistant staphylococci, report as resistant or do not report. See comments (4) and (9). O Amoxicillin-clavulanic acid 20/10 μg 20 19 4/2 8/4 O Ampicillin-sulbactam 10/10 μg 15 12 14 11 8/4 16/8 32/16 O Piperacillin-tazobactam 100/10 μg 18 17 8/4 16/4 O Ticarcillin-clavulanic acid 75/10 μg 23 22 8/2 16/2 CEPHEMS (PARENTERAL) (Including cephalosporins I, II, III, and IV. Please refer to Glossary I.) See comment (17). See comments (4) and (9). O Cefamandole 30 μg 18 15 17 14 8 16 32 O Cefazolin 30 μg 18 15 17 14 8 16 32 O Cefepime 30 μg 18 15 17 14 8 16 32 O Cefmetazole 30 μg 16 13 15 12 16 32 64 O Cefonicid 30 μg 18 15 17 14 8 16 32 O Cefoperazone 75 μg 21 16 20 15 16 32 64 O Cefotaxime 30 μg 23 15 22 14 8 16 32 64 O Cefotetan 30 μg 16 13 15 12 16 32 64 O Ceftazidime 30 μg 18 15 17 14 8 16 32 O Ceftizoxime 30 μg 20 15 19 14 8 16 32 64 O Ceftriaxone 30 μg 21 14 20 13 8 16 32 64 O Cefuroxime (parenteral) 30 μg 18 15 17 14 8 16 32 O Cephalothin 30 μg 18 15 17 14 8 16 32 O Moxalactam 30 μg 23 15 22 14 8 16 32 64 CEPHEMS (ORAL) See comment (15). See comments (4) and (9). O Cefaclor 30 μg 18 15 17 14 8 16 32 O Cefdinir 5 μg 20 17 19 16 1 2 4 O Cefpodoxime 10 μg 21 18 20 17 2 4 8 O Cefprozil 30 μg 18 15 17 14 8 16 32 O Cefuroxime (oral) 30 μg 23 15 22 14 4 8 16 32 O Loracarbef 30 μg 18 15 17 14 8 16 32
Clinical and Laboratory Standards Institute. All rights reserved. 65 Test/Report CARBAPENEMS See comment (17). See comments (4) and (9). Antimicrobial Content S I R S I R O Ertapenem 10 μg 19 16 18 15 2 4 8 O Imipenem 10 μg 16 14 15 13 4 8 16 O Meropenem 10 μg 16 14 15 13 4 8 16 GLYCOPEPTIDES B Vancomycin 2 4 8 16 For. (18) MIC tests should be performed to determine the susceptibility of all isolates of staphylococci to vancomycin. The disk test does not differentiate vancomycin-susceptible isolates of from vancomycin-intermediate isolates, nor does the test differentiate among vancomycin-susceptible, intermediate, and resistant isolates of coagulasenegative staphylococci, all of which will give similar size zones of inhibition. (19) The vancomycin 30-µg disk test detects S. aureus isolates containing the vana vancomycin resistance gene (VRSA). Such isolates will show no zone of inhibition around the disk (zone = 6 mm). The identification of isolates showing no zone of inhibition should be confirmed. Isolates of staphylococci producing vancomycin zones of 7 mm should not be reported as susceptible without performing a vancomycin MIC test. (20) Send any for which the vancomycin is 8 μg/ml to a reference laboratory. (21) testing is not reliable for testing vancomycin. Also refer to Supplemental Table 2C-S3 for S. aureus at the end of Table 2C, Section 12.1.3 in M07-A8, and Section 11.1.3 in M02-A10. For Use With M02-A10 and M07-A8 M100-S20 Table 2C
Table 2C Product Name: Infobase 2010 - Release Date: February 2010 66 Clinical and Laboratory Standards Institute. All rights reserved. Test/Report Antimicrobial GLYCOPEPTIDES (Continued) Content S I R S I R B Vancomycin 4 8 16 32 For coagulase-negative staphylococci. See comments (18) and (21). (22) Send any coagulase-negative Staphylococcus for which the vancomycin MIC is 32 μg/ml to a reference laboratory. See also Section 12.1.3 in M07-A8 and Section 11.1.3 in M02-A10. Inv. Teicoplanin 30 μg 14 11 13 10 8 16 32 (23) Teicoplanin disk diffusion interpretive criteria were not reevaluated concurrent with the reevaluation of vancomycin disk diffusion interpretive criteria during recent studies. Therefore, the ability of these teicoplanin interpretive criteria to differentiate teicoplaninintermediate and teicoplanin-resistant staphylococci from teicoplanin-susceptible strains is not known. LIPOPEPTIDES B Daptomycin 1 (24) testing is not reliable for testing daptomycin. See comment (7). AMINOGLYCOSIDES C Gentamicin 10 μg 15 13 14 12 4 8 16 O Amikacin 30 μg 17 15 16 14 16 32 64 O Kanamycin 30 μg 18 14 17 13 16 32 64 O Netilmicin 30 μg 15 13 14 12 8 16 32 O Tobramycin 10 μg 15 13 14 12 4 8 16 MACROLIDES (25) Not routinely reported on organisms isolated from the urinary tract. A A A Azithromycin or clarithromycin or erythromycin 15 μg 15 μg 15 μg 18 18 23 14 17 14 17 14 22 13 13 13 2 2 0.5 4 4 1 4 8 8 8 O Dirithromycin 15 μg 19 16 18 15 2 4 8 KETOLIDES B Telithromycin 15 μg 22 19 21 18 1 2 4
Clinical and Laboratory Standards Institute. All rights reserved. 67 Test/Report TETRACYCLINES Antimicrobial Content S I R S I R (26) Organisms that are susceptible to tetracycline are also considered susceptible to doxycycline and minocycline. However, some organisms that are intermediate or resistant to tetracycline may be susceptible to doxycycline, minocycline, or both. B Tetracycline 30 μg 19 15 18 14 4 8 16 B Doxycycline 30 μg 16 13 15 12 4 8 16 O Minocycline 30 μg 19 15 18 14 4 8 16 FLUOROQUINOLONES (27) may develop resistance during prolonged therapy with quinolones. Therefore, isolates that are initially susceptible may become resistant within three to four days after initiation of therapy. Testing of repeat isolates may be warranted. C Ciprofloxacin or 5 μg 21 16 20 15 1 2 4 C levofloxacin or 5 μg 19 16 18 15 1 2 4 C ofloxacin 5 μg 18 15 17 14 1 2 4 C Moxifloxacin 5 μg 24 21 23 20 0.5 1 2 U Lomefloxacin 10 μg 22 19 21 18 2 4 8 U Norfloxacin 10 μg 17 13 16 12 4 8 16 O Enoxacin 10 μg 18 15 17 14 2 4 8 (28) FDA approved for S. saprophyticus and S. epidermidis (but not for ). O Gatifloxacin 5 μg 23 20 22 19 0.5 1 2 O Grepafloxacin 5 μg 18 15 17 14 1 2 4 O Sparfloxacin 5 μg 19 16 18 15 0.5 1 2 Inv. Fleroxacin 5 μg 19 16 18 15 2 4 8 For Use With M02-A10 and M07-A8 M100-S20 Table 2C
Table 2C Product Name: Infobase 2010 - Release Date: February 2010 68 Clinical and Laboratory Standards Institute. All rights reserved. Test/Report Antimicrobial Content S I R S I R NITROFURANTOINS U Nitrofurantoin 300 μg 17 15 16 14 32 64 128 LINCOSAMIDES A Clindamycin 2 μg 21 15 20 14 0.5 1 2 4 (29) Inducible clindamycin resistance can be detected by disk diffusion using the D-zone test and by broth using a single well containing a combination of erythromycin and clindamycin. See Supplemental Tables 2C-S3 and 2C-S4, Section 12 in M02-A10, and Section 13 in M07-A8 for current recommendations. See comment (25). FOLATE PATHWAY INHIBITORS A Trimethoprim- 1.25/23.75 μg 16 11 15 10 2/38 4/76 sulfamethoxazole U Sulfonamides 250 or 300 μg 17 13 16 12 256 512 (30) Sulfisoxazole can be used to represent any of the currently available sulfonamide preparations. U Trimethoprim 5 μg 16 11 15 10 8 16 PHENICOLS C Chloramphenicol 30 μg 18 13 17 12 8 16 32 See comment (25). ANSAMYCINS B Rifampin 5 μg 20 17 19 16 1 2 4 (31) Rx: Rifampin should not be used alone for antimicrobial therapy. STREPTOGRAMINS C Quinupristindalfopristin 15 μg 19 16 18 15 1 2 4 (32) For reporting against methicillin-susceptible. OXAZOLIDINONES B Linezolid 30 μg 21 20 4 8 (33) When testing linezolid, disk diffusion zones should be examined using transmitted light. Organisms with resistant results by disk diffusion should be confirmed using an MIC method.
70 Clinical and Laboratory Standards Institute. All rights reserved. Supplemental Table 2C-S3. Screening Tests for β-lactamase Production, Oxacillin Resistance, meca-mediated Oxacillin Resistance Using Cefoxitin, Vancomycin MIC 8 μg/ml, Inducible Clindamycin Resistance, and High-Level Mupirocin Resistance in the Staphylococcus aureus for Use With Table 2C Screen Test β-lactamase Oxacillin Resistance meca-mediated Oxacillin Resistance Using Cefoxitin Organism and S. and group lugdunensis with S. lugdunensis penicillin MICs 0.12 µg/ml or zones 29 mm Test method Nitrocefin-based test Agar dilution diffusion Broth Medium NA MHA with 4% NaCl Clinical and Laboratory Standards Institute. All rights reserved. 109 Antimicrobial concentration Inoculum Incubation conditions Incubation length NA Induced growth (ie, growth taken from the zone margin surrounding an oxacillin or cefoxitin disk test on either MHA or a blood agar plate after 16 18 hours of incubation). Room temperature Up to 1 hour for nitrocefin-based test or follow manufacturer s directions 6 μg/ml oxacillin Direct colony suspension to obtain 0.5 McFarland turbidity. Using a 1-μL loop that was dipped in the suspension, spot an area 10 to 15 mm in diameter. Alternatively, using a swab dipped in the suspension and expressed, spot a similar area or streak an entire quadrant. 33 35 C; ambient air. (Testing at temperatures above 35 C may not detect MRSA.) 24 hours; read with transmitted light MHA CAMHB a Brain Heart Infusion (BHI) agar 30 µg cefoxitin disk Standard disk diffusion recommendations 33 35 C; ambient air. (Testing at temperatures above 35 C may not detect MRSA.) 4 µg/ml cefoxitin 6 μg/ml vancomycin Standard broth recommendations 33 35 C; ambient air. (Testing at temperatures above 35 C may not detect MRSA.) Vancomycin MIC 8 μg/ml Inducible Clindamycin Resistance and S. lugdunensis resistant to erythromycin and susceptible or intermediate to clindamycin High-level Mupirocin Resistance b,c Agar dilution diffusion Broth diffusion Broth MHA or blood CAMHB a MHA CAMHB a agar purity plate used with MIC tests Direct colony suspension to obtain 0.5 McFarland turbidity. Preferably, using a micropipette, spot a 10 μl drop onto agar surface. Alternatively, using a swab dipped in the suspension and the excess liquid expressed, spot an area 10 to 15 mm in diameter or streak a portion of the plate. 35 ± 2 C; ambient air 16 18 hours 16 20 hours 24 hours; read with transmitted light 15-µg erythromycin disk and 2-µg clindamycin disk spaced 15 26 mm apart Standard disk diffusion Recommendations or heavily inoculated area of purity plate 35 ± 2 C; ambient air 4 µg/ml erythromycin and 0.5 µg/ml clindamycin in same well Standard broth recommendations 35 ± 2 C; ambient air 200-µg disk Standard disk diffusion recommendations 35 ± 2 C; ambient air 16 18 hours 18 24 hours 24 hours; read with transmitted light Supplemental Table 2C-S3 Screening Tests for Staphylococcus aureus Single 256-μg/mL well Standard broth recommendations 35 ± 2 C; ambient air 24 hours; read with transmitted light
Clinical and Laboratory Standards Institute. All rights reserved. 71 Supplemental Table 2C-S3. (Continued) Screen Test β-lactamase Oxacillin Resistance Test method Results Further testing and reporting meca-mediated Oxacillin Resistance Using Cefoxitin Nitrocefin-based test Agar dilution diffusion Broth Nitrocefin-based Examine 21 mm = meca >4 µg/ml = test: conversion from carefully with positive meca positive yellow to red/pink = transmitted light β-lactamase for > 1 colony or 22 mm = meca 4 µg/ml = positive. light film of negative meca growth. negative β-lactamasepositive staphylococci are resistant to penicillin, amino-, carboxy-, and ureidopenicillins. > 1 colony = oxacillin resistant. Oxacillinresistant staphylococci are resistant to all β-lactam agents; other β- lactam agents should be reported as resistant or should not be reported. Cefoxitin is used as a surrogate for meca-mediated oxacillin resistance. Isolates that test as meca positive should be reported as oxacillin (not cefoxitin) resistant; other β-lactam agents should be reported as resistant or should not be reported. Because of the rare occurrence of oxacillin resistance mechanisms other than meca, isolates that test as meca negative but for which the oxacillin MICs are resistant (MIC 4 µg/ml) should be reported as oxacillin resistant. Vancomycin Inducible Clindamycin Resistance MIC 8 μg/ml Agar dilution diffusion Broth Examine Any growth = carefully with inducible transmitted light clindamycin for > 1 colony or resistance; light film of growth. > 1 colony = presumptive reduced susceptibility to vancomycin. Perform a vancomycin MIC using a validated MIC method to determine vancomycin MICs on S. aureus that grow on BHI vancomycin screening agar. Testing on BHI vancomycin screening agar does not reliably detect all vancomycinintermediate S. aureus strains. Some strains for which the vancomycin MICs are 4 μg/ml will fail to grow. Flattening of the zone of inhibition adjacent to the erythromycin disk (referred to as a D- zone) = inducible clindamycin resistance. Hazy growth within the zone of inhibition around clindamycin = clindamycin resistance even if no D-zone apparent. Report isolates with inducible clindamycin resistance as clindamycin resistant. No growth = no inducible clindamycin resistance A comment that This isolate is presumed to be resistant based on detection of inducible clindamycin resistance. Clindamycin may still be effective in some patients may be included. High-level Mupirocin Resistance b,c diffusion Broth Examine carefully with transmitted light for light growth within the zone of inhibition. No zone = highlevel resistance Any zone = the absence of highlevel resistance Report isolates with no zone as high-level resistant. Report any zone of inhibition as the absence of highlevel resistance. For single 256- µg/ml well: Growth = highlevel resistance No growth = the absence of highlevel resistance Report growth in the 256-µg/mL well as high-level resistant. Report no growth in the 256-µg/mL well as the absence of highlevel resistance. For Use With M02-A10 and M07-A8 M100-S20 Supplemental Table 2C-S3 Screening Tests for Staphylococcus aureus
Supplemental Table 2C-S3 Screening Tests for Staphylococcus aureus 72 Clinical and Laboratory Standards Institute. All rights reserved. Supplemental Table 2C-S3. (Continued) Screen Test Test method β-lactamase Oxacillin Resistance meca-mediated Oxacillin Resistance Using Cefoxitin Nitrocefin-based test Agar dilution diffusion Broth 29213 positive 25923 negative (or see manufacturer s recommendations) ATCC 29213 Susceptible ATCC 43300 Resistant 25923 meca negative (zone 23-29 mm) 43300 meca positive (zone 21 mm) ATCC 29213 meca negative (MIC 1-4 µg/ml) ATCC 43300 meca positive (MIC >4 µg/ml) Vancomycin MIC 8 μg/ml Inducible Clindamycin Resistance Agar dilution diffusion Broth Enterococcus faecalis ATCC 29212 Susceptible E. faecalis ATCC 51299 Resistant Footnotes 25923 for routine QC of disks; See Table 3 for use of supplemental QC strains QC recommendations ATCC BAA- 976 or ATCC 29213 no growth ATCC BAA-977 growth High-level Mupirocin Resistance b,c diffusion Broth 25923 (200-µg disk) mupa negative (zone 29 to 38 mm) BAA1708 mupa positive (no zone) 29213 mupa negative (MIC 0.06 0.5 µg/ml) E. faecalis ATCC 29212 mupa negative (MIC 16 to 128 µg/ml) BAA1708 mupa positive (growth in 256-µg/mL well) a. CAMHB = cation-adjusted Mueller-Hinton broth. b. Although not formally validated by CLSI document M23 based analyses, some studies have linked a lack of response to -based decolonization regimens with isolates for which the MICs are 512. Although this document does not provide guidance on interpretive criteria for, disk-based testing and the MIC screening test described here identify isolates for which the MICs are 512 µg/ml. c. References: Simor AE. Randomized controlled trial of chlorhexidine gluconate for washing intranasal, and rifampin and doxycycline versus no treatment for the eradication of methicillinresistant Staphylococcus aureus colonization. Clin Infect Dis. 2007;44:178-185; Harbarth S, Dharan S, Liassine N, Herrault P, Auckenthaler R, Pittet D. Randomized, placebo-controlled, double-blind trial to evaluate the efficacy of for eradicating carriage of methicillin-resistant Staphylococcus aureus. Antimicrob s Chemother. 1999;43:1412-1416; and Walker ES, Vasquez JE, Dula R, Bullock H, Sarubbi FA. Mupirocin-resistant, methicillin-resistant Staphylococcus aureus; does remain effective? Infect Control Hosp Epidemiol. 2003;24:342-346.