Table 3.

Etest MICs of β-lactam drugs for select bacterial isolates

IsolateOrganism nameMICa (μg/ml)
FOXbCROcCTXFEPIPMdAMPdSAMAMCPIPTZP
04-059Escherichia coli60.0640.0640.1250.19>2561261282
11-025Sphingomonas paucimobilis160.750.7510.1250.381.5180.032
04-020Bacteroides fragilis66432320.19480.750.380.220.75
04-021Bacteroides helcogenes46432480.125320.500.38320.75
04-098Bacteroides ovatus60.50.25>2560.064320.750.50.253
04-092Bacteroides stercoris16>25696480.192410.5>2560.75
04-042Bacteroides suis61612120.06480.190.0640.190.75
04-049Bacteroides thetaiotaomicron820.50.254>2563232>2561.5
04-036Bacteroides uniformis24124>2560.75120.250.19324
03-041Desulfovibrio vulgaris364321280.125320.750.5244
04-076Hallella seregens40.750.250.0320.250.250.0640.0320.750.023
P-41Bacillus cereus1612864>2560.094243644
11-022Bacillus cereus>256>256>256>25681668>2561
11-019Bacillus mycoides>256>256>256>25621244640.5
03-008Enterococcus casseliflavus128>256>256241.50.190.1250.191921.5
03-013Eubacterium biforme>25610.38>2560.75>256>256>256>256>256
03-126Bifidobacterium breve40.750.380.1250.250.0320.0230.0320.750.023
03-110Clostridium sp.44832>2560.1948196322
03-127Clostridium sp.16210.1250.0940.0640.0470.50.25
04-008Clostridium cocleatum60.750.3840.381.50.064>2560.750.023
  • a Abbreviations: FOX, cefoxitin; CRO, ceftriaxone; CTX, cefotaxime; FEP, cefepime; IPM, imipenem; AMP, ampicillin; SAM, ampicillin-sulbactam; AMC, amoxicillin-clavulanic acid; PIP, piperacillin; TZP, piperacillin-tazobactam.

  • b Interpretive standards from Etest product literature for obligate anaerobes: cefoxitin, 32 μg/ml; ceftriaxone, 64 μg/ml; cefotaxime, 64 μg/ml; imipenem, 16 μg/ml; ampicillin-sulbactam, 32 μg/ml; amoxicillin-clavulanic acid, 16 μg/ml; piperacillin, 128 μg/ml; piperacillin-tazobactam, 128 μg/ml.

  • c Ceftiofur is chemically similar to ceftriaxone. A ceftiofur MIC90 of 16 μg/ml was reported in one study for 41 Bacteroides sp. isolates in cattle (39).

  • d Interpretive standards were unavailable for the use of cefepime (aerobe MIC = 32 μg/ml) or ampicillin (Enterobacteriaceae MIC = 32 μg/ml) with obligate anaerobes.