TABLE 2

MICs of polymyxins for the studied strains and limits of detection of the SuperPolymyxin culture medium

StrainaSpeciesOriginMICbPolymyxin resistancecMechanism of polymyxin resistanceLowest detection limit (CFU/ml)dLowest detection limit in stools (CFU/ml)d
ColistinPolymyxin B
Yeast isolates
    FR-AC. albicansFranceNANANANA>107ND
Gram-positive cocci isolates
    FR-BS. aureusFranceNANANANA>107ND
    FR-CStaphylococcus epidermidisFranceNANANANA>107ND
    FR-DEnterococcus faeciumFranceNANANANA>107ND
    FR-EEnterococcus faecalisFranceNANANANA>107ND
Gram-negative rod isolates naturally resistant to polymyxins
    FR-01M. morganiiFrance>128>128RIntrinsic101101
    FR-02P. mirabilisFrance>128>128RIntrinsic101ND
    FR-03Proteus vulgarisFrance>128>128RIntrinsic101ND
    FR-04Providencia stuartiiFrance>128>128RIntrinsic101ND
    FR-05S. marcescensFrance>128>128RIntrinsic101ND
    FR-201B. cepaciaFrance>128>128RIntrinsic101eND
    FR-202Burkholderia gladioliFrance>128>128RIntrinsic101ND
Gram-negative rod isolates with an acquired mechanism of resistance to polymyxins
    FR-06K. pneumoniaeFrance3264RPmrA G53C101101
    FR-07K. pneumoniaeFrance3232RPmrA G53S101101
    FR-09K. pneumoniaeTurkey3264RPmrB L17Q101101
    FR-10K. pneumoniaeSouth Africa168RPmrB T157P101101
    FR-17K. pneumoniaeTurkey<128128RPhoQ R16C101101
    FR-21K. pneumoniaeFrance3264RMgrB N42Y/K43I101101
    FR-30K. pneumoniaeFrance>12864RMgrB truncated101101
    FR-31K. pneumoniaeFrance6432RMgrB truncated101ND
    FR-36K. pneumoniaeColombia128128RMgrB truncated101ND
    FR-40K. pneumoniaeFrance6464RMgrB ISEcp1-blaCTX-M-15101101
    FR-41K. pneumoniaeFrance>128128RMgrB IS102-like101ND
    FR-47K. pneumoniaeTurkey6432RMgrB I3903b-like101ND
    FR-48K. pneumoniaeSpain128128RMgrB IS903-like101ND
    FR-49K. pneumoniaeFrance6432RMgrB IS5-like101ND
    FR-54K. pneumoniaeColombia128128RMgrB ISKpn13101101
    FR-56K. pneumoniaeSpain6464RMgrB ISKpn26101ND
    FR-68K. pneumoniaeColombia6464RMgrB ISKpn14101101
    FR-70K. pneumoniaeColombia128128RmgrB promoter IS10R101ND
    FR-71K. pneumoniaeTurkey3232RmgrB promoter ISKpn14101ND
    FR-86K. pneumoniaeSpain6464RmgrB deletion nt 100102ND
    FR-89K. pneumoniaeColombia>128>128RmgrB deletion nt 23 to 33101ND
    FR-92K. oxytocaColombia6464RmgrB promoter ISKpn26-like101101
    FR-93E. coliFrance44RPlasmid-mediated mcr-1 gene102101
    FR-94E. coliSouth Africa1616RPlasmid-mediated mcr-1 gene101101
    FR-98E. coliSouth Africa88RPlasmid-mediated mcr-1 gene101ND
    FR-203A. baumanniiSwitzerland128128RPmrB G260D102101
    FR-100K. pneumoniaeFrance6464RUnknown101101
    FR-102K. pneumoniaeFrance3232RUnknown101ND
    FR-113K. pneumoniaeFrance>128>128RUnknown101ND
    FR-114K. pneumoniaeColombia64128RUnknown101ND
    FR-116K. pneumoniaeFrance6432RUnknown101ND
    FR-119E. coliFrance84RUnknown101ND
    FR-120E. coliFrance84RUnknown101101
    FR-121E. coliFrance44RUnknown101ND
    FR-122E. cloacaeColombia3216RUnknown101101
    FR-126E. cloacaeFrance>128>128RUnknown101102
    FR-135H. alveiFrance168RUnknown101101
    FR-204A. baumanniiUSA>128>128RUnknown102101
    FR-205A. baumanniiUSA88RUnknown102ND
    FR-206A. baumanniiUSA>128>128RUnknown102ND
    FR-207P. aeruginosaColombia6464RUnknown102f101
    FR-208P. aeruginosaFrance>128>128RUnknown101eND
    FR-209P. aeruginosaFrance>128>128RUnknown102fND
    FR-210S. maltophiliaFrance>128>128RUnknown101eND
    FR-211S. maltophiliaFrance3232RUnknown5.102eND
Gram-negative rod isolates susceptible to polymyxins
    FR-136E. coliATCC 259220.250.25SNA>107ND
    FR-212E. coliUSA0.120.12SNA>107ND
    FR-213E. coliColombia0.120.12SNA>107ND
    FR-214E. coliFrance0.120.12SNA>107ND
    FR-215E. coliFrance0.250.12SNA>107ND
    FR-216E. coliFrance0.250.12SNA>107ND
    FR-217K. pneumoniaeUSA0.120.12SNA5 × 106ND
    FR-218K. pneumoniaColombia0.120.5SNA>107ND
    FR-219K. pneumoniaeColombia0.120.12SNA>107ND
    FR-220K. pneumoniaeColombia0.50.25SNA5 × 106ND
    FR-221K. pneumoniaeColombia0.50.5SNA>107ND
    FR-222K. pneumoniaeFrance0.120.25SNA>107ND
    FR-223K. pneumoniaeFrance0.120.12SNA>106ND
    FR-224K. pneumoniaeFrance0.250.5SNA>106ND
    FR-225K. pneumoniaeFrance0.50.5SNA>107ND
    FR-226K. pneumoniaeSpain0.50.5SNA106ND
    FR-227K. pneumoniaeSpain0.50.5SNA107ND
    FR-228E. cloacaeColombia0.120.25SNA>107ND
    FR-229E. cloacaeColombia0.120.12SNA>107ND
    FR-230E. cloacaeFrance0.120.25SNA5 × 106ND
    FR-231Enterobacter aerogenesFrance0.120.12SNA>107ND
    FR-232Citrobacter freundiiColombia0.250.25SNA>107ND
    FR-233C. freundiiFrance0.120.5SNA5 × 106ND
    FR-234P. aeruginosaATCC 278530.50.5SNA5 × 106ND
    FR-235P. aeruginosaColombia10.25SNA>107ND
    FR-236P. aeruginosaColombia20.5SNA106ND
    FR-237P. aeruginosaColombia10.25SNA>107ND
    FR-238P. aeruginosaFrance20.25SNA106ND
    FR-239A. baumanniiColombia0.50.12SNA>107ND
    FR-240A. baumanniiFrance0.50.25SNA106ND
    FR-241A. baumanniiUSA0.250.25SNA106ND
  • a The strains FR-01 and FR-136 were used as positive and negative controls, respectively.

  • b MICs of colistin and polymyxin B were determined using the broth microdilution method. NA, not available.

  • c R, resistant; S, susceptible.

  • d Underlined CFU counts are considered to be results below cutoff values set at ≥1 × 103 CFU/ml. ND, not determinate.

  • e Positive culture after 36 h.

  • f Positive culture after 48 h.