Article Figures & Data
Figures
- FIG. 1.
The phenotypic appearance of an MBL-producing Serratia marcescens isolate carrying the blaIMP-4 gene. (A) Combined-disk test, using two imipenem (10 μg) disks, one with 292 μg EDTA, showing an increase in zone inhibition of >4 mm around the disk with EDTA. (B) Double-disk synergy test, using an IPM (10 μg) disk placed 20 mm (center to center) from a blank filter disk containing 292 μg EDTA. (C) Aztreonam (30 μg) disk with a >30-mm zone of inhibition.
- FIG. 2.
Increase (in millimeters) in zone of inhibition around the imipenem-EDTA disk compared with the imipenem disk alone for 52 MBL-negative (MBL -ve) and 54 MBL-positive (MBL +ve) clinical isolates.
- FIG. 3.
Inhibition zone diameters (in millimeters) around the aztreonam disk (30 μg) for the 84 metallo-β-lactamase-carrying isolates. Asterisks indicate Enterobacteriaceae isolates (n = 8) found to produce an AmpC-type or extended-spectrum β-lactamase.
Tables
- TABLE 1.
Results of the phenotypic method in the detection of MBL-producing gram-negative bacilli
Organism No. of isolates No. (%) of isolates positive on phenotypic plate MBL gene type MBL-positive isolates 84 Serratia marcescens 37 37 (100) IMP-4 P. aeruginosa 19 19 (100) IMP-4 P. aeruginosa 1 1 (100) VIM-4 Pseudomonas stutzeri 1 1 (100) VIM-2 Klebsiella pneumoniae 10 10 (100) IMP-4 Klebsiella oxytoca 1 1 (100) IMP-4 Escherichia coli 6 6 (100) IMP-4 Enterobacter cloacae 6 6 (100) IMP-4 Citrobacter koseri 1 1 (100) IMP-4 Acinetobacter junii 1 1 (100) IMP-4 Acinetobacter baumannii 1 1 (100) IMP-1 MBL-negative isolates 52 P. aeruginosa 15 1 (7) NDa Pseudomonas mendocina 1 0 (0) ND A. baumannii 10 0 (0) ND E. cloacae 5 0 (0) ND S. marcescens 4 0 (0) ND E. coli 4 0 (0) ND K. pneumoniae 3 0 (0) ND K. oxytoca 3 0 (0) ND Citrobacter braakii 1 0 (0) ND Achromobacter xylosoxidans 3 0 (0) ND Burkholderia cepacia 2 0 (0) ND Ralstonia pickettii 1 0 (0) ND ↵a ND, not detected.
- TABLE 2.
Summary of results for the combined-disk test and the double-disk synergy test in the detection of MBL-producing gram-negative bacilli
Phenotypic method No. of PCR-confirmed MBL-carrying organisms (n = 84) No. of PCR-confirmed non-MBL-carrying organisms (n = 52) Sensitivity (%) Specificity (%) Combined-disk test 84 (100%) 1 (2%) 100 98 Double-disk synergy test 66 (79%) 1 (2%) 79 98
