TABLE 3.
Concordance between BC-GN-detected resistance markers and other phenotypic and molecular assays used in this study and results of definitive antibiotic susceptibility testing for each isolate and ongoing empirical therapy
| BC-GN test gene product | Organism | Phenotypic test resultsa |
dASTb |
Ongoing empirical therapyc | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| DDST | EDTA | PBA | PCR | Cephalosporinsd | Carbapenemsd | TZP | TGC | GEN | AMK | SXT | CIP | CST | |||
| CTX-Me | E. coli | − | − | − | CTX-M-14 | R | S | S | S | S | R | R | RIF | ||
| E. coli | + | − | − | CTX-M-15/27 | R | S | I | R | S | R | R | CIP + MET | |||
| E. coli | + | − | − | CTX-M-15 | R | S | S | S | S | R | R | TZP | |||
| E. coli | + | − | − | CTX-M-15 | R | S | R | R | R | R | R | MEM | |||
| E. coli | + | − | − | CTX-M-15 | R | S | S | S | S | S | R | CIP | |||
| E. coli | + | − | − | CTX-M-15 | R | S | S | R | S | R | R | TZP | |||
| E. coli | + | − | − | CTX-M-15 | R | S | I | S | S | S | R | LVX + TZP | |||
| E. coli | + | − | − | CTX-M-15/14 | R | S | S | S | I | S | R | MEM | |||
| E. coli | + | − | − | CTX-M-15 | R | S | S | S | S | R | R | CIP | |||
| E. coli | + | − | − | CTX-M-15 | R | S | R | S | I | S | R | CIP + MET | |||
| E. coli | + | − | − | CTX-M-15 | R | S | S | R | I | R | R | MEM | |||
| E. colif | − | − | − | CTX-M-9 | S | S | R | S | S | R | R | TZP + DPC | |||
| K. pneumoniae | + | − | − | CTX-M-15 | R | S | R | S | S | S | R | TZP + MET | |||
| K. pneumoniae | + | − | − | CTX-M-15 | R | S | I | S | S | R | I | TZP + MET | |||
| KPC | K. pneumoniae | − | − | + | KPC-2 | R | R | R | I | S | R | S | R | S | TZP |
| K. pneumoniae | − | − | + | KPC-2 | R | R | R | I | R | S | R | R | S | VAN + TZP + AMK | |
| K. pneumoniae | − | − | + | KPC-2 | R | R | R | I | I | R | S | R | S | GEN + MEM + CST | |
| K. pneumoniae | − | − | + | KPC-2 | R | R | R | I | S | S | S | R | S | None | |
| K. pneumoniae | − | − | + | KPC-2 | R | R | R | R | I | R | R | R | S | TZP | |
| K. pneumoniae | − | − | + | KPC-2 | R | R | R | R | I | R | R | R | S | MEM + LZD | |
| K. pneumoniae | − | − | + | KPC-2 | R | R | R | I | I | R | R | R | R | GEN + MEM + CST | |
| K. pneumoniae | − | − | + | KPC-2 | R | R | R | R | S | R | R | R | S | GEN + MEM + CST | |
| K. pneumoniae | − | − | + | KPC-2 | R | R | R | I | S | R | R | R | S | GEN + MEM + CST | |
| OXA | Acinetobacter | OXA-58 | R | R | R | R | S | MEM | |||||||
| Acinetobacter | OXA-58 | R | R | R | R | S | LZD | ||||||||
| VIM | P. aeruginosa | VIM-1 | R | R | R | R | R | R | S | TZP | |||||
| P. aeruginosa | VIM-1 | R | R | R | R | S | R | S | MEM + CST | ||||||
| K. oxytoca | − | − | − | VIM-1 | R | R | R | R | S | R | I | S | CAZ | ||
DDST, double-disk synergy test; EDTA, EDTA synergy test; PBA, phenylboronic acid synergy test.
dAST, definitive antibiotic susceptibility testing; TZP, piperacillin-tazobactam; TGC, tigecycline; GEN, gentamicin; AMK, amikacin; SXT, trimethoprim-sulfamethoxazole; CIP, ciprofloxacin; CST, colistin; R, resistant; S, susceptible; I, intermediate.
In bold type are all the cases of empirical regimens that could have been changed earlier based on BC-GN resistance marker detection. RIF, rifampin; MET, metronidazole; MEM, meropenem; LVX, levofloxacin; DPC, daptomycin; VAN, vancomycin; LZD, linezolid; CAZ, ceftazidime.
All isolates but one E. coli showed a perfect concordance of susceptibility results to the different cephalosporins (ceftazidime and cefotaxime) and carbapenems (imipenem and meropenem) tested.
All CTX-M-positive isolates were resistant to ciprofloxacin, highlighting the risk of empirical use of a quinolone against CTX-M-producing organisms in our center.
CTX-M-positive E. coli isolate not showing an ESBL-producing phenotype in DDST or in dAST.