Table 3.
Seventy-eight E. coli isolates classified according to their beta-lactamase phenotype including the detected resistance mechanisms against beta-lactams and aminoglycosides by LC–MS/MS.
| Phenotype | n | Antibiotics | PEN/OXA | ESBL | AmpC | CPE | 16S-RMTase | AME | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CRX | CAZ | MEM | GEN | TOB | CIP | TEM | OXA-1 | CTX-M | CMY | cAmpC | OXA-48 | NDM | RmtB | AAC(3)-II | AAC(3)-VI | AAC(6′)-Ib | ANT(2″)-Ia | ||
| WT/PEN | 25 | S | S | S | S | S | S/R | 4 | – | – | – | 10 | – | – | – | – | – | – | – |
| WT/PEN/AME | 8 | S | S | S | R | R | S/R | 7 | 1 | – | – | 2 | – | – | – | 7 | – | – | 1 |
| ESBL/AmpC | 12 | S/R | S/R | S | S | S | S/R | 6 | – | 4 | 7 | 2 | – | – | – | – | – | – | – |
| ESBL/AmpC/AME | 14 | R | R | S | S/R | R | S/R | 7 | 11 | 12 | 3 | 2 | – | – | – | 10 | 1 | 11 | – |
| AmpC | 6 | S/R | R | S | S | S | S | 1 | – | – | – | 6 | – | – | – | – | – | – | – |
| AmpC/Quin | 3 | S | R | S | S | S/R | R | 3 | – | – | – | 3 | – | – | – | – | – | – | – |
| CPE | 3 | S/R | S/R | S/R | S | S | S | 2 | – | 1 | – | – | 2 | 1 | – | – | – | – | – |
| CPE/Quin | 7 | S/R | S/R | S/R | S/R | S/R | R | 4 | 6 | 5 | 3 | 3 | 3 | 4 | 2 | 1 | – | 5 | – |
Isolates were classified based on their susceptibility (S) or resistance (R) to ceftriaxone (CRX), ceftazidime (CAZ), meropenem (MEM), gentamicin (GEN), tobramycin (TOB) and ciprofloxacin (CIP) into wild type (WT) isolates and small spectrum penicillinase (PEN) and/or oxacillinase-producing (OXA) isolates, extended-spectrum beta-lactamase producers (ESBL) in combination with isolates producing AmpC beta-lactamases (AmpC), isolates that only produced E. coli chromosomal AmpC, or carbapenemase producing Enterobacterales (CPE). Isolates were further divided based on aminoglycoside resistance, mostly caused by aminoglycoside modifying enzymes (AME), and/or quinolone resistance (Quin). Small spectrum beta-lactamases/oxacillinases included TEM and OXA-1. ESBL and AmpC were represented by CTX-M, CMY and E. coli chromosomal AmpC. Carbapenemase producing Enterobacterales (CPE) included OXA-48 and New Delhi Metallo beta-lactamase (NDM) producing isolates. Mechanisms of aminoglycoside resistance included the 16S rRNA methyltransferase (rmtB), the acetyltransferases AAC(3)-II, AAC(3)-VI and AAC(6′)-Ib, and the nucleotidyltransferase ANT(2″)-I.