Table 1.
β-lactamase phenotypes encountered among the 912 strains analyzed
|
Antibiotics to which isolates were resistant | ||||||
|---|---|---|---|---|---|---|
| Penicillins, 1st & 2nd generation cephalosporins | 3rd Generation cephalosporins & Monobactams | 4th Generation cephalosporins | inhibitors | Cephamycins | Most probable Phenotypea | Total (%)n = 912 |
| AMP, KF, AMX |
− |
− |
− |
− |
NSBL |
103 (11) |
| AMP, AMX, KF OXA |
− |
− |
− |
− |
NSBL |
175 (19) |
| AMP, AMX, KF OXA |
− |
− |
AMC, AMS |
− |
IRT |
65 (7) |
| AMP, KF, AMX, |
− |
− |
AMC, AMS |
− |
IRT |
8 (1) |
| AMP, AMX, KF, CXM |
CTXb, AZTb |
− |
− |
− |
ESBL |
105 (12) |
| AMP, AMX , KF, CXM |
CTX, CAZ*, AZT |
− |
− |
− |
ESBL |
75 (8) |
| AMP, AMX, OXA KF, CXM |
CTXb, CAZb, AZT |
FEP |
AMS |
− |
ESBL |
67 (7) |
| AMP, AMX, OXA KF, CXM |
CTX, CAZ*, AZT |
FEP |
AMC, AMS |
− |
CMT |
40 (4) |
| AMP, AMX, OXA, KF, CXM |
CTX, CAZ, AZT |
FEP |
AMC, AMS, TZP |
− |
CMT |
180 (20) |
| AMP, AMX, OXA KF, CXM | CTX, CAZ, AZT | FEP | AMC, AMS, TZP | FOX | pAmpC | 94 (10) |
Resistance phenotypes of the 912 isolates investigated.
a: β-lactamase phenotypes observed in different isolates were defined as follow:- Narrow spectrum β-lactamases (NSBLs) were resistant to penicillins but were susceptible to other classes of β-lactam antibiotics. Isolates exhibiting the inhibitor resistant TEM phenotype (IRT) were those capable of degrading penicillins, were not inhibited by β-lactamase inhibitors but were susceptible to other classes of β-lactam antibiotics. The ESBL-producers were resistant to penicillins, 2nd and most 3rd generation cephalosporins, and exhibited intermediate resistance to 4th generation cephalosporins and were fully susceptible to cephamycins, carbapenems and β-lactamase inhibitors. The complex mutant TEMs (CMTs) were resistant to most β-lactams and β-lactamase inhibitors including TZP but were susceptible to cephamycins and carbapenems. Isolates with the pAmpC phenotypes were resistant to all generations of β-lactam antibiotics, were susceptible to carbapenems and were either susceptible or exhibited intermediate resistance to 4th generation cephalosporins.
b: appearance of zones of synergy between a given cephalosporin or monobactam and amoxicillin-clavulanic acid (AMC).
(−) isolate with a given phenotype were susceptible to a given set of antibiotics.