INVESTIGADORES
SAKA Hector Alex
congresos y reuniones científicas
Título:
Emergence of Resistance to Third Generation Cephalosporins (C3G) in Shigella flexneri (Sf) Isolates in Argentina
Autor/es:
M. GALAS; H. A. SAKA; R. MELANO; F. PASTERAN; M. RAPOPORT; H. LOPARDO; M. MARTINEZ; J. MULKI; C. CULASSO; I. MARQUEF; M. TURCO; S. GRENON; A. ROSSI.
Lugar:
Toronto, Canadá
Reunión:
Conferencia; 40th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC); 2000
Institución organizadora:
American Society for Microbiology
Resumen:
During 1997-99, according to WHONET-Argentina Network for antimicrobial susceptibility surveillance (33 institutions), elevated levels of resistance (%) to ampicillin-AM (90%), cotrimoxazole-CO (68% and chloramphenicol-CH (72%) were observed among Sf isolates (n=3334). Since first detection of TGC resistance in Argentina in this genus in 1997 to date, such resistance was found in 7 Sf. In order to estimate the TGC resistance mechanisms, antimicrobial susceptibility (diffusion and agar dilution, according to NCCLS), isoelectric focusing (IEF), PCR determinations and conjugation assays were performed.
Strain
3260
3127
3186
3244
Hpp22
Hp63
20091
State
Cordoba
Bs As
Bs As
Salta
Misiones
Chaco
Bs As
MIC µg/mL
FT
1
1
32
64
32
512
128
FC
.015
.015
.03
.06
.03
< .03
.03
CA
.5
2
2
4
2
4
4
CC
< .03
< .03
.06
.12
.06
< .03
.12
AM
512
1024
> 1024
> 1024
> 1024
1024
> 1024
CH
64
1
1
32
128
64
> 128
CO
512
.12
512
512
512
256
512
IEF1
7.6
5.4 + 7.6
5.4 + 7.9
5.4 + 7.9
5.4 + 7.9
5.4 + 7.9
5.4 + 8.4
5.4 + 7.9
PCR posotive
SHV
TEM; SHV
TEM; CTX-M
TEM; CTX-M
TEM; CTX-M
TEM; CTX-M
TEM; CTX-M
TEM; CTX-M
FT: cefotaxime; FC: FT + clavulanate (4 µg/mL); CA: ceftazidime; CC: CA + clavulanate (4 µg/mL).1 Underlined IEF indicates activity over TGC. Nor ciprofloxacin, nitrofurantoin neither fosfomycin resistance was detected. Resistance to TGC was unequivocal in 5/7 strains, with FT more affected than CA. Among these strains the ESBL (n) estimated were CTX-M-2 (4) and CTX.M-derived (pI=8.4) (1). In the remaining 2/7 strains, both TGC were poorly affected and SHV2 was estimated. Current NCCLS breakpoint for FT and CA failed to detect strains with SHV2, by both, diffusion and dilution methods. In all cases the resistance could be transferred. Emergence of TGC resistance could be the result of the use of these drugs against multi-resistant strains during the last years. Antimicrobial susceptibility surveillance of Sf is mandatory.