Detection of extended spectrum beta-lactamases-producing isolates and effect of AmpC overlapping.
BACKGROUND
Few reports about the prevalence and genetic basis of extended spectrum beta-lactamases (ESBLs) are available from Saudi Arabia. We sought to determine the prevalence of ESBL-producing Enterobacteriaceae in a university hospital in eastern Saudi Arabia and to characterize the ESBLs produced by these isolates at the molecular level.


METHODS
All clinical isolates of Escherichia coli, Klebsiella spp., and Proteus spp. collected over two years were evaluated for susceptibility to a panel of antimicrobials and were analyzed for the ESBL phenotype using screening and confirmatory tests. ESBL-positive isolates were then screened for the presence of genes encoding CTX-M, SHV, and TEM beta-lactamases by PCR.


CONCLUSIONS
The overall prevalence of ESBL-producing isolates was 4.8% (253/5256). Most isolates (80%) were from the inpatient department. The ESBL phenotype was more frequently detected in K. pneumonia. CTX-M genes were the most prevalent ESBL genes, detected in 82% of the studied isolates. The ESBL producers demonstrated a high multidrug resistance rate (96.6%). In transconjugation assay, the same ESBL gene pattern was transmitted from 29.7% of K. pneumoniae donors to the recipient strain, and the latter exhibited concomitant decreased aminoglycosides and co-trimoxazole susceptibility. We observed the presence of ESBL screen-positive but confirmatory-negative isolates (8.9%). Phenotypic tests for the production of AmpC β-lactamase tested positive in 52% of these isolates. Further studies are needed for appropriate detection of concomitant ESBL and AmpC enzyme production among such isolates. Continued surveillance and judicious antibiotic usage together with the implementation of efficient infection control measures are absolutely required.
Department of Microbiology and Immunology, Faculty of Medicine, Alexandria University, Egypt. drmanal2000@yahoo.com
Manal I
MI
Hassan
Khaled R
KR
Alkharsah
Alhusain J
AJ
Alzahrani
Obeid E
OE
Obeid
Amar H
AH
Khamis
Asim
A
Diab
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D004755:Enterobacteriaceae / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000453:epidemiology* / Q000382:microbiology*; D022761:Gene Transfer, Horizontal; D005838:Genotype; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010641:Phenotype; D015995:Prevalence; D012529:Saudi Arabia / Q000453:epidemiology; D055815:Young Adult; D001618:beta-Lactamases / Q000032:analysis / Q000235:genetics*
D004269:DNA, Bacterial; D001618:beta-Lactamases