Background: The production of extended-spectrum β-lactamases (ESBLs), in particular TEM and CTX-M type, by the strains of Proteus spp. is a contributing factor to the emergence of bacterial drug resistance. The aim of this study was to screen and determine of ESBLs genes among strains of Proteus spp. at Tehran hospitals.
Material/Methods: A total of 100 clinical isolates of Proteus species and 1 isolate of Morganella morganii were collected from hospitals in Tehran. Susceptibility of these isolates to various antibiotics was tested by disk diffusion method. Microbroth dilution assay was then used to determine the minimum inhibitory concentration (MIC) of ceftazidime. The phenotypic confirmatory test (PCT) was used for detection of ESBLs. Isolates showing MIC ≥4 µg/ml for ceftazidime were screened for detection of ESBLs genes by PCR. The genomic DNA from ESBL-producing isolates was extracted and analyzed by PFGE.
Results: During the study, 11.8% of the isolates were positive for ESBLs genes. The MICs of ceftazidime-resistant isolates were in the range of 4 to 8 µg/ml. The Frequencies of different genes encoding the ESBLs were as follows: blaCTX-M (n=13), blaTEM (n=10), blaVEB (n=7), blaSHV (n=1), and blaPER (n=0). Analysis of 12 ESBL-producing isolates by PFGE produced 5 distinct clusters designated as I–V.
Conclusions: The Detection of ESBL-producing isolates of Proteus spp. with similar PFGE pattern is alarming and suggests the clonal outbreaks with these strains at Tehran hospitals is likely, necessitating control over prescription of new generation cephalosporins.

Keywords: Microbial Sensitivity Tests, Iran, Hospitals, Gene Frequency, Electrophoresis, Gel, Pulsed-Field - methods, Drug Resistance, Bacterial - genetics, DNA, Bacterial - isolation & purification, Cephalosporins - pharmacology, Ceftazidime - pharmacology, Anti-Bacterial Agents - pharmacology, Polymerase Chain Reaction - methods, Proteus - metabolism, beta-Lactamases - isolation & purification