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Detection of Plasmid-mediated AmpC β-lactamases in Nosocomial Isoltes of Gram-negative Bacilli

Department of Pathological Analysis, College of Science, University of Thi-Qar, Iraq
*(e-mail:; Mobile :(+964)78107 38751)
(Received: December 15, 2022; Accepted : January 21, 2023)


Plasmid-mediated AmpC β-lactamases are uninducible in contrast to chromosomal AmpC, and they are frequently linked to widespread multidrug resistance. This study was aimed at detecting plasmid- mediated AmpC β-lactamases by phenotypic and genotypic methods in nosocomial Gram-negative isolates. Two hundred and fifty-four samples were collected from Al-Hussein and Al-Nasiriyah teaching hospitals in Al-Nasiriyah city, 194 from hospitalized patients (urine, burn swab surgical swab and sputum) and 60 samples from hospital environments (from medical staff, beds of patients, floor, ventilators, taps and operation hall). Out of 123 positive cultures of aerobic bacteria, 97 (78.86%) were Gram-negative bacilli; 89 (91.75%) from hospitalized patients and 8 (8.24%) from hospital environments. E. coli was the most common Gram-negative bacilli isolated. Carbapenems (imipenem and meropenem) were the most effective on nosocomial Gram-negative isolates. Out of 75 Gram-negative producing -lactamase isolates; 52 (69.33%) were AmpC -lactamase producers by cefoxitin susceptibility disc, while 28 (37.33%) by the AmpC disc test. The PCR product of plasmid-mediated AmpC -lactamase (blaDHA and blaCIT) genes were detected in 8 (26%) and 10 (33.33%), respectively. E. coli was the most prevalence isolates causing nosocomial infections among Gram-negative bacilli. Carbapenems (imipenem and meropenem) effected on nosocomial Gram-negative isolates. Klebsiella pneumonia was the predominant isolates carrying plasmid-mediated AmpC β-lactamase genes.
Key words : Nosocomial infections, Gram-negative bacilli, AmpC, CIT, DHA