Antibiotic Resistance Pattern and Biochemical Characterisation of an Extended-Spectrum β-Lactamase in an Intensive Care Unit | Chapter 6 | Microbiology and Biotechnology Research: An Overview Vol. 5

 

β-Lactamases production by bacteria remains the most important mechanism of natural and acquired resistance to β-lactams, particularly in Gram-negative bacteria. Over time, these β-enzymes have evolved in parallel with the massive use of β-lactams. Thus, we have witnessed the emergence and rapid diversification of new enzymes accompanied by broadening of their spectrum of activity and their diffusion among bacteria. Gram-negative bacteria producing beta-lactamase are of significant concern, particularly due to their prevalence in nosocomial infections. Remarkably, Enterobacter cloacae (E. cloacae) is recognised as a nosocomial pathogen that causes significant infections in hospitals, especially in recent years. During the nosocomial infections occurring in the intensive care unit of the military hospital of Tunis, the Enterobacter cloacae strain was isolated from a stool culture. This strain was found to have a high level of resistance to broad-spectrum β-lactams. The antibiotic susceptibility of the E. cloacae strain was determined on Mueller-Hinton agar by the standard disk diffusion procedure. Resistance profile against the various families of antibiotics was determined using the disc diffusion test. The minimal inhibitory concentration values showed that this strain was resistant to the β-lactams such as ampicillin and the extended spectrum cephalosporins (cefotaxime, ceftriaxon and cefpirome). Analysis of this strain by the disk diffusion test revealed synergies between amoxicillin-clavulanate (AMX-CA) and ceftriaxon, ceftazidime and cefotaxime. Cell sonicate of this isolate is very active against cefotaxime and showed a specific activity (AS) of 7.54 U/mg for the same antibiotic. This activity was inhibited by the sulbactam and the clavulanic acid. Isoelectrofocusing methods revealed that the crude extract of the E. cloacae strain showed 1 β- β-lactamase activity with an isoelectric point (pI) of about 8. This activity was transferred by conjugation and was highly expressed in the transconjugant. These findings provide an evaluation of the biochemical characteristics of a cefotaxime-hydrolysing β-lactamase encoded by a conjugative plasmid in Enterobacter cloacae, emphasising the need for continuous surveillance in a hospital setting.

 

 

Author(s) Details

Bourouis Amel
Laboratoire de Biochimie et Biotechnologie LR01ES05, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 El Manar II, Tunisie.

 

Chihi Hela
Laboratoire de Biochimie et Biotechnologie LR01ES05, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 El Manar II, Tunisie.

 

Ben-Achour Nehed
Laboratoire de Biochimie et Biotechnologie LR01ES05, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 El Manar II, Tunisie.

 

Bargellil Farouk
Service de Bactériologie, Hôpital Militaire de Tunis, 1089 Monfleury, Tunisie.

 

Naghmouchi Karim
Laboratoire de Biochimie et Biotechnologie LR01ES05, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 El Manar II, Tunisie.

 

Ben-Mehrez Kamel
Laboratoire de Biochimie et Biotechnologie LR01ES05, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 El Manar II, Tunisie.

 

 

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