African Journal of

  • Abbreviation: Afr. J. Biotechnol.
  • Language: English
  • ISSN: 1684-5315
  • DOI: 10.5897/AJB
  • Start Year: 2002
  • Published Articles: 12258

Full Length Research Paper

Biochemical characterization of a cefotaxime-hydrolysing β-lactamase encoded by a conjugative plasmid

Amel Bourouis1*, Hela Chihi1, Nehed Ben-Achour1, Chérifa Belhadj1, Mohamed Ben-Moussa2 and Omrane Belhadj1
  1Laboratoire de Biochimie et de Technobiologie, Faculté des Sciences de Tunis, Campus  Universitaire, 2092 El-Manar II, Tunisie. 2Service de Bactériologie, Hôpital Militaire de Tunis, 1089 Monfleury, Tunisie.
Email: [email protected]

  •  Accepted: 27 March 2009
  •  Published: 17 May 2010



During the nosocomials infections occurring in the intensive care unit of the military hospital of Tunis in 2005, the Enterobacter cloacae BW 1150 strain was isolated from a stool culture. This strain was found to have a high level resistance to broad-spectrum β-lactams. Resistance profile against the various families of antibiotics was determined using the disc diffusion test. The minimal inhibitory concentrations 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 BW 1150 strain showed 1 β- lactamase activity with an isoelectric piont (pI) of about 8. This activity was transferred by conjugation and was highly expressed in the transconjugant.


Key words: β-lactams, β-lactamases,  cefotaximase,  Enterobacter cloacae.