Occurrence of IMP-8, IMP-10, and IMP-13 metallo-β-lactamases located on class 1 integrons and other extended-spectrum β-lactamases in bacterial isolates from Tunisian rivers

Abstract

Background: Antibiotic-resistant bacteria have been surveyed widely in water bodies, but few studies have determined the diversity of antibiotic-resistant bacteria in river waters. This study was undertaken to investigate the origin of resistance among polluted river bacterial isolates in Tunisia. Methods: In this study 128 isolates resistant to β-lactam antibiotics were obtained from 2 polluted rivers in the north of Tunisia. Isolates were identified using Phoenix phenotyping criteria. The occurrence of bla_TEM, bla_SHV, bla_CTX-M, bla_CMY, bla_VIM, and bla_IMP was studied by polymerase chain reaction (PCR) amplification and sequencing, and the genetic relatedness of the 16 IMP-producing Klebsiella pneumoniae isolates was analyzed by comparison of XbaI pulsed-field gel electrophoresis (PFGE) profiles. Results: Using Phoenix phenotyping criteria, diverse genera of bacteria were identified with different rates of prevalence and with different minimum inhibitory concentrations against different antibiotics. The occurrence of bla_TEM, bla_SHV, bla_CTXM, bla_CMY, bla_VIM, and bla_IMP genes was confirmed. The DNA sequences upstream and downstream of bla_IMP genes were determined, revealing that all IMP-encoding genes constituted the first cassette of class 1 integrons, followed by aacA gene cassettes encoding aminoglycoside resistance. Comparison of PFGE profiles showed that only 2 of the isolates were clonal, the other 14 displaying unique profiles. The bla_CTX-M gene was the most dominant of the extended-spectrum β-lactamase (ESBL) genes, while the bla_TEM gene was the second-most dominant. Conclusion: The discovery of highly diverse ESBL-producing bacteria and metallo-β-lactamases, particularly bla_IMP, in polluted river water raises alarms with regard to the potential dissemination of antibiotic-resistant bacteria in communities through river environments.

Keywords::

• IMP-8
• IMP-10
• IMP-13
• polluted-river
• Tunisia

Declaration of interest: This work was supported and financed by the Ministry of Higher Education and Research of Tunisia and the Ministry of Sciences, Technology and Higher Education of Portugal.