Healthcare-associated infections due to cefotaxime-resistant Enterobacteriaceae (CRE) have become a major public health threat, especially in intensive care units (ICUs). Often acquired nosocomially, CRE can be introduced initially by patients at admission. This study aimed to determine the prevalence and genetic characteristics of CRE-intestinal carriage in ICU patients, to evaluate the rate of acquisition of these organisms during hospitalization, and to explore some of the associated risk factors for both carriage and acquisition. Between December 2014 and February 2015, the 63 patients admitted in the ICU of Charles Nicolle hospital were screened for rectal CRE colonization at admission and once weekly thereafter to identify acquisition. CRE fecal carriage rate was 20.63% (13/63) at admission and the acquisition rate was 42.85% (15/35). Overall, 35 CRE isolates were collected from 28 patients (25 Klebsiella pneumoniae, 7 Escherichia coli and 3 Enterobacter cloacae strains). Seven patients were simultaneously colonized with 2 CRE isolates. CTX-M-15 was detected in most of the CRE isolates (30/35, 88.23%).Three strains co-produced CMY-4 and 22 strains were carbapenem-resistant and co-produced a carbapenemase [OXA-48 (n=13) or NDM-1 (n=6)]. All isolates were multidrug resistant. Molecular typing of K. pneumoniae strains, revealed 8 Pulsed field gel electrophoresis (PFGE) patterns and 4 sequence types (ST) [ST101, ST147, ST429 and ST336]. However, E. coli isolates were genetically unrelated and belonged to A (n=2), B1 (n=2) and B2 (n=3) phylogenetic groups and to ST131 (2 strains), ST572 (2 strains), ST615 (one strain) and ST617 (one strain). Five colonized patients were infected by CRE (4 with the same strain identified from their rectal swab and 1 with a different strain). Whether imported or acquired during the stay in the ICU, colonization by CRE is a major risk factor for the occurrence of serious nosocomial infections. Their systematic screening in fecal carriage is mandatory to prevent the spread of these multidrug resistant bacteria.

Background: Actually, no data on the prevalence of plasmid colistin resistance in Tunisia are available among clinical bacteria. Objectives: This study aimed to investigate the current epidemiology of colistin resistance and the spread of the mcr gene in clinical Gram-negative bacteria (GNB) isolated from six Tunisian university hospitals. Methods: A total of 836 GNB strains were inoculated on COL-R agar plates with selective screening agar for the isolation of GNB resistant to colistin. For the selected isolates, mcr genes, beta-lactamases associated-resistance genes and molecular characterisation were screened by PCRs and sequencing. Results: Colistin-resistance was detected in 5.02% (42/836) of the isolates and colistin-resistant isolates harboured an ESBL (bla_CTX-M-15) and/or a carbapenemase (bla_OXA-48, bla_VIM) encoding gene in 45.2% of the cases. The mcr-1 gene was detected in four E. coli isolates (0.59%) causing urinary tract infections and all these isolates also contained the bla_TEM-1 gene. The bla_CTX-M-15 gene was detected in three isolates that also carried the IncY and IncFIB replicons. The genetic environment surrounding the mcr-carrying plasmid indicated the presence of pap-2 gene upstream mcr-1 resistance marker with unusual missing of ISApl1 insertion sequence. The Conclusions: This study reports the first description of the mcr-1 gene among clinical E. coli isolates in Tunisia and provides an incentive to conduct routine colistin susceptibility testing in GNB clinical isolates.

Background: Since 2012, few reports on the molecular epidemiology of Pseudomonas aeruginosa were reported in Tunisia. Objectives: This study aimed to evaluate carbapenem-resistance determinants and molecular epidemiology and to compare the carbapenemase-phenotypic detection methods of multidrug-resistant P. aeruginosa isolates. Methods: During a period of four years (2014 to 2017), all imipenem-ceftazidime-resistant P. aeruginosa isolates were retrospectively selected at the microbial laboratory of Charles Nicolle hospital of Tunis. These isolates were examined by the modified Hodge test, modified carbapenem inactivation method (mCIM), and another mCIM, called CIMTris, and their performance was evaluated using PCR analysis as the gold standard. Results: A total of 35 isolates were recovered among patients hospitalized in different units. All strains were colistin-susceptible.All carbapenem-resistant isolates showed a high-level resistance to carbapenems. CIMTris and mCIM showed 96.15% and 46.15% sensitivity and 44.44% and 100% specificity, respectively, for detecting carbapenemase production.Conclusions: CIMTris is a promising approach for detecting carbapenemase activity in P. aeruginosa and merits further testing. Moreover, this study described the first detection of GES-5- and GES-9-producing P. aeruginosa in Tunisia as well as the co-occurrence of the bla_GES-5 and bla_VIM-11 carbapenemase genes in one isolate. These findings are of great concern because the rapid dissemination of MDR strains represents a major therapeutic and epidemiological threat.