Samia Hammami

Nosocomial outbreak of imipenem-resistant Pseudomonas aeruginosa producing VIM-2 metallo-β-lactamase in a kidney transplantation unit

BackgroundTwenty four non replicate imipenem resistant P. aeruginosa were isolated between January and November 2008, in the kidney transplantation unit of Charles Nicolle Hospital of Tunis (Tunisia). This study was conducted in order to establish epidemiological relationship among them and to identify the enzymatic mechanism involved in imipenem resistance.MethodsAnalysis included antimicrobial susceptibility profile, phenotypic (imipenem-EDTA synergy test) and genotypic detection of metallo-β-lactamase (MBL) (PCR), O-serotyping and pulsed-field gel electrophoresis.ResultsAll strains showed a high level of resistance to all antimicrobials tested except to colistin. The presence of MBL showed concordance between phenotypic and genotypic methods. Sixteen isolates were identified as VIM-2 MBL-producers and 13 of them were serotype O4 and belonged to a single pulsotype (A).ConclusionsThis study describes an outbreak of VIM-2-producing P. aeruginosa in a kidney transplantation unit. Clinical spread of blaVIM-2 gene is a matter of great concern for carbapenem resistance in Tunisia.

Emergence of carbapenem-resistant OXA-48 carbapenemase-producing Enterobacteriaceae in Tunisia

We screened 21 extended spectrum β-lactamase-producing Enterobacteriaceae with reduced susceptibility to carbapenems for carbapenemase production. Five strains (four Klebsiella pneumoniae and one Citrobacter freundii) showed carbapenemase production, which was identified as OXA-48. The bla(OXA-48) gene was detected on ~54 kb plasmids belonging to IncA/C in one case. Two isolates harboured IS1999, which is involved in bla(OXA-48) mobilization. Carbapenem resistance in enterobacteria should be regarded as an emerging clinical problem in our hospital and necessitates rigorous surveillance in order to limit its spread.

Characterization and Molecular Epidemiology of Extended Spectrum Beta-Lactamase Producing Enterobacter cloacae Isolated from a Tunisian Hospital

In 2009, out of the 66 nonrepetitive Enterobacter cloacae collected at Charles Nicolle hospital in Tunisia, 44 were extended spectrum β-lactamase (ESBL) producers. The aim of the current study was to detect and characterize the genes encoding the ESBLs including blaTEM, blaSHV, and blaCTX-M groups by polymerase chain reaction and sequencing. Pulsed-field gel electrophoresis (PFGE) analysis was used to determine the genetic relatedness between isolates. All strains were susceptible to carbapenems. They were resistant to fluoroquinolones, gentamicin, tobramycin, and trimethoprim+sulfamethoxazole but variably resistant to netilmicin, amikacin, and tetracyclines. Sequence analysis of the polymerase chain reaction products revealed the presence of blaCTX-M-15 (39 strains), blaSHV-12 (6 strains), and blaSHV-27 (1 strain). The coexistence of two ESBLs was observed in two isolates harboring, respectively, SHV-12+CTX-M-15 and SHV-27+CTX-M-15. PFGE revealed 36 unrelated profiles. Diffusion of E. cloacae producing CTX-M-15 ESBL in our hospital is the consequence of dissemination of identical or related plasmids harboring the CTX-M-15 gene.

Characterization of Extended Spectrum β-Lactamase-Producing Escherichia coli in Community-Acquired Urinary Tract Infections in Tunisia

This study was conducted to investigate the molecular epidemiology of extended spectrum β-lactamase (ESBL)-producing Escherichia coli in community-acquired (urinary tract) infections (CA-UTI) in Tunisia. Between January 2007 and December 2009, 15 E. coli isolates were collected at the laboratory of microbiology of Charles Nicolle Hospital of Tunis. Microbial identification was done with conventional methods. Antibiotic susceptibility was determined by disk diffusion method and ESBL detection was done with double-disk synergy test. ESBL typing was performed by polymerase chain reaction (PCR) and sequencing. Phylogenetic groups, virulence factors, and sequence type (ST)131 were determined by PCR. Genetic relatedness between strains was examined by pulsed-field gel electrophoresis (PFGE) after restriction with XbaI. The prevalence of ESBL-producing E. coli in CA-UTI was 0.046%. The majority of isolates were multidrug resistant. ESBL types were CTX-M-15 (n=13) and SHV-12 (n=2). The most common phylogenetic group was B2 (n=11) and virulence score was greater than or equal to 9 in nine strains. PFGE revealed 12 clusters. The majority of isolates (n=14) belonged to ST131 clone and 11 of them were CTX-M producers. In conclusion, this is the first detailed documentation of CA-ESBLs producing E. coli in Tunisia. Of particular concern is the emergence in our community of the highly diffusing CTX-M-15-B2-ST131 E. coli clone, which requires strengthening surveillance measures to countervail this emergent public health problem.

High prevalence of extended-spectrum and plasmidic AmpC beta-lactamase-producing Escherichia coli from poultry in Tunisia

This study was conducted to detect extended spectrum beta-lactamases (ESBLs) and plasmidic AmpC beta-lactamase (pAmpC-BL)-producing Escherichia coli isolates in industrial poultry samples were collected from healthy chickens of the three farms. Samples were inoculated onto desoxycholate-lactose-agar plates supplemented with cefotaxime (2mg/L). E. coli was identified by biochemical and molecular methods and antibiotic susceptibility testing by the disk diffusion method. Genes encoding ESBLs and pAmpC-BL were detected by PCR and sequencing. Phylogenetic groups were determined by triplex PCR. The molecular typing of strains was done by pulsed field gel electrophoresis (PFGE) and Multilocus Sequence Typing (MLST) in those isolates showing different PFGE patterns. Cefotaxime-resistant E. coli isolates were recovered in 48 of 137 fecal samples (35%), and one isolate/sample was further studied. The following beta-lactamase genes were detected: blaCTX-M-1 (29 isolates, isolated in all three farms), blaCTX-M-15 (5 isolates, confined in farm II), blaCTX-M-14 and blaCMY-2 (one isolate and 13 isolates, respectively, in farm III). The 48 cefotaxime-resistant isolates were distributed into phylogroups: B1 (n=21), A (n=15) and D (n=12). PFGE analysis revealed 19 unrelated patterns: 15 different profiles among ESBL-positive strains and 4 among the CMY-2-positive isolates. The following sequence types-associated phylogroups were detected: a) CTX-M-1-positive strains: lineages ST542-B1, ST212-B1, ST58-B1, ST155-B1 and ST349-D; b) CTX-M-15-positive strain: lineage ST405-D; c) CTX-M-14-positive strain: lineage ST1056-B1; d) CMY-2-positive strains: lineages ST117-D, ST2197-A, and ST155-B1. Healthy chickens constitute an important reservoir of ESBL- and pAmpC-BL-producing E. coli isolates that potentially could be transmitted to humans via the food chain or by direct contact.

High Prevalence of Gut Microbiota Colonization with Broad-Spectrum Cephalosporin Resistant Enterobacteriaceae in a Tunisian Intensive Care Unit.

Healthcare-associated infections due to cefotaxime-resistant (CTX-R) Enterobacteriaceae have become a major public health threat, especially in intensive care units (ICUs). Often acquired nosocomially, CTX-R Enterobacteriaceae can be introduced initially by patients at admission. This study aimed to determine the prevalence and genetic characteristics of CTX-R Enterobacteriaceae-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 CTX-R Enterobacteriaceae colonization at admission and once weekly thereafter to identify acquisition. CTX-R Enterobacteriaceae fecal carriage rate was 20.63% (13/63) at admission. Among the 50 non-carriers, 35 were resampled during their hospitalization and the acquisition rate was 42.85% (15/35). Overall, 35 CTX-R Enterobacteriaceae isolates were collected from 28 patients (25 Klebsiella pneumoniae, seven Escherichia coli, and three Enterobacter cloacae strains). Seven patients were simultaneously colonized with two CTX-R Enterobacteriaceae isolates. CTX-M-15 was detected in most of the CTX-R Enterobacteriaceae 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)]. Molecular typing of K. pneumoniae strains, revealed eight Pulsed field gel electrophoresis (PFGE) patterns and four 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 (two strains), ST572 (two strains), ST615 (one strain) and ST617 (one strain). Five colonized patients were infected by CTX-R Enterobacteriaceae (four with the same strain identified from their rectal swab and one with a different strain). Whether imported or acquired during the stay in the ICU, colonization by CTX-R Enterobacteriaceae 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.

Molecular Characterization of Extended Spectrum β-Lactamases, Ampccephalosporinases and Carbapenemases in Klebsiellapneumoniae Causing Bacteremia at Charles Nicolle Hospital of Tunisia.

Purpose of the Study: This study was conducted to detect and characterize the genes encoding extended spectrum β-lactamases and associated β-lactamases (carbapenemases and Ambler Class C β-lactamases). Patients and Methods: In 2011, out of the 65 non-duplicative Klebsiellapneumoniae collected from blood culture at Charles Nicolle hospital of Tunisia, 36 were resistant to 3rd generation cephalosporin. Results: All strains showed a double disk synergy test positive. They were mainly isolated in intensive care unit (31%). They were frequently resistant to most antibiotics tested, except colistin and tigecyclin. Five isolates (13%) showed reduced susceptibility to carbapenems. blaCTX-M-15 was harbored by 35 strains and blaSHV-12 by one. blaCTX-M-15 were associated with blaTEM-1 (n=21), blaOXA-48 and blaCMY-2 (n=1) and blaOXA-48and blaTEM-1 (n=4). The conjugation wassuccessfulfor4/5 strains (3 harboring blaCTX-M-15 and one blaSHV-12). The plasmids carrying the blaCTX-M-15 were assigned to IncN or IncL/M only for 2 strains. The remaining blaCTX-M-15-carrying plasmid was negative for all of the replicons tested as well as the blaSHV-12-carrying plasmid. Conclusion: Our results confirm the spread of CTX-M-15 in our institution. To our knowledge, this is the first report of K. pneumoniae coproducing CTX-M-15, CMY-2 and OXA-48. The implementation of preventive measures against the spread of these multiresistant bacteria is needed.