Raoudha Dziri

Characteristics of extended-spectrum β-lactamase (ESBL)- and pAmpC beta-lactamase-producing Enterobacteriaceae of water samples in Tunisia

The presence of extended-spectrum beta-lactamase and plasmid-mediated AmpC beta-lactamase producing Enterobacteriaceae (ESBL-Eb and pAmpC-Eb, respectively) was analyzed in 57 wastewater and 57 surface-water samples in Tunisia. Twenty-four of the 57 wastewater samples (42.1%) and one of the 57 surface-water samples (1.7%, a river that received effluents of a wastewater-treatment-plant) contained ESBL-Eb or pAmpC-Eb; one ESBL/pAmpC-Eb per positive sample was further characterized. Beta-lactamase genes detected were as follows: blaCTX-M-1 (10 Escherichia coli),blaCTX-M-15 (eight E. coli, one Klebsiella pneumoniae, one Citrobacter freundii), blaCTX-M-14 (one E. coli) and blaCMY-2 (four E. coli). The blaTEM-1, blaOXA-1 or blaSHV-1 genes were also found in 72% of these isolates. The ISEcp1, orf477 or IS903 sequences were found upstream or downstream of blaCTX-M genes. Class 1 integrons were present in 16 of the 25 ESBL-Eb/pAmpC-Eb strains (64%), and contained five different gene-cassette arrays. Most of the strains (76%) showed a multiresistant phenotype and qnr genes were identified in four strains. Molecular typing of ESBL/CMY-2-producing E. coli isolates showed 23 different PFGE-patterns and 15 different sequence-types (ST10, ST46, ST48, ST58, ST69, ST101, ST117, ST131, ST141, ST288, ST359, ST399, ST405, ST617, and the new ST4530); these strains were ascribed to phylogroups A (11 isolates), B1 (3 isolates), D (6 isolates) and B2 (3 isolates). From one to five plasmids were detected in each strain (size from 30kb to >240kb) and ESBL or pAmpC genes were transferred by conjugation in 69.5% of the E. coli strains. In conclusion, ESBL-Eb and pAmpC-Eb strains are frequently detected in wastewater samples and they might be a source for dissemination in other environments with repercussion in public health.

Environmental Staphylococcus aureus contamination in a Tunisian hospital

One hundred hospital environment samples were obtained in 2012 in a Tunisian hospital and tested for Staphylococcus aureus recovery. Antimicrobial resistance profile and virulence gene content were determined. Multilocus-sequence-typing (MLST), spa-typing, agr-typing and SmaI-pulsed-field gel electrophoresis (PFGE) were performed. Two methicillin-resistant S. aureus (MRSA) isolates typed as: ST247-t052-SCCmecI–agrI were recovered from the intensive care unit (ICU). Ten samples contained methicillin-susceptible S. aureus (MSSA) and these samples were collected in different services, highlighting the presence of the tst gene encoding the toxic shock syndrome toxin as well as the lukED, hla, hlb, hld and hlgv virulence genes in some of the isolates. In conclusion, we have shown that the hospital environment could be a reservoir contributing to dissemination of virulent S. aureus and MRSA.

Characterization of extended-spectrum β-lactamase (ESBL)-producing Klebsiella, Enterobacter, and Citrobacter obtained in environmental samples of a Tunisian hospital.

The assessment of the hospital environment as a reservoir of ESBL-producing Enterobacteriaceae in Tunisian hospitals is scarcely analyzed, except for Escherichia coli. The aim of this study was to evaluate the presence of ESBL-producing non-E. coli Enterobacteriaceae (ESBL-EbNoEc) in 300 samples of abiotic surfaces and the hands of patients and staff of a Tunisian Hospital, and to characterize the ESBL genes of the recovered isolates. ESBL-EbNoEc were recovered in 28 of 300 (9.3%) analyzed samples and were identified as Klebsiella pneumoniae (n= 11), Enterobacter cloacae (n=11), Citrobacter freundii (n=4) and Klebsiella oxytoca (n=2). The bla genes identified by PCR and sequencing among the strains were as follows: 11 K.pneumoniae strains [blaCTX-M-15+ blaTEM-1+ blaSHV-11 (n=6); blaCTX-M-15+ blaTEM-1+ blaSHV-28 (n=3); blaCTX-M-15+ blaTEM-1+ blaSHV-1 (n=2)], 11 E. cloacae strains [blaCTX-M-15 (n=6); blaCTX-M-15+ blaTEM-1b (n=2); blaCTX-M-15+ blaTEM-1b+ blaOXA-1 (n=1);blaCTX-M-15+ blaOXA-1 (n=1);blaSHV-12 (n=1)], 4 C. freundii strains [blaCTX-M-15] and 2 K. oxytoca strains [blaCTX-M-15 (n=1); blaSHV-12 (n=1)]. The ISEcp1 and orf477 sequences were identified upstream and downstream of the blaCTX-M-15 gene, respectively, in 3 K. pneumoniae and 3 E. cloacae isolates. The PFGE analysis demonstrated three unrelated pulsotypes in K. pneumoniae strains and five pulsotypes in E. cloacae. The uncontrolled dissemination of ESBL-producing bacteria, even in the hospital environment, has become a real problem and new strategies and hygienic rules are needed to stop this bacterial dissemination.

Metallo-β-lactamases and class D carbapenemases in south-east Tunisia: Implication of mobile genetic elements in their dissemination

Carbapenem resistance in Gram-negative bacteria constitutes a major clinical problem. We characterized molecular features among carbapenem-resistant Gram-negative clinical isolates collected from Southeastern Tunisian Island Hospital. Eighteen carbapenem-resistant clinical isolates (13 Klebsiella pneumoniae, 1 Proteus mirabilis, 1 Enterobacter cloacae, 3 Acinetobacter baumannii) were recovered during April 2015-August 2016. Molecular characterization of antimicrobial resistance was performed using polymerase chain reaction (PCR) and sequencing. Molecular typing of carbapenemase-producing K. pneumoniae was performed by pulsed-field gel electrophoresis (PFGE) after XbaI digestion and multilocus sequence typing (MLST). Conjugation experiments were conducted and type/number/size of plasmids were characterized by PCR-Based-Replicon-Typing and PFGE after S1 digestion. Carbapenemase genes were detected in K. pneumoniae [blaNDM-1(8), blaNDM-1+blaOXA-48(1), blaOXA-48(4)], P. mirabilis [blaOXA-48(1)], E. cloacae [blaVIM-2(1)] and A. baumannii [blaOXA-23(3)]. K. pneumoniae isolates were typed as ST15, ST1412 and ST147 and showed seven different pulsotypes. The genetic structure surrounding blaNDM-1 was composed of ISAba125 and ble. The blaVIM-2 carried by E. cloacae was located within the variable region of a class1 integron and blaOXA-48 gene was inserted into Tn1999.2. IncA/C and IncFIIA replicons were implicated in dissemination of blaNDM-1 and a non-typeable 48.5 kb plasmid in the propagation of blaOXA-48. The emergence of carbapenemase-producing Gram-negative species in a Tunisian hospital shows the need for preventive strategies and hygiene measures to minimize their spread. Although conjugative plasmids play an important role in rapid carbapenemase genes dissemination, other mobile genetic elements, such as insertion sequences, transposons and integrons, are involved in acquisition of these resistances.