Wejdène Mansour1, Marisa Haenni2, Estelle Saras2, Raoudha Grami3, Yosra Mani4, Anis Ben Haj Khalifa5, Souhail El Atrouss6, Mohamed Kheder7, Mohamed Fekih Hassen6, Noureddine Boujâafar8, Olfa Bouallegue9, Jean-Yves Madec2. 1. Unité de recherche: Résistances bactériennes émergentes et sécurité des soins «UR12SP37», Laboratoire de microbiologie, Hôpital Universitaire Sahloul, Sousse, Tunisia; Institut Supérieur des Sciences Appliquées et de Technologie de Mahdia, Hiboun, Tunisia. Electronic address: wejdene.mansour@gmail.com. 2. French Agency for Food, Environmental and Occupational Health & Safety (ANSES), Unité antibiorésistance et virulence bactériennes, Lyon, France. 3. Unité de recherche: Résistances bactériennes émergentes et sécurité des soins «UR12SP37», Laboratoire de microbiologie, Hôpital Universitaire Sahloul, Sousse, Tunisia; French Agency for Food, Environmental and Occupational Health & Safety (ANSES), Unité antibiorésistance et virulence bactériennes, Lyon, France. 4. Unité de recherche: Résistances bactériennes émergentes et sécurité des soins «UR12SP37», Laboratoire de microbiologie, Hôpital Universitaire Sahloul, Sousse, Tunisia. 5. Laboratoire de microbiologie, Hôpital Tahar Sfar, Mahdia, Tunisia; Faculté de pharmacie de Monastir, Université de Monastir, Monastir, Tunisia. 6. Service de réanimation, Hôpital Tahar Sfar, Mahdia, Tunisia. 7. Laboratoire de microbiologie, Hôpital Tahar Sfar, Mahdia, Tunisia. 8. Unité de recherche: Résistances bactériennes émergentes et sécurité des soins «UR12SP37», Laboratoire de microbiologie, Hôpital Universitaire Sahloul, Sousse, Tunisia; Faculté de pharmacie de Monastir, Université de Monastir, Monastir, Tunisia. 9. Unité de recherche: Résistances bactériennes émergentes et sécurité des soins «UR12SP37», Laboratoire de microbiologie, Hôpital Universitaire Sahloul, Sousse, Tunisia; Faculté de médecine de Sousse, Université de Sousse, Sousse, Tunisia.
Abstract
OBJECTIVES: Mechanisms of colistin and carbapenem resistance among a collection of Klebsiella pneumoniae isolates recovered in a university hospital in Tunisia were studied. METHODS: In vitro antimicrobial susceptibility testing, S1 nuclease pulsed-field gel electrophoresis (S1-PFGE), Southern blotting and PCR-based replicon typing (PBRT) were performed. Extended-spectrum β-lactamases (ESBLs), carbapenemases, AmpC-type enzymes and mgrB genes were detected by PCR and sequencing. Clonality of isolates was assessed by PFGE and multilocus sequence typing (MLST). RESULTS: Of 940 Enterobacteriaceae isolates recovered from June 2015 to March 2016 in Tahar Sfar Hospital (Mahdia, Tunisia), 220 were identified as K. pneumoniae, among which 29 were carbapenem-resistant. Carbapenem resistance was mostly due to expression of blaOXA-48 or blaOXA-204 in combination with blaCMY-4. Seven isolates carried blaNDM-1, of which two also harboured blaOXA-48, together with blaCMY-16 in one of them. All but two isolates also harboured blaCTX-M-15. All 20 blaOXA-48 genes were part of transposon Tn1999 on an IncL plasmid, whereas blaOXA-204 was found on transposon Tn2016 on an IncA/C plasmid. Finally, all blaNDM-1 genes were located within a Tn125 transposon on an IncFIIk plasmid. Interestingly, 7 (24.1%) of 29 carbapenem-resistant isolates were resistant to colistin, of which 6 were assigned to ST101, had similar PFGE profiles and presented the same 2-kb insertion in the mgrB gene. CONCLUSIONS: This study reports, for the first time in Tunisia, the full molecular characterisation of colistin resistance in K. pneumoniae. There is an urgent need for control measures and prudent use of colistin in treatment of infections with carbapenemase-producing K. pneumoniae.
OBJECTIVES: Mechanisms of colistin and carbapenem resistance among a collection of Klebsiella pneumoniae isolates recovered in a university hospital in Tunisia were studied. METHODS: In vitro antimicrobial susceptibility testing, S1 nuclease pulsed-field gel electrophoresis (S1-PFGE), Southern blotting and PCR-based replicon typing (PBRT) were performed. Extended-spectrum β-lactamases (ESBLs), carbapenemases, AmpC-type enzymes and mgrB genes were detected by PCR and sequencing. Clonality of isolates was assessed by PFGE and multilocus sequence typing (MLST). RESULTS: Of 940 Enterobacteriaceae isolates recovered from June 2015 to March 2016 in Tahar Sfar Hospital (Mahdia, Tunisia), 220 were identified as K. pneumoniae, among which 29 were carbapenem-resistant. Carbapenem resistance was mostly due to expression of blaOXA-48 or blaOXA-204 in combination with blaCMY-4. Seven isolates carried blaNDM-1, of which two also harboured blaOXA-48, together with blaCMY-16 in one of them. All but two isolates also harboured blaCTX-M-15. All 20 blaOXA-48 genes were part of transposon Tn1999 on an IncL plasmid, whereas blaOXA-204 was found on transposon Tn2016 on an IncA/C plasmid. Finally, all blaNDM-1 genes were located within a Tn125 transposon on an IncFIIk plasmid. Interestingly, 7 (24.1%) of 29 carbapenem-resistant isolates were resistant to colistin, of which 6 were assigned to ST101, had similar PFGE profiles and presented the same 2-kb insertion in the mgrB gene. CONCLUSIONS: This study reports, for the first time in Tunisia, the full molecular characterisation of colistin resistance in K. pneumoniae. There is an urgent need for control measures and prudent use of colistin in treatment of infections with carbapenemase-producing K. pneumoniae.