An intermittent outbreak of Burkholderia cepacia contaminating hematopoietic stem cells resulting in infusate-related blood stream infections.

Microbial contamination of hematopoietic stem cells (HSC), used for autologous and allogenic transplantations, is rare but could cause serious blood stream infection in transplanted patients. These infections occur immediately, or later following the formation of biofilm on the catheter lumen. The present study describes an intermittent B. cepacia HSC contamination associated with nosocomial bacteremia: from October 2011 to April 2015, 17 B. cepacia strains were isolated in HSC bags (n = 14) and blood cultures (n = 3) in patients hospitalized in the National Bone Marrow Transplant Center. Two epidemiologic investigations in the National Blood Transfusion Center, allowing the isolation of three strains in hygiene samples, and four interventions in this institution were done. To identify the source of this contamination, a molecular investigation was done on 23 B. cepacia strains isolated in our center from 2007 to 2015. PFGE analysis revealed five clusters. The major cluster included 18 strains isolated from HSC bags (n = 14), blood culture (n = 1), and water cans and bath (n = 3). The second cluster (B) including only two and the remaining clusters (C, D, and E) contained single strains isolated before the epidemic period. These findings confirmed that the origin of the outbreak was the contaminated water used in the water bath during the thawing step of HSC bags. Based on this result, new sterile water was used for every defrosting, but HSC bags contamination persisted. In May 2015, the water bath was replaced with a dry bath and no B. cepacia strain was isolated from that date to April 2020.

Extended spectrum beta-lactamase-producing Enterobacteriaceae infections in hematopoietic stem cell transplant recipients: Epidemiology and molecular characterization.

BACKGROUND: Extended spectrum ß-lactamase-producing Enterobacteriaceae (ESBL-E) create a therapeutic challenge and have high potential for dissemination. The purpose of our study was to investigate the epidemiology of these infections in hematopoietic stem cell transplant (HSCT) recipients and to determine the genes encoding ESBL. MATERIAL/METHODS: This retrospective study comprised adult patients hospitalized at the National Bone Marrow Transplant Center (NBMTC) and infected with ESBL-E post-HSCT between January 2006 and December 2016. The search for the ESBL and carbapenemase genes was performed by polymerase chain reaction (PCR) amplification. Molecular typing was performed by pulsed field gel electrophoresis (PFGE) after digestion with XbaI. RESULTS: Forty ESBL-E were responsible for infections in 34 HSCT recipients (3.3% of total HSCT recipients). Prior hospital stay, prior antibiotic therapy and prior colonization with ESBL-E were reported in 62.5%, 70% and 50% of the infectious episodes, respectively. The initial antibiotic treatment was appropriate in 67.7% of cases. Imipenem was the most prescribed antibiotic (64.5%). The mortality rate due to ESBL-E infection was 8.8%. The ESBL-E, isolated mainly from blood cultures (40%), belonged mostly to K. pneumoniae (n=19) and E. coli (n=17). Associated antibiotic resistance rates were 17.5% for ertapenem, 85% for ciprofloxacin and 30% for amikacin. The predominant gene encoding ESBL was blaCTX-M (55%). Among the seven carbapenem-resistant strains, four had the blaOXA-48 gene and two the blaKPC gene. There was no clonal relationship between the strains. CONCLUSION: There was low prevalence of ESBL-E infections in HSCT recipients in our center, with no epidemic distribution but non-negligible mortality rate.

Description of a novel mutation in the atpC gene in optochin-resistant Streptococcus pneumoniae strains isolates from Tunisia.

Identification of Streptococcus pneumoniae among other α-haemolytic streptococci is based on phenotypic or genotypic characteristics such as colony morphology, bile solubility and optochin susceptibility. This study reports three optochin-resistant S. pneumoniae strains isolated from immunocompromised patients in Tunisia. The three isolates were positive for the bile solubility test. Biochemical identification with API® 20 Strep was not discriminatory for two strains. The three strains had different serotypes (6C, 19F and 23F) and three different sequence types (ST386, ST320 and ST326). Sequencing of the atpA and atpC genes for each strain showed only modification in atpC. The mutations Met13→Val or Val48→Ile were observed in two strains. However, in the third strain a novel type of mutation (Val15→Ile) was identified.

Molecular characterisation and epidemiology of extended-spectrum ß-lactamase-producing Klebsiella pneumoniae isolates from immunocompromised patients in Tunisia.

OBJECTIVES: This study investigated the prevalence of extended-spectrum ß-lactamase-producing Klebsiella pneumoniae (ESBL-KP) strains in the National Bone Marrow Transplant Center of Tunis between 2002 and 2011 as well as their associated antimicrobial resistance patterns and molecular features. METHODS: Antimicrobial susceptibility was determined by the disk diffusion method according to CA-SFM guidelines. All of the strains were screened for ß-lactamase genes, plasmid-encoded AmpC genes and integrons. Carbapenemase genes were analysed by PCR and sequencing for strains showing reduced susceptibility to ertapenem. Genetic relatedness was determined by pulsed-field gel electrophoresis (PFGE) and multilocus sequencing typing (MLST). RESULTS: A total of 128 non-repetitive ESBL-KP strains (23.4%) responsible for infection or colonisation were recovered among 548 K. pneumoniae strains. The isolates were also multidrug-resistant. Molecular analysis revealed the prevalence of blaSHV-type (92.2%), followed by blaOXA-1 (81.3%) and blaCTX-M-1 group (73.4%). Four ertapenem-resistant ESBL-KP strains (3.1%) carried the blaOXA-48 gene associated with the blaCTX-M-15 gene. Class 1 integrons were the most prevalent among the isolates (85.2%). High diversity was demonstrated by PFGE with limited clonal dissemination of 1 major (n=13 strains) and 11 minor clusters (each comprising 2-3 strains). MLST of representative strains also showed high diversity with two main epidemic clones: ST15, associated with the major cluster; and ST101, associated with five minor clusters (n=11 strains). CONCLUSIONS: This study provides relevant information on the epidemiology of ESBL-KP strains in oncohaematology patients, of which 18.8% belonged to the specific CTX-M-15 K. pneumoniae clones ST15 and ST101.

First Description of KPC-2-Producing Escherichia coli and ST15 OXA-48-Positive Klebsiella pneumoniae in Tunisia.

The aim of this study was to investigate the molecular features among Klebsiella pneumoniae and Escherichia coli strains showing a resistant/intermediate-resistant phenotype to ertapenem (R/IR-ERT), implicated in colonization/infection in patients of the Hematology and Graft Units of the National Bone Marrow Transplant Center of Tunisia (3-year period, 2011-2014). The major carbapenemase, extended-spectrum beta-lactamase, and plasmidic AmpC beta-lactamase genes were analyzed and characterized by PCR and sequencing. Genetic relatedness was determined by pulsed-field gel electrophoresis (PFGE) using XbaI and multilocus sequencing typing. The blaOXA-48 and blaKPC carbapenemase genes were detected among R/IR-ERT isolates. All R/IR-ERT K. pneumoniae strains (n = 19) had blaOXA-48 gene, and 14/19 strains also harbored the blaCTX-M-15 gene. Eight different PFGE patterns were detected among these K. pneumoniae isolates, and they showed eight different sequences types, ST11 and ST15 being the most prevalent ones. Two out of three R/IR-ERT E. coli isolates carried blaOXA-48 and one coproduced the blaCTX-M-15 gene. One E. coli strain, ascribed to the new sequence type ST5700, harbored the blaKPC-2 gene. E. coli isolates were not clonally related and belonged to different sequence types (ST5700, ST227, and ST58). To our knowledge, this is the first report in Tunisia of either KPC-2 carbapenemase in E. coli or OXA-48 carbapenemase in K. pneumoniae of lineage ST15.