High rates of intestinal colonization with carbapenemase producing Enterobacteriaceae in hematopoietic stem cell transplant recipients.

Carbapenem resistant Enterobacteriaceae (CRE) are major human pathogens because, these cause high number of difficult-to-treat infections. Allogeneic hematopoietic stem cell transplant (AHSCT) recipients are highly exposed to these type of bacteria. The aim of our study was to investigate prevalence of CRE colonization in AHSCT patients and to determine genes encoding carbapenem resistance. A retrospective study conducted between January 2015 and December 2019, involved 55 patients colonized with CRE strains. We determined the rate of antibiotic resistance according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) and the carbapenem resistance genes by PCR assays for genes encoding most frequent ß-lactamases namely, blaGES, blaKPC, blaIMI, blaNDM, blaVIM, blaIMP and blaOXA-48. Eighty-one episodes of CRE colonization were recorded in 55 patients, mainly suffering from acute leukaemia (30%) and aplastic anemia (26%). History of hospitalization was noted in 80 episodes. Prior antibiotic treatment, severe neutropenia and corticosteroid therapy were respectively found in 94%, 76% and 58% of cases. Among the 55 patients, six patients (11%) developed a CRE infection. The CRE responsible for colonization were carbapenemase producers in 90% of cases. They belonged mostly to Klebsiella pneumoniae (61/81) and Escherichia coli species (10/81). Antibiotic resistance rates were 100% for ertapenem, 53% for imipenem, 42% for amikacin, 88% for ciprofloxacin and 27% for fosfomycin. Molecular study showed that blaOXA-48 gene was the most frequent (60.5%), followed by blaNDM (58%). Thirty-five (43%) strains were co-producers of carbapenemases. In our study, we report a high rate of CRE intestinal colonization in AHSCT recipients of our center.

Diagnostic low-dose X-ray radiation induces fluoroquinolone resistance in pathogenic bacteria.

PURPOSE: The crisis of antibiotic resistance has been attributed to the overuse or misuse of these medications. However, exposure of bacteria to physical stresses such as X-ray radiation, can also lead to the development of resistance to antibiotics. The present study aimed to investigate the effect of exposure to diagnostic low-dose X-ray radiation on the bacterial response to antibiotics in two pathogenic bacteria, including the Gram-positive Staphylococcus aureus and Gram-negative Salmonella enteritidis. METHODS: The bacterial strains were exposed to diagnostic X-ray doses of 5 and 10 mGy, which are equivalent to the doses delivered to patients during conventional radiography X-ray examinations in accordance with the European guidelines on quality criteria for diagnostic radiographic images. Following exposure to X-ray radiation, the samples were used to estimate bacterial growth dynamics and perform antibiotic susceptibility tests. RESULTS: The results indicate that exposure to diagnostic low-dose X-ray radiation increased the number of viable bacterial colonies of both Staphylococcus aureus and Salmonella enteritidis and caused a significant change in bacterial susceptibility to antibiotics. For instance, in Staphylococcus aureus, the diameter of the inhibition zones for marbofloxacin decreased from 29.66 mm before irradiation to 7 mm after irradiation. A significant decrease in the inhibition zone was also observed for penicillin. In the case of Salmonella enteritidis, the diameter of the inhibition zone for marbofloxacin was 29 mm in unexposed bacteria but decreased to 15.66 mm after exposure to 10 mGy of X-ray radiation. Furthermore, a significant decrease in the inhibition zone was detected for amoxicillin and amoxicillin/clavulanic acid (AMC). CONCLUSION: It is concluded that exposure to diagnostic X-ray radiation can significantly alter bacterial susceptibility to antibiotics. This irradiation decreased the effectiveness of fluoroquinolone and ß-lactam antibiotics. Specifically, low-dose X-rays made Staphylococcus aureus resistant to marbofloxacin and increased its resistance to penicillin. Similarly, Salmonella Enteritidis became resistant to both marbofloxacin and enrofloxacin, and showed reduced sensitivity to amoxicillin and AMC.

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.

Coagulase negative Staphylococcus bacteremia in hematopoietic stem cell transplant recipients: Clinical features and molecular characterization.

The purpose of our study was to investigate the epidemiology of coagulase negative staphylococci (CoNS) responsible for bacteremia in hematopoietic stem cell transplant (HSCT) recipients and to determine the prevalence and the genetic background of methicillin resistance. The prevalence of CoNS bacteremia was 7.4% (54/728), higher in allograft (10.7%) than in autograft (4.7%) recipients. A sepsis or a septic shock were observed in 9% of cases. No deaths were attributable to CoNS bacteremia. The methicillin resistance rate was 81%. All MR-CoNS, harbored mecA gene and 90% were typeable with SCCmec typing using PCR amplification. The SCCmec type IV was the most frequent (44%). Clonal dissemination of MR- Staphylococcus epidermidis strains was limited. Our study showed a low prevalence and favorable outcome of CoNS bacteremia in HSCT recipients with limited clonal diffusion. However, they were associated with a significant rate of severe infections and a high rate of methicillin resistance, mediated by SCCmec IV element in most cases.

Multidrug resistant bacteremia in hematopoietic stem cell transplant recipients.

BACKGROUND: Bacteremia become fearsome in hematopoietic stem cell transplant (HSCT) recipients with the emergence of multidrug-resistant (MDR) strains. AIM: Our purpose was to investigate the prevalence of MDR bacteremia in HSCT recipients at the Tunisian National Bone Marrow Transplant Center, associated factors and attributable mortality rate. METHODS: Our retrospective study (January 2010-December 2017) included all MDR bacteremia in the Hematology department. MDR rods were: extended spectrum beta-lactamase producing Enterobacterales (ESBL-E), P. aeruginosa and A. baumannii resistant to at least three families of antibiotics, methicillin-resistant S. aureus (MRSA) and vancomycin resistant E. faecium (VRE). RESULTS: The prevalence of MDR bacteremia among HSCT recipients was 5.9% (48/816) with a stable trend over time (rs=0.18). Neutropenia, prior hospitalization, prior antibiotherapy and prior colonization with MDR pathogens were observed in 59%, 58%, 48% and 31% of cases, respectively. Imipenem was the most prescribed first-line antibiotic (50%). The attributable mortality rate was 13%. MDR bacteria (n=48) belonged to ESBL-E (60%), P. aeruginosa (19%), A. baumannii (13%), MRSA (4%) and VRE (4%). For ESBL-E and P. aeruginosa, the rates of antibiotic resistance were respectively, 17% and 44% to imipenem, 31% and 56% to amikacin and 15% and 0% to colistin. Strains of A. baumannii were susceptible only to colistin. The MRSA (n=2) were resistant to ciprofloxacin and gentamicin and susceptible to glycopeptides. The VRE (n=2) were susceptible to linezolid and tigecycline. CONCLUSION: Low prevalence of MDR bacteremia in HSCT recipients but high attributable mortality rate, requiring reinforcement of hygiene measures.