The Antibiotic sensitivity of Stenotrophomonas maltophilia in a 5-year period and investigation of clonal outbreak with PFGE.

INTRODUCTION: Stenotrophomonas maltophilia, which is able to form a biofilm, has mostly been related to catheters when it is the agent in hospital infections; these infections generally present as bacteremia and pneumonia, which may progress with complications and result in death. METHODOLOGY: The study included 153 S. maltophilia strains isolated from clinical samples sent to our hospital laboratory between 1 January 2014 and 30 June 2018. The bacteria were identified and their antibiotic sensitivity was determined using the VITEK-2 automated system. PFGE (Pulsed Field Gel Electrophoresis): The strains isolated from 34 patient clinical samples and from 1 patient bedcover were taken for PFGE examination. RESULTS: The TMP/SXT and levofloxacin sensitivity of 153 S. maltophilia strains was examined. TMP/SXT resistance was determined to be 39% and levofloxacin resistance at 5%. Among 35 S. maltophilia strains, seven genotypes were identified using the PFGE method. While three strains showed a specific genotype profile, the other 32 were determined to consist of four clusters. The cluster rate was therefore 91.4% (32/35). CONCLUSIONS: There was a clonal relationship between the vast majority of the 35 S. maltophilia isolates, which suggests that there was a cross-contamination problem in the hospital. One strain (#4) was identified by dendrogram analysis showed a high rate of similarity to the other strains and was determined to be the common source of the cross-contamination.

[Antimicrobial susceptibility and molecular characterization of multidrug-resistant Acinetobacter baumannii isolated in an university hospital]. / Bir üniversite hastanesinde izole edilen çok ilaca dirençli Acinetobacter baumannii izolatlarinin antimikrobiyal duyarliligi ve moleküler karakterizasyonu.

Acinetobacter baumannii, an aerobic, non-motile, gram-negative bacterium is an important nosocomial pathogen which shows resistance to the most antibiotics. Carbapenems are the most commonly used antibiotics for the treatment of infections caused by this pathogen. However the emergence of resistance against carbapenems in an increasing rate generates serious problems for antimicrobial therapy. The aims of this study were to detect the antibiotic susceptibility, and the presence of blaOXA resistance genes of clinical A.baumannii isolates and to determine the clonal relationship between these isolates. A total of 79 A.baumannii strains isolated from various clinical specimens (37 respiratory tract samples, 11 wound, 10 blood, 8 catheters, 6 tissue, 5 urine, 2 abscess) of the patients admitted to Mersin University Medical School Hospital between May 2012-January 2013, were included in the study. The isolates were identified by conventional methods and Vitek®2 Compact automated system. Antibiotic susceptibilities of the isolates were determined by Kirby-Bauer disk diffusion method and evaluated according to CLSI criteria. The presence of blaOXA-51, blaOXA-23, blaOXA-24, blaOXA-48 and blaOXA-58 genes were detected by an in-house polymerase chain reaction (PCR), and the clonal relationship between the isolates were identified by pulsed-field gel electroforesis (PFGE) using the ApaI restriction enzyme. In our study, all of the isolates were susceptible to colistin, while the resistance rates against piperacillin-tazobactam, ciprofloxacin, imipenem, meropenem, cefoperazone/sulbactam, trimethoprim-sulfamethoxazole, ceftazidime, levofloxacin, gentamicin, tetracycline, ampicillin-sulbactam, amikacin, netilmicin and tigecycline were 97.5%, 96.2%, 94.9%, 94.9%, 93.6%, 91.1%, 88.6%, 86%, 83.6%, 77.2%, 69.6%, 55.7%, 27.8% and 3.8%, respectively. All the isolates were identified as A.baumannii with the OXA-specific PCR and OXA16S rDNA sequence analysis. All of the isolates (100%) harboured blaOXA-51 and 71 (89.9%) harboured blaOXA-23 gene, however they were all negative for blaOXA-24, blaOXA-48 and blaOXA-58 genes. According to PFGE results 10 pulsotypes were identified, of these eight pulsotypes formed 77 (97.5%) similar strains with indistinguishable PFGE profiles ranging between 3-30 [A (n= 30), B (n= 20), C (n= 9), D (n= 5), E (n= 4), F (n= 3), G (n= 3), H (n= 3)]. When compared with the other clones, clones A and B were dominant among the samples and they have exhibited high level of antibiotic resistance. The rest two pulsotypes [I (n= 1), J (n= 1)] were in close relation with the main cluster. No common outbreak isolate was detected, but the relationship between the majority of the strains pointed out that there was a cross contamination problem in our hospital. In conclusion blaOXA-51 and blaOXA-23 were detected as predominant genes responsible from carbapenem resistance in our clinical A.baumannii strains, and it was considered that the high prevalence of clones A and B may constitute a threat in terms of hospitalized patients.