ABSTRACT
Stenotrophomonas maltophilia has emerged as an important nosocomial pathogen. Treatment of S. maltophilia infections is difficult due to increasing resistance to multiple antibacterial agents. In this 12-month cross-sectional study, from 2017 to 2018, 117 isolates were obtained from different clinical sources and identified by conventional biochemical methods. Antibiotic susceptibility tests were performed according to CLSI 2018. Minocycline disk (30 µg) and E-test strips for ceftazidime, trimethoprim-sulfamethoxazole and chloramphenicol were used. PCR confirmed isolates. The frequency of different classes of integrons (I, II) and resistance gene cassettes (sul1, sul2, dfrA1, dfrA5 and aadB) were determined by PCR. The results showed the highest frequency of resistance to chloramphenicol and ceftazidime with 32 cases (27.11%). Among strains, 12 cases (10.25%) were resistant to trimethoprim-sulfamethoxazole (the lowest frequency of resistance), while 19 (16.1%) isolates were resistant to minocycline. Frequency of sul1, int1, aadB, sul2, dfrA5 genes were 64 (55.08%), 26 (22.3 %), 18 (15.25%) and 17 (14.4%), 14 (11.86%), respectively. int2 and dfrA1 were not detected. Although we have not yet reached a high level of resistance to effective antibiotics such as trimethoprim-sulfamethoxazole, as these resistances can be carried by a plasmid, greater precision should be given to the administration of these antibiotics.
ABSTRACT
The emergence of penicillin non-susceptible Streptococcus pneumoniae (PNSP) isolates can pose significant challenges to today's health-care system. Resistant clonal isolates are disseminated in different regions and countries, and this study was focused on the description of the epidemiological spread of these strains. Clinical samples were collected from individuals admitted to hospitals affiliated to the Tehran University of Medical Sciences, Iran. To investigate the molecular characteristics of PNSP isolates, they were subjected to molecular typing using multi-locus sequence typing (MLST). Serotype distributions of S. pneumoniae isolates were also evaluated by multiplex PCR assay. The most prevalent serotypes in the PNSP isolates were 23F, 19F, 14, 3 and 9V. Two isolates were considered as a non-vaccine serotype. The MLST analysis showed that PNSP isolates belonged to five different clonal complexes (CC180, CC217, CC81, CC63 and CC320) and 42% (5/12) of the sequence types were novel (12936, 12937, 12938, 12939 and 12940). This study indicates the high level of heterogeneity that is present among PNSP isolates. Unexpected high genetic diversity in small populations indicates consecutive diversification of resistant strains.
