A multidrug-resistant Stenotrophomonas maltophilia clinical isolate from Kamuzu Central Hospital, Malawi

Abstract

Background: Stenotrophomonas maltophilia is a significant opportunistic pathogen that is associated with high mortality in immunocompromised individuals. In this study, we describe a multidrug-resistant (MDR) S. maltophilia clinical isolate from Kamuzu Central Hospital (KCH), Lilongwe, Malawi.

Methods: A ceftriaxone and meropenem nonsusceptible isolate (Sm-MW08), recovered in December 2017 at KCH, was referred to the National Microbiology Reference Laboratory for identification. In April 2018, we identified the isolate using MALDI Biotyper mass spectrometry and determined its antimicrobial susceptibility profile using microdilution methods. Sm-MW08 was analysed by S1-PFGE, PCR, and Sanger sequencing, in order to ascertain the genotypes that were responsible for the isolate's multidrug-resistance (MDR) phenotype.

Results: Sm-MW08 was identified as S. maltophilia and exhibited resistance to a range of antibiotics, including all β-lactams, aminoglycosides (except arbekacin), chloramphenicol, minocycline, fosfomycin and fluoroquinolones, but remained susceptible to colistin and trimethoprim-sulfamethoxazole. The isolate did not harbour any plasmid but did carry chromosomally-encoded bla_L1 metallo-β-lactamase and bla_L2 β-lactamase genes; this was consistent with the isolate's resistance profile. No other resistance determinants were detected, suggesting that the MDR phenotype exhibited by Sm-MW08 was innate.

Conclusion: Herein, we have described an MDR S. maltophilia from KCH in Malawi, that was resistant to almost all locally available antibiotics. We therefore recommend the practice of effective infection prevention measures to curtail spread of this organism.

Keywords: Kamuzu Central Hospital; Malawi; Stenotrophomonas maltophilia; carbapenem; ceftriaxone.

Figure 1

Antimicrobial susceptibility profile of S. maltophilia Sm-MW08 clinical isolate recovered at Kamuzu Central Hospital, Malawi. All results were interpreted using CLSI version M100-S24 guidelines except for colistin which was interpreted using EUCAST version 9.0 guidelines and arbekacin which was defined based on previous reports. MIC, minimum inhibitory concentration.

Figure 2

S. maltophilia Sm-MW08 harboured both bla_L1 metallo-β-lactamase and bla_L2 β-lactamase genes. Bacterial DNA was extracted using PowerSoil DNA isolation kit (Qiagen) followed by a multiplex PCR using Ex-Taq DNA polymerase (TaKaRa) at 98 °C initial denaturation for 3 min, 35 cycles of 98 °C denaturation for 30 s, 60°C annealing for 30 s and 72°C extension for 40 s. PCR products were analysed by Electrophoresis on a 2% gel. Primer sequences were designed during this study.