Stenotrophomonas maltophilia from Nepal Producing Two Novel Antibiotic Inactivating Enzymes, a Class A β-Lactamase KBL-1 and an Aminoglycoside 6′-N-Acetyltransferase AAC(6′)-Iap

Seven drug-resistant strains of Stenotrophomonas maltophilia were isolated from patients at two university hospitals in Nepal. S. maltophilia JUNP497 was found to encode a novel class A β-lactamase, KBL-1 (Kathmandu β-lactamase), consisting of 286 amino acids with 52.98% identity to PSV-1. Escherichia coli transformants expressing bla(KBL-1) were less susceptible to penicillins. The recombinant KBL-1 protein efficiently hydrolyzed penicillins. The genomic environment surrounding bla(KBL-1) was a unique structure, with the upstream region derived from strains in China and the downstream region from strains in India. S. maltophilia JUNP350 was found to encode a novel 6′-N-aminoglycoside acetyltransferase, AAC(6′)-Iap, consisting of 155 amino acids with 85.0% identity to AAC(6′)-Iz. E. coli transformants expressing aac(6′)-Iap were less susceptible to arbekacin, amikacin, dibekacin, isepamicin, neomycin, netilmicin, sisomicin and tobramycin. The recombinant AAC(6′)-Iap protein acetylated all aminoglycosides tested, except for apramycin and paromomycin. The genomic environment surrounding aac(6′)-Iap was 90.99% identical to that of S. maltophilia JV3 obtained from a rhizosphere in Brazil. Phylogenetic analysis based on whole genome sequences showed that most S. maltophilia isolates in Nepal were similar to those isolates in European countries, including Germany and Spain. IMPORTANCE The emergence of drug-resistant S. maltophilia has become a serious problem in medical settings worldwide. The present study demonstrated that drug-resistant S. maltophilia strains in Nepal harbored novel genes encoding a class A β-lactamase, KBL-1, or a 6′-N-aminoglycoside acetyltransferase, AAC(6′)-Iap. Genetic backgrounds of most S. maltophilia strains in Nepal were similar to those in European countries. Surveillance of drug-resistant S. maltophilia in medical settings in Nepal is necessary.