To detect carbapenemases in clinical isolates of Enterobacteriaceae collected from patients in a university hospital in Thailand between October 2010 and August 2011. A total of 4818 Enterobacteriaceae isolates were screened for the presence of carbapenemases by ertapenem and imipenem disc diffusion tests. All positive screening isolates were subjected to modified Hodge test, phenylboronic acid– and EDTA–carbapenem combined disc tests and two multiplex PCRs of bla_IMP, bla_VIM, bla_SPM, bla_SIM and bla_GIM, and of bla_KPC, bla_NDM and bla_OXA-48. Carbapenemase-producing isolates were typed by PFGE and then characterized by antimicrobial susceptibility tests. Conjugation was performed using a broth culture mating method. Two isolates each of Escherichia coli, Klebsiella pneumoniae and Citrobacter freundii produced NDM-1, whereas two other isolates of K. pneumoniae produced IMP-14a. DNA fingerprints revealed that the metallo-β-lactamase (MBL)-producing isolates were of different strains except for clonal strains of C. freundii. In vitro transfer of carbapenem resistance was successful for the eight MBL-producing isolates. All MBL producers were susceptible to colistin and tigecycline. The six NDM-producing isolates were recovered from the urine of three patients, who had no history of travel outside Thailand. Interestingly, one patient had chronic urinary tract infections caused by a K. pneumoniae strain and two strains of E. coli producing NDM-1. Surveillance of carbapenemases, particularly NDM-1, in Enterobacteriaceae is urgently needed to control and prevent the spread of these resistance determinants in our country.

Myristicafragrans Houtt. (Nutmeg) is a widely known folk medicine across several parts of Asia, particularly used in antimicrobial treatment. Bacterial resistance involves the expression of efflux pump systems (chromosomal norA and mepA) in methicillin-resistant Staphylococcus aureus (MRSA). Crude extract (CE) and essential oil (EO) obtained from nutmeg were applied as efflux pump inhibitors (EPIs), thereby enhancing the antimicrobial activity of the drugs they were used in. The major substances in CE and EO, which function as EPIs, in a descending order of % peak area include elemicin, myristicin, methoxyeugenol, myristicin, and asarone. Here, we investigated whether the low amount of CE and EO used as EPIs was sufficient to sensitize MRSA killing using the antibiotic ciprofloxacin, which acts as an efflux system. Interestingly, synergy between ciprofloxacin and CE or EO revealed the most significant viability of MRSA, depending on norA and mepA, the latter being responsible for EPI function of EO. Therefore, CE and EO obtained from nutmeg can act as EPIs in combination with substances that act as efflux systems, thereby ensuring that the MRSA strain is susceptible to antibiotic treatment.

Background: Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) in Thailand occur most frequently in healthcare facilities. However, reports of community-associated MRSA are limited. Methods: We characterized 14 MRSA isolates from outpatients (O-1 to O-14) by phenotypic and genotypic methods and compared them with 5 isolates from inpatients (I-1 to I-5). Thai MRSA isolates from a healthcare worker (N-1) and a pig (P-1) were also included as ST9 MRSA strains from other sources. Results: All MRSA isolates from the outpatients and inpatients were multidrug-resistant (resistant to ≥3 classes of antimicrobials). All of them except strains O-2 and I-3 carried type III SCCmec and belonged to agrI, coagulase IV, spa type t037 or t233, which related to ST239. The strain O-2 (JCSC6690) carried type IX SCCmec and belonged to agrII, coagulaseXIc, spa type t337 and ST9, whereas the strain I-3 carried a type III SCCmec and belonged to ST1429. Nucleotide sequence determination revealed that the type IX SCCmec element in strain O-2 was distinct from that in a Thai ST398 strain (JCSC6943) previously identified in 2011; nucleotide identities of ccrA and ccrB were 93 and 91%, respectively and several open reading frames (ORFs) at the joining regions were different. PCR experiments suggested that strain O-2 and N-1 carried similar SCCmec element, whereas that of strain P-1 was different, suggesting that distinct ST9-MRSA–IX clones might be spreading in this province. Conclusions: The SCCmecIX-ST9 MRSA clones of distinct SCCmec subtypes might have emerged in the Thai community and might also have disseminated into the hospital.