Gram-negative multidrug-resistant organisms (GN-MDRO) producing β-lactamases (ESBL, plasmid-mediated AmpC β-lactamases and carbapenemases) are increasingly reported throughout Asia. The aim of this surveillance study was to determine the rate of bacterial colonization in patients from two hospitals in the Mongolian capital Ulaanbaatar. Rectal swabs were obtained from patients referred to the National Traumatology and Orthopaedics Research Centre (NTORC) or the Burn Treatment Centre (BTC) between July and September 2014, on admission and again after 14 days. Bacteria growing on selective chromogenic media (CHROMagar ESBL/KPC) were identified by MALDI-ToF MS. We performed susceptibility testing by disk diffusion and PCR (blaIMP-1, blaVIM, blaGES, blaNDM, blaKPC, blaOXA-48, blaGIM-1, blaOXA-23, blaOXA-24/40, blaOXA-51, blaOXA-58, blaOXA-143, blaOXA-235, blaCTX-M, blaSHV blaTEM and plasmid-mediated blaAmpC). Carbapenemase-producing isolates were additionally genotyped by PFGE and MLST. During the study period 985 patients in the NTORC and 65 patients in the BTC were screened on admission. The prevalence of GN-MDRO-carriage was 42.4% and 69.2% respectively (p<0.001). Due to the different medical specialities the two study populations differed significantly in age (p<0.029) and gender (p<0.001) with younger and more female patients in the burn centre (BTC). We did not observe a significant difference in colonization rate in the respective age groups in the total study population. In both centres most carriers were colonized with CTX-M-producing E. coli, followed by CTX-M-producing K. pneumoniae and CTX-M-producing E. cloacae. 158 patients from the NTORC were re-screened after 14 days of whom 99 had acquired a new GN-MDRO (p<0.001). Carbapenemases were detected in both centres in four OXA-58-producing A. baumannii isolates (ST642) and six VIM-2-producing P. aeruginosa isolates (ST235). This study shows a high overall prevalence of GN-MDRO in the study population and highlights the importance of routine surveillance, appropriate infection control practice and antibiotic prescribing policies to prevent further spread especially of carbapenemases.

Objective The aim of the study was to compare the rate of gram-negative multi-drug resistant organism (GN-MDRO) colonization at admission and during hospitalization and to describe the strains and antibiotic resistance genes acquired during hospitalization. Methods Rectal swabs were collected from patients hospitalized at the National Trauma Center (NTC), Mongolia, at the time of admission and after 14 days of hospitalization as has been detailed on our previous study. GN-MDRO antibiotic resistance was determined using EUCAST standards, and resistance genes were detected using multiplex PCR. Results A total of 158 patients were screened, and baseline colonization rate at admission was 29.1% (46/158). The rate went up to 69.9% (110/158) after 14 days of hospitalization (p<0.001). Of all participants, 74 patients (46.8%) screened GN-MDRO negative at admission acquired colonization by day 14. Other 36 patients (22.8%) maintained colonization that was screened positive at both time points. Only 38 patients (24.0%) remained free of GN-MDRO during hospitalization. There was a difference in GN-MDRO acquisition between these groups. Patients who were negative at admission acquired up to 3 GN-MDRO species, and there were 10 different species isolated. Reversely, patients who were screened positive at both time points had fairly homogenous isolates; up to 5 species of Enterobacterales were identified at admission and day 14 hospitalization. Overall, Enterobacterales were the dominant colonizers (61.4%, 97/158), and all Enterobacterales were resistant to cefotaxime as CTX-M resistance was our inclusion criteria. Conclusion GN-MDRO baseline colonization rate on admission was high and, alarmingly, doubled during hospitalization in the study area. Enterobacterales was the predominant colonizer and was highly resistant to 3rd generation cephalosporin. This data supports a need for an improved infection control policy including routine surveillance of the GN-MDROs and improved antibiotic stewardship program.