This paper describes the results and outcomes of a survey conducted to investigate the presence of mcr-1 in 5169 domestic animal-origin samples collected by the USDA-Food Safety and Inspection Service between October 2018 and May 2019. Samples from chicken rinse (N = 1787), ground beef (N = 1369), beef trim (N = 1057), poultry (N = 363), raw pork (N = 416) and catfish (N = 177) were enriched in non-selective media and transferred to 96 well plates with a selection medium containing CaCl2, colistin and vancomycin. A novel ELISA was used to screen for the mcr-1 gene product (MCR-1). Only a single colistin resistant Escherichia coli carrying a mcr-1 gene was isolated from raw pork with a MIC of 8 mg/L, which resulted in an overall mcr-1 presence in raw pork of 0.24% and less than 0.02% in the total samples tested. This study represents the first large-scale investigation of mcr-1 in the U.S. meat, poultry, and catfish. Further examination of the positive isolate, Escherichia coli 2492 (EC2492), by whole genome sequencing revealed that this strain contained a 4.8 Mb chromosome and six plasmids. The mcr-1 gene was located on an IncI2 type plasmid and other five resistance genes, tetA, tetR, sul2, aph (3")-Ib and aph (6)-Id identified were located on an IncB/O/K/Z plasmid. In silico analysis assigned EC2492 to ST101 and serotype O54:H21. In conclusion, while the survey results indicated that mcr-1 is rare in the U.S. animal derived foods, that one positive isolate was found suggests that continued vigilance to minimize further spread of mobile colistin resistance is warranted.

Major challenges remain when attempting to quantify and evaluate the impacts of contaminated environments and heterogeneity in the cohorting of health care workers (HCWs) on hospital infections. Data on the detection rate of multidrug-resistant Acinetobacter baumannii (MRAB) in a Chinese intensive care unit (ICU) were obtained to accurately evaluate the level of environmental contamination and also to simplify existing models. Data-driven mathematical models, including mean-field and pair approximation models, were proposed to examine the comprehensive effect of integrated measures including cohorting, increasing nurse-patient ratios and improvement of environmental sanitation on MRAB infection. Our results indicate that for clean environments and with strict cohorting, increasing the nurse-patient ratio results in an initial increase and then a decline in MRAB colonization. In contrast, in contaminated environments, increasing the nurse-patient ratio may lead to either a consistent increase or an initial increase followed by a decline of MRAB colonization, depending on the level of environmental contamination and the cohorting rate. For developing more effective control strategies, the findings suggest that increasing the cohorting rate and nurse-patient ratio are effective interventions for relatively clean environments, while cleaning the environment more frequently and increasing hand washing rate are suitable measures in contaminated environments.

In 2008, an intensive care unit (ICU) in a large Chinese hospital was moved from a 6-bed old ward to a 20-bed new ward. After the move, the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in patients and environmental sites decreased significantly, but the number of ICU-acquired cases per imported MRSA case increased from 1.4 to 4.1. This study suggests that the nurse cohorting level and hand hygiene compliance are strong predicators of MRSA transmission in ICUs.

BACKGROUND:The gene for New Delhi metallo-β-lactamase 1 (NDM-1) has been reported to be transmitted via plasmids which are easily transferable and capable of wide distribution. We report the isolation of two NDM-1 producing strains and possible in vivo transfer of blaNDM-1 in a patient.METHODS:Clinical samples were collected for bacterial culture and antibiotic susceptibility testing from a patient during a 34-day hospitalization. The presence of blaNDM-1 was detected by PCR and sequencing. Plasmids of interest were sequenced. Medical records were reviewed for evidence of association between the administration of antibiotics and the acquisition of the NDM-1 resistance.RESULTS:A NDM-1 positive Raoultella planticola was isolated from blood on the ninth day of hospitalization without administration of any carbapenem antibiotics and a NDM-1 positive Escherichia coli was isolated from feces on the 29th day of hospitalization and eight days after imipenem administration. The blaNDM-1 was carried by a 280 kb plasmid pRpNDM1-1 in R. planticola and a 58 kb plasmid pEcNDM1-4 in E. coli. The two plasmids shared a 4812 bp NDM-1-ISCR1 element which was found to be excisable from the plasmid as a free form and transferrable in vitro to a NDM-1 negative plasmid from E. coli.CONCLUSION:blaNDM-1 was embedded in an ISCR1 complex class 1 integron as a novel 4812 bp NDM-1-ISCR1 element. The element was found to be able to self excise to become a free form, which may provide a new vehicle for NDM-1 dissemination. This mechanism could greatly accelerate the spread of NDM-1 mediated broad spectrum β-lactam resistance.

Here we report the draft genome sequence of one Acinetobacter genomic species 3 strain, D499, which harbors the bla(NDM-1) gene. The total length of the assembled genome is 4,103,824 bp, and 3,896 coding sequences (CDSs) were predicted within the genome. A previously unreported bla(NDM-1)-bearing plasmid was identified in this strain.