Stewardship / Resistance Scan for Oct 10, 2017

MCR-1 in US, China patients
MDROs in nursing homes
Infections in African kids

Studies describe MCR-1 cases, prevalence in US

Three studies presented at IDWeek 2017 in San Diego last week focused on the emerging colistin-resistance gene MCR-1 in the United States.

Two of the abstracts were case reports. In one, investigators from the Centers for Disease Control and Prevention (CDC) and the Connecticut Department of Health reported that MCR-1 was isolated from two Connecticut residents—an adult and an unrelated child—who had diarrhea. The gene was identified in an Escherichia coli isolate from the child and a Salmonella Enteritidis isolate from the adult, and the plasmids containing the gene were identical by DNA sequencing. Both patients reported recent travel to the Dominican Republic.

In the other case report, researchers from the University of Michigan Medical School and the Michigan Department of Health and Human Services described three patients from a single health system who had travel-associated colistin-resistant E coli. The presence of the MCR-1 gene in the patients' urine was confirmed by polymerase chain reaction testing. All isolates were carbapenem susceptible. No healthcare-associated epidemiologic links were identified, but all three patients had travelled internationally within the prior 6 months—one to Kenya and China, one to Lebanon, and one to Mexico.

The authors of the case reports conclude that increased surveillance is needed to understand the scope and risk factors associated with MCR-1–mediated resistance, with a particular focus on the role of international travel.

In the third abstract, investigators from the CDC and state health departments in Virginia, Tennessee, Minnesota, and Connecticut screened 70,000 nontyphoidal Salmonella isolates from humans, retail meat, and food animals for the presence of MCR-1. No Salmonella isolates with MCR-1 were found in retail meat and food animals, but four human cases of Salmonella with MCR-1 were identified: Salmonella Corvallis in an 18-year-old man from Tennessee, Salmonella Enteritidis in a 55-year-old woman from Connecticut and a 47-year-old man from Minnesota, and Salmonella Typhimurium in a 57-year-old woman from Virginia. All patients had traveled internationally in the 10 days prior to illness onset.

The researchers say the absence of MCR-1 in the retail meat and food animals is likely because colistin has not been used in food animal production in the United States.

MCR-1 was first identified in E coli samples from pigs, pork products, and humans in China in 2015. Since then, it has been detected in human, animal, food, and environmental samples in more than 30 countries.
Oct 5 IDWeek abstract 383
Oct 5 IDWeek abstract 384
Oct 5 IDWeek abstract 324


Chinese study finds 6.2% prevalence of MCR-1 in patients' fecal samples

Of more than 8,000 fecal samples collected from inpatients and outpatients in China in recent years, 6.2% were MCR-1–positive, and more than a third of the positive samples were resistant to third-generation cephalosporins, researchers reported today in Clinical Infectious Diseases.

The investigators analyzed 8,022 samples collected from April 2011 through March 2016 from three hospitals in Guangzhou, a port city of 14 million people. Of the total samples, 497 (6.2%) were MCR-1–positive, and 182 (2.3%) were Enterobacteriaceae that harbored MCR-1 resistant to third-generation cephalosporins, a worrisome combination. Those Enterobacteriaceae—most commonly Escherichia coli—were often multidrug resistant.

The researchers also found that the presence of MCR-1 increased from 0% to 31% over the course of the study. The MCR-1 Enterobacteriaceae resistant to third-generation cephalosporins did not appear until recent years.

Whole-genome sequencing revealed similarity with published MCR-1 plasmid sequences and pointed to spread among animal and human reservoirs. The authors concluded, "The high prevalence of mcr-1 in multidrug-resistant E. coli colonizing humans is a clinical threat; diverse genetic mechanisms (strains/plasmids/insertion sequences) have contributed to the dissemination of mcr-1, and will facilitate its persistence."
Oct 10 Clin Infect Dis abstract


Widespread MDRO carriage found in nursing homes, long-term care

Two point-prevalence studies conducted in southern California suggest that multidrug-resistant organisms (MDROs) are prevalent in the region's nursing homes and long-term care facilities.

In a study conducted as part of the CDC's SHIELD (Shared Healthcare Intervention to Eliminate Life-threatening Dissemination of MDROs) Orange County project, investigators performed point-prevalence screening on adult patients in 38 facilities (17 hospitals, 18 nursing homes, and 3 long-term acute care facilities) from September 2016 through April 2017.

They screened for methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), extended-spectrum beta-lactamase (ESBL), and carbapenem-resistant Enterobacteriaceae (CRE) using nares, skin, and peri-rectal swabs. All hospital patients were under contact precautions.

The overall prevalence of any MDRO among patients was 64% in nursing homes, 80% in long-term acute care facilities, and 64% in hospitals. MRSA infections were most common in nursing homes (42%) and hospitals (37%), while VRE infections were most common in long-term acute-care facilities (55%). Known MDRO patients also harbored another MDRO 49%, 63%, and 34% of the time in nursing homes, long-term acute care facilities, and hospitals, respectively. In the long-term acute care facilities, MDRO point prevalence was 38% higher than the usual admission prevalence.
Oct 6 IDWeek oral abstract 1712

In the other study, investigators conducted a baseline point-prevalence study in fall 2016 of MDRO colonization in residents of 28 southern California nursing homes participating in a decolonization trial. A total of 2,797 swabs were obtained from 1,400 residents. Nasal swabs were processed for MRSA, and skin swabs were processed for MRSA, VRE, ESBL, and CRE. In addition, environmental swabs were collected from high-touch objects in resident rooms and common areas.

Overall, 48.6% of residents harbored MDROs, mainly MRSA (37%) and ESBL (16%). Resident MDRO status, however, was known for only 11% of MRSA and 18% of ESBL carriers, while only 4% of VRE and none of the CRE carriers were known to harbor the organisms. Bedbound residents were more likely to be MDRO colonized than ambulatory residents (58.7% vs. 45.7%). Environmental swabbing revealed that 93% of common area objects (nursing stations, hand rails, and drinking fountains) and 74% of resident room objects (bedside tables, bedrails, and door knobs) harbored an MDRO.

The authors of the two studies, which were presented at IDWeek 2017 in San Diego late last week, say the findings indicate that MDROs are as widespread in highly interconnected nursing homes and long-term acute care facilities as they are in hospitals, and that strategies to reduce MDRO colonization and transmission in these settings should be part of regional MDRO prevention efforts.
Oct 6 IDWeek oral abstract 1696


Gram-negative bacteria common in resistant infection in African kids

Though recent and high-quality data are lacking, a meta-analysis of antimicrobial resistance in children in sub-Saharan Africa found that gram-negative organisms were the predominant cause of early-onset neonatal sepsis and were also responsible for a high proportion of infections among older children, according to a study yesterday in The Lancet Infectious Diseases.

The UK and Australian researchers systematically reviewed 1,075 studies on antimicrobial resistance in African children and included 18 in their final analysis and provided data on 67,451 isolates of pathogenic bacteria.

They reported that gram-negative organisms were the predominant cause of early-onset neonatal sepsis, with a high prevalence of extended-spectrum beta-lactamase-producing organisms. In older children, gram-positive bacteria were responsible for a high percentage of infections, with high prevalence of non-susceptibility to treatment advocated by World Health Organization therapeutic guidelines.

The authors conclude, "There are few up-to-date or representative studies given the magnitude of the problem of antimicrobial resistance, especially regarding community-acquired infections. Research should focus on differentiating resistance in community-acquired versus hospital-acquired infections, implementation of standardised reporting systems, and pragmatic clinical trials to assess the efficacy of alternative treatment regimens."
Oct 9 Lancet Infect Dis study

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