Our weekly wrap-up of antimicrobial stewardship & antimicrobial resistance scans

MRSA outbreak reported among infants at LA hospital

Ten infants in the neonatal intensive care unit (NICU) at a Los Angeles hospital have been infected with a strain of methicillin-resistant Staphylococcus aureus (MRSA) over the past several months, the Los Angeles Times reported yesterday.

According to the paper, lab tests confirmed that five infants at UC Irvine Hospital had been infected with the same strain of MRSA in the middle of December. Two more babies became infected later that month, followed by another positive test in February and two more in late March. In addition, four hospital employees have been colonized with the same strain.

None of the 10 infants, who were already critically ill when they tested positive, have active infections.

This is the first the public is hearing of the outbreak. The Times learned about the infections after a member of a state advisory committee on hospital-acquired infections filed a complaint with the state, arguing that hospital officials should have informed pregnant women who were preparing to give birth at the hospital.

Hospital officials tell the paper they didn't believe it was necessary to inform expecting families about the outbreak, and county health officials say notifying the public was unnecessary because they had no evidence that infants treated in the UC Irvine NICU were at higher risk of MRSA than infants being treated at other hospitals. But since last month, the hospital has been disclosing the outbreak in a letter to parents of all infants in the unit.

Hospital officials tell the paper they have not yet found the source of the MRSA infections, but are working aggressively to prevent further infections. 
Apr 13 Los Angeles Times story

Researchers find NDM-producing Enterobacteriaceae at Irish beach

Researchers in Ireland are reporting the identification of carbapenemase-producing Enterobacteriaceae (CPE) in Irish recreational waters and sewage.

In a report published yesterday in Eurosurveillance, the researchers say they isolated New Delhi metallo-beta-lactamase (NDM)-producing Escherichia coli and Klebsiella pneumoniae from fresh water and seawater samples collected at two beaches located near an untreated human sewage ocean discharge pump and two fresh water streams that flow into the ocean. The samples were collected from May 2016 to January 2017 from the two streams (Stream A and Stream B) and from seawater at the two beaches (Beach A and Beach B), and additional samples were collected from the sewage collection system, the sewage storage tank, and the sewage outflow. Genetic analysis of the isolates was performed using pulsed-field gel electrophoresis (PFGE).

NDM-producing E coli was isolated from samples from Stream B, the sewage collection system, the sewage storage tank, and from the sewage outflow. All isolates were resistant to ampicillin, cefotaxime, cefoxitin, cefpodoxime, ceftazidime, ciprofloxacin, ertapenem, meropenem, and nalidixic acid, and were genetically indistinguishable from a human isolate submitted to the National Carbapenemase Producing Enterobacteriaceae Reference Laboratory Service (CPERLS).

NDM-producing K pneumoniae was isolated from samples from the sewage collection system and storage tank and from seawater at the two beaches. The isolates were resistant to ampicillin, cefotaxime, cefoxitin, cefpodoxime, ceftazidime, ciprofloxacin, ertapenem, gentamicin, kanamycin, meropenem, nalidixic acid, and tetracycline, and were 83% and 97% similar to a human isolate from CPERLS.

The researchers say they believe human sewage outflow is the source of the NDM-producing Enterobacteriaceae in the seawater, and that the fresh water streams were contaminated by backwash of sewage during high tide. To their knowledge, this is the first identification of CPE in bathing seawater in Europe. Their concern is that people using the beach may be intermittently exposed to the multidrug-resistant bacteria.

"It appears therefore that there is potential for environmental contamination to contribute to a transition of CPE from largely healthcare-associated organisms, to organisms affecting the general population and the veterinary sector," the authors write. "From a public health perspective, the findings focus attention on the need to accelerate programmes to cease discharge of untreated sewage into the environment."
Apr 13 Euro Surveill rapid communication

ASP tied to lower broad-spectrum antibiotic use in pediatric hospital

Originally published by CIDRAP News Apr 12

A German study in Infection found that implementation of an antibiotic stewardship program (ASP) was associated with lower rates of broad-spectrum antibiotic prescribing, better dosage accuracy, shorter therapy, and cost savings in a pediatric hospital.

The study enrolled children from four non-surgical pediatric wards in a 61-bed Munich hospital that admits about 3,800 children a year. The researchers compared 273 patients in the pre-ASP period (Sep-Dec 2014) with 263 in the post-intervention period (Sep-Dec 2015).

The investigators found that use of cephalosporins and fluoroquinolones decreased by 35.5% and 59.9%, respectively, while use of penicillins increased by 15.0%. Overall days of therapy and length of therapy dropped 10.5% and 7.7%, respectively. In addition, dosage accuracy climbed from 78.8% to 97.6%, and guideline adherence for community-acquired pneumonia improved from 39.5% to 93.5%.

In addition, the ASP saved €330,000 ($351,000) per year, the authors said.

They conclude, "Our data demonstrate that implementation of an ASP was associated with a profound improvement of rational antibiotic use and, therefore, patient safety."
Apr 10 Infection study

Study reveals spread of drug-resistant MRSA strains in Ireland

Originally published by CIDRAP News Apr 12

A new study in PLoS One reveals the emergence and extensive spread of multiple strains of a multidrug-resistant, community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) clone within and between hospitals, healthcare facilities (HCFs), and communities in Ireland.

In the study, researchers investigated 89 MRSA isolates (of the community-associated ST1-MRSA-IV clone) recovered from multiple hospital, healthcare, and community sources from 2013 to 2016. The vast majority of the isolates (78 of 89, or 88%) were healthcare-associated (HCA) MRSA, with many (46 isolates) recovered from a single hospital outbreak and the rest from 16 separate hospitals and 4 HCFs. Eleven of the isolates were community-associated.

Seventy-five of the isolates (84%) were multidrug resistant, exhibiting phenotypic resistance to three or more clinically relevant antibiotic classes, with 50 of 89 isolates (56%) showing high-level resistance to mupirocin.

Whole-genome sequencing and single-nucleotide variation analysis of the isolates identified the concurrent circulation of two closely related strains of ST1-MRSA-IV and multiple sporadic strains. Further investigation revealed that strain 1 spread within and between five different hospitals, two HCFs, and the community, with healthcare workers as a possible reservoir of the strain. Isolates from strain 2 were recovered from eight hospitals, one nursing home, and the community. The outlier strains were recovered from eight hospitals and the community.

"The extensive spread of this CA-MRSA clone within and between the Irish community and hospitals/HCFs highlights the need for infection prevention and control measures that consider CA-MRSA transmission routes into hospitals," the authors write.

Since current national guidelines in Ireland recommend MRSA screening only for patients at risk of HCA-MRSA, the authors argue that infection prevention and control measures should now consider CA-MRSA risk factors as well. They also suggest screening of healthcare workers, as travel of staff between facilities is common in Ireland.
Apr 11 PLoS One research article

Very high rate of MRSA colonization found in Portuguese swine

Originally published by CIDRAP News Apr 12

Researchers in Portugal have found a high rate of MRSA colonization in swine and swine workers at two Portuguese farms, according to a study yesterday in PLoS One.

The aim of the study was to assess whether healthy pigs are contributing to the reservoir of MRSA in Portugal, which has a nosocomial MRSA prevalence of nearly 50%, one of the highest in Europe. For the investigation, researchers evaluated the prevalence, antimicrobial resistance patterns, and clonal profile of MRSA isolates from two pig farms and looked for possible transmission to workers on the farms and their families.

The researchers screened nasal samples from a total of 101 piglets, 5 farm workers, and 4 household members for MRSA colonization. Overall, 99% of the piglets (49 of 50 on farm A and all 51 on farm B), 80% of the farm workers (4 of 5), and 25% of the household members (1 of 4) were nasally colonized with MRSA. All of the116 isolates recovered belonged to a single sequence type—ST398, the main livestock-associated MRSA lineage—associated with two predominant spa types, t011 and t108.

High rates of the isolates were resistant to tetracycline (100%), clindamycin (97%), erythromycin (96%), chloramphenicol (84%), and gentamycin (69%), with 12% showing resistance to quinupristin-dalfopristin.

The authors suggest the high rate of MRSA colonization among the pigs might be caused by animal-to-animal transmission aided by the crowded conditions on the farms, a theory supported by the spread of only two spa types. In addition, they argue, the fact that two of the farmers carried the same lineage found in the pigs "corroborates the idea that pig farming is a significant risk factor for MRSA carriage in humans."
Apr 11 PLoS One research article

Study finds rising carbapenem resistance in Enterobacter cloacae

Originally published by CIDRAP News Apr 10

New data from the Veteran's Health Administration (VHA) suggests rising carbapenem resistance in Enterobacter cloacae, researchers report in Emerging Infectious Diseases.

Carbapenem-resistant K pneumoniae emerged as an epidemic in US healthcare settings over a decade ago, but it's not the only Enterobacteriaceae species that has exhibited resistance to carabapenems, and recent outbreaks of E cloacae harboring K pneumoniae carbapenemase (KPC) have raised concerns about carbapenem resistance in E cloacae complex (E cloacae, E asburiae, E kobei, E hormaechei, E xiafangensis). Using clinical and microbiologic data from the VHA network, researchers set out to observe national trends of carbapenem resistance and nonsusceptibility in K pneumoniae and E cloacae complex during the past decade.

For the study, the researchers identified 128,431 K pneumoniae and 38,219 E cloacae complex isolates from 140 VA facilities in 40 states and tested them for susceptibility to carbapenems. The data showed that carbapenem-resistant K pneumoniae and E cloacae complex both spread beyond the eastern United States from 2006-2015, with carbapenem-resistant E cloacae centered in the Southwest and Pacific Coast by 2014-2015.

But while carbapenem resistance and nonsusceptibility rates among K pneumoniae isolates remained steady over the decade (over 1% resistance and 3%-4% nonsusceptibility), rates of resistance and nonsusceptibility increased in E cloacae complex, with more than 4% of isolates showing nonsusceptibility to carbapenems and 2.5% showing resistance in 2014-2015.

These results, the authors write, indicate that a "second epidemic of carbapenem-resistant E cloacae complex appears to be unfolding." Although the genetic background is not well defined, they hypothesize that carbapenem-resistant E cloacae complex "contains genotypes with epidemic potential associated with increasing rates of carbapenem resistance observed at the VHA."

The authors suggest integration of susceptibility testing with molecular characterization at the VHA could help clarify the changing epidemiology of carbapenem-resistant Enterobacteriaceae in the United States.
Apr 7 Emerg Infect Dis research letter

Tigecycline- and carbapenem-resistant K pneumoniae in Taiwan

Originally published by CIDRAP News Apr 10

A Taiwanese study has found a high mortality rate in patients with tigecycline- and carbapenem-resistant K pneumoniae, researchers report in PLoS One.

In the study, researchers with Taiwan's National Defense Medical Center collected clinical isolates of carbapenem nonsusceptible K pneumoniae isolates from 21 hospitals across the country from January 2012 through December 2014. They were looking to explore the clinical characteristics and outcome of carbapenem-resistant K pneumoniae that is also resistant to tigecycline, one of the few remaining antibiotic options for treatment of carbapenem-resistant bacterial infections. They also wanted to determine the mechanisms of resistance.

Overall, 1,093 isolates were collected, and 16 of those were identified as tigecycline- and carbapenem-resistant K pneumoniae. The patients were, for the most part, critically ill, with 10 suffering from urinary tract infections. Other infections included pneumonia (2), biliary tract infections (2), bacteremia (1), and peritonitis (1). The 30-day mortality of the 16 patients was 44%, with a much higher mortality rate in the non-urinary tract infection patients (83% vs. 20%). Comparison with a case control group showed that the mortality for tigecycline-susceptible carbapenem-resistant K pneumonia infection was 31%.

Pulsed-field gel electrophoresis and multilocus sequence typing revealed no dominant clone or sequence type among the isolates, and quantitative real-time polymerase chain reaction analysis identified over-expression of both the efflux pump genes acrB and oqxB in seven of the isolates and oqxB in another seven. But because overexpression of these genes was not detected in two of the isolates, the researchers believe other factors may be involved in mediating tigecycline resistance.

Given how difficult the infections are to treat, the authors conclude that "efforts are urgently needed to improve the knowledge of the epidemiological status of tigecycline resistance accompanied by carbapenem resistance in order to tackle its spread."
Apr 7 PLoS One research article