Stewardship / Resistance Scan for Dec 05, 2018

News brief

Severe MRSA ST398 infections reported in China, Australia

Two articles yesterday in Emerging Infectious Diseases describe severe infections caused by highly virulent strains of methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST) 398, a clonal type that is usually associated with animals.

In one article, Chinese researchers report on two MRSA ST398 strains isolated from two patients with severe surgical site infections. Antimicrobial susceptibility testing showed that both strains were resistant to beta-lactam antibiotics but were susceptible to most other antibiotics. Whole-genome sequencing  (WGS) showed the isolates had similar resistance genes (blaZ and mecA) and virulence factors, but did not harbor the tetM tetracycline-resistance gene, which is typically found in livestock-associated (LA) MRSA.

The patients denied any livestock contact, and further genetic analysis showed characteristics of community-associated (CA) MRSA isolates. When tested in a mouse infection model, the strains caused abscesses that were significantly larger than those caused by other CA-MRSA strains previously isolated from patients in China and South Korea.

In the second article, Australian scientists report on a MRSA ST398 isolated from a patient with MRSA bacteremia. Antimicrobial susceptibility testing showed that the isolate was only resistant to beta-lactams, and WGS revealed the presence of the blaZ and mecA resistance genes and several virulence factors, but not the tetM gene.

Phylogenetic analysis indicated the strain had a much closer relationship to CA-MRSA ST398 isolates previously described in China than to LA-MRSA ST398 isolates that have been frequently identified in pigs in Australia. The scientists were not able to establish whether the patient—who was from Singapore but working in Australia—had contact with livestock or had visited China before his illness.

"Unlike LA-MRSA ST398, CA-MRSA ST398 has been shown to be highly virulent and has become the predominant CA-MRSA circulating in Shanghai, China," the authors of the study write. "Thus, continued monitoring of this strain's epidemiology and preventing its widespread transmission is essential.

LA-MRSA ST398 was first identified in pigs and pig farmers in 2003 and is the predominant lineage of LA-MRSA in Europe and North America. To date, most human infections have been found in people with direct animal contact.
Dec 4 Emerg Infect Dis article #1
Dec 4 Emerg Infect Dis article #2

 

Study finds antibiotic cycling not tied to lower C diff, MRSA incidence

In another study yesterday in Emerging Infectious Diseases, researchers in Northern Ireland reported that an antibiotic cycling strategy implemented at a teaching hospital did not lead to a reduced incidence of healthcare-associated Clostridioides difficile (HA-CDI) or healthcare-associated (HA) MRSA.

The intervention at Antrim Area Hospital involved cyclical restrictions of amoxicillin-clavulanic acid, piperacillin-tazobactam, and clarithromycin over a 2-year period (October 2013 to September 2015). The intervention was based on an analysis of epidemiologic data from 2007 through 2012 that identified macrolides and piperacillin-tazobactam as significantly associated with HA-MRSA and amoxicillin-clavulanic acid as significantly associated with HA-CDI. The policy restricted use of piperacillin-tazobactam and macrolides on alternate months and amoxicillin-clavulanic acid for 2 consecutive months every 4 months.

To determine whether the strategy had an impact on HA-MRSA and HA-CDI incidence and new extended-spectrum beta-lactamase (ESBL) incidence and resistance, the researchers used segmented regression analysis to compare outcome measures before and after introduction of the policy and between the intervention hospital and a control hospital. They also looked at whether any effect observed during the intervention was reversed upon return to standard policy.

The results showed that during the intervention, HA-CDI incidence did not change and HA-MRSA increased significantly at the intervention hospital, while resistance of new ESBL isolates to amoxicillin-clavulanic acid and piperacillin-tazobactam decreased significantly. But after the hospital returned to its standard antibiotic policy, incidence of HA-MRSA decreased, incidence of new ESBLs increased, and ESBL resistance to piperacillin-tazobactam increased.

The authors conclude, "Our results suggest that antibiotic cycling is not an appropriate strategy to reduce the incidence of HA-MRSA or HA-CDI but might be effective in reducing ESBLs." 
Dec 4 Emerg Infect Dis study

 

Study: Antibiotic 'time-out' strategy doesn't reduce overall use

A multicenter study yesterday in Clinical Infectious Diseases found that a provider-drive antibiotic "time-out" (ATO) did not have an impact on overall antibiotic use but was associated with a decrease in inappropriate therapy.

The ATO strategy, which involves structured conversations during clinical rounds to determine if modification or discontinuation of antibiotic therapy is warranted, was implemented across 11 units located in six hospitals in Maryland. The ATO took place on antibiotic days 3 to 5, and patients receiving any of 23 selected study antibiotics for at least 3 calendar days were eligible.

In the quasi-experimental study, researchers compared hospital antibiotic days of therapy (DOT) per patient admission and total antibiotic DOT per admission during a 6-month baseline period and a 9-month intervention period. They also evaluated the appropriateness of antibiotic therapy on days 3 to 5.

Among the study population, the average hospital DOT was 12.7 per admission and total DOT was 18.9 per admission in the baseline period and 12.2 and 18.2, respectively, in the intervention period. After controlling for study unit and season, there was no difference between hospital DOT or total DOT per admission in the baseline versus intervention period. However, modification in the antibiotic prescription was more common, and there was a decrease in inappropriate antibiotic therapy on days 3 to 5, in the intervention period (45% in the baseline vs. 31% in the intervention).

"We believe that the results of our study contribute to existing evidence supporting the need for ASPs [antibiotic stewardship programs] to achieve goals of optimizing prescriptions and reducing overall antibiotic use," the authors of the study write. "The ATO may be a useful adjunct, but not a replacement for other stewardship interventions."
Dec 4 Clinical Infect Dis study

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News Scan for Dec 05, 2018

News brief

About 1% of NW Missouri population hosts antibodies to Heartland virus

A new study from Centers for Disease Control and Prevention (CDC) and Missouri researchers tested specimens collected from blood donors in northwestern Missouri, and found Heartland virus antibodies in 0.9% of samples. The study appeared yesterday in Emerging Infectious Diseases.

Human cases of Heartland virus and infected ticks have been found in northwestern Missouri in recent years, but this was the first study to establish the seroprevalence of the virus in the general population of that region.

The blood specimens were collected from four consecutive blood drives conducted at the end of 2013. A total of 487 blood donors were tested, median age was 52 years (range, 16 to 87 years), and 225 (46%) were men. Seven donors (0.9%, 95% confidence interval, 0.4% to 4.2%) had Heartland virus antibodies confirmed by plaque reduction neutralization tests, and five of them lived in the same county (Daviess).

"These results suggest that several infections have gone unidentified because they were asymptomatic or the infected persons did not seek care, were not tested, or were ill before the identification of Heartland virus as a cause of human disease," the authors said.
Dec 4 Emerg Infect Dis study

 

South Sudan reports yellow fever outbreak near DRC border

According to the weekly update from the World Health Organization's (WHO's) regional office in Africa, South Sudanese officials report a yellow fever outbreak in the southwestern part of the country, near the border with the Democratic Republic of the Congo (DRC).

So far, one 25-year-old man has been diagnosed as having yellow fever in Nzara County, Gbudue state. The patient was initially suspected as having Ebola, as he had recently traveled to the DRC, which is battling the second-largest Ebola outbreak in history.

The man tested negative for Ebola virus but positive for yellow fever, prompting the South Sudanese ministry of health to declare a yellow fever outbreak on Nov 29.

"The affected area is very rural and located close to the border with the Democratic Republic of the Congo, where the case-patient had travelled before falling ill," the WHO said. "South Sudan had the last documented reactive yellow fever vaccination campaign in 2003 in Imatong (present day Torit), following an outbreak that affected 178 people, with 27 deaths. The country has not yet introduced yellow fever vaccine into the national immunization programme."
Nov 30 WHO bulletin

 

WHO says Paris Agreement will reduce infectious disease deaths

The WHO, in a special report on health and climate change in light of the United Nations Climate Change Conference (COP24), held this week in Katowice, Poland, said addressing climate change will reduce deaths caused by infectious diseases.

By meeting Paris Agreement goals, WHO said nations could also improve the health of citizens. The organization said 1 million lives could be saved from air pollution by 2050, and that addressing air quality was the public health step that could expect the most gains from the Paris Agreement.

Vector control and flooding are also affected by the Paris Agreement, the WHO said, and both are factors in infectious disease transmission. The agency said the vectorial capacity of mosquitoes that transmit dengue fever has risen by 10% since the 1950s, and climate change has led to increased flooding, which can result in unhygienic conditions primed for infectious diseases.

"Only approximately 0.5% of multilateral climate funds dispersed for climate change adaptation have been allocated to health projects," the WHO warned in a news release. "The report calls for countries to account for health in all cost-benefit analyses of climate change mitigation. It also recommends that countries use fiscal incentives such as carbon pricing and energy subsidies to incentivize sectors to reduce their emissions of greenhouse gases and air pollutants."
Dec 5 WHO
report
Dec 5 WHO press release

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