Stewardship / Resistance Scan for Dec 14, 2018

Staph bacteria in hog workers
CRP testing in Thailand, Myanmar
Preop screening for silent bacteriuria

Study: Use of face masks by hog workers linked to reduced staph exposure

Consistent use of a face mask was associated with reduced exposure to antibiotic-resistant and livestock-associated strains of Staphylococcus aureus among industrial hog operation (IHO) workers and their household members, according to a study yesterday in Environmental Health Perspectives.

In the observational study, a team led by scientists at Johns Hopkins Bloomberg School of Public Health examined the relationship between IHO work activities and nasal carriage of drug-resistant, livestock-associated S aureus among IHO workers in North Carolina and their household contacts. In particular, the researchers were interested in whether use of personal protective equipment, including gloves, coveralls, and face masks, was related to S aureus nasal carriage patterns and household members' exposure to these bacteria. While previous studies have shown that livestock-associated and drug-resistant S aureus can spread between hogs, IHO workers, and household contacts of IHO workers, the impact of protective equipment in preventing the spread of the pathogen is unclear.

In bi-weekly intervals over a period of 4 months, participants provided nasal swabs and answered questionnaires that assessed demographic information, household-level characteristics, and habitual activities. A total of 101 IHO workers and 79 household members completed 1,456 study visits.

Among the most noteworthy findings was that IHO workers who wore a face mask more than 80% of the time, compared to those who wore a face mask less than 80% of the time, were less likely to carry multidrug-resistant S aureus (odds ratio [OR], 0.31; 95% confidence interval [CI], 0.11 to 0.83), tetracycline-resistant S aureus (OR, 0.32; 95% CI, 0.12 to 0.88), scn-negative (livestock-associated) S aureus (OR, 0.50; 95% CI, 0.23 to 1.10), and S aureus putatively associated with clonal complex (CC) 398 or CC9, the two predominant lineages of livestock-associated S aureus (OR, 0.51; 95% CI, 0.21 to 1.20).

Household contacts of those workers were also less likely carry scn-negative S aureus (OR, 0.12; 95% CI, 0.04 to 0.40)], tetracycline-resistant S aureus (OR, 0.14; 95% CI, 0.04 to 0.53), and S. aureus putatively associated with CC398 or CC9 (OR, 0.20; 95% CI, 0.05 to 0.81), compared with the household members of IHO worker who wore face masks less than 80% of the time.

"Findings from this longitudinal study suggest that consistent face mask use may reduce nasal carriage of livestock-associated, antibiotic-resistant S aureus in IHO workers' and their household members," the authors of the study conclude. They suggest future trials to test the preventive efficacy of face masks and other personal protective equipment are needed.
Dec 13 Environ Health Perspect study


C-reactive protein testing associated with small reduction in prescribing

Researchers in Thailand and Myanmar report in The Lancet Global Health that testing febrile patients for C-reactive protein (CRP) at the point of care was associated with a modest but significant reduction in antibiotic prescribing.

The randomized controlled trial involved 2,410 patients with a documented fever recruited from six primary care clinics in Thailand and three primary care clinics (plus one outpatient department) in Myanmar from June 2016 through August 2017. Patients were randomly assigned in a ratio of 1:1:1 to either a control group or one of two CRP testing groups, which used thresholds of 20 milligrams per liter (mg/L, group A) or 40mg/L (group B) to guide antibiotic prescribing. The primary outcome was the prescription of any antibiotic from day 0 to day 5 and the proportion of patients who were prescribed an antibiotic when CRP concentrations were above and below the 20 mg/L or 40 mg/L thresholds.

During the trial, 318 of 807 patients (39%) in the control group were prescribed an antibiotic by day 5, compared with 290 of 803 patients (36%) in CRP group A and 275 of 800 patients (34%) in CRP group B. While antibiotic use in all three groups was lower than documented in retrospectively collected data on patients with fever in the two countries, the findings indicate that only the higher threshold for CRP was associated with significant reductions in prescribing.

The adjusted odds ratio (aOR) of 0.80 (95% CI, 0.65 to 0.98) and risk difference of −5.0 percentage points (95% CI, −9.7 to −0.3) between group B and the control group were significant, although lower than anticipated, but the reduction in prescribing in group A compared with the control group was not significant (aOR, 0.86 [0.70 to 1.06]; risk difference −3.3 percentage points [–8.0 to 1.4]).

Patients with high CRP concentrations in both intervention groups were more likely to be prescribed an antibiotic than in the control group (group A versus control group, P < 0.0001; group B vs control group, P < 0.0001), and those with low CRP concentrations in both groups were more likely to have an antibiotic withheld (group A vs. control group, P < 0.0001; group B vs control group, P < 0.0001). No differences in the prevalence of clinical recovery were observed between the two groups. Twenty-four serious adverse events were recorded during the trial, consisting of 23 hospital admissions and one death, which occurred in CRP group A.

The authors of the study say that even though the effect size was smaller than anticipated, the modest reduction in prescribing associated with CRP testing could have a significant impact in Southeast Asia, a region where antibiotic prescribing in primary care is widespread and poorly regulated.

"With the majority of human antibiotic consumption occurring in the community and in patients with fevers and respiratory illness in particular, even small reductions in prescription could imply a large alleviation of drug pressure," they write. "Further modelling and cost-effectiveness analyses are required to explore whether these reductions and the cost of achieving them are warranted from an economic and global health perspective."
Dec 14 Lancet Glob Health study


VA study suggests 'no clinical utility' to preoperative urine screening

The results of a retrospective cohort study of Veterans Administration (VA) patients indicate that screening for or treating preoperative asymptomatic bacteriuria (ASB) does not reduce the risk for postoperative infections, researchers reported yesterday in JAMA Surgery.

For the study, researchers from Boston University School of Medicine, Harvard Medical School, and the VA Boston Healthcare System set out to characterize the association between detection and treatment of ASB and postoperative outcomes. While ASB is associated with increases in surgical site infection (SSI) and urinary tract infection (UTI) after nonurologic procedures, there is limited data on whether preoperative screening for ASB, and subsequent antibiotic therapy directed against the colonizing organism, improves clinical outcomes. As a result, clinical practice patterns vary widely, with some hospitals obtaining preoperative urine cultures as part of the standard care.

The study involved 68,265 veterans who underwent cardiac, orthopedic, or vascular surgery at 109 VA health facilities from October 2008 through September 2013.  The researchers reviewed the medical records, looking for preoperative urine culture results, antibiotic prophylaxis, and 30-day SSI and UTI outcomes. The primary outcome was the association between preoperative ASB and postoperative SSI. The secondary outcomes included postoperative UTI and the association between antimicrobial therapy for ASB and postoperative infectious outcomes.

Of the 68,265 patients, 17,611 (25.8%) were eligible for inclusion in the primary analysis. Preoperative urine cultures were performed in 17,749 (26.0%) patients, and the results were positive in 755 (4.3%), of which 617 (81.7%) were classified as ASB. With adjustments for age, American Society of Anesthesiologists class, smoking status, race/ethnicity, sex, and diabetes status, patients with or without ASB had similar odds of SSI (2.4% vs 1.6%; adjusted odds ratio [aOR], 1.58; 95% CI, 0.93 to 2.70; P = .08).

The lack of association between ASB and SSI persisted when the analysis was stratified by surgery type, except for cardiac procedures, in which a 3-fold increase was observed among preoperative patients with ASB. Urinary tract infection occurred in 14 (3.3%) of 423 patients with ASB and 196 (1.5%) of 12,913 patients without ASB (aOR, 1.42; 95% CI, 0.80 to 2.49; P = .22). 

Receipt of antibiotic therapy with activity against the ASB organism was not associated with a reduced SSI risk (aOR, 1.01; 95% CI, 0.28-3.65; P = .99) or with reduced risk of postoperative UTI (aOR 0.68; 95% CI, 0.20 to 2.30; P = .54). In addition, the ASB organisms matched a postoperative wound culture in only two cases, both Staphylococcus aureus. The authors say the data suggest "there is no clinical utility to preoperative screening of urine cultures for cardiac, orthopedic, and vascular procedures." 

An accompanying commentary by a clinician from Baylor College of Medicine adds that the study could have important implications for stewardship. "Interventions that have focused on reducing urine cultures or suppressing their results have reduced the antibiotic treatment of ASB," writes Barbara Trautner, MD, PhD. "Eliminating routine preoperative urine cultures will reduce the number of positive urine culture results in asymptomatic patients, in turn reducing unnecessary antibiotic use."
Dec 12 JAMA Surg study
Dec 12 JAMA Surg

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