June 2018: Antimicrobial stewardship and infection control

Good news for antibiotic stewardship in the community setting: creating a "regional antibiogram" is feasible. This is important because patients often split care or are transferred between hospitals within the same region, and because it might help generate larger sample sizes and more accurately describe the antibiotic susceptibility of uncommon organisms. In this study, investigators combined antibiogram data for 13 organisms from 20 hospitals across North Carolina and southern Virginia. None of the hospitals had more than 1 pathogen-antibiotic combination with a susceptibility rate >2 standard deviations from the regional mean. Unfortunately, most of the data they report is in the form of standard deviations; it would have really nice to have their regional antibiogram as a supplementary material so we could see the actual percentage variation in susceptibilities between hospitals. They do show this information for a couple of organism-antibiotic pairings, but it's hard to know if those are representative without the whole dataset. PMID: 29681253

 

Can we use invermectin to control the spread of malaria? We know that malaria causes people to exhale volatile gases that attract mosquitoes, and that mosquitoes prefer to feed on people infected with malaria. So what if we gave mosquito poison to people infected with malaria to prevent further transmissions? The investigators randomized patients diagnosed with malaria to receive 3 days of either high-dose ivermectin or placebo. Then they collected blood samples from the patients during and up to a month after treatment, fed the blood to mosquitos, and observed how many of the mosquitoes died. Mosquitoes who fed on the blood of the ivermectin-treated patients had a significantly higher mortality rate in the following two weeks. Ivermectin is cheap and well-tolerated, so this seems like a great opportunity to improve upon malaria control in endemic areas. PMID: 29602751

 

The antihelminthic niclosamide may be useful for intestinal decolonization of VRE. Vancomycin-resistant Enterococcus (VRE) is an important nosocomial pathogen in patients with immunosuppression, severe multicomorbidity, prolonged hospitalization, or prolonged antibiotic exposure. Some centers try to decolonize the GI tracts of patients with VRE (e.g. with oral bacitracin) in order to avoid invasive VRE infections. Niclosamide, an oxidative uncoupler used to treat tapeworm infections, is poorly absorbed from the GI tract and hence could be a good "GI tract decolonizer."

In the first part of this study, the authors showed that niclosamide had inhibitory activity against clinical isolates of VRE Enterococcus faeciumIn the second part of the study, the authors gave niclosamide to VRE E. faecium-colonized mice, demonstrating a 2-log (99%) reduction in VRE fecal burden within 3 days of treatment and a 3-log (99.9%) reduction within 7 days of treatment. Niclosamide actually outperformed linezolid as a decolonizing agent, probably because linezolid is too rapidly absorbed from the GI tract into systemic circulation. One last thing worth mentioning about the study is that they found several strains of E. faecalis were resistant to niclosamide. This might be important, because while most vancomycin-resistant isolates are E. faeciumE. faecalis is generally considered the more pathogenic species, so if it turns out that niclosamide decolonization just selects for VRE E. faecalis, that would be A Very Bad Thing. PMID: 29432868

 

This recent meta-analysis reiterates what several studies have consistently shown: the MRSA nasal screen is a great way to rule out MSRA pneumonia. The study included data from 22 studies compromising 5163 patients. The authors stratified the data by type of pneumonia (either community and healthcare associated pneumonias or ventilator associated pneumonias). They found three important trends across the studies. First, PCR was nasal screening was superior to culture-based screening for MRSA pneumonia (sensitivity 78% vs 58% and specificity 92% vs 88%). Second, nasal screening performed more poorly in prospective versus retrospective studies (sensitivity 56% vs 73% and specificity 81% vs 90%). Third, nasal screening more accurate for predicting non-VAP versus VAP pneumonia (sensitivity 77% vs 40% and specificity 89% vs 93%). Across all studies, the positive predictive value of a MRSA screen was low (PPV 45% assuming a 10% prevalence of MRSA pneumonia), whereas the negative predictive value was high (NPV 97%), including in the subset of patients with VAP (NPV 95%). In conclusion, the MRSA nasal screen is an effective tool for ruling out MRSA pneumonia, particularly in CAP and HCAP and when PCR screening is used. PMID: 29340593