News Scan for Aug 25, 2017

Dog-linked tularemia
;
Resistance in 'lonely' microbes
;
Measles vaccination gap

Tularemia investigation links Arizona's woman's illness to dog

An investigation into a 73-year-old Arizona woman's death related to a Francisella tularensis infection (tularemia) in June 2016 revealed that she probably contracted the bacterium, classified by federal health officials as a tier 1 select agent, from her pet dog. Researchers from Arizona and the US Centers for Disease Control and Prevention (CDC) reported their findings yesterday in Morbidity and Mortality Weekly Report (MMWR).

The woman had pulmonary sarcoidosis and initially sought treatment for onset of fever, muscle pain, loss of appetite, and diarrhea, and her doctors suspected colitis and advised her to stop taking amoxicillin that had been prescribed for a dental infection. Two days later she was hospitalized for breathing problems and confusion, and chest x-rays found pneumonia and an effusion.

Her stool tested positive for Clostridium difficile, and she was treated with metronidazole and vancomycin. The woman's condition continued to deteriorate, and she died 3 days later. The medical team didn't suspect F tularensis until blood culture confirmed it about a week after she died.

A probe into the source of her illness found that she lived in a semirural area but did not take part in outdoor activities. She had recently traveled to Hawaii, but postmortem examination found no bites or other physical signs of the disease.

The patient's dog has been sick in late May after it had a rabbit carcass in its mouth. A sample of the dog's blood was positive for F tularensis, and the woman's property was found to have numerous rabbits, and a squirrel found dead tested positive for F tularensis, with a type A.II strain that matched the human sample.

The authors said the patient probably inhaled F tularensis during close contact with her dog and that human illnesses from dogs have been documented before. They concluded that the pulmonary sarcoidosis may have contributed to illness severity, and the woman's C diff infection may have worsened the tularemia infection. They concluded that the nonspecific nature of tularemia infections makes diagnosis difficult and assessing animal exposures and related contact might help focus clinical suspicions of the disease.
Aug 24 MMWR report

 

Microbes living at lower densities develop resistance faster, study says

UK researchers have discovered that microbes living at low populations densities—dubbed "lonely" microbes—have higher rates of mutations that cause antibiotic resistance, according to their study yesterday in PLoS Biology.

A team of scientists from the universities of Manchester, Keele, and Middlesex previously had found that "lonely" Escherichia coli bacteria were nearly 10 times as likely to mutate to resist antibiotics as those living in dense populations. The new study expands their research to 26 microbial species, including viruses, and involved 70 years of data and nearly 500 mutation measurements.

They found that both in the literature and in their own lab experiments the relationship held across the microbes, with higher population densities leading to lower rates of resistance mutations and lower densities leading to the converse. The authors call their finding "density-associated mutation-rate plasticity" (DAMP).

Lead author Rok Krasovec, PhD, said in a University of Manchester news release, "What's exciting about DAMP is that it requires protein molecules that do the same thing in very different microbes, meaning that we can start to understand why mutation rates vary like this. This means that our results could be the first step towards manipulating microbial DAMP clinically as a way to slow the evolution of antibiotic resistance."
Aug 24 PLoS Biol study
Aug 24 University of Manchester news release

 

Study probes gap in kindergartner measles vaccination

According to CDC research published yesterday in Vaccine, 90.9% of incoming US kindergartners have received the recommended two doses of measles-containing vaccine (MCV).

The highest achievable coverage for the vaccine is 98.6%, meaning there's a 7.7% vaccination gap. All vaccination coverage estimates were based on provider-reported histories.

To analyze the gap, the researchers conducted a national survey of 1,465 parents of children ages 5 to 7 years throughout the winter of 2013 and 2014 to understand vaccine exemptions. Of the undervaccinated children, they found that 2.7% were attributable to a requested vaccine exemption. Among undervaccinated children whose parents did not request an exemption, 41.6% had a missed opportunity or a skipped dose of a MCV.

Currently, all 50 states and the District of Columbia require two doses of MCV by kindergarten entry. But often, the authors say, schools fail to fully implement these vaccination laws. Doing so would help close the MCV coverage gap, they wrote.
Aug 24 Vaccine study

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