French study finds loss of plasmid-related drug resistance rare

A new study from a team of French researchers suggests that when bacteria acquire plasmids containing drug-resistant genes, they rarely lose them.

In the study, published in Antimicrobial Agents and Chemotherapy, the researchers inoculated pigs with a strain of non-pathogenic Escherichia Coli (E coli M63) carrying plasmids—small strands of DNA—encoded for resistance to cephalosporin antibiotics and other antimicrobials, and placed the pigs with non-inoculated pigs. The purpose was to document how plasmid-encoded resistance spreads and how persistent it is. Because the pigs weren't treated with any extended-spectrum cephalosporin (ESC) antibiotics, there was no selection pressure favoring the persistence of ESC-resistant bacteria.

The researchers then collected fecal samples from the pigs and grew 353 E coli isolates. Genomic sequencing determined that out of the 353 isolates, only 3 lost the plasmid and were ESC-susceptible.

"Our results show that once a plasmid encoding resistance genes is transferred to a bacterial host, the probability that the bacteria will lose the encoded resistances is quite low, even absent a selective pressure," corresponding author Isabelle Kempf, DVM, from the Universite de Bretaigne Loire in France, said in a news release from the American Society for Microbiology (ASM), which publishes the journal.

Kempf and her colleagues say the finding is significant because cephalosporin antibiotics are critical to human health, and the gene for cephalosporin resistance is frequently carried on plasmids. They say developing a better understanding of how plasmids work, along with tools to counteract them, could lead to the creation of new tools to combat antimicrobial resistance.

Aug 1 Antimicrob Agents Chemother study

Aug 1 ASM news release

MERS camel outbreak in Jordan, new cases in Saudi Arabia

After a slowdown in the past 2 weeks, the Saudi Arabia Ministry of Health (MOH) reported two new cases of MERS-CoV today. Both patients are expatriates, and neither was linked to a recent outbreak at the King Khalid University Hospital in Riyadh.

A 52-year old woman from Al Jubail is in stable condition after presenting with symptoms of Middle East respiratory syndrome coronavirus (MERS-CoV). The MOH said she was a healthcare worker and contracted MERS in a healthcare setting. Last week the MOH said a man from Al Jubail also has MERS-CoV.

The second case involves a 49-year old man from Al Hofuf who is also in stable condition. The MOH listed him as having indirect contact with camels. Exposure to camels, including drinking raw camel milk, has been linked to several MERS cases in Saudi Arabia.

The new cases bring Saudi Arabia's MERS-CoV total to 1,443, including 608 deaths, since 2012.

In other MERS-CoV news, two camel herds were diagnosed as having the virus in Jordan, according to a report issued by the World Organization for Health Animal (OIE) today. The outbreaks occurred on May 16 and had a morbidity rate of 51.4% (36 of 70 susceptible camels).

One outbreak took place on a farm in Ar Ramtha, and the other took place in the village of Az-Zarqa. Camels can pass infections to humans, but the exact route of transmission is still unknown.

Aug 2 MOH report

Aug 2 OIE report

PAHO: 1,708 new cases of chikungunya

The Pan American Health Organization (PAHO) late last week reported 1,708 new suspected or confirmed chikungunya cases, bringing the total in the Americas this year to 214,547.

The country with the highest increase in the Jul 29 report was Honduras, with 617 new cases, bringing that country's total for the year to 12,907. Bolivia reported 570 new cases, raising that country's total to 19,588.

The previous PAHO report showed more than 15,000 new cases in Brazil, but no new cases were reported in that country this week.

The chikungunya outbreak began in December 2013 on St. Martin in the Caribbean with the first recorded cases of the disease in the Americas.

Jul 29 PAHO update

BARDA awards $120 million for anthrax vaccine development

The US Biomedical Advanced Research and Development Authority (BARDA) awarded Altimmune, of Gaithersburg, Md., $120.2 million to clinically develop NasoShield, the company's anthrax vaccine candidate. NasoShield will soon begin phase 1 of clinical testing, Altimmune said in a news release yesterday.

The anthrax vaccine candidate is meant to provide complete protection after one intranasal dose. According to Altimmune, NasoShield was as effective as the gold-standard multidose anthrax vaccine in animal models. The company also said NasoShield offers a more stable and complete immune response than the existing vaccine.

Anthrax is caused by infection with Bacillus anthracis, a bacterium that's easily inhaled. Though naturally occurring in soil, B anthracis has been used as a biological weapon. Anthrax can cause severe illness and death.

Aug 1 Altimmune press release