Study: MCR-4 and MCR-5 genes prevalent in China's pigs, poultry
A research team based in China yesterday reported that the newly identified colistin-resistance genes MCR-4 and MCR-5 occur widely in the country's pigs and poultry, according to a study in PLoS One.
They used a polymerase chain reaction (PCR) test to directly detect the genes in anal and nasal swabs from 1,454 apparently healthy pigs in nine of China's provinces and cloacal and oropharyngeal samples from 1,836 poultry from live-bird markets in 24 provinces.
For both of the genes, prevalence was significantly higher in swine than in poultry swabs. MCR-4 was found in 41.4% of pigs and 11.5% of poultry, and MCR-5 was present in 31.1% of pigs and 5.6% of poultry. Poultry species that harbored the gene included geese, chickens, pigeons, and ducks. In both animal types, MCR-4 and MCR-5 prevalence was higher in the nasal and oropharyngeal swabs than in anal and cloacal swabs.
Researchers found both of the genes in swabs from 2.6% of poultry and 18.3% of pigs.
The authors noted that the levels of genes detected using PCR of swabs is considerably higher than those obtained with studies on bacterial isolates and may more accurately reflect the true prevalence of the genes. "However, the data did not enable us to determine the bacterial species that carried the resistance genes, or the location of the mcr in plasmids or in the bacterial chromosomes," they wrote.
The high levels of MCR-4 and MCR-5 in pigs and poultry from a large part of China is probably linked to prolonged and widespread use of colistin—a last-resort antibiotic—as a growth promoter, but the two genes might also be prevalent in other countries, as well, the team wrote. They also said the higher levels of the genes in nasal and oropharyngeal swabs suggests that bacteria in saliva or respiratory secretions might play key roles in maintaining and transmitting colistin-resistance genes in pigs and poultry.
Mar 14 PLoS One report
CARB-X funds new test to diagnose whole-blood infections
CARB-X, the Combating Antibiotic Resistant Bacteria Biopharmaceutical Accelerator, announced an award of $1 million to HelixBind, a Massachusetts-based company producing a new diagnostic test for whole-blood samples. The test will provide resistance information for invasive bloodstream infections, and HelixBind will have the opportunity to receive another $1 million in funding based on project achievements.
"The world urgently needs new diagnostics, antibiotics, vaccines and other products to protect us from current and emerging drug-resistant bacteria. All the projects in the Powered by CARB-X are in the early stages of development, but if successful, they offer great potential in the fight against life-threatening drug-resistant bacteria," said Kevin Outterson, JD, executive director of CARB-X, in a press release.
HelixBind's test eschews blood cultures, potentially saving time and money for clinicians. This means patients with sepsis, a life-threatening blood infection, can be treated with appropriate antibiotics sooner.
The test is the third diagnostic assay funded by CARB-X since 2016. CARB-X's portfolio includes 27 novel antibiotics, diagnostics, and other product that address drug resistance.
Only 2 single antibiotics shown effective against Staphylococcus biofilms
A lab-based study of commonly used antibiotic combinations effective against Staphylococcus biofilms in periprosthetic joint infections (PJIs) found that gentamicin and daptomycin were the only effective single-agent treatments. Researchers from Scotland reported their findings yesterday in the Journal of Antimicrobial Chemotherapy.
Locally delivered antibiotics play a key role alongside surgical debridement in managing PJI, but there is little evidence on whether a single agent or combination of drugs is better. Commercial bone cements for PJI typically include gentamicin, either with clindamycin or vancomycin.
The investigators used the dissolvable bead microfilm assay to determine the minimum biofilm eradication concentration (MBEC) for the different medications and drug combinations against staphylococcal PJIs. Then they modified the tractional inhibitory concentration index to craft a fractional biofilm eradication concentration index to evaluate synergism or antagonism among the antibiotics.
Only gentamicin (MBED 64 milligrams per liter [mg/L]) and daptomycin (MBEC 64 mg/L) were effective at clinically achievable concentrations. The researchers also observed that other antibiotics alone or in combination were ineffective. Also, they noted that combining bactericidal antibiotics (except for daptomycin) with gentamicin showed a synergistic effect, though bacteriostatic antibiotics had an antagonistic effect when combined with gentamicin.
Though gentamicin and daptomycin have different mechanisms of action, both affect membrane integrity, which might provide an antistaphylococcal effect, including against methicillin-resistant Staphylococcus aureus, the authors wrote. "Further investigation of these findings may be useful in evaluating optimal use of antibiotic combinations in the management of PJI," they concluded.
Mar 14 J Antimicrob Chemother abstract