Gonorrhea in Seattle-area MSM increasingly less susceptible to key drug
Seattle researchers report that, among men who have sex with men (MSM) in Seattle and King County, Washington, 5% have gonorrhea with reduced susceptibility to azithromycin, according to a study today in Clinical Infectious Diseases.
The researchers looked at data from a county sexually transmitted disease clinic from 2012 to 2016, with an emphasis on the most recent 3 years. The US Centers for Disease Control and Prevention recommends that gonorrhea be treated with ceftriaxone plus azithromycin, so resistance to azithromycin could affect gonorrhea control efforts.
The analysts found that, in 2012 and 2013, none of the 263 patients from whom Neisseria gonorrhoeae was isolated showed reduced susceptibility to azithromycin, and 93% of these cases involved MSM. In 2014, 2015, and 2016, in contrast, the rates of reduced susceptibility among MSM were 5.4%, 4.8%, and 4.6%, respectively, for a 5.0% cumulative rate.
The authors conclude, "The World Health Organization recommends changing treatment guidelines when >5% of isolates are resistant to a recommended drug. The emergence of potentially resistant [azithromycin] gonorrhea should prompt reconsideration of current treatment recommendations, and highlights the need to develop new therapies for gonorrhea."
Oct 16 Clin Infect Dis study
Screening study identifies new antibiotic resistance genes
Swedish researchers who analyzed more than 10,000 bacterial genomes and plasmids from human and environmental samples across the globe found 76 novel resistance genes, which formed 59 previously undescribed gene families of metallo beta-lactamase enzymes. The genes enable resistance to carbapenems, a group of antibiotics reserved for serious infections caused by multidrug-resistant pathogens.
Writing in the Oct 12 edition of Microbiome, the investigators focused on identifying class B1 novel metallo beta-lactamases, which are the most clinically important enzyme subclass. In a press release, from Chalmers University of Technology in Sweden, they said resistance genes are rare, and a lot of DNA data need to be examined before a new gene is identified.
They also noted that identifying a resistance gene is challenging if it hasn't been seen before. So the group developed new computational methods to find DNA patterns associated with antibiotic resistance, and by testing the ones they found in the lab, they could see if their predictions were correct.
Eighteen of 21 genes they tested had the ability to hydrolyze imipenem in an Escherichia coli host. Also, two of the novel genes had atypical zinc-binding motifs in their active sites that hadn't been seen before in metallo beta-lactamases.
As part of their study, the team conducted a phylogenetic analysis, showing that metallo beta-lactamases fell into five evolutionary origin groups. Except for one, all previously characterized mobile metallo beta lactamases probably came from genes in Shewanella, a family of marine bacteria, and other Proteobacterial species.
The experts concluded that the findings more than double the number of known B1 metallo beta-lacamases, and the next step is to look for genes that provide resistance to other types of antibiotics. Erik Kristiansson, PhD, professor of biostatistics at Chalmers and the study's principal investigator, said, "The novel genes we discovered are only the tip of the iceberg."
Oct 12 Microbiome abstract
Oct 16 Chalmers University press release