Stewardship / Resistance Scan for Feb 01, 2017

Spread of MCR-1 gene
Resistant asymptomatic malaria
ESBL bacteria in travelers

MCR-1 identified in California; Vietnam notes link to ag colistin use

The Los Angeles County Department of Public Health (LAC DPH) reported yesterday that a bacterial isolate harboring the MCR-1 gene, which confers resistance to the last-resort antibiotic colistin, has been identified in a patient with an Escherichia coli infection.   

Department officials said in a press release that the patient had most likely acquired the E coli infectionduring international travel, and that there has been no evidence that the infection is spreading in the local healthcare community. The MCR-1 gene has now been reported in six human cases in the United States.
Jan 31 LAC DPH press release

Meanwhile, a study yesterday in Emerging Infectious Diseases suggests that the spread of the MCR-1 gene in Vietnam is linked to the use of colistin in agriculture. The drug is one of the most commonly used antimicrobials in animal production in Vietnam.

For the study, investigators conducted a systematic, cross-sectional study examining antimicrobial drug use colonization with antimicrobial-resistant E coli in chickens and human in Tien Giang province. They collected fecal samples from 204 chicken farms and 204 rectal swabs from chicken farmers, and additionally collected rectal swabs from age- and sex-matched individuals from the same districts who were not involved in poultry farming.

In a total of 204 chicken and 510 human fecal specimens, the adjusted prevalence of MCR-1 was 59.4% in the chicken samples and 20.6% in the human samples. Of the 200 E coli isolates collected, the MCR-1 gene was detected in 10 of 78 isolates from chickens (12.8%), 2 of 50 isolates from chicken farmers (4%), and in none of the 78 isolates from non-farmers. MCR-1 was also detected in 9 of 38 and 1 off 44 extended spectrum beta-lactamase (ESBL)-producing E coli isolates from chickens and chicken farmers, respectively.

An investigation of risk factors indicated that colonization with MCR-1–carrying bacteria in chickens is associated with the use of colistin on chicken farms, while colonization in humans is associated with exposure to MCR-1–positive chickens, with zoonotic transmission explaining the high prevalence of the gene (34.7%) in farmers.

"Given the potentially serious consequences of the spread of the mcr-1 gene from food production animals to humans, prudent use of antimicrobial drugs in animal production should be enforced globally, including in small-scale and household farms," the authors write.
Jan 31 Emerg Infect Dis dispatch


Myanmar study finds evidence of drug resistance in asymptomatic malaria

Researchers investigating malaria infections in an artemisinin resistance containment zone in Myanmar identified isolates from asymptomatic malaria infections that contained a resistance gene, according to a study yesterday in Emerging Infectious Diseases.

The investigators, from Myanmar and South Korea, analyzed isolates from 1,182 people in the containment zone, which is known to harbor mosquitoes containing the Plasmodium falciparum parasite resistant to the antimalarial drug artemisinin, as well as P vivax resistant to chloroquine. Of the 1,182 people, 549 (46%) had had malaria in the previous 5 years.

The researchers discovered that 28 isolates were from asymptomatic people. Of those, 22 were caused by P vivax, 4 by P falciparum, and 2 by P malariae. Two of the P falciparum isolates harbored K13 mutations, an established artemisinin-resistance marker. Three of the P vivax isolates contained other drug-resistance markers.

The authors conclude, "Our results indicated that drug-resistant malaria parasites may be spreading, even in the containment areas or (pre-)elimination areas; this issue should, therefore, be addressed at a policy level. Detection and elimination of asymptomatic infections are of vital importance."
Jan 31 Emerg Infect Dis study


Chinese report notes high rate of travel in those with ESBL bacteria

A study in the latest issue of The Lancet Infectious Diseases shows that more than two thirds of Chinese patients with extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) infections had traveled recently.

The Chinese/UK/US team collected 3,476 third-generation cephalosporin-resistance Enterobacteriaceae isolates from fecally colonized outpatients (3,322 Escherichia coli, 124 Klebsiella pneumoniae, 16 Proteus mirabilis, and 14 Enterbacter cloacae). Of the 3,476 isolates, 2,115 (61%) were positive for at least one ESBL gene.

Among outpatients with ESBL-E isolates, 1,457 (69%) of 2,115 people had documented travel in the previous 6 months; 273 (19%) of them had traveled abroad and 1,184 (81%) had not. The most common destinations outside of China were other parts of Asia (45%), Europe (24%), and the United States (20%).

The authors conclude, "Although the temporal relationship of travel and sampling in our retrospective analysis makes it difficult to conclude whether patients were colonised with ESBL-E at the time, during, or after travel, our findings suggest that further studies, and perhaps microbiological surveillance, of ESBL-E in international travellers from areas with high colonisation prevalence are warranted."
February Lancet Infect Dis report

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