Antimicrobial Resistance Scan for Oct 18, 2016

News brief

MRSA acquisition low in those exposed to index patients, study finds

The rate of MRSA acquisition is low among contacts of patients colonized or infected with methicillin-resistant Staphylococcus aureus (MRSA), according to a study yesterday in the American Journal of Infection Control.

In the single-center study, researchers at the Sunnybrook Health Sciences Centre in Toronto obtained surveillance cultures from 2,133 patients who had been exposed to780 index patients from 2004 to 2014. The index patients had been colonized or infected with MRSA, and their contacts were either roommates of in an adjacent bed space to the index patient for at least 24 hours. Surveillance cultures were obtained from the contact patients 0, 3, 6, and 9 days after exposure from 2004 to 2008, and then 0, 5, and 10 days after exposure from 2008 to 2015.

At the end of the study period, the researchers found that of the 1,389 contact patients who had completed the surveillance screening, only 79 (5.7%) had acquired MRSA. But the rate of acquisition was higher (8.8%) in the group that completed the screening in the hospital than in those who were diagnosed as having MRSA post-discharge (2.5%). This indicates, the authors said, that the positivity rate for MRSA contacts decreases over time from exposure.

The authors said the results suggest it may be appropriate to reassess the need to flag MRSA contacts at hospital discharge.
Oct 17 Am J Infect Control study

Children of hog workers have more drug-resistant S aureus

A study today conducted by the Johns Hopkins Bloomberg School of Public Health suggests children in the households of workers at large industrial hog farms may be more vulnerable to drug-resistant forms of S aureus.

Large hog farms commonly administer small doses of antibiotics for growth promotion and disease prevention, which can promote antibiotic resistance. In addition, evidence has begun to emerge in Europe of swine workers and their families being infected with livestock-associated antibiotic-resistant S aureus. With that in mind, the researchers wanted to investigate the nasal carriage of resistant S aureus in children in the homes of US hog workers.

For the study, published in Environmental Health Perspectives, researchers collected and compared data on 400 adult-child pairs in the top-ten hog-producing counties in North Carolina, the second-largest hog-producing state in the nation. One set of 198 pairs included a parent who was employed full time at an industrial hog operation (IHO) and a child under the age of 7 years in the same household. The 202 community referent (CR) pairs included a parent from the community who did not work on a hog farm and a child under the age of seven.

The participants filled out a questionnaire and provided investigators with a nasal swab, which was analyzed for the presence of S aureus, MRSA, and multidrug-resistant S aureus (MDRSA).

Among the adults in the study, the investigators found that S aureus nasal carriage prevalence was higher in the hog workers than in the CR parents (53% vs 31%), MRSA prevalence was low in both groups (2% vs 4%), and MDRSA prevalence was similar (12% vs 8%). But among the children, the differences were much starker, especially for drug-resistant S aureus. While nasal carriage of S aureus was higher among children of hog workers than those in the CR household (49% vs 31%), so was nasal carriage of MRSA (14% vs 6%) and MDRSA (23% vs 8%).

The investigators also found evidence suggesting that S aureus, MRSA, and MDRSA prevalence was higher in the children of hog workers who brought home personal protective equipment than it was in the children of hog workers who didn't bring this equipment home.

The authors of the study say the findings need to be confirmed in other populations, and that potential pathways and mechanisms of exposure should be more closely studied. And while none of the children in the study became sick, the investigators also say further studies should be done to determine whether the nasal carriage prevalence of drug-resistant S aureus in children of hog workers represents a risk for infection.

"Before this study, we didn't know how common it was for children living with industrial hog operation workers in North Carolina to carry antibiotic-resistant S. aureus in their noses," study leader Christopher Heaney, PhD, MS, said in a Johns Hopkins press release. "Now that we know how prevalent MRSA and MDRSA are, important next steps are to learn how children are becoming exposed and whether there are implications for their health."
Oct 18 Environ Health Perspect study
Oct 18 Johns Hopkins press release

News Scan for Oct 18, 2016

News brief

MERS infects 2 more in Saudi Arabia

Saudi Arabia's Ministry of Health (MOH) today announced two new MERS-CoV cases, plus the death of a recently reported patient.

One of the cases involves a 72-year-old Saudi man from Riyadh who had primary exposure to MERS-CoV (Middle East respiratory syndrome coronavirus), meaning he didn't contract his infection from another sick person. The man is hospitalized in critical condition. The second patient is a 47-year-old man who isn't a Saudi citizen from Buraydah in central Saudi Arabia. An investigation revealed the man—listed in stable condition—got sick after direct contact with camels.

The death occurred in a 73-year-old Saudi man from Hofuf whose illness was announced on Oct 15. The MOH said the man had underlying health problems.

Today's new developments push Saudi Arabia's case total to 1,461 and the number of deaths from the disease to 612.
Oct 18 Saudi MOH statement

Promising results noted in single-dose cholera vaccine field trial

One dose of cholera vaccine, rather than the recommended two doses given at least 2 weeks apart, helps prevent infection and may offer some degree of herd protection, according to a case-cohort study conducted during a 2015 outbreak in South Sudan. Researchers based at Johns Hopkins Bloomberg School of Public Health published their findings yesterday in the November issue of The Lancet Global Health.

The strategy could help stretch limited supplies of vaccine and streamline immunization campaigns during crisis situations.

In the face of an outbreak that began in May 2015 in a refugee camp in Juba, South Sudan's capital and largest city, the country's health ministry, Doctors without Borders, and other partners for the first time deployed a single-dose regimen in a field setting and at the same time launched a trial to measure vaccine effectiveness. From Aug 9 to Sep 29 they enrolled 87 people with suspected cholera infections and an 898-person cohort from throughout Juba.

Health officials had only 250,000 doses of Shanchol oral cholera vaccine (Shantha Biotechnics, Hyderabad, India) from the global vaccine stockpile to cover the Juba population, estimated to range from 500,000 to 1 million, so they agreed on a plan to maximize the supply to immunize people in high-risk parts of the city. According to the study, 165,000 people were vaccinated during two campaigns, one in late July and the other in the middle of August.

Of the 87 people with suspected cholera, 34 were confirmed as positive for the disease and 1 had indeterminate results. Of the 858 cohort members who were seen for a follow-up visit, none developed cholera. Researchers calculated the adjusted vaccine effectiveness at 87.3% (95% confidence interval, 70.2% to 100%), much higher than earlier estimates for the single-dose regimen, which ranged from 33% to 67%.

The researchers said vaccine effectiveness could be higher due to indirect effects or because they showed effectiveness over a shorter period than other studies. The group said the findings support the use of a single-dose strategy to help control outbreaks in similar settings.

In a related commentary in the same issue, Louise Ivers, MD, senior health and policy advisor at Partners in Health and associate professor of medicine at Harvard Medical School in Boston, wrote that the study adds more evidence about the role oral cholera vaccines can play in controlling the disease. She added that a study that measures herd protection is helpful for gauging the public health usefulness of the tool.

She also lauded the group's work in an evolving outbreak situation. "More studies like this are needed for us to understand the right approaches for use of cholera vaccine." Ivers echoed the authors' caveat that results for the single-dose vaccine strategy may be different for cholera-naive populations than for groups who have already been exposed to Vibrio cholerae, the bacterium that causes the disease.

Also, questions remain about which other public health activities should be combined with the vaccine to control outbreaks, Ivers wrote.
Nov Lancet Glob Health abstract
Nov Lancet Glob Health commentary