April 21 (HealthDay News) -- In hospitals and other health-care facilities with endemic methicillin-resistant Staphylococcus aureus (MRSA), aggressive screening of health-care workers should be combined with other measures to help reduce infection rates, new research suggests.

The Swiss and South African authors, who reviewed data from 169 studies of 33,318 health-care workers in 37 countries, found that 4.6 percent of the workers carried MRSA, and, of these, 5.1 percent had clinical MRSA infections.

"Poor infection control practices were implicated in both acquisition and transmission of MRSA by personnel, but even good adherence to infection control -- including masks and hand hygiene -- did not entirely prevent transmission of MRSA from heavily colonized staff to patients," they wrote.

A recent review of MRSA outbreaks suggested that health-care worker screening should focus on those with symptoms of MRSA infection, but this approach would likely miss a large number of MRSA-infected workers with no symptoms, the review authors said.

"Screening of infected health-care workers only will likely miss a large number of asymptomatic personnel capable of transmitting MRSA to patients, since staphylococcal carriage is mainly dependent on whether the person is a nasal carrier (of MRSA)... Our search revealed 18 studies with proven, and 26 studies with likely, transmission to patients from (health-care workers) who were not clinically infected with MRSA," the authors wrote.

Screening of health-care workers should be conducted "irrespective of the presence of risk factors or pus-producing infections as part of pre-employment examination, or [especially during large MRSA outbreaks] even periodically and unannounced before a work shift," they said.

In addition, nose and throat samples should be taken with separate swabs, since MRSA eradication therapy differs depending on the location of the MRSA, the authors recommended.

They acknowledged that cost makes MRSA screening unfeasible in many health-care facilities but noted that close health-care worker surveillance is conducted in regions -- such as Scandinavia, the Netherlands and Western Australia -- with low MRSA prevalence.

"We recommend screening of health care workers during outbreak investigations and during early stages of an institutional epidemic when MRSA prevalence is still low or when a new MRSA strain is propagating rapidly. In settings with endemic MRSA or limited resources, priority should be given to staff in high risk units such as intensive care units, burn units, or surgical wards," the review authors wrote.

The review was expected to be published in the May issue of the The Lancet Infectious Diseases.

SOURCE: The Lancet, news release, April 15, 2008