MRSA Infections Among People Who Inject Drugs, 2005–2016

This page summarizes a report in CDC's MMWR by CDC and its Emerging Infections Program partners in several states, on surveillance data from 2005 to 2016.

The opioid epidemic and infection

In the United States, age-adjusted opioid overdose death rates rose by more than 200% during 1999–2015, and heroin overdose death rates rose nearly 300% during 2011–2015. Past-year heroin use among people 12 and older was 62.5% higher in 2011–2013 than in 2002–2004, and 114.3% higher among non-Hispanic whites. Rising injection drug use has fueled increases in HIV and hepatitis C, and in serious bacterial infections such as endocarditis, osteomyelitis, and skin and soft tissue infections where the epidemic is spreading.

CDC looked at what this meant for invasive methicillin-resistant Staphylococcus aureus (MRSA) infection: MRSA isolated from a normally sterile site, such as blood, cerebrospinal fluid or bone.

The data

The analysis used active, population- and laboratory-based surveillance from the Healthcare-Associated Infections/Community Interface part of CDC's Emerging Infections Program, in six sites: three counties in California, all of Connecticut, eight counties in Georgia, and one county each in Minnesota, New York and Tennessee. Three more sites with data only through 2014, counties in Colorado, Maryland and Oregon, were checked for trends.

A case counted as community-associated if the person had none of the health care risk factors: culture taken more than 3 days after hospital admission; dialysis, hospitalization, surgery or long-term care in the previous 12 months; or a central venous catheter within 2 days before the culture.

Findings

Far higher risk. In 2011, the estimated rate of invasive MRSA was 472.2 per 100,000 among people 13 and older who had injected drugs in the past year, against 29.0 per 100,000 among those who had not, a rate ratio of 16.3 (95% CI 15.7–16.8).

Different patients. Of 39,050 invasive MRSA cases in the six sites during 2005–2016, 2,093 (5.4%) were in people who inject drugs. Compared with other patients, they were younger (median age 45 vs. 63) and much more likely to have community-associated infections (odds ratio 4.4). Their infections were often of types associated with nonsterile injection.

A rising share. The percentage of invasive MRSA cases in people who inject drugs fell from 6.4% in 2005 to 3.5% in 2010, then climbed steadily to 9.2% in 2016; from 2011 alone it went from 4.1% to 9.2%. In the counties in Connecticut, Georgia, Minnesota and Tennessee, the share roughly doubled after 2011. The same dip-then-rise appeared in two of the extra sites through 2014, and resembles trends in acute hepatitis C and in heroin overdose deaths, both of which began climbing around 2010. The shift toward more cases among white people mirrors the opioid epidemic itself.

What it means

Attention to injection drug use has focused on blood-borne infections such as HIV and hepatitis B and C. But infections from skin bacteria such as S. aureus matter too, and programs aimed only at blood-borne pathogens may not prevent them. As nonsterile injection increases, invasive MRSA is likely to increase with it.

Effective measures include:

• preventing opioid misuse through guideline-concordant prescribing;
• treating opioid use disorder with medication-assisted therapy;
• comprehensive community syringe services programs that provide sterile injection equipment and safe disposal;
• education on safer injection, wound care and the early warning signs of serious infection.

Limitations

• Injection drug use may be misrecorded in medical records, over- or understating the share of cases.
• Rates rely on national estimates of MRSA cases and of the number of people who inject drugs, which may be inaccurate.
• Rates use 2011, the only year with a population estimate of people who inject drugs, and may understate risk if injection practices have since become riskier.
• Site-level counts of people who inject drugs were unavailable, so site-specific rates could not be calculated.
• Surveillance of methicillin-sensitive S. aureus began only in 2016, so it could not be included.

Sources

• Jackson KA, Bohm MK, Brooks JT, et al. "Invasive Methicillin-Resistant Staphylococcus aureus Infections Among Persons Who Inject Drugs — Six Sites, 2005–2016." MMWR 67(22). https://www.cdc.gov/mmwr/volumes/67/wr/mm6722a2.htm
• The report's visual abstract and figure are not reproduced, because the report was prepared jointly with state health departments and universities in the Emerging Infections Program.