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Significant increases in resistance to tetracyclines and trimethoprim-sulfamethoxazole were witnessed over a 10-year period, particularly in the southern United States, according to a cross-sectional study from the VA. Overall, the pattern for methicillin-resistant Staphylococcus aureus (MRSA) became less common over the study period, the investigators pointed out, but they saw differing patterns on resistance.
âRegional stratification over time showed that the Northeast had slightly higher rates of clindamycin resistance but lower rates of tetracycline resistance, while the South had notably higher rates of resistance to tetracyclines and TMP-SMX [trimethoprim-sulfamethoxazole], particularly among MRSA isolates,â the investigators wrote.
The study published in JAMA Network Open.
Study Parameters and Other Takeaways
The investigators pointed out the VA is the only nationwide integrated provider of health care in the US and has curated microbiological data from its electronic medical record system for all S aureus isolates obtained within outpatient settings. This was a cross-sectional study utilizing data from VA clinics collected from adult outpatients with S aureus infection in the contiguous 48 states and Washington, DC, from January 2010 through December 2019.
Investigators reviewed a total of 382,149 S aureus isolates from 268,214 unique outpatients. A majority of the patients were male (94.29%). were analyzed. There was a decrease in the proportion of MRSA nationwide, from 53.6% in 2010 to 38.8% in 2019.
The investigators analyzed data looking at resistance to clindamycin, TMP-SMX, and macrolides. In reviewing MRSA isolates, they saw a significant increase in tetracycline resistance going from 3.6% in 2010 to 12.8% in 2019;Â TMP-SMX resistance went from 2.6% in the first year to 9.2% in the last year; and increases in clindamycin resistance went from 24.2% in 2010 to 30.6% in 2019.
Conversely, there was a significant decrease in macrolide resistance with it going from 73.5% in 2010 to 60.2% in 2019.The investigators also pointed out that multidrug co-occurrence of resistance was rare.
The Pathogenâs Reach
S aureus otherwise known as staph, is a bacterium commonly found on the skin and in the nose of about 30% of individuals according to the Centers for Disease Control and Prevention (CDC). Although S aureus does not cause any harm, it can sometimes cause infections. It can present in a number of ways including skin and soft tissue infections, bloodstream infections, pneumonia, and osteomyelitis. In healthcare settings, infections can lead to serious or fatal outcomes.2
MRSA, in particular, remains a problematic infection to treat. The investigators point out a few factors that may be leading to the increase of MRSA in the south.
âPrior work has suggested that the combination of sociodemographic factors (eg, crowding, poverty), climate factors (eg, heat, humidity), and antibiotic prescribing patterns have contributed to consistently higher rates of antimicrobial resistance in the South,â the investigators write. âClimate factors and changing behavior in patient population also likely play a role in the seasonality of S aureus infections observed in the patient cohort.â
Must Watch: To learn more about clinical management of Acute Bacterial Skin and Skin Structure Infections (ABSSSI), check out our video series in which Bruce Jones, PharmD, FIDSA, BCPS provides commentary on treating challenging patients with comorbidities.
