(P120) STAPHYLOCOCCUS AUREUS TETRACYCLINE RESISTANCE AND ASSOCIATED RESISTANCE TO OTHER ANTIBIOTICS IN A DOXY-PEP-ELIGIBLE POPULATION

Wednesday, September 18, 2024

4:15 PM - 5:15 PM EST

Primary Author(s)

Rachel N. Mittelstaedt, MD (she/her/hers)

Clinical and Research Fellow and Graduate Assistant
Massachusetts General Brigham

Co-Author(s)(s)

DH

David Helekal, PhD

Harvard T. H. Chan School of Public Health
GR

Gregory K. Robbins, MD

Massachusetts General Hospital
SK

Sanjat Kanjilal, MD, MPH

Harvard Medical School & Harvard Pilgrim Healthcare Institute
YG

Yonatan H. Grad, MD, PhD

Associate Professor
Harvard T.H. Chan School of Public Health
Boston, Massachusetts, United States

Background:
Doxycycline post-exposure prophylaxis (doxy-PEP) decreases the incidence of bacterial sexually transmitted infections (STIs) among men who have sex with men and transgender women (MSMTW). However, doxy-PEP may select for increased tetracycline resistance and associated co-resistance to other antibiotics. The extent of tetracycline resistance and co-resistance in Staphylococcus aureus in MSMTW are unknown.

Methods:
We performed a retrospective analysis of all Staphylococcus aureus cultures collected in people assigned male at birth who were either HIV-positive or prescribed HIV-PrEP, 18 or older, and receiving care at two tertiary care centers in Boston, MA between May 2015 and May 2022. Unique episodes of infection were defined as all positive cultures collected from a patient within a 14-day period. We analyzed rates of resistance defined by the CLSI mean inhibitory concentration (MIC) breakpoints to common anti-staphylococcal antibiotics among tetracycline-resistant (TET-R) vs tetracycline-susceptible isolates (TET-S). We tested for significance with Fisher’s exact test and corrected for multiple comparisons.

Results:
Among 534 patients, 837 unique isolates of S. aureus were identified. Of 834 isolates with tetracycline MICs, 707 (84.8%) were susceptible, 4 (0.5%) were intermediate, and 123 (14.7%) were resistant to tetracycline. Of TET-R specimens, 12.2% were resistant to doxycycline, compared to 0% of tetracycline-susceptible TET-S specimens (p = < 0.001); 54.1% of TET-R specimens and 43.7% of TET-S specimens were resistant to oxacillin (p = 0.15), 20.3% of TET-R specimens and 9.8% of TET-S specimens were resistant to trimethoprim-sulfamethoxazole (p = 0.007), and 35.0% of TET-R specimens versus 11.1% of TET-S specimens were resistant to clindamycin (p < 0.001).

Conclusion:
In doxy-PEP eligible patients at two Boston hospitals, S. aureus tetracycline resistance is associated with higher rates of resistance to common anti-staphylococcal antibiotics. Selection for tetracycline resistance may increase the prevalence of more antibiotic-resistant S. aureus in this population.