Staphylococcus, not MRSA? A final report of carriage and conversion rates in nursing students.

Objective: To evaluate and characterize staphylococcal carriage, possibly including methicillin-resistant Staphylococcus aureus (MRSA), and conversion rates in nursing students across clinical semester rotations and to describe risk factors.

Design: A prospective longitudinal cohort design with six times of measurement. Data collected August 2010 to May 2012. Institutional Review Board approval (2010F5693).

Setting: Texas State University, San Marcos, TX.

Participants: Eighty-seven nursing students.

Interventions: A positive MRSA swab was considered an end point for participation. Intervention offered was bactroban (mupirocin) for nasal decolonization and an oral antibiotic, doxycycline; follow-up post treatment collection sample was done to verify decolonization prior to next clinical rotation.

Main outcome measures: Screening for Staphylococcus aureus and MRSA identification; confirmation and antibiotic susceptibility by Vitek 2; self-administered questionnaires delineating demographics and risk factors; panel logistic regression models by Stata version 13.

Results: MRSA colonization did not increase. S. aureus incidence was 17.7 - 26.4%. Staphylococcal species incidence other than S. aureus increased (9.2 - 82.3%). The following odds ratio (OR) associations were found to be statistically significant: boil or skin infections with S. aureus (OR = 2.94, p < .01), working or volunteering in a healthcare facility odds with species other than S. aureus (OR = 4.41, p < .01) and gym and sports facilities odds with S. other (OR 2.45, p < .01). The most frequently occurring species at Wave 5 was S. hominis (21 isolates) while the most frequently occurring species at Wave 6 was S. epidermidis (25 isolates).

Conclusions: MRSA colonization did not increase during longitudinal study. S. aureus colonization remained fairly stable throughout the study (17 - 26%). Species colonization with non S. aureus species (e.g. S. hominis, S. epidermis, S. haemolyticus) increased significantly (9.2 - 82.3%) during clinical rotations. Knowledge of infection control and compliance may have contributed to an absence of MRSA colonization; however, the colonization by other staphylococci has been shown to be a risk factor for MRSA acquisition.