Surgical site infection rates per 100 surgeries by month for gram-positive cocci (A), S. aureus
(B), MSSA (C), and gram-negative bacilli (D). Polynomial regression analysis resulted in a best-fit line that showed statistically significant seasonal variation with the highest SSI prevalence rate during the summer months for gram-positive cocci (A), S. aureus (B), and MSSA (C), and during the nonsummer months for gram-negative bacilli (D).