TABLE 3.

Prevalence rates of SSIs following spine surgery with 95% CIs for 2 separate definitions of summer

Definition of Summer	Organism	Prevalence Rate for Summer (95% CI)	Prevalence Rate for Rest of Yr (95% CI)	Prevalence Rate Ratio (95% CI)	p Value
June–September
	All SSIs	1.28 (1.12–1.44)	1.03 (0.93–1.13)	1.24 (1.06–1.45)	0.008
	GPC	1.02 (0.88–1.16)	0.80 (0.71–0.89)	1.27 (1.06–1.52)	0.008
	S. aureus	0.78 (0.66–0.91)	0.60 (0.52–0.68)	1.06 (1.06–1.60)	0.01
	MSSA	0.48 (0.38–0.58)	0.32 (0.26–0.37)	1.52 (1.16–1.99)	0.002
	MRSA	0.30 (0.22–0.38)	0.28 (0.23–0.34)	1.06 (0.77–1.46)	0.74
	GNR	0.20 (0.13–0.26)	0.21 (0.17–0.26)	0.92 (0.62–1.35)	0.47
July–September
	All SSIs	1.33 (1.15–1.53)	1.04 (0.95–1.14)	1.29 (1.09–1.52)	0.003
	GPC	1.04 (0.88–1.21)	0.82 (0.73–0.90)	1.28 (1.06–1.55)	0.01
	S. aureus	0.79 (0.64–0.94)	0.62 (0.54–0.69)	1.28 (1.03–1.59)	0.03
	MSSA	0.47 (0.35–0.58)	0.34 (0.28–0.39)	1.37 (1.03–1.83)	0.03
	MRSA	0.32 (0.23–0.42)	0.28 (0.23–0.33)	1.16 (0.83–1.63)	0.38
	GNR	0.23 (0.15–0.30)	0.20 (0.16–0.24)	1.12 (0.75–1.69)	0.57

GNR = gram-negative rods; GPC = gram-positive cocci.