Relative Frequency of Nosocomial Pathogens at a University Hospital by Site from 1980 to 2008

Background: Information on the relative frequency of nosocomial pathogens by site is important for clinicians to select empirical therapy for healthcare-associated infections. The spectrum of nosocomial pathogens may have changed with time due to increased use of broad-spectrum antibiotics, invasive procedures, and increasing numbers of immunocompromised patients. Although annual frequency of nosocomial pathogens by site is reported by the National Healthcare Safety Network, there is no report of relative frequency of change of nosocomial pathogens over time from a single hospital.

Objective: To review the relative frequencies of nosocomial pathogens isolated at a university hospital by site 1980–2008.

Methods: Data were collected through comprehensive surveillance by full-time ICPs at the University of North Carolina Health Care, a 757 bed teaching facility. To analyze 29 years of data, 6 5-year blocks were created for each site. The 6 5-year blocks of nosocomial pathogens were compared by X² analysis and trends for each pathogen were estimated by regression analysis.

Results: Overall, at least one pathogen was isolated from 35,510 (85.2%) of the 41,660 nosocomial infections.

	Total (1980-2008)			Slope Estimate
Organism	Rank	N	%	Overall	BSI	UTI	HAP	SSI
S. aureus	1	5483	15.4	0.083†	-0.016	0.167‡	0.174†	0.208†
E. coli	2	3753	10.6	-0.065†	-0.256†	-0.061†	-0.154†	-0.039
CoNS	3	3587	10.1	0.109†	0.237†	0.014	0.013	0.047¶
Candida/yeast	4	3494	9.8	0.014	-0.074§	0.027	-0.079¶	0.138‡
Enterococcus spp	5	3138	8.8	0.098†	0.236†	0.102†	0.142	-0.058¶
P. aeruginosa	6	2954	8.3	-0.081†	-0.161†	-0.083†	-0.013	-0.108‡
Klebsiella spp	7	2186	6.2	-0.080†	-0.095‡	-0.034	-0.164†	-0.231†
Enterobacter spp	8	2097	5.9	-0.097†	-0.146†	-0.052¶	-0.105‡	-0.127‡
Other streptococci	9	1252	3.5	-0.105†	-0.045	0.114	-0.156†	-0.070¶
Other anaerobes	10	1044	2.9	0.058§	-0.620†	-1.679	0.451	-0.181†
† p≤0.0001, ‡ p≤0.001, § p≤0.01, ¶ p≤0.05, only data for top 10 pathogens displayed, all data will be presented.

In BSI, CoNS and Enterococcus were significantly increased while E.coli, Candida, P. aeruginosa, Klebsiella and Enterobacter were significantly decreased 1980-2008. For UTIs, S. aureus and Enterococcus showed significantly increasing trends whereas E. coli, P. aeruginosa, and Enterobacter showed significantly decreasing trends. In HAP, S. aureus increased while E. coli, Candida, Klebsiella, Enterobacter, and other streptococci, decreased. In SSI, S. aureus, CoNS, and Candida showed increasing trends whereas Enterococcus, P. aeruginosa, Klebsiella, Enterobacter, other streptococci and other anaerobes decreased.

Conclusions: Significant changes in relative frequency in nosocomial pathogens by site occurred over the 29-year period. Results showed significant increasing trends of S. aureus in UTI, HAP and SSI, CoNS in BSI and SSI, Candida in SSI, and Enterococcus in BSI and UTI.