The prevalence of nosocomial and community acquired infections in a university hospital: an observational study.

Background: Nosocomial infections (NI) increase morbidity and mortality. Studies of their prevalence in single institutions can reveal trends over time and help to identify risk factors.

Methods: In March and April 2010, data were prospectively recorded from all inpatients at the Hannover Medical School (Germany) except those treated in the pediatric, psychosomatic, and psychiatric services. The data were acquired systematically by chart review and by interviews with the medical staff. Infections were classified according to the definitions of the Centers for Disease Control and Prevention (CDC). Information was obtained on underlying diseases, invasive procedures, the use of antibiotics, devices (the application of specific medical techniques such as drainage, vascular catheters, etc.), and detected pathogens.

Results: Of the 1047 patients studied, 117 (11.2%) had a total of 124 nosocomial infections, while 112 (10.7%) had 122 community-acquired infections. The most common NI were surgical site infections (29%), infections of the gastrointestinal tract (26%) and respiratory tract (19%), urinary tract infections (16%), and primary sepsis (4%). The most common pathogens were Escherichia coli, coagulase-negative staphylococci, Candida spp., Enterococcus spp., and Pseudomonas aeruginosa. Multivariable regression analysis revealed the following independent risk factors for NI: antibiotic treatment in the last 6 months (odds ratio [OR] = 2.9), underlying gastrointestinal diseases (OR = 2.3), surgery in the last 12 months (OR = 1.8), and more than two underlying diseases (OR = 1.7). Each additional device that was used gave rise to an OR of 1.4. Further risk factors included age, length of current or previous hospital stay, trauma, stay on an intensive care unit, and artificial ventilation.

Conclusion: In this prevalence study, NI were a common complication. Surgical site infections were the single most common type of NI because of the large number of patients that underwent surgical procedures in our institution. More investigation will be needed to assess the benefit of prevalence studies for optimizing appropriate, effective preventive measures.