9 days for patients without an infection, P=0.0001). The distribution

of the bacterial and yeast infections according to two classification schemes, namely 48 hour cut-off interval was based on traditional classification of infections (CDC criterion) and carrier state criterion. Table 1: The comparison of characteristics of the patients with and without nosocomial infection during hospitalization Inhibitors,research,lifescience,medical #see more randurls[1|1|,|CHEM1|]# Based on the CDC criteria 70.5% of all the infections were classified as nosocomial and 29.5% of them as community infections. Using the carrier state criteria, 27 (61.3%) infections were classified as PE, 10 (22.7%) infections as SE and 7 (15.9%) as EX. In all three categories (PE, SE, EX), the most common one (95% [42 out of 44 infections]) was the lower airways infection (table 2). Primary endogenous and SE in most cases were caused by PPM that can be carried by healthy people as well (community bacteria). Primary endogenous infection in most cases (8 out of 24; 29.6%) was caused by E. coli, and SE was mostly (8 out of 10, 80%) caused by C. albicans. The most common EX were Inhibitors,research,lifescience,medical Klebsiella species and Pseudomonas aeruginosa, which are the typical nosocomial pathogenous microorganisms. Table 2: The distribution of pathogens based on carrier state criterion Inhibitors,research,lifescience,medical Discussion The terms “exogenous” and

“endogenous”, derived from the Greek word “genous”, which mean “depend” or “develop”, and tell us whether the infections originated in the patient’s inner or his outer environment.13 Inhibitors,research,lifescience,medical There is no evidence that infections occurring on, or at a specific time after ICU admission, are attributable solely to micro-organisms transmitted via the hands of care givers and, hence, acquired during the ICU stay.14 It also still remains uncertain from the literature whether the given time cut-off refers to the number of days on the ICU or the number of days following intubation. The failure of the CDC guidelines

to specify a time cut-off has led to Inhibitors,research,lifescience,medical the introduction of arbitrary and different time cut-offs, and to the use of the type of micro-organism causing the infections to distinguish between community-, hospital-, and ICU-acquired infections. Clinicians, in extending the time cut-off, appreciated below that infections developing in the first days after ICU admission have nothing to do with the ICU microbial ecology, and hence acknowledged that incubation time represents an inaccurate criterion for classifying infections in the critically ill patients. According to the pathogenesis of ICU-acquired infections, acquisition of a PPM is followed by carriage and overgrowth of that micro-organism before colonization and infection of an internal organ may occur. Undoubtedly, this process takes more than 2, 3, or 4 days to develop. Therefore, a low respiratory tract infection due to a PPM already carried in the throat and/or gut on admission and developing in a ventilated trauma patient after 3, 4, or even 10 days of ICU admission, can not be considered as ICU acquired.