Intensive care units (ICUs) are where the most severely ill patients are treated and where the highest mortality rates occur. Nosocomial infection and mortality in ICUs are more prevalent than in other wards of the hospital ^1,2 Underlying diseases, impaired host defenses, invasive devices, immunosuppressive therapy, use of antibiotics, and colonization with resistant microorganisms render patients highly susceptible to nosocomial infections in ICUs ^1,2.

Nosocomial infection is associated with a considerable increase in morbidity and mortality of patients at a hospital as well as to significant increases in costs ³. Nosocomial infections occur in 5% to 17% of hospitalized patients ⁴. In ICUs, where the frequent use of invasive procedures and multiple therapies expose patients to an increased risk, prevalence rates are even higher ^3-6.

In view of the relevance and impact of such observations, it is crucial to know the prevalence rates and nature of nosocomial infections to achieve satisfactory results in controlling this important phenomenon. The present study was undertaken to determine the prevalence rates of infection for Anesthesiology and Reanimation ICU (AR-ICU) patients in our hospital, identify the most common infectious agents and their resistance patterns, and establish the prevalence rates of ICU-acquired infections.

Patients and setting: An observational prospective study was conducted in the Anesthesiology and Reanimation ICU of "Firat Tıp Merkezi" from November 1, 2004 to February 28, 2005.

All patients over 16 yrs of age who had been hospitalized in a participating ICU over the 24-hr period were eligible. Information regarding demographics (age and gender), operative status during the preceding month, underlying and/or concomitant diseases, clinical status at admission to the ICU including the nature and number of organ and system failures, as well as the Acute Physiology and Chronic Health Evaluation II (APACHE II) ⁹ score was collected. Diagnostic, therapeutic, and prophylactic interventions performed during the week preceding the study day (from November 1, 2004, to February 28, 2005) were recorded. The presence or absence of intravascular and urinary catheters, tracheal intubation, tracheostomy, mechanical ventilation, wounds and chest and intracranial drains, peritoneal dialysis, hemodialysis/hemofiltration, central parenteral nutrition, peripherally administered infusion of hyperosmolar solutions, administration of immunosuppressive drugs, prophylactic agents for stress ulcer, and prophylactic antibiotics was also recorded.

Surveillance procedures and definitions: Up to two days following discharge, all patients admitted to the unit were evaluated on a daily basis for NI, in compliance with NNISS (National Nosocomial Infection Surveillance System) methodology, by the same professional, an infectious diseases physician. NI was defined based on standard definitions, taking into consideration if it was acquired in the unit, regardless of length of stay, provided there was no evidence of the infection being in incubation or a continuation of the disease that led to the hospitalization, or up to two days following discharge from the unit. Infection site definitions were in agreement with CDC definitions ⁷ Death occurring up to one week after diagnosis, with no further justifying causes, was considered associated mortality.

Cultures: The cultures employed were: cultures of blood (more than 2 positive pairs of culture for the same pathogen), urine (> 10,000 CFU when collected from urinary catheter and 100,000 CFU when not), endotracheal aspirate (≥10,000 CFU for a single pathogen), and catheters (≥ 10,000 CFU for a single pathogen) and surgical wounds. Identification of bacteria isolated from ICU-acquired infections were performed using conventional methods and API 20E ⁸ and antimicrobial susceptibility tests were performed with Kirby-Bauer disk diffusion method according to the suggestions of Clinical and Laboratory Standards Institute (CLSI) ⁹.

Statistical analysis: Fischer exact and Chi-squared tests were used; P< 0.05 was considered significant.

A total of 182 patients who admitted to ICU, 60 patients developed 131 NI. The NI incidence was 72%; ventilator associated pneumonia (VAP) was the most common NI (41.2%), followed by urinary tract catheter-associated infection (UTI) (28.2%), bloodstream infections (BSI) (13.7%), sepsis (6.9%), and surgical site infection (SSI) (4.6%). Pseudomonas spp. was the most common pathogen identified in the Nıs (31.3%), followed by (%), and yeasts (Table 1).

Table 1: Distribution of hospital acquired infections

The most frequent isolated microorganisms from patients were as follows: Pseudomonas aeruginosa (31.3%), Staphylococcus aureus (11.5%), Coagulase negative staphylococci (CoNS) (10.7%), Acinetobacter baumanii (9.2%), Candida spp. (8.4%), Escherichia coli (8.4%), Enterobacter spp. (4.6%), Enterococcus spp. (3.1%) and others (12.8%). Methicillin resistance was 96% at staphylococci. It was observed Gram-negative microorganisms had multiresistant pattern. When investigated to antibiotic susceptibility; the most effective antibiotics to Pseudomonas spp. were piperacillin-tazobactam (89.7%), imipenem (81.6%), meropenem (53.8%) and cefoperazone-sulbactam (48.6%), while affectivity of antibiotics to Acinetobacter spp. were imipenem (100%), sefoperazon-sulbactam (100%), meropenem (85.7%) and piperacillin-tazobactam (54.5%) (Table 2).

Table 2: Distribution of isolated microorganisms

The most responsible agents isolated from endotracheal aspirate specimens for VAP and pneumonia were P. aeruginosa (%25.9), Pseudomonas spp. (%22.2), MRSA (%16.7), methicillin resistant CoNS (%9.3), E. coli (%7.4), Acinetobacter spp (%7.2), and others, respectively. Candida spp. (%29.7), E. coli (%18.9), P. aeruginosa (%18.9), Pseudomonas spp. (%8.1) and Enterobacter spp. (%8.1) were the most responsible microorganisms’ isolated urine. Methicillin resistant CoNS (%22.2), Acinetobacter spp. (%22.2), A. baumanii (%11.1), P. aeruginosa (%11.1), Pseudomonas spp. (%11.1) were the most responsible agents for laboratory diagnosed BSIs.

Rates of nosocomial infection in patients requiring more than 1 week of advanced life support within an ICU in the United States are 3 to 5 times higher than in patients who are hospitalized but do not require ICU care ^3,10,11. Nosocomial infections are emerging as an important problem in many developing countries as well although data on epidemiology of nosocomial infections in developing countries is limited ¹². Nosocomial infections are associated with high morbidity, mortality, and hospital costs. A key aspect of nosocomial infections control is surveillance, as shown by the Study on the Efficacy of Nosocomial Infection Control Programs, which reported that surveillance combined with an infection control program reduces nosocomial infections by approximately 30% ¹³

We found high overall rates of nosocomial infection in our ICU as 72%. In a study performed at Erciyes University at 1997, ICU acquired infections (ICU-AIs) rates were declared as 25.8% ¹⁴, in an another study performed at Selcuk University, ICU-AIs rates were informed as 84.9% on year 1999-2000 ¹⁵. From the point view of ICU-AIs, comparisons between hospitals can not be appropriate for the reason of different conditions of ICUs and surveillance methods applied.

Regarding the site of infection, the most prevalent infection site was pneumonia with the rates of 20-40%, and followed by UTI, bacteremia, SSI and others, respectively ¹⁶. A study performed at Kocaeli University, the most prevalent infection sites at the first fifth month of 1999 were declared as bloodstream infections (32%), UTI (16%) and SSI (13%) ¹⁷. Esen and Leblebicioglu ¹⁸ performed a one-day point prevalence study in Turkey ICUs, they observed pneumonia and lower respiratory tract infection (28.0%), laboratory confirmed blood stream infection (23.3%) and urinary tract infection (15.7%) were the most frequent types. In the present study, ventilator associated pneumonia was the most common NI (41.2%), followed by urinary tract catheterassociated infection (28.2%), bloodstream infections (13.7%), sepsis (6.9%), and surgical site infection (4.6%).

Gram-negative bacteriae were the most isolated agents from ICUs and Pseudomonas spp. takes part first in these microorganisms. The most isolated Gram-positive agent is S. aureus ^2-4. In a study done by Erbay et al. ¹⁹ P. Aeruginosa (22.6%), Staphylococcus aureus (22.2%) and Acinetobacter spp. (11.9%) were found the most responsible agents in ICUs acquired infections, and, Esen and Leblebicioğlu ¹⁸ declared The most frequently reported isolates were P. Aeruginosa (20.8%), S. aureus (18.2%), Acinetobacter spp. (18.2%) and Klebsiella spp. (16.1%). In our ICU, the most isolated agent were Pseudomonas spp. (31.3%), S. aureus (11.5%), CoNS (10.7%), Acinetobacter spp. (9.2%), Candida spp. (8.4%) and Escherichia coli (8.4%). It was attracted to attention that the role of Candida spp. is increasing in our ICU. This can be due to excessive use of antibiotics. To evaluate the antimicrobial susceptibility, it was observed the microorganisms were multidrug resistant. The least resistance showed by Gram-negative bacteriae in our ICU was found as imipenem, meropenem, piperasilin-tazobactam ve cefoperazone-sulbactam. Among the 29 S. aureus isolates, 28 (96%) of them were methicillinresistant strains (MRSAs), and all were sensitive to vancomycin. This problem reaches the great extents in our ICU. Circulation of multidrug resistant MRSA in hospital should lead to surveillance. Improved compliance with handwashing is needed to prevent MRSA spread out.

In conclusion, the prevalence data that we obtained are consistent with results as reported from many other regions of our country. Surveillance should be focused on patients in intensive care units. Every hospital have to be make a continuous surveillance in ICUs to detect the infection sites, antimicrobial susceptibility, risk factors to prevent and treatment for these infections successfully and make effort to carry out infection control policies.