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Objective: Ventilator Associated Pneumonia (VAP) has an imperative place amongst nosocomial infections leading to increase morbidity and mortality rates. The present study aimed to determine risk factors for acquisition of ventilator- associated pneumonia in an intensive care unit (ICU). Methods: A nested case-control study was carried out from September 2007 to June 2008. All 183 patients hospitalized at the adult ICU ward in Be’sat Hospital, Sanandaj city western Iran over a 48 hour period were included. Bacteriologic diagnosis and antibiotic susceptibility patterns were performed based on Edward & Ewing’s methods and CLSI system guidelines. Results : Of the 149 samples which were taken from endotracheal tubes of 183 patients, 48 cases were diagnosed for VAP with an incidence rate of 26.2%. Mean duration of hospitalization was 23.4±10.2 days. The maximum and minimum antibiotic resistance for the gram negative bacteria was 93.3% for Cefalotin and 50% for Amikacin. The main risk factors for acquisition of ventilator- associated pneumonia were mechanical ventilation (Adjusted OR: 1.55, 95% CI: 1.37-1.74), history of antibiotic consumption (AOR: 8.92, CI: 1.16- 66.66) and fever (AOR: 3.11, CI: 1.22- 7.93). Conclusions: VAP is significantly related to ICU hospitalization, mechanical ventilation and history of antibiotics consumption. Cefalotin and Amikacin showed the highest and lowest antibiotic resistance against gram negative bacteria respectively.

Background and Aim: In recent decades, widespread antibiotic resistance in nosocomial infections due to gram-negative bacteria which can cause high mortality rates have significantly increased, especially in intensive care units. Polymyxin resistance, colistin in particular, as the last therapeutic resort, has been reported globally. The purpose of this study was to evaluate the mechanisms of resistance to colistin and the logical approach to the use of this antibiotic. Materials and Methods:The research method was a narrative review. Data were collected by searching WOS (Web of Science), Scopus, PubMed, SID (Scientific Information Database), Science Direct, and Google Scholar search engines by using the keywords of colistin, antibiotic resistance, gram-negative bacteria, epidemiology, Iran, extended-spectrum beta-lactamases (ESBLs), molecular mechanisms or combinations of them from 2000 to 2019. Results:The most common molecular mechanisms of colistin resistance were mcr-1, mcrlike genes, increased pmrC expression, outer membrane changes in gram-negative bacteria, and mutations in the mgrB. Combination therapy using colistin with other antibiotics was an effective treatment strategy in life-threatening infections. Conclusion: mcr-1 and pet-1 transferase were the most prevalent molecular mechanisms for colistin resistance and combinations of colistin with other antibiotics were effective in the treatment of severe infections.

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