Pattern of Resistance to Pseudomonas infection in the North of Iraq: Emphasis on the Potential Role of a Combination Antibiogram


Background: The wide misuse of broad spectrum antibiotics causes increase in the ratio of antibiotic resistance in Iraq. Data are limited on the prevalence, pattern of resistance, and factors associated with resistant organisms. Objective: The aim of this study was to determine the isolation prevalence and antibiotic resistance ratio of P. aeruginosa species isolated in the North of Iraq and to determine the optimum effect of a combination antibiogram and its potential role in empiric treatment. Patients and Methods: The study samples were collected from the two cities Mosul and Duhok. Mosul samples were taken from inpatient specimens sent for culture and antibiotic sensitivity in Al-Salam teaching hospital for a three-year-period (2003-2005). Duhok samples were obtained mainly from outpatient specimens sent to the laboratory of one of the two main private hospitals in the city for another three-year-period (2007-2009). P. aeruginosa was identified by conventional methods and API 20 E (Biomerieux). Their antibiotic susceptibility was tested using the Kirby-Bauer plate diffusion method. Detection of combination effects was performed on Duhok samples by in vitro testing of different antimicrobial combination patterns commonly used in routine empirical practice. For this purpose combinations were chosen of the top four individual drugs demonstrating the highest susceptibilities by the standard antibiogram.Results: Out of 8038 and 1878 clinical specimens submitted for culture in Mosul and Duhok, respectively, 180 and 21 clinically significant isolates of P. aeruginosa were isolated, resulting in a prevalence of 5.2% and 1.6%, respectively. The most common isolates were from pus, followed by urine specimens and ear discharges. The isolates in males were twice that of females. The pattern of resistance revealed that amikicin had the highest sensitivity (89.7%) followed by imipenem, tobramycin and piperacillin (85.6%, 84.1 %, and 82.1%, respectively). Cefotaxime showed the lowest sensitivity rate (66.4%) followed by ceftazidim, carbinicillin, ciprofloxacin and gentamycin (70.1%, 74.6%, 76.1%, and 79.1%, respectively). The study revealed that the optimum combination therapy with the highest sensitivity rate were the combination of amikacin with either piperacillin or imipenem (95.2%) and piperacillin with tobramycin (95.2%).Conclusions and Recommendations A relatively high resistance rate to first line anti-pseudomonal drugs was observed, which should lead to continuous evaluation of hospital and community resistance pattern, the use of optimum combination therapy should be considered in the rational use of anti-pseudomonas drugs.Keywords: Pseudomonas aeruginosa, Resistance pattern, Prevalence