Pseudomonas aeruginosa isolates from urinary tract infection and their antimicrobial susceptibility pattern with special reference to carbapenems

Background: Urinary tract infections (UTIs) are one of the most common bacterial infections affecting humans. Incidence of UTIs in women in the age group of 20-40 years is found to be around 25 to 30%. Incidence in older women above 60 years of age is from 4 to 43%. Catheterization of urinary tract is one of the most common independent risk factor for UTI. Despite advances in antimicrobial therapy, the mortality and morbidity associated with P. aeruginosa induced UTIs remain significantly high. The aim of this study is to determine the antimicrobial susceptibility pattern of P. aeruginosa isolated from urinary tract infection with special reference to Carbapenem resistance and to guide clinicians for appropriate antimicrobial therapy for reduction of morbidity & mortality in hospitalized patients.
Materials and Methods: This is a retrospective analysis from January 2016 to December 2017. Urine samples collected in appropriate sterile manner were screened for polymorphonuclear leucocytes and bacteria by routine microscopic examination. Isolated Pseudomonas aeruginosa strains in significant count which are oxidase positive, non-lactose fermenters from MacConkey’s agar were identified with Matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). Antibiotic susceptibility was performed by VitekCompactTM 2 (Biomeuriux, France) as per CLSI standards establishing MIC (Minimum Inhibitory Concentration).
Results: During the study period we have received 17011 urine samples for routine microscopy and aerobic culture and antimicrobial susceptibility. Of 17011 urine samples, 5407 samples were from male patients and 11604 were from female patients. Of 5407 urine samples from male, 422(7.8%) patients grew P. aeruginosa. Of 11604 urine samples from female, 265(2.2%) patients grew P. aeruginosa. Overall positivity rate for P. aeruginosa from 17011 urine samples was 4.03%. Of the 687 isolates of P. aeruginosa, 407(59.24%) isolates were sensitive to Doripenem, 15 were intermediate and 265(38.57%) were resistant.Of the 687 isolates of, 405(58.95%) isolates were sensitive, 12 were intermediate and 270 (39.30%) were resistant with Imipenem. Of the 687 isolates, 437(63.60%) isolates were sensitive to Meropenem, 19 were intermediate and 231(33.62%) were resistant. The average susceptibility of P. aeruginosa with carbapenems was 60.59% and resistance was 37.16%. Among three carbapenems, meropenem is found to have better susceptibility in-vitro as compared to imipenem and doripenem but in-vivo studies are needed further to establish the comparison and efficacy.
Discussion: P. aeruginosa infections are increasing both in hospital and in general community. It has been reported as one of the leadingnosocomial pathogen. P. aeruginosa is the third leading causeof hospital-acquired urinary tract infections (UTIs), accounting for about 12 % of all hospital acquired infections. Extensive use ofantimicrobial agents as empirical therapy without evidence of culture susceptibility pattern and local antibiogram has resulted in development of drug resistance including multidrug resistant (MDR) and extensively drug resistant (XDR) organisms.Infectionscaused by P. aeruginosa are difficult to treat andoften require combination of drugs to prevent emergence of drug resistance. High rates ofresistance to antibiotics are associated with nosocomial P. aeruginosa strains.
Conclusion: P. aeruginosa remains one of the most important and difficult to treat nosocomial pathogen. MDR strains are increasingly being reported and, in these cases, the choice of therapy often becomes very limited. While the medical community awaits the development of new drugs, MDR P. aeruginosa strains are likely to represent an increasing threat, and every effort should be made to preserve as long as possible, or to restore, the efficacy of currently available agents.