Resistance Trends among Pseudomonas aeruginosa Isolates in a Tertiary Care Centre in South Gujarat

It is necessary to determine the susceptibility pattern of clinical isolates especially nosocomial one in the clinical settings for making strategy for effective empirical treatment & to reduce incidence of multidrug resistant bugs. Aim of this study was to detect the antimicrobial susceptibility pattern of P. aeruginosa isolates from clinical samples between January 2014 to December 2015, received at department of Microbiology, GMC, Surat. Clinical isolates were confirmed as P. aeruginosa by phenotypic methods/Vitek2 compact system as per availability. Genetic sequencing could not be performed due to unavailability. Antimicrobial susceptibility tests were performed by Kirby-Bauer disc diffusion method/Vitek2 compact system & Interpretation was done according Clinical and Laboratory Standards Institute (CLSI) of that year [1] [2]. Seven hundred fifty seven P. aeruginosa strains were studied during the study period. Most of the isolates were from surgery ward (62%), followed by orthopaedic ward (15%). 65% of the total isolates were from swab samples followed by urine (7%), pus, fluid (5%) & devices (4%). 60% isolates were resistant to Ceftazidime & for other drugs resistance pattern was as follows: Cefepime (52%), Levofloxacin (49%), Ticarcillin/clavulanic acid (49%), Meropenem & Gentamycin (44%), Ciprofloxacin (43%), Amikacin (41%), Tobramycin (39%), Netlimycin (36%), Piperacillin (32%), Aztreonam (31%), Piperacillin/tazobactam (26%), Imipenem (23%) , Doripenem (12%) & Gatifloxacin (10%). As there is predominance of isolates from surgical ward in present study & resistance to carbapenem group of drugs was also found, indicating that most of the infection caused by Pseudomonas aeruginosa may be nosocomial.


Introduction
There is increase in multidrug resistance in clinical isolates in all the clinical settings these days.It is matter of concern as it can become a cause of threat to public health.There is need for making strategies that are efficient to prevent further increase of drug resistance in clinical isolates.Regular monitoring of antimicrobial susceptibility pattern of clinical isolates can greatly contribute in making preventive strategies for multidrug resistance.Prevalence of P. aeruginosa is 15% -80% in chronic wounds [3].P. aeruginosa is an organism that is present in many diverse environmental settings.It has ability to survive on minimal nutritional requirements and it can tolerate a variety of physical conditions.All these properties have allowed this organism to persist in both community and hospital settings.P. aeruginosa can be isolated from a variety of sources in hospital settings like respiratory therapy equipment, antiseptics, soap, sinks, mops, medicines, and physiotherapy and hydrotherapy pools [4].Pseudomonas aeruginosa is an important cause of hospital acquired infection due to all these properties.P. aeruginosa & P. maltophila are causative agents of 80% opportunistic infections caused by Pseudomonas [5].It causes wide variety of infections.There is availability of various antimicrobial agents with anti-pseudomonas activity these days but Peudomonas aeruginosa is still an important cause of morbidity & mortality in hospitalized patients.Therefore, this study has been carried out to study the current antimicrobial sensitivity pattern of Pseudomonas aeruginosa in patients attending New Civil Hospital, Surat.

Material & Method
It was a retrospective study done in Department of Microbiology, GMC, Surat.
Antibiotic susceptibility pattern of P. aeruginosa isolated from the clinical samples of patients attending the New Civil Hospital, those were received in department of Microbiology, GMC, Surat during period of January 2014-December 2015 were analyzed.Repeat isolates from same sample of patient within 2 days of isolation of first isolate were not included in study (there is no standard currently available which tell about optimal frequency to do repeat antimicrobial susceptibility testing of repeat isolate from same sample when an organism is isolated from the same specimen source repeatedly but, testing every 2 to 5 days is thought sufficient) [6].Species level identification was done by phenotypic methods (oxidase test, growth at 42˚C, TSI test, arginine decarboxylation, OF sugar fermentation test) & Vitek 2 compact system as per availability.Genetic sequencing could not be done due to unavailability.

Discussion
Prevalence rate of Pseudomonas aeruginosa was 23 % (757 out of 3329) of all gram negative organism isolated from various clinical samples received in department of microbiology, GMC, Surat from January 2014-December 2015.

Limitations
1) Modified hodge test could not be done to confirm carbapenemase resistance.
2) There is need to do molecular study to identify resistant gene prevalent in setting.

Conclusion
Injudicious use of drugs is one of main contributors to emerging resistance of P. aeruginosa to antimicrobial therapy.It also contributes to appearance of multi- drug resistant strains of bacterium.Most of the isolates in present study were from surgical ward & isolated mainly in swab sample.Resistance to carbapenem group of drugs was also found.These findings indicate that most of the infection caused by Pseudomonas aeruginosa may be iatrogenic or hospital acquired.

Figure 1 .
Figure 1.Showing antimicrobial susceptibility testing of P. aeruginosa by Kirby-bauer technique.

Figure 3 .
Figure 3. Sample-wise isolation rate of P. aeruginosa in present study.(Showing isolation rate of P. aeruginosa from various clinical samples in present study.Type of sample is plotted on X-axis & percentage isolation rate is plotted on Y-axis.Highest rate of isolation was from samples followed by urine (7%), pus & fluid (5%), & devices (4%), Blood culture & drains (1%).).