Abstract
Antimicrobial resistance particularly in Gram-negative bacilli is an increasing problem worldwide. Pseudomonas spp. is one the most common Gram-negative bacteria associated with nosocomial infections and therefore, its trend of antimicrobial resistance needs to be studied. The aim of this study was to evaluate the rate of antimicrobial resistance and changes in resistance pattern over a period of five years (2012-2016) in Pseudomonas spp. isolated from trauma patients attending a tertiary care hospital in north India. During the study, a total of 2444 Pseudomonas spp. were isolated from the various clinical sample. The most common species isolated was P. aeruginosa (2331, 95%). The highest level of resistance was observed against levofloxacin (1678, 69%) and the lowest level of resistance was observed against tobramycin (1254, 51%). Irrational and inappropriate use of antibiotics was found to be responsible for multidrug resistance in Pseudomonas spp. Hence, there is an urgent need to emphasize strict antibiotic policy to minimize the misuse of antimicrobials.
Keywords: Antimicrobial, infection, resistance, surveillance, susceptibility
Pseudomonas is an aerobic, motile, Gram-negative bacterium and has been implicated in diverse healthcare associated infections (HCAIs) such as pneumonia, urinary tract infection, skin and soft-tissue infections, in severe burns and in infections among immunocompromised individuals1,2,3,4,5. Multidrug-resistant Pseudomonas is especially associated with increased mortality because no adequate therapeutic options exist6,7,8. Therefore, there is a need to conduct monitoring studies of Pseudomonas spp. for its resistance pattern. The present study was undertaken to find out the drug resistance and antibiotic susceptibility patterns in Pseudomonas spp. isolated from different clinical specimens of trauma patients at a tertiary care hospital of India.
This retrospective cross-sectional study comprised clinically significant isolates of Pseudomonas spp. that were isolated from trauma patients from January 2012 to December 2016. The study was approved by the Institutional Ethics Committee with written consent. Demographic details including age, gender and clinical history of patients were recorded from laboratory maintained computerized database. The isolates were collected from different clinical specimens such as blood, pus, tracheal aspirate, urine and sputum from wards, intensive care units (ICUs) and follow up patients. All these samples were processed as per standard microbiological methods. The bacterial isolates were identified to the species level by the VITEK2 system (BioMérieux, Lyon, France). The antimicrobial susceptibility data were derived from VITEK 2 system according to clinical and laboratory standard institute guidelines9. The standardized custom sensitivity panel used in the VITEK 2 system included 25 different antimicrobials for susceptibility testing of all Gram-negative isolates, but for the present study, only the susceptibilities of Pseudomonas spp. to common anti-pseudomonal agents were analyzed. The resistance of Pseudomonas spp. to individual antimicrobials was presented in absolute numbers and percentages and was analyzed year-wise. Statistical analysis was done by SPSS version 21 software (IBM SPSS Statistics, Version 21.0. Armonk, NY: IBM Corp.).
During the study period (January 2012 to December 2016), a total of 16,210 bacterial isolates were obtained, of which Pseudomonas spp. accounted for 2444 (15%). Of the total 2444 clinical isolates, P. aeruginosa (2331, 95%) was the most common species followed by P. luteola (22, 1%), P. putida (62, 2.5%), P. stutzeri (12, 0.4%), P. mendocina (15, 1%) and P. pseudoalcaligenes (2, 0.1%). The mean age of the patients was 34±1.94 yr (range 1-87 yr). Pseudomonas spp. were most commonly isolated from tracheal aspirate (420, 23.3%) followed by pus/wound swab (409, 22.7%), urine (375, 20.9%), blood (225, 12.5%), bronchoalveolar lavage (212, 11.8%), cerebrospinal fluid (50, 2.8%), tissue (42, 2.3%), drain fluid (21, 1.2%), central venous pressure tips (18, 1%), pleural fluid (7, 0.4%), bones (6, 0.3%), sputum (3, 0.2%) and other samples (12, 0.7%).
The prevalence of Pseudomonas spp. in our hospital setting was maximal in neurosurgery ward (590, 31 %), followed by surgery ward (417, 22%), surgical ICU (367, 19%), neurosurgical ICU (284, 15%), follow up outpatient department (163, 9%), emergency department (39, 2%) and orthopaedics ward (37, 2%). The year-wise and the total resistance pattern of the Pseudomonas isolated from 2012 to 2016 are described in the Table. All isolates were multidrug resistant. The highest level of resistance was observed against levofloxacin (1678, 69%) followed by gentamicin (1657, 68%), ciprofloxacin (1639, 67%), ceftazidime (1623, 66%), meropenem (1533, 63%), cefepime (1541, 63%), amikacin (1419, 58%), piperacillin (1363, 56%), imipenem (1301, 53%) and the lowest level of resistance was noted against tobramycin (1254, 51%). A decreasing rate of antimicrobial resistance was observed in amikacin, cefepime, piperacillin and ceftazidime from 2012 to 2016. The level of resistance of levofloxacin was constant during 2014-2016. Although ciprofloxacin, gentamycin, imipenem and meropenem showed an elevated level of resistance, no trend of resistance was observed.
Table.
Resistance pattern of Pseudomonas spp. against different antimicrobials, n (%)
| Antimicrobials | Year | Total (%) | P | ||||
|---|---|---|---|---|---|---|---|
| 2012 (n=540) | 2013 (n=538) | 2014 (n=546) | 2015 (n=423) | 2016 (n=397) | |||
| Amikacin | 389 (72) | 301 (56) | 300 (55) | 211 (50) | 218 (55) | 1419 (58) | <0.001 |
| Cefepime | 415 (77) | 355 (66) | 333 (61) | 228 (54) | 210 (53) | 1541 (63) | <0.001 |
| Ciprofloxacin | 410 (76) | 328 (61) | 371 (68) | 300 (71) | 230 (58) | 1639 (67) | <0.001 |
| Gentamicin | 405 (75) | 344 (64) | 371 (68) | 275 (65) | 262 (66) | 1657 (68) | <0.001 |
| Imipenem | 318 (59) | 247 (46) | 333 (61) | 224 (53) | 179 (45) | 1301 (53) | <0.001 |
| Piperacillin | 340 (63) | 307 (57) | 289 (53) | 228 (54) | 199 (50) | 1363 (56) | 0.009 |
| Tobramycin | 416 (77) | 441 (82) | N/A | N/A | 397 (100) | 1254 (51) | <0.001 |
| Ceftazidime | 410 (76) | 409 (76) | 333 (61) | 241 (57) | 230 (58) | 1623 (66) | <0.001 |
| Meropenem | 394 (73) | 317 (59) | 355 (65) | 241 (57) | 226 (57) | 1533 (63) | <0.001 |
| Levofloxacin | 410 (76) | 339 (63) | 371 (68) | 288 (68) | 270 (68) | 1678 (69) | <0.001 |
N/A, not available
Infections with multidrug-resistant Pseudomonas are not only associated with considerable morbidity and mortality, but it also presents an economic burden as these are associated with high treatment costs and longer duration of hospital stay when compared to those associated with their drug-susceptible counterparts10,11. Identification and selection of an appropriate antibiotic to initiate therapy are essential to optimize the clinical outcome12. The isolation rate of Pseudomonas spp. in our trauma setting was 15 per cent which was similar to results published earlier13,14. The rates in this study were different from our previous report15. In the present study, the Pseudomonas isolates were mainly obtained from tracheal aspirate followed by pus/wound samples that were similar to some previous studies16. The highest level of resistance was observed in levofloxacin, and the lowest level of resistance was observed against tobramycin. The observed rate of antibiotic resistance in our study against aminoglycosides such as amikacin and gentamicin was consistent with earlier studies17,18. Drug resistance against quinolones such as ciprofloxacin and levofloxacin showed high resistance in our study which was in contrast with a previous study where clinical isolates were more susceptible to these antibiotics19. Cephalosporins are regarded as anti-pseudomonal drugs, particularly ceftazidime which is a third generation cephalosporin and shows efficacy in such infections. However, this drug also encountered higher resistance (66%) in our study as shown earlier20. The major limitation of our study was that molecular characterization of resistant isolates (genes and clones) could not be performed as the study was based on laboratory-maintained database.
Multidrug resistance in bacterial population is a great challenge in the treatment of patients with pseudomonal infections. This calls for monitoring and optimization of antimicrobial use. The strengthening of laboratory services at national and international levels will ensure effective surveillance of antimicrobial resistance. Further studies should focus on better administration of the existing antibiotic armamentarium, along with antibiotic stewardship programme.
Financial support & sponsorship: None.
Conflicts of Interest: None.
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