|Year : 2015 | Volume
| Issue : 1 | Page : 56-59
Prevalence of multidrug resistant Pseudomonas aeruginosa infection in burn patients at a tertiary care centre
Puneet Bhatt1, Khushi Ram Rathi1, Santanu Hazra2, Alok Sharma3, Vishal Shete2
1 Department of Pathology, Command Hospital, Pune, India
2 Department of Microbiology, AFMC, Pune, India
3 Department of Reconstructive Surgery, Command Hospital, Pune, India
|Date of Web Publication||11-Dec-2015|
Dr. Puneet Bhatt
Department of Pathology, CH (SC), Pune - 411 040, Maharashtra
Source of Support: None, Conflict of Interest: None
Background: Pseudomonas aeruginosa is an important cause of hospital acquired infection especially in patients admitted in critical care units such as intensive care units and burn care units. Because of its considerable potential to become resistant to important anti-pseudomonal agents, infection of burn wounds by P. aeruginosa, especially by multi-drug resistant (MDR) strains has become a major problem. Aim: This study was carried with an aim to determine the antimicrobial resistance pattern and prevalence of MDR P. aeruginosa infection among burns patients at a tertiary care center. Materials and Methods: This cross-sectional study was carried out from June 2013 to July 2014 in microbiology laboratory of a tertiary care center. In this study, 102 nonrepetitive clinical samples from patients admitted in burn unit were collected and the isolates were identified by conventional phenotypic methods. The antibiotic sensitivity testing of all P. aeruginosa isolates was done using Kirby-Bauer disc diffusion method and the results were interpreted according to the Clinical and Laboratory Standards Institute guidelines. Results: Out of 102 clinical samples, P. aeruginosa was isolated from 56 (54.9%) samples. Out of these 56 isolates, 43 (76.8%) isolates were MDR. Majority of the isolates were resistant to amikacin (73.2%), gentamicin (84%), tobramycin (75%), ceftazidime (76.79%), ciprofloxacin (71.4%), cefepime (64.6%), piperacillin (80.36%) and imipenem (61%). Conclusion: The prevalence of P. aeruginosa infection in patients admitted in burns unit was found to be 54.9%. This study showed an increased prevalence (76.8%) of MDR P. aeruginosa infection in burn patients.
Keywords: Antimicrobial susceptibility testing, Clinical and Laboratory Standards Institute, Kirby-Bauer disc diffusion method, multi-drug resistant, Pseudomonas aeruginosa
|How to cite this article:|
Bhatt P, Rathi KR, Hazra S, Sharma A, Shete V. Prevalence of multidrug resistant Pseudomonas aeruginosa infection in burn patients at a tertiary care centre. Indian J Burns 2015;23:56-9
|How to cite this URL:|
Bhatt P, Rathi KR, Hazra S, Sharma A, Shete V. Prevalence of multidrug resistant Pseudomonas aeruginosa infection in burn patients at a tertiary care centre. Indian J Burns [serial online] 2015 [cited 2019 Jul 19];23:56-9. Available from: http://www.ijburns.com/text.asp?2015/23/1/56/171656
| Introduction|| |
Pseudomonas aeruginosa is a leading cause of healthcare associated infection especially in patients admitted to critical care units such as intensive care units (ICUs) and burn care centers.  It is an opportunistic pathogen and can survive in the hospital environment. P. aeruginosa infection is associated with increased morbidity and mortality in immunosuppressed patients.  A breach in the protective skin barrier, reduced immunity, and prolonged hospital stay are important factors responsible for infection of burn wound with such opportunistic pathogens especially multi-drug resistant (MDR) P. aeruginosa.  The presence of dead, denatured tissues and moist environment makes the burn wound vulnerable to infection by P. aeruginosa. Patients and their relatives are important sources of P. aeruginosa in ICU or other critical care units and have become a potential source of healthcare-associated infections.  P. aeruginosa is naturally resistant to many antibiotics and it is increasingly becoming resistant to many anti-pseudomonal agents. Therefore, treatment of burn patients infected with P. aeruginosa becomes very difficult due to limited treatment options. 
Resistance mechanisms of P. aeruginosa are derived genetically which may act independently or in concert with others. An isolate resistant to at least three of the four agents: Imipenem, ceftazidime, ciprofloxacin and tobramycin is defined as MDR P. aeruginosa. 
Pseudomonas aeruginosa is naturally resistant to penicillin and most of the β-lactam antibiotics.  Carbapenems are the antibiotic of choice for treatment of P. aeruginosa infections. However, gradually increasing resistance to carbapenems has become a major concern. Resistance may be mediated by loss of the OprD porin, upregulation of multi-drug efflux pumps and production of certain β-lactamases and carbapenemases. ,
Mechanisms of aminoglycoside resistance in P. aeruginosa are due to reduced uptake of aminoglycosides across the outer and cytoplasmic membranes associated with the production of aminoglycoside-modifying enzymes.
Modification of DNA gyrase is responsible for the development of resistance to quinolones.
The use of polymyxins (polymyxin B and colistin) were limited due to their nephrotoxicity. However, emergence of resistance against most effective anti-pseudomonal agents has resulted in the need for use of these agents. 
This study was conducted with an aim to determine the antimicrobial resistance pattern and prevalence of MDR P. aeruginosa infection among burns patients at a tertiary care center.
| Materials and Methods|| |
Isolation and identification
This cross-sectional study was carried out from June 2013 to July 2014 in the microbiology laboratory of a tertiary care center. In this study, 102 nonrepetitive clinical samples from patients admitted in burns ward were collected and P. aeruginosa isolates were identified by conventional phenotypic methods for gram staining, colony morphology, motility, oxidase test, Hugh-Leifson oxidation-fermentation test, susceptibility to polymyxin B and pyocyanin production.
Antimicrobial susceptibility testing
All isolates were tested for their susceptibility to various antibiotics by Kirby-Bauer disc diffusion method [Figure 1]. All the results were interpreted according to Clinical and Laboratory Standards Institute guidelines 2013 (M100-S23).
|Figure 1: Kirby-Bauer disc diffusion method for antimicrobial susceptibility testing of Pseudomonas aeruginosa isolates|
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| Results|| |
Out of 102 samples, the most common clinical specimen received in the microbiology laboratory was surface wound swabs (85/102) followed by serous fluid (10/102) and tissue (7/102). A total of 110 isolates were obtained from 102 samples because 08 isolates yielded more than one organism. The most commonly isolated organism was P. aeruginosa (56), followed by Staphylococcus aureus (27), Acinetobacter baumannii (19), Escherichia More Details coli (4), CoNS (3) and Citrobacter freundii (1). Thus, the prevalence of P. aeruginosa infection among burn patients was found to be 54.9%.
Antimicrobial susceptibility testing was carried out for all the 56 isolates of P. aeruginosa by Kirby-Bauer disk diffusion method. The antibiogram of these isolates [Figure 2] shows that 45 (80.36%) isolates were resistant to piperacillin and 37 (66%) were resistant to the piperacillin-tazobactum combination. A total of 43 isolates (77%) showed resistance to the anti-pseudomonal cephalosporin, ceftazidime and 36 (65%) isolates were found to be resistant to cefepime. Among the aminoglycosides, 41 (73%) isolates were found to be resistant to amikacin, 47 (84%) to gentamicin and 42 (75%) isolates were resistant to tobramycin. A total 40 (71%) isolates were resistant to ciprofloxacin and 26 (47%) were resistant to levofloxacin. Imipenem resistance was seen in 34 (61%) isolates whereas 30 (54%) isolates were found to be resistant to meropenem.
According to the definition of MDR P. aeruginosa, 43 isolates out of 56 (76.8%) were found to be MDR P. aeruginosa.
Interestingly, all the 56 isolates (100%) were found to be susceptibile to colistin.
| Discussion|| |
Pseudomonas aeruginosa is a major pathogenic species in the family Pseudomonadaceae. P. aeruginosa is associated with colonization of otherwise healthy humans and animals.  It is one of the most serious causes of healthcare-associated bacterial infection and is responsible for 10% of hospital-acquired infection.  It has the considerable potency to become resistant to many antibiotics and increasingly more antimicrobial resistant strains are being encountered in clinical practice, leaving the treating physician with limited treatment options that lead to a severe adverse outcome. ,
Skin is the first line of defense against microbial invasion. However, due to breach in the skin barrier, debridement, and manipulation, burn wounds become vulnerable to infection. Cross contamination with MDR P. aeruginosa is a major cause of infection and septic mortality in burn patients.
In the present study, the most prevalent organism isolated from burn patients was P. aeruginosa (54.9%). Similarly, other studies such as Arslan et al.  and Naqvi et al.  also showed a prevalence of P. aeruginosa infection among burn patients to be 53.97% and 59.6% respectively. However, Ekrami and Kalantar  showed a prevalence of 37.5%.
Piperacillin, the extended spectrum penicillin, was indicated for the treatment of P. aeruginosa infection. However, due to the high prevalence of β-lactamase producing strains, β-lactamase inhibitors are combined with it. In the present study, 81% isolates were resistant to piperacillin. Similarly, the study by Naqvi et al.  showed 81.8% isolates to be resistant to piperacillin. In the present study, 66% isolates were found to be resistant to piperacillin-tazobactum combination whereas Moazami-Goudarzi and Eftekhar  have shown increased resistance to piperacillin- tazobactam combination (87.2%) and Naqvi et al.  showed 81.8% resistance.
Among aminoglycosides, 73% isolates were resistant to amikacin, 84% to gentamicin and 75% isolates were resistant to tobramycin. Naqvi et al.  showed 70.5% isolates resistant to amikacin, 93.2% to gentamicin and 95.5% to tobramycin. Moazami-Goudarzi and Eftekhar  showed 89.4% P. aeruginosa isolates resistant to amikacin and 92.4% to tobramycin. Nasrabadi and Hajia  also found 73% isolates to be resistant to amikacin, 80% to gentamicin and 82% to tobramycin.
Carbapenems are the antibiotics of choice for MDR P. aeruginosa infection but increasing resistance against carbapenems has now become a serious concern.  In this study, it was found that 61% isolates were resistant to imipenem and 54% were resistant to meropenem. However, Moazami-Goudarzi and Eftekhar,  in their study, found 94.7% isolates resistant to both imipenem and meropenem.
In this study, 76.8% isolates were MDR, which is slightly more than the finding of Saderi et al. who found 69% isolates to be MDR. However, Moazami-Goudarzi and Eftekhar  showed 100% MDR isolates in burns patients.
The absence of new anti-pseudomonal agents against MDR P. aeruginosa has amplified the problem. Therefore, polymyxin B and colistin are becoming the last resort for the treatment of such infections. Consequently, these agents have to be instituted early in the management in patients who have as a consequence of their injury, a severely challenged renal function, and, therefore, contribute to increased morbidity and mortality. Use of these two agents was stopped since 1980 due to dose-related nephrotoxicity.  Colistin should mainly be used as salvage therapy in combination with one or more antimicrobials.  In the present study, all strains were found to be sensitive to polymyxin B and colistin. These findings further emphasize the need for antibiotic discipline and to follow the recommended hospital antibiotic policy to prevent the proliferation of MDR strains of P. aeruginosa in the community.
| Conclusion|| |
The prevalence of P. aeruginosa infections in burn patients was found to be 54.9%, and the prevalence of multi-drug resistance among these isolates was 76.8. Such a high prevalence of MDR P. aeruginosa infection in burn patients is a cause for concern because it poses a serious therapeutic challenge due to very limited treatment options. This situation warrants the implementation of an efficient infection control program and regular surveillance of antimicrobial resistance in P. aeruginosa isolates in order to establish a rational antibiotic policy for the better management of such infections. Colistin still retains a high sensitivity and could, therefore, be used as a therapeutic alternative in case of multi-drug resistance. Our armamentarium against the MDR P. aeruginosa infections is severely restricted and has toxic side effects that can be lethal by themselves in severely compromised patients. Indiscriminate use of antibiotics, particularly from the β-lactams and carbapenem group needs to effectively curbed.
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[Figure 1], [Figure 2]