Pseudomonas aeruginosa Isolation of Post-operative Wound in a Referral Hospital in Haryana, India

Original Article Vol. 26 No. 2 Pseudomonas aeruginosa isolation in post-operative wound:- Ruhil K, et al. Pseudomonas aeruginosa Isolation of Post-operative Wound in a Referral Hospital in Haryana, India Kiran Ruhil, Bharti Arora, Himanshu Adlakha ABSTRACT The objective of our study was to determine the prevalence of Pseudomonas aeruginosa isolation of post-operative wound and its susceptibility pattern to commonly used antibiotics. During a twoyear period from November 2006 to December 2008, 260 clinical specimens were received as post-operative wound swabs, in Department of Microbiology, Agroha (Hisar), Haryana, India. Of the 260 bacterial isolates, 72 (27.7%) were P. aeruginosa, followed by Escherichia coli (53, 20.4%), Klebsiella spp. (, 16.5%), Staphylococcus aureus (41, 15.7%), Proteus spp. (14, 5.3%), Acinetobacter spp. (, 3.8%), and Citrobacter freundii (2, 0.8%). There was no growth in 25 (9.6%) specimens. P. aeruginosa isolation was higher in male patients and most common in the age group of 16-40 years. The susceptibility pattern showed the organism to be most commonly susceptible to imipenem, followed by meropenem, cefoperazone/sulbactam, ticarcillin/clavulanate, and amikacin. (J Infect Dis Antimicrob Agents 2009;26:-8.) INTRODUCTION Surgical site infection (SSI) is an important cause of hospital-acquired infections among surgical patients. Patients who develop wound infections have longer hospital stays, more expensive hospitalizations, and increased mortality. 1 The development of wound infections depends on the integrity and protective functions of the skin. 2 Pseudomonas aeruginosa is a leading cause of nosocomial infections, ranking the second among Gram-negative pathogens reported to the United States national nosocomial infection surveillance system. P. aeruginosa contributes substantially to wound-related morbidity and mortality, worldwide. The organism enters into the blood, causing sepsis that may spread to the skin and lead to ecthyma gangrenosum, a black necrotic lesion. 3 It produces several substances that are thought to enhance the colonization and infection of host tissue. 4 These substances together with a variety of virulence factors, including lipopolysaccharides (LPSs), exotoxin A, leukocidin, extracellular slime, Department of Microbiology, Maharaja Agrasen Medical College, Agroha (Hisar), Haryana, India. Received for publication: March 17, 2009 Reprint request: Kiran Ruhil, Department of Microbiology, Maharaja Agrasen Medical College, Agroha (Hisar), Haryana, India. Keywords: Pseudomonas aeruginosa wound, post-operative wound, wound swab

44 J INFECT DIS ANTIMICROB AGENTS May-Aug. 2009 proteases, phospholipase, and several other enzymes make P. aeruginosa the most clinically significant bacteria among glucose non-fermenting bacteria. P. aeruginosa has the capacity to carry plasmids containing genes that regulate antimicrobial resistance, and this feature has led to the appearance of some P. aeruginosa strains that are resistant to normally reliable antibiotics. 5 Exposure to antimicrobials of different classes can result in the emergence of mutant strains that are highly resistant to several antimicrobials. Such multidrug-resistant (MDR) phenotypes can present a major therapeutic problem in various clinical settings. 6 The selective pressure from the use of antimicrobial agents is a major determinant for the emergence of resistant strains. The objective of our study was to determine the prevalence of P. aeruginosa isolation of postoperative wound in our hospital and its antimicrobial susceptibility pattern. MATERIALS AND METHODS The study was conducted in the clinical bacteriology laboratory, Department of Microbiology, Maharaja Agrasen Medical College, Agroha (Hisar), India. All specimens received from patients hospitalized from November 2006 to December 2008 were processed for isolation and identification of bacterial pathogens according to the standard microbiological techniques. 7 Clinical specimens Post-operative wound swabs were collected aseptically with a sterile cotton wool swab from different wards in the hospital. Media The following media including blood agar, MacConkey agar, chocolate agar, nutrient agar and slopes, peptone water, and Simmon citrate agar were used in our study. The media were prepared according to the manufacturers instructions in a 500-mL bottle and sterilized by autoclaving at 121 C for 15 minutes. Methods All wound swabs collected for bacteriology investigations during the study period were treated according to the established methods of treating wound swabs. Gram stain preparations were made from all swabs. Incubation of plates The plates were incubated at 37 C for 18-24 hours in an incubator. The plates were read the following day but extended to 48 hours if there was no bacterial growth within 24 hours. Isolated colonies were subjected to Gram staining and biochemical tests for identification. Identification Identification was carried out according to the standard biochemical tests. 7 Antibiotic testing Antimicrobial susceptibility testing was performed on Muller Hinton agar (Hi Media, Mumbai) plates by the disc diffusion method according to the National Committee for Clinical Laboratory Standards (NCCLS) guidelines. 8 The standard strain used as a control was P. aeruginosa ATCC 27853. Antibiotics used in our study were piperacillin (0 μg), ceftazidime (30 μg), cefepime (30 μg), imipenem ( μg), meropenem ( μg), ampicillin/sulbactam (/ μg), piperacillin/ tazobactam (0/ μg), ticarcillin/clavulanate (75/ μg), cefoperazone/sulbactam (75/ μg), gentamicin ( μg), tobramicin ( μg), amikacin (30 μg), and ciprofloxacin (5 μg).

Vol. 26 No. 2 Pseudomonas aeruginosa isolation in post-operative wound:- Ruhil K, et al. 45 RESULTS A total of 260 specimens were obtained from post-operative wound of all patients hospitalized at surgical, pediatrics, orthopedic, obstetrics, and gynecology wards. Isolation The most common isolated organism from post-operative wounds was P. aeruginosa (72 isolates, 27.7%), followed by Escherichia coli (53 isolates, 20.4%), Klebsiella spp. ( isolates, 16.5%), Staphylococcus aureus (41 isolates, 15.7%), Proteus spp. (14 isolates, 5.3%), Acinetobacter spp. ( isolates, 3.8%), and Citrobacter freundii (2 isolates, 0.8%) (Table 1). There was no growth in 25 (9.6%) samples. The abscess drainage was the most common type of post-operative wound (16.5%), followed by the surgery of diabetic foot (12.3%), Caesarean section (11.9%), open knee surgical wound (11.9%) (Table 2). Table 1. All organisms isolated from post-operative wounds. Table 2. Type The number of wound swabs in relation to the type of surgery. of surgery Number of specimens Abscess drainage 16. 5 Diabetic foot 32 12. 3 Caesarean section 31 11. 9 Open knee wound 31 11. 9 Liver abscess 23 8. 8 Herniorrhaphy 15 5. 7 Abdominal abscess 14 5. 3 Nail removal 12 4. 6 Perianal fistula 11 4. 2 Septoplasty 3. 8 Mastoidectomy 3. 8 Organism Numbe r Neck abscess 7 2. 6 Pseudomonas aeruginosa 72 27. 7 Escherichia coli 53 20. 4 K lebsiella spp. 16. 5 Staphyloccus aureus 41 15. 7 Skin grafting 6 2. 3 Lipoma excision 6 2. 3 Bone excision 5 1. 9 Thyroidectomy 4 1. 5 P roteus spp. 14 5. 3 A cinetobacter spp. 3. 8 Citrobacter freundii 2 0. 8 No growth 25 9. 6 The frequency of P. aeruginosa isolation in relation to age is shown in Table 3. The most frequent isolation of the P. aeruginosa was noted in the age group of 16-40 years (47.2%), followed by those of 4,160 years (41.6%) and of > 60 years (6.9%). Total 260 0 45 Susceptibility P. aeruginosa was most commonly susceptible

46 J INFECT DIS ANTIMICROB AGENTS May-Aug. 2009 Table 3. The frequency of Pseudomonas aeruginosa isolation in relation to the age group. Age group (ye ars) Numbe r of specimens Numbe r of isolation 0-15 3 4 16-40 127 34 47. 2 41-60 8 30 41. 6 > 60 15 5 6. 9 to imipenem (76.9%), followed by meropenem (70.4%), cefoperazone/sulbactam (62.1%), ticarcillin/ clavulanate (60.7%), and amikacin (53%) (Table 4). DISCUSSION A surgical wound infection is a post-operative complication that brings about embarrassment to the surgeon, considerable financial burden, undue discomfort to the patient and sometimes death. 9 Our study shows that P. aeruginosa was most prevalent (27.7%) among all the pathogens isolated from the surgical wound. Our results were in consistent with similar studies carried out by Anupurba and colleagues which showed P. aeruginosa was isolated in 32 percent of isolates. Oguntibegri and Nwobu in their study concluded it as 33.3 percent 11 and Hani and colleagues found a prevalence rate of 27.78 percent. 12 Stephen and colleagues in a similar study reported a frequency of P. aeruginosa isolation rate of 18.8 percent. 13 We therefore report it as a significant finding which is in agreement with that obtained in other hospitals. The frequency of P. aeruginosa isolation was found to be maximal in patients who underwent Caesarian section in the study by Oguntibeju and Nwobu 11 and in those with surgical wound infections and Caesarian section in the study by Hani and colleagues. 12 In our study, it was most commonly isolated in procedures involving drainage of abscesses and diabetic foot operations, followed by Caesarian section operations. When factors such as age and sex of the patient were considered, we found the occurrence of P. aeruginosa was higher in the age group of 16-40 years. Stephen and colleagues found P. aeruginosa was more commonly isolated in the age group of 21-30 years. 13 We found the prevalence rate was higher in male patients, compared with females. Jamshaid and colleagues also reported P. aeruginosa infections were more common in males (61.78%) 3, and Stephen and colleagues also reported in their study that male patients (57.3%) had the higher isolation rates. 13 The maximal susceptibility of P. aeruginosa isolates was against imipenem (76.9%) and meropenem (70.4%). Navaneeth and colleagues in their study noted the susceptibility of 88 percent each to imipenem and meropenem among P. aeruginosa isolates. 14 Bonfiglio and colleagues in their study summarized that meropenem was the most active compound against P. aeruginosa isolates, followed by amikacin. 15 Viren and colleagues concluded that all antibacterials tested in their study did not demonstrate good antibacterial activity against P. aeruginosa isolates with the exception of imipenem and meropenem and that P.

Vol. 26 No. 2 Pseudomonas aeruginosa isolation in post-operative wound:- Ruhil K, et al. 47 Table 4. The susceptibility pattern of Pseudomonas aeruginosa isolated in post-operative wounds. Antibacte rial of susce ptibility Imipenem 76. 9 Meropenem 70. 4 Cefoperazone/sullbactam 62. 1 Ticarcillin/clavulanate 60. 7 Amikacin 53 Piperacillin/tazobactam 45. 8 Ciprofloxacin 36 Ceftazidime 35. 8 Tobramicin 30. 5 Gentamicin 29. 1 Cefepime 25. 2 Piperacillin 13. 6 Ampicillin/sulbactam 12 aeruginosa isolates showed a susceptibility of 80.36 percent against carbapenems. 16 Although we found carbapenems to be the most successful drugs in vitro against P. aeruginosa, there is a likelihood of resistance to even these as seen in studies carried out on multidrug-resistant phenotype of P. aeruginosa. 6 Resistance to carbapenems is most likely to occur through the interplay of excess β-lactamase production, impermeability via a loss of porin protein Opr D, together with the up-regulation of multi-drug efflux systems, primarily Mex Amex B- Opr M. 17 47 We therefore recommended through our study that a use of carbapenems should be reserved for polymicrobial infection, concomitant anaerobic bacterial infection and where P.aeruginosa is resistant to other primary antibiotics. References 1. Kirkland KB, Briggs JP, Trivette SL, Wilkinson WE, Sexton DJ. The impact of surgical-site infections in the 1990s: attributable mortality, excess length of hospitalization, and extra costs. Infect Control Hosp Epidemiol 1999;20:725-30.

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