|Year : 2016 | Volume
| Issue : 1 | Page : 62-68
Microbiological and quantitative analysis of burn wounds in the burn unit at a tertiary care hospital in Kashmir
Tahir Saleem Khan, Akram Hussain Bijli, Adil Hafeez Wani
Department of Plastic, Reconstructive Surgery and Burns, Sher-I-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India
|Date of Web Publication||12-Dec-2016|
Tahir Saleem Khan
Department of Plastic, Reconstructive Surgery and Burns, Sher-I-Kashmir Institute of Medical Sciences, Soura, Srinagar - 190 001, Jammu and Kashmir
Source of Support: None, Conflict of Interest: None
Background: The burn wound represents a susceptible site for opportunistic colonization by organisms of endogenous and exogenous origin. The present study was undertaken to analyze the microflora of burn wounds of the burn patients from a tertiary care hospital in Kashmir, India. Materials sand Methods: The study included all patients with acute burns admitted from January 2010 to December 2011 (2 years). The standard techniques, as practiced during collection of microbiological specimens, were used during wound swab/biopsy collection. Results: 74.19% of swab cultures yielded single isolates. On swab culture, Pseudomonas aeruginosa was the commonly isolated organism (46.86%). Staphylococcus aureus was the most common isolate isolated during 1st postburn week (30.86%). 258/288 (89.58%) blood cultures were sterile. 8/58 (13.79%) blood cultures were positive during the second postburn week. S. aureus was the most common organism grown on blood culture (44.44%). P. aeruginosa was mostly sensitive to polymyxin B (86.0%), amikacin (40.0%), and ciprofloxacin (37.3%), respectively. S. aureus was most commonly sensitive to linezolid (85.0%) and vancomycin (78.8%%) whereas Acinetobacter spp. was sensitive to polymyxin B (65.3%), piperacillin/tazobactam (44.9%), and amikacin (38.8%). Patients (27.27%) who showed local signs of burn wound infection and positive blood culture were subjected to burn wound biopsy. 93.33% of patients who had counts >105 colony-forming unit/g of tissue showed significant association with local signs of burn wound infection and positive blood culture for any organism. Conclusion: The microbiological surveillance of burn wounds needs to be continued for a rational antibiotic policy and prevention of emergence of resistant organisms. Burn wound biopsy culture is an effective tool for quantitative analysis of burn wounds; however, subjecting this biopsy to histological examination is more predictable of burn wound infection and its correlation with burn wound sepsis.
Keywords: Biopsy, burn wound, sepsis, swab culture
|How to cite this article:|
Khan TS, Bijli AH, Wani AH. Microbiological and quantitative analysis of burn wounds in the burn unit at a tertiary care hospital in Kashmir. Indian J Burns 2016;24:62-8
|How to cite this URL:|
Khan TS, Bijli AH, Wani AH. Microbiological and quantitative analysis of burn wounds in the burn unit at a tertiary care hospital in Kashmir. Indian J Burns [serial online] 2016 [cited 2017 Nov 19];24:62-8. Available from: http://www.ijburns.com/text.asp?2016/24/1/62/195527
| Introduction|| |
The burn wound represents a susceptible site for opportunistic colonization by organisms of endogenous and exogenous origin. Patient factors such as age, extent of injury, and depth of burn in combination with microbial factors such as type and number of organisms, enzyme and toxin production, and motility determine the likelihood of invasive burn wound infection. Individual patients, usually those with extensive burns in whom wound closure is difficult to achieve, may develop a variety of bacterial and nonbacterial burn wound infections.
About 75% of the mortality associated with burn injuries is related to sepsis, especially in developing countries. Overcrowding in burns units, a major cause of cross infection, in these countries, makes it essential to monitor the bacterial flora of these wounds and their antibiotic sensitivity patterns on a regular basis so that proper drug therapy is initiated at an appropriate time. Any change in wound appearance, with or without associated clinical changes, should be evaluated by biopsy.
Quantitative cultures of the biopsy sample may identify predominant organisms but are not useful for making the diagnosis of invasive burn wound infection. Histologic examination of the biopsy specimen, which permits staging the invasive process, is more reliable means of differentiating wound colonization from invasive infection. A diagnosis of invasive burn wound infection necessitates change of both local and systemic therapy and in the case of bacterial and fungal infections, prompt surgical removal of the infected tissue.
The present study was undertaken to study the microflora of burn wounds of burn patients from a tertiary care hospital in Kashmir, India. This study will help to assess the burden of infections, and the antimicrobial susceptibility testing will help in formulating proper antibiotic policy for these patients.
| Materials and Methods|| |
This study included all patients with acute burns treated in our department from January 2010 to December 2011 with an aim (1) to determine the bacteriology of the patients admitted in our burn unit and their antibiotic susceptibility. (2) Correlation between quantitative culture obtained by wound biopsy and sepsis in burn patients.
Microbiological analysis of the wound in the form of wound swab/quantitative cultures and blood cultures with antibiotic sensitivity was done on weekly basis. Burn wound swabs/biopsies were taken using the standard technique of collection of microbiological specimen and were processed under the supervision of microbiologist. The specimens were cultured under aerobic conditions, using Nutrient agar, MacConkey agar, and Blood agar at 37°C for 24 h. The isolates were identified by culture, staining, and required biochemical tests and their antibiotic sensitivity determined using Kirby-Bauer disc diffusion technique.
Biopsy was collected by scalpel. Topical antimicrobials were wiped away from site with sterile water soaked gauze if visible. Biopsies were not taken from burns that were entirely superficial or from burns which were already grafted.
| Results|| |
Overall, 341 surface swabs and 288 blood cultures were taken on weekly basis in 110 patients in our study. 253/341 (74.19%) swab cultures yielded single isolates whereas multiple isolates were seen in only 36/341 (7.62%) swab cultures. No growth (sterile) was reported in 52/341 (15.25%) swab cultures taken in our series [Table 1]. A maximum number of single isolates was seen in 1st postburn week 63/253 (24.90%) [Table 2].
Pseudomonas aeruginosa was the commonly isolated organism (46.86%) followed by Staphylococcus aureus (26.38%) and Acinetobacter spp. (12.70%), respectively. S. aureus was the most common isolate, isolated during 1st postburn week (30.86%), and P. aeruginosa was isolated commonly during 2nd postburn week (24.00%) [Table 3]. 89.58% of blood cultures were sterile (9.37%) cultures showed growth of single isolate, whereas multiple isolates were detected in 1.04% of blood cultures [Table 4]. 8/58 blood cultures (13.79%) were positive during 2nd postburn week [Table 5]. S. aureus (44.44%) was the most common organism grown followed by P. aeruginosa (36.11%). Maximum number of isolates 14/36 (38.88%) were reported during 2nd postburn week [Table 6].
Commonly isolated organism P. aeruginosa was sensitive to polymyxin B (86.0%), amikacin (40.0%), and ciprofloxacin (37.3%), respectively. S. aureus was most commonly sensitive to linezolid (85.0%) and vancomycin (78.8%%) whereas Acinetobacter spp. was sensitive to polymyxin B (65.3%), piperacillin/tazobactam (44.9%), and amikacin (38.8%) [Table 7].
Patients having at least two general signs (signs of inflammatory response syndrome) and positive blood culture and/or local signs of burn wound infection were taken as patients having sepsis. Patients (27.27%) who showed local signs of burn wound infection and positive blood culture were subjected to burn wound biopsy. 28/30 (93.33%) of patients had counts >105 colony-forming unit [CFU]/g of tissue and showed significant positive association in those patients who showed local signs of burn wound infection and positive blood culture for any organism [Table 8].
| Discussion|| |
Infection remains a foremost concern in the management of burn wounds because the large raw area with its serous exudate may act as a huge culture plate on which organisms can establish and multiply. Fresh burns are usually sterile but progressively become colonized with one or more bacterial species as the patient's stay in burn unit increases. The role of the different bacterial species in burn pathology varies from mere colonization, local tissue sepsis, and interference with healing and grafting, to invasion of blood stream with subsequent septicemia and death, especially with sepsis caused by Gram-negative bacteria.,
In our study, 74.19% of swab cultures yielded single isolates whereas multiple isolates were seen in only 7.62% of the swab cultures. The maximum number of single isolates was seen in 1st postburn week, 63/253 (24.90%). Overall, P. aeruginosa was the commonly isolated organism (46.86%) followed by S. aureus (26.38%) and Acinetobacter spp. (12.70%). S. aureus was the most common isolate, isolated during 1st postburn week 25/68 (36.76%), and P. aeruginosa was isolated commonly during 2nd postburn week 36/64 (56.26%). No isolates of beta-hemolytic streptococci were encountered in our study. As far as, the overall colonizing organism is concerned our findings are consistent with those reported by Kaushik et al. These authors reported that the isolates obtained from the culture of wound swabs were single in the majority of cases (78.0%). Pseudomonas was the most commonly cultured organism (54.2%) followed by S. aureus (20.8%). No isolates of beta-hemolytic streptococci or diphtheroid were encountered. Similar observations were made by Revathi et al., who reported P. aeruginosa as the most common isolate (36%) from the burn patients followed by S. aureus (19%). Peng et al. also reported P. aeruginosa as the most common isolate (36.24%) followed by S. aureus (18.01%) and Acinetobacter baumannii (14.37%). Our observations are in contrast to a number of studies from various countries which reported S. aureus as the most common colonizing organisms in their patients. Ozumba and Jiburum  from Africa, however, reported most common colonizing organism as Klebsiella species (26.7%) followed by S. aureus (25.6%).
Burn injury causes depression of immune response and severe catabolism proportional to the extent of injury. The dysfunction of immune response, a large cutaneous bacterial load, the possibility of gastrointestinal bacterial translocation, prolonged hospitalization, and invasive diagnostic and therapeutic procedures, all contribute to sepsis. In our study, we observed that 89.58% of blood cultures were sterile whereas 10.41% were positive for any organism. 9.37% cultures showed growth of single isolate whereas multiple isolates were detected in 1.04% of blood cultures. Our observations are in contrast to that of Bang et al., who reported multiple isolates in 13% of the blood cultures. The maximum number of blood cultures in our study (8/58, 13.79%) were positive during 2nd postburn week. S. aureus was the most common organism grown (44.44%) followed by P. aeruginosa (36.11%) and both were isolated most commonly from the blood cultures taken during 2nd postburn week. Similar observations were made by Bang et al., who reported 54.4% of septicemic episodes due to S. aureus in their series. The good proportion of patients in our study also had Pseudomonas septicemia that could be possibly attributed to the factor that early wound excision and immediate skin grafting was not done in our patients and the chances of burn wound colonization and tissue invasion by organisms increases with the passage of time. It has been seen that P. aeruginosa infection decreases following surgical removal of all necrotic tissue and immediate grafting. Similar observations were made by other authors in their study.
Microbiological surveillance of burn patients, which was routinely done in our patients, helped in learning the type of organisms and facilitated the choice of antibiotics prophylaxis. Further, the antibiotic sensitivity of the organisms to different antibiotics varied depending on the isolate. In our study, commonly isolated organism P. aeruginosa was sensitive to polymyxin B (86.0%), amikacin (40.0%), and ciprofloxacin (37.3%), respectively. The sensitivity of Pseudomonas to prototype antipseudomonal drug, ceftazidime was noted in only 12% of our patients. S. aureus was most commonly sensitive to linezolid (85.0%) and vancomycin (78.8%%) whereas Acinetobacter spp. was sensitive to polymyxin B (65.3%), piperacillin/tazobactam (44.9%), and amikacin (38.8%). Our findings are in contrast to those reported by some authors. Atoyebi et al. reported in their study that only 15% of staphylococci were sensitive to cloxacillin and most of the organisms cultured were sensitive to ceftazidime (93.5%). Guggenheim et al. noted that S. aureus was less susceptible to broad-spectrum antibiotics such as ciprofloxacin or penicillinase-stable penicillins; however, it was susceptible to others such as co-trimoxazole or netilmicin. Revathi et al. reported that Pseudomonas spp. was most susceptible to ceftazidime (83%) and cefoperazone (82%). Whereas drugs most effective against other Gram-negative organisms were amikacin, netilmicin, and ciprofloxacin. Vancomycin was effective in 100% of Gram-positive organisms. Ozumba and Jiburum  reported a very high degree of resistance to the commonly used antibiotics against the organisms isolated due to the rampant use of broad-spectrum antibiotics on empirical basis as only 25% of the patients in their study could afford the cost of cultures in their study. Norbury et al. have reported the emergence of resistant organisms in burn patients, and the use of new classes of antibiotics has helped the clinicians to overcome this.
The reason for taking tissue biopsy in our patients was to determine the correlation between the critical bacterial load (>105 CFU/g of tissue) and the patients showing signs of sepsis. This correlation was found significant as observed from our findings that 28/30 (93.33%) patients in whom wound biopsy was taken for quantitative culture had counts >105 CFU/g of tissue. Similar observations were noted by Bharadwaj et al. in a study of assessment of burn wound sepsis in fifty patients in which 87.5% of the patients with significant bacterial count on biopsy culture showed signs of clinical sepsis. Likewise Uppal et al. found wound biopsy to be more valuable as it gave the critical load (>105 CFU/g of tissue) of the organism beyond which metastatic invasion of the organism would take place (P < 0.01). Our observation, however, is in disagreement with that of Steer et al., who could not establish a relationship between bacterial counts and sepsis or graft loss.
Although there was a significant correlation between sepsis and obtaining counts beyond the critical level in patients with clinical or hematologically documented sepsis, it remains not a very effective tool for prediction of sepsis in burn patients as noted by above authors  and because of the following reasons. (1) The counts between biopsies taken can vary more than between surface swabs taken because the bacteria on the surface of the wound can migrate and distribute more evenly across the burn than bacteria within the wound. (2) Errors in the quantification can arise if drying of the biopsies occurs before processing or if there is variation in the amount of viable and nonviable tissues present. (3) Variation in the completeness of homogenization can occur during the processing. This makes us to conclude that there are currently better modalities of prediction of sepsis in burn wounds such as histological examination of burn wound biopsies which show accurately the level of invasion of the organisms in the burn wound from mere colonization to the invasion of viable tissues with vascular and lymphatic involvement. Further, it has been also seen that the mortality among burn patients increases as the biopsy determined stage increases with the critical differentiation being between colonization and tissue invasion.
| Recommendations/conclusion|| |
- The microbiological surveillance of burn wounds of patients needs to be continued so that a rational antibiotic policy could be adopted while treating these patients to prevent the emergence of resistant organisms
- Burn wound biopsy culture is an effective tool for quantitative analysis of burn wounds; however, subjecting this biopsy to histological examination to determine the level of invasion by the infecting organism is more accurate and predictable of burn wound infection and its correlation with burn wound sepsis.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]