Antibiotic susceptibility pattern of bacterial isolates from wound infection in Chitwan Medical College Teaching Hospital, Chitwan , Nepal

A wound is a breach in the skin, and exposure of subcutaneous tissue following loss of skin integrity. It provides a moist, warm, nutritive conducive to microbial colonization and proliferation. Wound contaminants may not persist, but species that grow and divide may become established, causing wound colonization or infection. The outcome depends on the interaction of complex host and microbial factors. Infection in a wound delays healing and may cause wound breakdown, herniation, or complete wound dehiscence.


Introduction
A wound is a breach in the skin, and exposure of subcutaneous tissue following loss of skin integrity. It provides a moist, warm, nutritive conducive to microbial colonization and proliferation 1 . Wound contaminants may not persist, but species that grow and divide may become established, causing wound colonization or infection. The outcome depends on the interaction of complex host and microbial factors 2 . Infection in a wound delays healing and may cause wound breakdown, herniation, or complete wound dehiscence 3 .
Many bacteria species live on human skin, in the nasopharynx, gastrointestinal tract and other parts of the body with little potential for causing disease because of first line defense within the body. Surgical operation, trauma, burns, diseases, nutrition and other factors affect these defenses. The skin barrier is disrupted by every skin incision, and microbial contamination is inevitable despite the best skin preparation 4 .
Despite technological advances in surgery and wound infection has been regarded as the most common nosocomial infection, especially in patients undergoing surgery 5 . An important cause of illness, wound infection results in prolonged hospital stay and increased trauma care and treatment costs; in general, wound management practices become more resource demanding 1 . The severity of complications depends largely on the infecting pathogen and site of infection 6 .
Wound infections have been a problem in the field of medicine for a long time. Advances in control of infections have not completely eradicated this problem because of development of drug resistance 7 . The widespread uses of antibiotics, together with the length of time over which they have been available have led to major problems of resistant organisms contributing to morbidity and mortality 8 . Antimicrobial resistance can increase complications and costs associated with procedures and treatment 9 . Knowledge of the causative agents of wound infection has proven to be helpful in the selection of appropriate antimicrobial therapy and on infection control measures taken in health institutions 2 . Hence, the present study was designed to update knowledge on bacteriology of wounds and the sensitivity pattern of the causative agents to the common antibiotics used in Chitwan Medical College Teaching Hospital, Bharatpur ,Chitwan, Nepal.

Methods
This study included patients with acute and chronic wounds with purulent discharge or painful spreading erythema around a wound. This included cutaneous abscesses, traumatic wounds, foot ulcers and pressure ulcers. Total 200 patients of all the age groups attending Chitwan Medical College Teaching Hospital during a period of 6 months (from December 2011 to June 2012) were included in the study. Informed consent was obtained from the patients. Pus was collected from wound with the help of sterile disposable cotton swab and immediately inoculated onto Blood agar and MacConkey agar media and incubated at 37˚C for 24 hours. After incubation, identification of bacteria from positive culture plates was done with the standard microbiological technique, which included study of colony morphologies, staining and biochemical reactions. The antibiotic sensitivity test of the entire isolates was performed by Kirby-Bauer disk diffusion method on Muller Hinton agar or blood agar medium using antibiotic disks of HiMedia Laboratories Pvt. Limited A-406, Bhaveshwar Plaza, LBS Marg, Mumbai-400086, India.

Discussion
Wound is a major concern among healthcare practitioners, not only in terms of increased trauma to the patients but also in view of its burden on financial resources and the increasing requirement for cost effective management within health care systems 1 .
In the present study 75% of pus culture was found to be positive for bacterial growth. Staphylococcus aureus strains accounted for 65.3% of the total bacterial isolates recovered from wound followed by Enterobacter was 100% sensitive to ampicillin, amikacin, cotromoxazole & ofloxacin. It was equally sensitive [66.6%] to gentamicin, cefotaxime, ceftriaxone and ciprofloxacin.
Another gram negative bacilli Acinetobacter species was 100% sensitive to gentamicin, amikacin & ofloxacin whereas [50%] sensitive to ciprofloxacin. Hundred percent of these organisms were found to be resistant to cefotoxime, ceftriaxone, ampicillin and cotrimoxazole.

Conclusion
This study reveals that a variety of bacterial pathogens are responsible for wound infection in Chiwtan, Nepal. Staphylococcus aureus was found to be the most common organism isolated. Majority of the bacterial isolates were resistant to almost all the antimicrobials employed. Among all the bacterial isolates, Escherichia coli was found to be highly resistant to commonly used antibiotics. High rate of multiple antibiotic resistance among both gram positive and gram negative bacterial species have been observed, which may have impact on prolonging wound healing and increasing the cost of therapy to patients. Thus, it is highly recommended to perform antimicrobial susceptibility testing before administration of antibiotics.