This cross-sectional study was conducted for a period of six months (January 2013 to June 2013) in a rural tertiary care hospital of Uttarakhand state, India. Prior to the sample collection, approval from Institutional Ethical Committee was obtained. The study population included 137 patients suffering from SSIs in the various surgical wards (orthopedic, general surgery, ophthalmology, obstetrics and gynecology, otorhinolaryngology) of our hospital. Patients of both sex, age > 14 years, who had surgical wound pus discharge, with serous or seropurulent discharge and with signs of sepsis present concurrently (warmth, erythema, induration, tenderness, pain, raised local temperature) were included. Patients who had suture abscesses, wounds with cellulitis and no drainage were excluded from the study. A detailed history regarding age, sex, type of illness, diagnosis, type and duration of surgery performed, antibiotic therapy and the associated co-morbid diseases was obtained from the patients.

Using sterile cotton swabs, two pus swabs/ wound swabs were collected aseptically from each patient suspected of having SSI. Gram stained preparations were made from one swab for provisional diagnosis. The other swab was inoculated on 5% sheep blood agar (BA) and Mac Conkey agar (MA) plates and incubated at 37°C for 48 hours before being reported as sterile. Growth on culture plates was identified by its colony characters and the battery of standard biochemical tests [7,8]. Antimicrobial sensitivity testing (AST) was carried out by modified Kirby Bauer disc diffusion method on Muller Hinton agar and results were interpreted in accordance with Clinical Laboratory Standards Institute guidelines [9]. Methicillin resistance was detected by taking cefoxitin (30μg) as a surrogate marker and was confirmed by using PBP2a latex agglutination test (Oxoid Ltd, Hampshire, UK). Staphylococcus aureus - ATCC 25923, Escherichia coli - ATCC 25922 and Pseudomonas aeruginosa - ATCC 27853 were used as control strains for AST. All dehydrated media, reagents and antibiotic discs were procured from Hi Media Laboratories Pvt. Ltd., Mumbai, India.

From January 2013 to June 2013 a total of 768 patients underwent the major surgeries in various departments of our hospital, out of which 137 patients (17.8%) were clinically diagnosed of having SSIs. Out of the total 137 samples processed, 132 (96.4%) yielded aerobic bacterial growth and a total of 139 bacterial isolates were obtained. Monomicrobial growth was seen in 125 samples while seven samples showed polymicrobial growth. The mean age of the patients was 43.8 years (range 14 to 85 years) and the peak incidence of SSI was observed in age group > 50 years (51.8%). [Table/Fig-1] shows the age wise distribution of various morphotypes in SSIs. Males (74.6%) were more commonly affected than females (25.5%) and the sex ratio male: female was 2.9:1.

Among the 139 bacterial isolates, S. aureus (50.4%) and E. coli (23.02%) were the commonest organisms. [Table/Fig-2] depicts the characterization of various bacterial isolates obtained from patients with SSIs. Antimicrobial susceptibility testing was carried out for all 139 isolates and the results are depicted in [Table/Fig-3]. Staphylococcus aureus strains showed a high degree of resistance for ampicillin (85.7%). Methicillin resistance was seen in 15.7% of all the S.aureus isolates. Gram negative isolates showed even higher rate of resistance and commonly prescribed agents like gentamicin, cotrimoxazole and ciprofloxacin were found resistant for most of the gram negative isolates. Meropenem showed good activity against most of the gram negative isolates, except for P. aeruginosa strains which showed high resistance for meropenem (72.7%) also.

Despite the advances in surgical techniques and better understanding of the pathogenesis of wound infection, management of SSIs remains a significant concern for surgeons and physicians in a health care facility. Patients with SSIs face additional exposure to microbial populations circulating in a hospital set up which is always charged with microbial pathogens. The unrestrained and rapidly spreading resistance to the available array of antimicrobials further contributes to the existing problem. Most of the SSIs are hospital acquired and vary from hospital to hospital. The rate of SSIs has been reported to be 2.5% to 41.9% [10]. In the present study the overall rate of SSI was 17.8% which was in concordance with the study conducted by Satyanarayana et al., who reported the overall rate of SSI as 13.7% in their study [11]. Various other studies from India have shown the rate of SSI to vary from 6.1% to 38.7% [10,12–14] . However in comparison to the Indian hospitals the rate of infection reported from other countries is quite low, for instance in USA it is 2.8% and in European countries it is reported to be 2-5% [11]. The lack of attention towards the infection control measures, inappropriate hand hygiene practices and over crowded hospitals can be the major contributory factors for high infection rate in Indian hospitals.

The predominance of male patients was seen in this study with male: female ratio of 2.9:1and this finding was in contrast to the other studies where a much higher number of female patients have been reported [4,5]. The patients with age >50 years had a higher incidence of SSI (51.8%) in comparison to an incidence of 12.4% among the patients who were ≤30 years of age. Advancing age is an important factor for the development of SSIs, as in old age patients there is low healing rate, low immunity, increased catabolic processes and presence of co-morbid illness like diabetes, hypertension, etc [13]. Regarding the duration of the operation a prolonged time was found to be a significant risk factor for SSI and it was observed that as the order and the duration of surgery increased, the rate of infection also increased.

Staphylococcus aureus, gram positive cocci, is a major human pathogen and a predominant cause of SSIs worldwide with a prevalence rate ranging from 4.6% to 54.4% [14]. In the present study predominance of S. aureus (50.4%) was seen and this finding was consistent with reports from other studies [5,10,12,15,16]. Infection with S. aureus is most likely associated with endogenous source as it is a member of the skin and nasal flora and also with contamination from environment, surgical instruments or from hands of health care workers [16,17]. S. aureus was the single predominant gram positive bacterial isolate obtained in this study. Special interest in S. aureus SSI is mainly due to its predominant role in hospital associated infection and emergence of methicillin resistant S.aureus (MRSA) strains. In our study methicillin resistance was seen in 15.7% of S.aureus isolates. This finding was in tandem with the study conducted by Aggarwal et al., [18], who reported methicillin resistance in 10% of the isolates, however it is in contrast with the study conducted by Kownhar et al., [15] who reported higher incidence of 21.7%. Still higher incidences of 45% and 58.2% of MRSA have been documented by Eagye et al., [19] and Kaye et al., [20] respectively. We found that all the S. aureus strains (irrespective of methicillin resistance) were sensitive to vancomycin, teicoplanin and linezolid. This finding can be of relevant clinical use for the formulation of antibiotic policy of our hospital.

Gram negative isolates comprised of 49.6% of all the aerobic bacterial isolates. E. coli (46.4%) was the commonest gram negative bacteria isolated followed by P. aeruginosa (15.9%) and Citrobacter spp (15.9%). Similar observations have been reported by various other authors also [4,5,14]. Few studies have reported P.aeruginosa as the most frequent isolate in SSI [6,21] which remains a third most isolated strain in this study. Presence of enteric organisms could be attributed to the patient’s normal endogenous microbial fecal flora [10] E. coli invasion of the wound is a clear case of poor hospital hygiene.

Antibiotic susceptibility results revealed that a high degree of resistance was seen for majority of the bacterial isolates. For gram positive bacteria vancomycin, teicoplanin, linezolid and amikacin were found to be the most effective antibiotics. The degree of resistance was even higher among the gram negative bacteria and the commonly used drugs were found to be more resistant with an average resistance range from 50% to 100%. Meropenem, piperacillin-tazobactam, and amikacin were found to be the most effective antimicrobial agents whereas ampicillin, amoxicillin-clavulanate and cefotaxime were among the most resistant drugs. P.aeruginosa strains isolated in the present study were found highly resistant in comparison to the previous studies [6,5]. The development and spread of resistant bacterial strains has emerged as a global problem. The appearance of multi drug resistant (MDR) strains over the past decades has been regarded as an inevitable genetic response to the strong selective pressure imposed by antimicrobial chemotherapy which plays a crucial role in evolution of antibiotic resistant bacteria.

All cases in our study received prophylactic antimicrobials prior to the surgery. Current recommendations for antimicrobial prophylaxis to prevent SSI advise that an antimicrobial agent be administered within 60 minutes prior to surgery and discontinued soon afterward [22]. However, more than 50% of our patients received preoperative antimicrobials more than six hours before surgery and almost all patients were treated with antimicrobials after surgery. Many of them were even treated until the day of discharge in an attempt to prevent infection while they were hospitalized. The most widely used combination was a third generation cephalosporin and an aminoglycoside. However, the antimicrobial susceptibility results showed that the isolated bacterial strains were mostly resistant to these agents. Invariably the maximum resistance was observed for ampicillin by nearly all the isolates and this was found to be statistically significant for all except Proteus species [Table/Fig-3]. The frequent empirical prescription of these antimicrobials as a treatment and prophylaxis in our hospital might have contributed for observed high degree of resistance. This situation raises a serious concern and calls for immediate revision of antibiotic policy and antibiotic prescribing guidelines.

The rate of SSI observed in this study was comparable to other similar studies carried out in developing countries including India; however the bacterial isolates detected from our patients showed a high degree of resistance for commonly prescribed antimicrobials in our setup. Although the studies with bigger sample size are sought to make it statistically more relevant.

Inspite of the modern surgical and sterilization techniques and the use of prophylactic antimicrobials, SSIs still continue to pose an important clinical challenge. They impose a substantial burden of disease both on patients as well as healthcare services in terms of pharmacotherapeutic and pharmacoeconomic losses. Although SSIs cannot be completely eliminated, but reduction of the rate of infection to minimal can have significant benefits by reducing the wastage of healthcare resources, patient morbidity and mortality. This can be achieved by optimal preoperative, intraoperative and postoperative patient care. Also there is good evidence that attention to multiple patient related and procedure related risk factors can decrease the risk of SSIs significantly. This would be supplemented with proper infection control measures and a sound antibiotic policy which will surely result in better patient care, safety and healthcare outcomes.

The limitation of our study was that, anaerobic bacterial profile and fungal cultures were not done on the wound swabs obtained from SSIs. Further prospective studies can be undertaken in this regard.

To establish the most suitable empirical treatment for each patient, it is very important to know the microbial epidemiology of each institution. The information obtained from this study allows a better understanding of the microbial etiology of SSIs in our hospital which may have epidemiological and therapeutic implications. Using the results of this study, an initiative for establishing improved hospital antimicrobial policy and antimicrobial prescribing guidelines should be undertaken. Also the inappropriate and prolonged use of antibiotics should be avoided as this can lead to the development of resistant micro organisms which are even more difficult to get rid of.