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 Table of Contents  
Year : 2016  |  Volume : 18  |  Issue : 1  |  Page : 12-16

Effects of antibiotic prophylaxis on surgical wounds: A study in a tertiary care centre of central Kerala

1 Department of Microbiology, Government Medical College, Thrissur, Kerala, India
2 Department of Microbiology, Amrita Institute of Medical Sciences, Kochi, Kerala, India
3 Department of General Surgery, Government Medical College, Thiruvananthapuram, Kerala, India

Date of Web Publication28-Jun-2016

Correspondence Address:
Sujatha Vattamparambil Sankaran
Department of Microbiology, Government Medical College, Thrissur, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-1282.184752

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Background and Objectives: Effectiveness of prophylactic antibiotics is based on the susceptibility of the common potential pathogens to those antibiotics. Irrational use of drugs has an adverse impact on treatment outcome and financial burden to patients. Aims: Objective of this study was to evaluate the effect of antibiotic prophylaxis on surgical site infections and wound colonisation. Materials and Methods: A cross-sectional study was conducted among the patients of general surgery wards of a tertiary care hospital of central Kerala. Swabs collected from surgical wound sites after 48 h of surgery were analysed for bacteriological profile and antibiotic prophylaxis given. Statistical analysis was done by Epi Info. Results: Three hundred and ten cases were studied including 75.5% elective and 24.5% emergency cases. Cefotaxime (55.2%) and third generation cephalosporin combination with β-lactamase inhibitors (35.5%) were commonly used for antibiotic prophylaxis. Infection rates were 2.1% in clean surgeries, 8.1% in clean-contaminated and 22.8% in contaminated types of surgeries with an overall infection rate of 8.1%. Escherichia coli (45%) and Staphylococcus aureus (34.5%) were the predominant wound pathogens. Colonisation in 28.1% wounds with S. aureus as the major coloniser (72.8%) was noticed. Susceptibility of E. coli to Cefotaxime was 15.4% in infections and 20% in colonisation. Infection rates were higher in the group with multiple antibiotic usages for 5 days (40%) or above (52%). Colonisation increased on prolonged administration of multiple antibiotics (40%) and without using antibiotics (39%). Clean wounds without antibiotic prophylaxis were not infected. Conclusions: This study revealed that antibiotic prophylaxis is not required for clean wounds. Short duration of antibiotics usage based on the local susceptibility pattern is to be adopted. Antibiotic usage has to be restricted, and prophylactic regime with third-generation cephalosporin has to be curtailed.

Keywords: Antibiotic prophylaxis, antibiotic susceptibility, surgical site infection, wound colonisation

How to cite this article:
Sankaran SV, Rajagopal GK, Achamkulangara S. Effects of antibiotic prophylaxis on surgical wounds: A study in a tertiary care centre of central Kerala. J Acad Clin Microbiol 2016;18:12-6

How to cite this URL:
Sankaran SV, Rajagopal GK, Achamkulangara S. Effects of antibiotic prophylaxis on surgical wounds: A study in a tertiary care centre of central Kerala. J Acad Clin Microbiol [serial online] 2016 [cited 2023 Feb 8];18:12-6. Available from: https://www.jacmjournal.org/text.asp?2016/18/1/12/184752

  Introduction Top

Antimicrobial prophylaxis is used to reduce the incidence of post-operative wound infections. Surgical site infection (SSI) is defined as infections that occur within 30 days at the site of surgery. The effectiveness of prophylactic antibiotics is based on the microbial resistance pattern of the potential pathogens prevalent in that region. The prophylactic regimen need not eradicate every pathogen. Irrational use of drugs increases the incidence of antibiotic resistance and makes a significant impact on treatment outcomes and economic burden to the patients.

Commonly, the source of the infecting organism in SSIs is the patient's own flora or the hospital environment. Hand hygiene measures are important to prevent cross infection through the colonised hands.

The Centres for Disease Control and Prevention guidelines for the prevention of SSIs emphasise the importance of good patient preparation, aseptic practice, attention to surgical technique and appropriate antimicrobial prophylaxis.[1]

  Materials And Methods Top

A cross-sectional study was conducted in 310 patients in a tertiary care hospital of Kerala state in South India after the approval of the Institutional Review Board. Patients of either sex above 15 years and admitted in general surgery wards were included in the study during a period 1st September 2010–31st August 2011, one year. Critically ill patients and cases with dirty surgical wounds where incision is through infected area were excluded.

Patient's data were collected in a pre-designed pro forma which included age, sex, type of surgical procedure, risk factors, antibiotics prescribed, dose, time and duration of administration. After 48 h of surgery, dressings on the surgical wounds were removed. Any evidence of wound infection was indicated by local inflammatory change or discharge from wound site. Swabs were collected from the wound site for bacteriological analysis and antibiotic susceptibility using standard laboratory methods. Colonisers were defined based on the appearance of wound, where there was no inflammation or discharge and Gram staining where pus cells were absent or only occasional. Each case was followed up till the day of discharge. The cases were categorised into six groups based on the number and duration of antibiotic administration. The effect of antibiotics on wound colonisation and infection were analysed for each category. Statistical analysis was done using Ep Info-7 Software (Developed by CDC).

  Results Top

A total of 310 cases were studied including 234 (75.5%) elective and 76 (24.5%) emergency surgeries. There were 194 clean wounds (62.6%), 37 clean contaminated (11.9%) and 79 contaminated (25.5%) types.

The antibiotics were given based on the type of surgeries and risk factors. Only the clean cases were operated without prophylactic antibiotics or had perioperative doses. Out of 310 patients, 264 (85.2%) cases received prophylactic antibiotics. Twenty-five patients (8.1%) developed SSI and colonisers were isolated in 87 (28.1%) cases. The categories of antibiotic use [Figure 1] and the patterns of bacterial growth in each category are shown in [Table 1].
Figure 1: Category of prophylactic antibiotic usage

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Table 1: Wound infection and colonisation after antibiotic prophylaxis

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Cefotaxime was given for 171 patients (55.2%). There were 49 (28.7%) colonised and 12 (7%) infected cases in this group. Among the 110 patients (35.5%) who received third generation cephalosporin-sulbactam combination, 30 cases (27.3%) had wound colonisers and 5 (4.5%) developed infection. In clean-contaminated and contaminated surgeries, Metronidazole was added. Other drugs used were Ciprofloxacin (2.9%), Piperacillin-Tazobactam combination (1.9%), Gentamicin (1.9%), Amikacin (1.6%), Penicillin (1.3%), and Ampicillin (1.3%).

Staphylococcus aureus was isolated as the major (73%) wound coloniser [Figure 2]. The most common pathogen isolated was  Escherichia More Details coli (45%) followed by S. aureus (35%) [Figure 3].
Figure 2: Bacterial isolates from colonised wounds

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Figure 3: Bacterial isolates from wound infection

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The antibiotic sensitivity pattern of isolates from colonisation and wound infection was compared [Table 2] and [Table 3].
Table 2: Comparison of antibiotic sensitivity of Gram positive isolates between coloniser and pathogen

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Table 3: Comparison of antibiotic sensitivity among Gram negative isolates between coloniser and pathogen

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The effect of antibiotics on wound colonisation and wound infection was analysed based on the pattern of antibiotic prophylaxis they had, using Chi-square test [Table 4].
Table 4: Antibiotic usages with colonisation and infection (n=121)

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Chi-square test was used to study the association of duration of antibiotic usage and its outcome. There was a statistically significant difference in the rate of colonisation and infection observed in multiple drug users for more than 5 days (χ2 - 29.2, P = 0.000) compared to those with drugs used <5 days.

  Discussion Top

The microbial load at the wound site is important in determining wound infection even with the usage of routine antibiotic prophylaxis. The protective function of skin is disrupted by skin incision, and microbial contamination becomes inevitable in spite of adequate skin preparation.[2] Colonisation occurs with potentially pathogenic microorganism, and so any wound has the risk of infection.

Infection rate in clean cases was 2.1%. Infection rates were 8.1% in clean-contaminated and 22.8% in contaminated cases. The accepted range is 1–5% in clean, 3–11% for clean-contaminated and 10–17% for contaminated wounds.[3]

Appropriate antibiotic for prophylactic use depend on the most likely infecting organism encountered during the surgical procedure. Infections can be prevented by achieving adequate concentration of the drug in the blood and tissues during and shortly after the procedure.[4]

The antibiotics and duration differed based on the wound class and risk factors. Only the clean cases were operated without antibiotic prophylaxis or with perioperative antibiotics, and none of them were infected. Results from two other studies also highlight this fact.[5],[6] In a study of 360 inguinal mesh herniorrhaphy cases, Perez et al. in Manila reported that single-dose pre-operative antibiotic administration markedly decrease wound infection.[5] After a study in 6123 patients, Fonseca et al. in Brazil reported that replacing with a single dose antibiotic prophylaxis before elective surgery was found to be sufficient rather than giving a 24 h regimen.[6]

Out of 310 patients, 264 (85.2%) cases had prophylactic antibiotics and 129 (48.9%) of them received single drug. S. aureus was colonised in 18.2% of cases with the prolonged use of single drug beyond 5 days, and 50% of them were Methicillin-resistant S. aureus (MRSA). One case each was infected in the groups where single drug for 5 days or beyond was given. The wound healed with cleaning and dressing without further change of antibiotics in both the cases.

When multiple antibiotics were used for up to 5 days, colonisation was noticed in 26.1% of wounds under this category with an infection rate of 10.4%. These rates were further increased to 40% and 52%, respectively, on prolonging multiple drugs usage.

In a study from New Delhi, Rehan et al. reported that SSIs developed in 14% of patients even if they received prophylactic antibiotics for more than 5 days.[7]

In the present study, all the pathogenic Gram negative bacill were resistant to Ampicillin (100%). Third generation cephalosporins were used commonly for prophylaxis as it was readily available in the hospital supply. However, E. coli isolates from the infected wound sites showed high resistance to first generation cephalosporins (92.3%) and third generation cephalosporins (84.6%). Resistance to Ciprofloxacin (69.2%) and Gentamicin (61.5%) were also high. In a study by Sarma et al., Enterobacteriaceae isolates showed resistance to Ampicillin (100%), Amikacin (22%), Gentamicin (56%).[8] According to Mohanty and Kapil for Gram negative bacteria which account for 54.04% of the pathogenic isolates, single drug therapy would not be useful without an antibiotic sensitivity report. However, a combination of beta-lactam and beta-lactamase inhibitor would be more useful.[9]

In this study, MRSA accounted for 30% of the S. aureus isolates (34.5%) in wound infection. Among 40 MRSA, more (37) were colonisers and only three were real pathogens.

The prevalence of MRSA was found to be higher than other study reports. Sonawane et al. from Mumba reported 29.26% of the pathogens isolated from wound infections were S. aureus and 27.85% of them were MRSA.[10] In another study at Nagpur by Tahnkiwale et al., 26.92% of MRSA were recovered from pus and wound swabs.[11] According to Kownhar et al., Chennai, one of the most prevalent bacteria was S. aureus (37%) that comprised 21.7% MRSA.[12] Hand hygiene recommendations are important to prevent cross-infection through the colonised hands.[13]

  Conclusions Top

Overall SSI rate was 8.1%. E. coli and S. aureus were predominant pathogens in the study group. Among MRSA, more (37) were colonisers and only three were real pathogens. Most of the pathogens were resistant to the third generation cephalosporin. The excessive antibiotic usage and Cefotaxime prophylaxis need to be revised. This study revealed that antibiotic prophylaxis is not required for clean wounds and should be limited for patients with added risk factors. Prolonged use of antibiotics does not reduce the infections. It is necessary to adopt antibiotics for short duration based on the local susceptibility pattern. Reduce the microbial load of infected wound by debridement and cleaning which is more effective rather than changing antibiotics. Continuous monitoring of antibiotic sensitivity pattern is required to get the local information of the epidemiology of drug-resistant bacteria.


Dr. K. Prith Nair, Professor and HOD of Microbiology and Dr. P. K. Mohanan, Additional Professor of General Surgery, Government Medical College, Thrissur, for their expert advice and support.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Owens CD, Stoessel K. Surgical site infections: Epidemiology, microbiology and prevention. J Hosp Infect 2008;70 Suppl 2:3-10.  Back to cited text no. 1
Anguzu JR, Olila D. Drug sensitivity patterns of bacterial isolates from septic post-operative wounds in a regional referral hospital in Uganda. Afr Health Sc 2007;7:148-54.  Back to cited text no. 2
Anaya DA, Dellinger EP. Surgical infections and choice of antibiotics. In: Townsend CM, Beauchamp RD, Evers BM, Mattox KL, editors. Sabiston Textbook of General Surgery: The Biological Basis of Modern Surgical Practice. 18th ed. Philadelphia: Saunders Elsevier; 2008. p. 299-327.  Back to cited text no. 3
Belagal Y, Mc A, Thejesw P, Sheetal DU, Bhagwath V, Shenoy KA, et al. A critical evaluation and comparison of antimicrobial prophylaxis in elective surgeries across three hospitals. J Clin Diagn Res 2013;7:1073-7.  Back to cited text no. 4
Perez AR, Roxas MF, Hilvano SS. A randomized, double-blind, placebo-controlled trial to determine effectiveness of antibiotic prophylaxis for tension-free mesh herniorrhaphy. J Am Coll Surg 2005;200:393-7.  Back to cited text no. 5
Fonseca SN, Kunzle SR, Junqueira MJ, Nascimento RT, de Andrade JI, Levin AS. Implementing 1-dose antibiotic prophylaxis for prevention of surgical site infection. Arch Surg 2006;141:1100-13.  Back to cited text no. 6
Rehan HS, Kakkar AK, Goel S. Pattern of surgical antibiotic prophylaxis in a tertiary care teaching hospital in India. Int J Infect Control 2010;6. Available from: . [Last accessed on 2012 Jan 12].  Back to cited text no. 7
Sarma JB, Bhattacharya PK, Kalita D, Rajbangsh M. Multidrug resistant enterobacteriaceae including metallo-β-lactamase producers are predominant pathogens of healthcare-associated infections in an Indian teaching hospital. Indian J Med Microbiol 2011;29:22-7.  Back to cited text no. 8
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Mohanty S, Kapil A, Dhawan B, Das BK. Bacteriological and antimicrobial susceptibility profile of soft tissue infections from northern India. Indian J Med Sc 2004;58:10-5.  Back to cited text no. 9
Sonawane J, Kamath N, Swaminathan R, Dosan K. Bacterial profile of surgical site infections and their antibiograms in a tertiary care hospital in Nav Mumbai. Bombay Hosp J 2010;52:358-61.  Back to cited text no. 10
Tahnkiwale SS, Roy S, Jalgaonkar SV. Methicillin resistance among isolates of Staphylococcus aureus : Antibiotic sensitivity pattern and phage typing. Indian J Med Sc 2002;56:330-4.  Back to cited text no. 11
Kownhar H, Vignesh R, Sekar R, Velu V, Rao UA. High isolation rate of Staphylococcus aureus from surgical site infections in an Indian hospital. J Antimicrob Chemother 2008;61:758-60.  Back to cited text no. 12
Pittet D, Allegranz B, Boyce J. The World Health Organization guidelines on hand hygiene in healthcare and their consensus recommendations. Infect Control Hosp Epidemiol 2009;30:611-22.  Back to cited text no. 13


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3], [Table 4]

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