Prevalence of Nosocomial Infection in Surgical Wounds among Postoperative Patients and their Antimicrobial Susceptibility Pattern

Abba Ruba Sunanthini, C (2015) Prevalence of Nosocomial Infection in Surgical Wounds among Postoperative Patients and their Antimicrobial Susceptibility Pattern. Masters thesis, Madras Medical College, Chennai.


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BACKGROUND: Surgical site infections accounts for about 24% of all nosocomial infections among 16 million patients who undergo surgery every year. SSIs have a major impact on the patient’s quality of life since they are associated with considerable morbidity, occasional mortality, extended hospital stay and financial burden on the patient and the health care provider. The present cross sectional study was done to isolate and identify the aerobic and anaerobic microorganisms causing SSI and to evaluate the antibiotic susceptibility pattern of these pathogens, to assess the risk factors for SSI, to assess the microbial contamination levels in operating theatres and postoperative wards using both active and passive sampling methods and to assess any linkage between the environmental isolates and the isolates causing SSI. MATERIALS AND METHOD: The present study was done in the Institute of Microbiology, Madras Medical College, Chennai. The samples were collected from 200 postoperative inpatients with clinically diagnosed SSI in the department of General surgery, Cardio Thoracic surgery and Vascular Surgery, Rajiv Gandhi Government General Hospital, Chennai. Infected wounds were studied bacteriologically. Samples such as wound swabs from the infected wound site, blood from peripheral vein were collected as indicated and processed as per standard operating procedure (SOP). Environmental sampling from operation theatres and postoperative wards, nasal swabs from anterior nares and hand imprint culture of hospital personnel were collected and processed as per SOP. The results were analyzed. Antibiotic resistance pattern of 2 MRSA strains from general surgical SSI patient were found to be similar to 1 MRSA strain from General surgery Operation theatre. These strains were subjected to 16S rRNA gene amplification and Amplified Ribosomal DNA Restriction Analysis (ARDRA) to identify the strain relatedness. RESULTS: The overall postoperative surgical site infection rate was 15.56%. Males (64.29%) had a higher SSI rate compared to females (35.71%). The rate of SSI was higher (10.22%) in clean contaminated surgeries (class II) compared to 5.3% in clean surgeries (class I). There was a significant increase in the rate of infection with the an increase in duration of the pre-operative hospitalization, ASA score > 2 and duration of surgery. In general surgery, the infection rate was highest in post appendicectomy wounds and lowest in wounds following thyroidectomy, adrenelectomy and hysterectomy. In Cardiothoracic surgery SSI rate was higher in patients who underwent lobectomy and least in valve replacement surgery. In Vascular surgery the SSI rate was higher in bypass graft wounds. The commonest aerobic isolate from the surgical wound infections was Escherichia coli, followed by Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumonie and the least common was Proteus mirabilis. In general surgical patients anaerobes namely, Peptostreptococcus spp. and Bacteroides fragilis were isolated. Among all the wounds, isolation of monomicrobials predominated over polymicrobials. Majority of the Gram negative isolates were sensitive to Amikacin and Piperacillin Tazobactum but were resistant to commonly prescribed antimicrobial agents namely Cephalosporins, Gentamycin and Ciprofloxacin. Cefotaxime and Ceftriaxone, the commonly used third generation cephalosporins as surgical prophylaxis to prevent SSIs were found to be less effective against most of the gram negative organisms. The present study also observed an increase in SSIs caused by ESBL producing enteric Gram negative bacilli. Air sampler system was found to measure the microbial burden more accurately compared to settle plate method. Environmental sampling done in the operation theatres and postoperative wards revealed that the Index of microbial contamination of air were within acceptable limits. 16S rRNA gene amplification and Amplified Ribosomal DNA Restriction Analysis (ARDRA) performed on the MRSA isolates with similar antibiotic resistant pattern, revealed that the isolates from SSI were distinct from the one isolated from the OT. CONCLUSION: The conclusion drawn from the present study indicates the necessity for implementing routine wound culture and sensitivity and the test reports to guide the choice of antibiotics, periodic review and adherence to Hospital infection control policy and guidelines. The study also recommends consideration of anaerobic bacteria as a cause in all SSIs, identification of relevant gene responsible for antibiotic resistance of the pathogens by molecular methods as an epidemiologic measure, limiting the use of third generation cephalosporin in surgical prophylaxis to prevent development of further resistance to these antibiotics, performance of routine surveillance of all Operation Theatres once in every two months instead of once in four months done presently and strict adherence to the OT protocol on asepsis and to prefer newer less toxic disinfecting agents.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Nosocomial Infection ; Surgical Wounds ; Postoperative Patients ; Antimicrobial Susceptibility Pattern.
Subjects: MEDICAL > Microbiology
Depositing User: Punitha K
Date Deposited: 23 May 2018 02:37
Last Modified: 27 May 2018 04:30

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