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Microbial profile and antibiotic susceptibility pattern of orthopedic infections in a tertiary care hospital: a study from South India.

INTRODUCTION

Orthopedic infections are one of the most common which can occur in approximately 1% of all orthopedic operations. [1] The most common orthopedic infections are surgical site infections (SSI) and implant infections in open or closed wounds. [2,3] Wound is a breach in the skin leading to exposure of subcutaneous tissue caused by trauma, surgeries, burns, diabetic ulcers, etc. It provides a moist, warm and nutrient environment that is conductive to microbial colonization and proliferation that leads to serious bacterial infections and death. Wound infections are one of the most common hospital-acquired infections and are an important cause of morbidity and account for 70-80% mortality. [4]

SSI as defined by US Centers for Diseases Control in 1992, is an infection occurring within 30-90 days after a surgical operation (or within 1 year if an implant is left in place after procedure) and affecting either incision or deep tissues at the operation site. [5] Orthopedic wound infections are one of the common causes of high morbidity and are difficult to treat. Due to the use of implants for open reduction and internal fixation, which are foreign bodies to the body, orthopedic wounds are at increased risk of microbiological contamination and infection. [6] Bone infection, at sites of relatively poor vascularity, can be difficult to treat, often requiring prolonged courses of antimicrobial therapy in association with surgical drainage or debridement. Delayed or ineffective treatment causes significant morbidity in terms of pain, loss of function and the need for further surgery and antibiotics.(tm)

In addition to the irrational use of broad spectrum antibiotics, the changing pattern of microbial etiology and increasing antimicrobial resistance makes orthopedic infections a challenge for both the patient and clinician.

Keeping this in mind, the following study was aimed in finding out the various organisms causing orthopedic wound infections and to identify the antibiotic susceptibility pattern of the isolated organisms.

MATERIALS AND METHODS

This study was conducted in the Department of Microbiology, Narayana Medical College and Hospital, Nellore, from June 2015 to May 2016. Swabs were collected from infected wounds from orthopedic patients with aseptic precautions and immediately transported to the laboratory for culture and antibiotic sensitivity testing.

Swabs were inoculated on blood agar and MacConkey agar. Plates were incubated at 37[degrees]C for 24-48 h and examined for the presence of bacteria. All positive cultures were identified by colony morphology, Gram-staining and biochemical reactions. [8] Antimicrobial susceptibility testing was done on Muller-Hinton agar using antibiotic discs from Hi Media.

For Gram-positive organisms ampicillin, cefoxitin, cefixime, azithromycin, ofloxacin, amikacin, clindamycin, amoxicillin + clavulanic acid, vancomycin, and linezolid were used. For Gram-negative bacilli ampicillin, cefixime, ceftriaxone, cotrimoxazole, ciprofloxacin, ofloxacin, gentamicin, amikacin, amoxicillin-clavulanic acid, cefoperazone-sulbactam, piperacillin-tazobactam, and Imipenem were used.

For Pseudomonas spp. cefixime, ceftazidime, co-trimoxazole, ciprofloxacin, gentamicin, amikacin, cefoperazone + sulbactam, piperacillin + tazobactam, meropenem, polymyxin - B, and aztreonam were used. The test results were interpreted as sensitive, intermediate susceptible or resistant according to the Clinical and Laboratory Standards Institute guidelines. [9]

RESULTS

Out of 100 pus samples collected from orthopedic patients 68 (68%) samples yielded growth and 32 (32%) samples had no growth (Table 1).

Among the 68 culture positive, cases 33 (48%) were Gram-positive cocci and 35 (52%) were Gram-negative bacilli. Out of Gram-positive cocci Staphylococcus aureus 17 (25%) was the most common organism followed by CONS 15 (22%) and Enterococci 1 (1.5%) (Table 1).

Among Gram-negative bacilli Pseudomonads, 18 (26.4%) were the most common organisms followed by Escherichia coli 5 (7.3%), Citrobacter sps. 5 (7.3%), Klebsiella sps. 4 (6%), Proteus sps. 2 (3%), and Acinetobacter sps. 1 (1.5%) (Table 1).

This showed that Gram-positive cocci are the most common causes of orthopedic infections followed by Pseudomonas. Among the Gram-positive cocci, all were sensitive to vancomycin and linezolid followed by clindamycin and amikacin (Table 2). Among the Gram-negative bacilli, most of the isolates were sensitive to piperacillin + tazobactam followed by amikacin and imipenem. Among the Pseudomonads, most of the isolates were sensitive to polymyxin B, piperacillin + tazobactam and meropenem (Tables 3 and 4).

DISCUSSION

In our study, out of 100 samples, 68% samples yielded growth. Among them, predominant organisms were Gram-negative bacilli with Pseudomonas (18 isolates) being most common organism with the highest sensitivity to piperacillin + tazobactam, imipenem and amikacin. Among the Gram-positive organisms isolated, S. aureus (17 isolates) was the most common organism with maximum sensitivity to vancomycin and linezolid.

The culture positivity rates of 68% found in our study coincides with study conducted by Gomez et al., [10] which showed 60% positivity. This is slightly higher than the findings of the study conducted by Lakshminarayana et al. who reported culture positivity of 45.31%. [11] The prevalence of Gram-negative bacteria is slightly higher 51.5% than Gram-positive cocci 48.5% which is in correlation with study done by Amatya et al. [12] and Sule et al. [13]

Pseudomonas aeruginosa is the predominant isolate (26.4%) in our study which is similar to Amatya et al. [12] who isolated P. aeruginosa. A study conducted by Benabdelsalem et al. also reported Pseudomonas as predominant Gram-negative bacilli with 17.6% isolates. S. aureus is the second isolate (25%) in our study which is in concordance with studies done by Sule et al. [13] and Benabdelsalem et al. (33.1%). [14]

In our study, members of Enterobacteriaceae family showed high sensitivity to imipenem followed by amikacin and piperacillin-tazobactam. This is similar to sensitivity reported by Mahamood. [15] Our study revealed polymyxin B, meropenem and piperacillin - tazobactam are most sensitive drugs against Pseudomonads which is in correlation with the study conducted by Shanmugam et al. [16] All the Grampositive isolates were sensitive to vancomycin and linezolid in our study which was consonance with findings of Roel et al. [17] in their study.

From our results, ampicillin and cephalosporins cannot be recommended for use as an empirical therapy in orthopedic infections. Based on our antibiotic susceptibility data, we suggest that piperacillin-tazobactam and meropenem are the most effective against Gram-negative bacilli and clindamycin, vancomycin and linezolid are effective against Gram-positive organisms. This finding in our study might provide added advantage to clinicians in treating patients with better chances of reduction in morbidity and mortality. The limitation in our study was that anaerobic bacterial profile and fungal cultures were not done. There is a need for further larger studies including these profiles.

CONCLUSION

As there is high antibiotic resistance observed in our study, it is necessary for routine microbial analysis of samples and their antibiogram. Multidisciplinary collaboration with orthopedic surgeons, infectious disease specialist and clinical microbiologist is needed to reduce the incidence of orthopedic infections. There is a need for formulation of antibiotic policy and formulary restriction.

DOI: 10.5455/ijmsph.2017.1165105122016

REFERENCES

[1.] Orthopedic Infections: Current Concepts. Available from: http://www.houstonmethodist.org/basic.cfm?id=36831. [Last accessed on 2015 Jun 06].

[2.] Nichols RL. Current strategies for prevention of surgical site infections. Curr Infect Dis Rep. 2004; 6(6):426-34.

[3.] Agrawal AC, Jain S, Jain RK, Raza HK. Pathogenic bacteria in an orthopaedic hospital in India. J Infect Dev Ctries. 2008;2:120-3.

[4.] Jain V, Ramani VK, Kaore N. Antimicrobial susceptibility pattern amongst aerobic bacteriological isolates in infected wounds of patients attending tertiary care hospital in central India. Int J Curr Microbiol Appl Sci. 2015; 4(5):711-9.

[5.] Jain A, Bhatawadekar S, Modak M. Bacteriological profile of surgical site infection from a tertiary care hospital, from Western India. Indian J Appl Res. 2014; 4(1):397-400.

[6.] Viswajith, Anuradha K, Venkatesha D. Evaluation of aerobic bacterial isolates and its drug susceptibility pattern in orthopedic infections. JMSCR. 2014; 2(6):1256-62.

[7.] Darley ES, MacGowan AP Antibiotic treatment of gram-positive bone and joint infections. J Antimicrob Chemother. 2004; 53:928-35.

[8.] Forbes BA, Sahm DF, Weissfeld AS. Bailey and Scotts, Diagnostic Microbiology. 12th ed. USA: Mosby; 2007. p. 62-77.

[9.] Clinical and Laboratory Standards Institute. M100-S24 Performance Standards for Antimicrobial Susceptibility Testing; Twenty-Fourth Informational Supplement. Wayne, PA: CLSI; 2014. p. 50-68.

[10.] Gomez J, Rodriguez M, Banos V, Martinez L, Antonia C, Antonia M. Orthopedic implant infection: Prognostic factors and influence of prolonged antibiotic treatment in its evolution. Prospective study: 1992-1999. Enferm Infecc Microbiol Clin. 2003; 21:232-6.

[11.] Lakshminarayana SA, Chavan SK, Prakash R, Sangeetha S. Bacteriological profile of orthopedic patients in a tertiary care hospital, Bengaluru. Int J Sci Res. 2013; 4(6):2319-7064.

[12.] Amatya J, Rijal M, Baidya R. Bacteriological study of the post operative wound samples and antibiotic susceptibility pattern of the isolates in B&B hospital. JSM Microbiol. 2015; 3(1):1019.

[13.] Sule AM, Thanni L, Sule-Odu O, Olusanya O. Bacterial pathogens associated with infected wounds in Ogun State University Teaching hospital, Sagamu, Nigeria. Afr J Clin Exp Microbiol. 2002; 3(1):13-6.

[14.] Benabdelsalem A, Berrady MA, Khermaz M, Mahfoud M, Berrada MS, Elyaacoubi M. Bacteriological profile of surgical site infections in orthopedic surgery about 142 cases. Int J Sci Technol Res. 2014; 3(3):271-7.

[15.] Mahamood A. Bacteriology of surgical site infections and antibiotic susceptibility pattern of the isolates at a tertiary care Hospital in Karachi, Pakistan. J Pak Med Assoc 2000; 50(8):256-9.

[16.] Shanmugam P, Jeya M, Linda S. Bacteriology of diabetic foot ulcers with a special reference to multidrug resistant strains. J Clin Diagn Res. 2013; 7(3):441-5.

[17.] Roel T, Devi S, Devi M, Sahu B. Susceptibility pattern of aerobic bacterial isolates from wound swab. Indian Med Gaz. 2014; 148(10):355-9.

How to cite this article: Devi PV, Reddy PS, Shabnum M. Microbial profile and antibiotic susceptibility pattern of orthopedic infections in a tertiary care hospital: A study from South India. Int J Med Sci Public Health 2017; 6(5):838-841.

Vasundhara Devi P, Sreenivasulu Reddy P, Shabnum M

Department of Microbiology, Narayana Medical College, Nellore, Andhra Pradesh, India

Correspondence to: Shabnum M, E-mail: shabnummusaddiq@gmail.com

Received: November 26, 2016; Accepted: December 05, 2016
TABLE 1: Bacteriological profile of orthopedic infections

Bacterial isolates        n (%)

Staphylococcus aureus    17 (25)
CONS                     15 (22)
Enterococci              1 (1.5)
Escherichia coli         5 (7.3)
Klebsiella sps.           4 (6)
Citrobacter sps.         5 (7.3)
Proteus sps.              2 (3)
Acinetobacter sps.       1 (1.5)
Pseudomonas sps.        18 (26.4)
Total                    68(100)

TABLE 2: Antibiotic susceptibility patterns of Gram-positive cocci

Antibiotic                    Staphylococcus aureus (17) (%)

                              Sensitive   Resistant

Ampicillin                     5 (30)      12 (70)
Cefoxitin                      12 (70)     5 (30)
Cefixime                       4 (24)      13 (76)
Azithromycin                   9 (53)      8 (47)
Ofloxacin                      9 (53)      8 (47)
Amikacin                       14 (82)     3 (18)
Clindamycin                    15 (88)     2 (12)
Amoxicillin+clavulanic acid    8 (47)      9 (53)
Vancomycin                    17 (100)      0 (0)
Linezolid                     17 (100)      0 (0)

Antibiotic                    CONS (15) (%)

                              Sensitive   Resistant

Ampicillin                     10 (67)     5 (33)
Cefoxitin                     15 (100)      0 (0)
Cefixime                       7 (47)      8 (53)
Azithromycin                   9 (60)      6 (40)
Ofloxacin                      11 (73)     4 (27)
Amikacin                       12 (80)     3 (20)
Clindamycin                    10 (67)     5 (33)
Amoxicillin+clavulanic acid    13 (87)     2 (13)
Vancomycin                    15 (100)      0 (0)
Linezolid                      15(100)      0 (0)

Antibiotic                    Enterococci (1) (%)

                              Sensitive   Resistant

Ampicillin                     1 (100)      0 (0)
Cefoxitin                      1 (100)      0 (0)
Cefixime                        0 (0)      1 (100)
Azithromycin                    0 (0)      1 (100)
Ofloxacin                      1 (100)      0 (0)
Amikacin                        0 (0)      1 (100)
Clindamycin                     0 (0)      1 (100)
Amoxicillin+clavulanic acid    1 (100)      0 (0)
Vancomycin                     1 (100)      0 (0)
Linezolid                      1 (100)      0 (0)

TABLE 3: Antibiotic susceptibility pattern of Pseudomonads (18)

Antibiotic                Sensitive %   Resistant %

Cefixime                     1 (5)        17(95)
Ceftazidime                 4 (22)        14 (78)
Cotrimoxazole               5 (28)        13 (72)
Ciprofloxacin               12 (67)       6 (33)
Amikacin                    7 (39)        11(61)
Gentamicin                  9 (50)        9 (50)
Cephaperazone+sulbactam     8 (45)        10(55)
Piperacillin+tazobactam     13 (72)       5 (28)
Meropenem                   14 (78)       4 (22)
Polymyxin B                 16 (89)       2 (11)
Aztreonam                   7 (39)        11(61)

TABLE 4: Antibiotic sensitivity pattern of Gram-negative bacilli

Antibiotic                    Escherichia coli 5 (%)

                              Sensitive   Resistant

Ampicillin                     1 (20)      4 (80)
Cefixime                        0 (0)      5(100)
Ceftriaxone                    1 (20)      4 (80)
Ofloxacin                      2 (40)      3 (60)
Amikacin                       4 (80)      1 (20)
Cotrimoxazole                  1 (20)      4 (80)
Ciprofloxacin                  2 (40)      3 (60)
Gentamicin                     3 (60)      2 (40)
Cefoperazone+sulbactam         3 (60)      2 (40)
Piperacillin+tazobactam        5(100)       0 (0)
Amoxycillin+clavulanic acid    1 (20)      4 (80)
Imipenem                       4 (80)      1 (20)

Antibiotic                    Klebsiella sps. 4 (%)

                              Sensitive   Resistant

Ampicillin
Cefixime                          0 (0)    4(100)
Ceftriaxone                      1 (25)    3 (75)
Ofloxacin                        2 (50)    2 (50)
Amikacin                         3 (75)    1 (25)
Cotrimoxazole                    1 (25)    3 (75)
Ciprofloxacin                    2 (50)    2 (50)
Gentamicin                       2 (50)    2 (50)
Cefoperazone+sulbactam           3 (75)    1 (25)
Piperacillin+tazobactam          3 (75)    1 (25)
Amoxycillin+clavulanic acid       0 (0)    4(100)
Imipenem                        4 (100)     0 (0)

Antibiotic                    Citrobacter sps. 5 (%)

                              Sensitive   Resistant

Ampicillin                      0 (0)      5 (100)
Cefixime                       1 (20)      4 (80)
Ceftriaxone                    1 (20)      4 (80)
Ofloxacin                      2 (40)      3 (60)
Amikacin                       1 (20)      4 (80)
Cotrimoxazole                  2 (40)      3 (60)
Ciprofloxacin                  2 (40)      3 (60)
Gentamicin                     2 (40)      3 (60)
Cefoperazone+sulbactam         1 (20)      4 (80)
Piperacillin+tazobactam        1 (20)      4 (80)
Amoxycillin+clavulanic acid     0 (0)      5 (100)
Imipenem                       4 (80)      1 (20)

Antibiotic                    Proteus sps. 2 (%)

                              Sensitive   Resistant

Ampicillin                      0 (0)      2(100)
Cefixime                        0 (0)      2 (100)
Ceftriaxone                    2 (100)      0 (0)
Ofloxacin                      1 (50)      1 (50)
Amikacin                        0 (0)      2 (100)
Cotrimoxazole                   0 (0)      2 (100)
Ciprofloxacin                  2 100)       0 (0)
Gentamicin                      0 (0)      2 (100)
Cefoperazone+sulbactam         1 (50)      1 (50)
Piperacillin+tazobactam        1 (50)      1 (50)
Amoxycillin+clavulanic acid    2 (100)      0 (0)
Imipenem                       1 (50)      1 (50)

Antibiotic                    Acinetobacter sps. 1 (%)

                              Sensitive   Resistant

Ampicillin                      0 (0)      1(100)
Cefixime                        0 (0)      1 (100)
Ceftriaxone                     0 (0)      1 (100)
Ofloxacin                       0 (0)      1 (100)
Amikacin                       1 (100)      0 (0)
Cotrimoxazole                   0 (0)      1 (100)
Ciprofloxacin                   0 (0)      1 (100)
Gentamicin                     1 (100)      0 (0)
Cefoperazone+sulbactam         1 (100)      0 (0)
Piperacillin+tazobactam         0 (0)      1 (100)
Amoxycillin+clavulanic acid
Imipenem                       1 (100)      0 (0)
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Title Annotation:Research Article
Author:P., Vasundhara Devi; P., Sreenivasulu Reddy; M., Shabnum
Publication:International Journal of Medical Science and Public Health
Article Type:Report
Geographic Code:9INDI
Date:May 1, 2017
Words:2301
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