Prevalence and antibiotic sensitivity pattern of bacteria isolated from nosocomial infections in orthopaedic patients

Rajvir Singh¹  , Rama Sikka¹ , N.K Maggu²  , Deep¹ , Antrikshdeep¹  ,Uma Chaudhary   ¹    P.S Gill¹    , P.K Sehgal³

1. Department of Microbiology , Pt. B.D. Sharma PGIMS,  Rohtak

2. Department of Orthopaedics, Pt. B.D. Sharma PGIMS, Rohtak

3. Department of Blood Transfusion , Pt. B.D. Sharma PGIMS, Rohtak

Address for Correspondence:

Rama Sikka
Department of Microbiology
Pt. B.D. Sharma PGIMS,  Rohtak

Phone : 01262-212636, 01262-213986
Fax     :
E-mail : ramasehgal30@yahoo.com

Abstract:

Open reduction and internal fixation (ORIF) of fractures with implants and prosthesis has become the predominant modality of treatment of fractures in most trauma centers. Incidentally, this is associated with postoperative wound infection (POWI) reported to be in the range 0.8 to13%. The aim of the study was to study the occurrence and sensitivity pattern of various infections in orthopaedic patients for a better management, thereby reducing both mortality and costs. Multidrug resistant gram negative isolates causing SSIs and UTIs predominated in orthopaedic patients. Moreover the rate of infection was relatively high in patients of open and multiple fractures .

J.Orthopaedics 2010;7(2)e3

Keywords:

SSIs;Nosocomial infections;Antimicrobial resistance

Introduction:

Nosocomial infections are a significant problem throughout the world and rates range from as low as 1% in a few countries in Europe and America to more than 40% in parts of Asia, Latin America and Sub Saharan Africa.¹  However during the past few years , there has been a remarkable improvement in the field of diagnosis of orthopaedic infections due to newer techniques and sophisticated tools, better health care systems , particularly in urban areas , increasing awareness of patients and invention of newer more effective and less toxic antimicrobials for combating osteoarticular infections.² Open reduction and internal fixation (ORIF) of fractures with implants and prosthesis has become the predominant modality of treatment of fractures in most trauma centers.³ This is not only because of the better understanding of biomechanics of implantable materials but more importantly because of the better functional outcome in these patients.^3,4  ORIF is a major procedure to alleviate pain and to improve mobility in people with damaged joints.  Less than 10% of prosthesis recipients develop implant associated complication during their lifetime, predominantly as aseptic failure. Incidentally this is associated with postoperative wound infection (POWI) reported to be in the range 0.8 to13% , for both deep and superficial infections with attendant morbidity and cost. ⁵ The microbiology of POWI and their relative rates vary from one hospital to another . In Nigeria, Mbamali⁶ observed that in 60% of his patients with implant infection ,the etiological agent was S.aureus. Other organisms isolated in that study were Pseudomonas pyocyanea and Klebsiella spp.  Oguachuba⁷ found that in 41.9% of the wounds, infections were caused by Proteus spp. while S.aureus accounted for 25.6% of cases. Coliforms (13.9%), Streptococcus spp., Pseudomonas spp. and Klebsiella spp.were the other isolates reported by this author. However the pattern of isolates from USA was slightly different in which gram negative organisms predominated ⁸.

Limited studies are available in Indian literature regarding prevalence of nosocomial infections in orthopaedic patients, their etiological agents and antimicrobial sensitivity pattern of isolates. So the present study was conducted to delineate the occurrence and sensitivity pattern of such infections for a better management, thereby reducing both mortality and costs.

Materials and Methods:

Study centre :

This was a prospective study carried out at a tertiary care hospital in India over aperiod of one year.

Patient selection:

One hundred and ninety eight patients, who were admitted in the orthopaedic ward were included in the study. Various samples like throat swabs, nasal swabs, urine and swabs from surgical sites were collected aseptically from all patients admitted for surgery at the time of admission. Patients with any evidence of infection at the time of admission were excluded from the study. Similar samples were collected after 48 hours of hospital stay from the same patients.

Processing of specimens:

 Swabs from open fractures , bed sores and wounds clinically suspected to be infected  were collected with all aseptic precautions to avoid contamination and were immediately transported to the Microbiology laboratory. The pathogens were identified by standard laboratory procedures including gram’s staining ,motility  ,colony characters and biochemical reactions. ⁹Antibiotic susceptibility testing was done by Kirby-Bauer disc diffusion method .¹⁰  Following antimicrobials were used

(A) For Gram positive aerobic isolates:

Penicillin (2 units), oxacillin (1mg), cephalexin (30mg) doxycycline(30mg),erythromycin (15mg), clindamycin (2mg), linezolid(30mg), cotrimoxazole (25mg),vancomycin (30mg), ofloxacin (5mg), gatifloxacin (5mg), amoxycillin / clavulanic acid (20mg/10mg ), pristinamycin (15mg ) .

(B)  For Gram negative aerobic isolates:

Amoxycillin (10mg), cephalexin (30mg), gentamicin (10mg),  amikacin (30mg),  amoxycillin / clavulanic acid (20mg/10ug), piperacillin/tazobactam (100mg/10mg), cefepime (30mg), ceftazidime/clavulanic acid (30mg/10mg),cefoperazone/sulbactam (75mg/30mg), cefotaxime (30mg), ciprofloxiacin (5mg),meropenem (10mg), aztreonam (30mg), ceftazidime (30mg), netilmicin (30mg), gatifloxacin (5mg) .

(C)  For Pseudomonas species:

Ceftazidime (30mg), gentamicin (10mg), amikacin (30mg), piperacillin/tazobactam (100mg/10mg), cefepime (30mg), cefoperazone/sulbactam (75mg/30mg), aztreonam (30mg), ofloxacin (5mg), imipenem (10mg), , ceftriaxone (30mg)  , netilmicin(30mg), ceftizoxime  (30mg).  All the antibiotic discs used were obtained from Hi-Media Laboratories Pvt. Ltd.

Results :

Study population and patient characterstics:

From the total number of 198 patients investigated in the present study , 76.3% were males and 23.7% were females and their ages ranged between 5 to 83 years with a mean age of 42.06 years.

Incidence of various types of infection :

Based on the results of culture ,37(18.6%) had a positive bacterial culture. Among  three patients of UTI, Candida albicans was isolated. The incidence of various types of infections in 198 patients enrolled for the present study in relation to orthopaedic illness and procedures is described in the table 1.

Table 1:  Site wise distribution of bacterial isolates in relation to orthopaedic illnesses and     procedures

Pathogens :

Most frequently isolated organisms were S.aureus ( 22.5%) ,E. coli (20%), K. pneumoniae (17.5%),  Enterobacter spp(10%), P. aeruginosa (10%), Citrobacter spp. (7.5%) and A. baumanii (5%) and Candida albicans (7.5%). SSIs and UTIs were observed in 18.6% and 11.1% of patients respectively ( Table2).

Table 2: Distribution of  various bacteria isolated in various nosocomial infections

Antimicrobial susceptibility pattern:

Table 3 shows the antibiotic sensitivity pattern of various gram negative isolates other than  P.aeruginosa from orthopaedic patients.

Table 3: Resistance pattern of gram-negative bacteria other than P.aeruginosa from orthopaedic patients

Am : amoxycillin, G : gentamicin, Ak : amikacin, Cf :ciprofloxacin, Gf : gatifloxacin , Ac : amoxycillin/clavulanic acid, Cp : cephalexin, Ca : ceftazidime, Cac : ceftazidimne/clavulanic acid, Ce : Cefotaxime, Cpm : cefipime Pt : Piperacillin/tazobactam, Ao : aztreonam, Nt : netilmicin, Mr : meropenem.

Figures in parenthesis indicate percentages.

Among the 9 isolates of S.aureus ,four were MRSA. Resistance to other tested drugs ranged from 33% to 77%.  However, no isolate showed resistance to vancomycin and linzeolid.  All the strains of P.aeruginosa were resistant to most of the antibiotics tested. Only 50% of the strains showed sensitivity to imipenem and piperacillin/tazobactam , while being resistant to  ceftazidime  , cefepime , ceftriaxone , ceftizoxime,  gentamicin ,amikacin, cotrimoxazole , doxycycline , netilmicin, ofloxacin and aztreonam. . Multiple drug resistance was observed in 86.5% of isolates from various nosocomial infections.

Discussion :

Infections in orthopaedic patients is an unresolved problem. Infections occur even though orthopaedicians perform thoroughly clean procedures during surgery and patients are strictly managed before and after surgery. According to present results ¸positive cultures were seen in 18.6% of patients, while Akbas et al¹¹ reported positive cultures in 7.2% of cases.  Mohanty et al¹² and Agrawal et al² have reported the rate of isolation  to be 34% and 53% respectively.  Different institutions have different protocols at the time of admission to the hospital regarding antibiotic prophylaxis, which has great influence on relative percentage of isolation of bacteria. Moreover ,  the rate of isolation was 18.3% in cases of fractures which was higher than that reported by Onche et al¹³ (7.5%). However, other workers have reported it to range between 0.8-13% for both deep and superficial infections. This higher rate of isolation among the patients of fractures in the present study may be because of the fact that many of these fractures were multiple fractures and open fractures which tend to have higher risk of bone infection due to easy access of bacteria into the bone, than with closed fractures. Additionally, an association with severe soft tissue damages in these patients put them at a higher risk of infection.    

However, bacterial growth from patients of osteomyelitis was relatively less in present study (20%). Results of the current study show that most frequent nosocomial infections in orthopaedic patients were SSIs (59.9%) which is higher than other  workers. ^13,14  High rates of contaminated, dirty and trauma related wounds in our study might have contributed to the high incidence of SSIs. UTIs in the present study were more common in patients of spinal injury.  As patients of spinal injury are catheterized for longer times, it increases the chances of UTI in these patients.

Results of our study showed that gram negative infections continue to be a major threat since gram negative pathogens were isolated from 75.6% of cases. E. coli remained the most common pathogen (28.5%) ,followed by K. pneumoniae (25%), Enterobacter spp. and P. aeruginosa (14.3% each), Citrobacter spp (10.7%) and A. baumanii (7%).  Agrawal et al² have reported  similar results but other authors have observed a different spectrum. This may be due to the fact that type of flora in wards and OTs in different hospitals vary and also  keeps  on changing over the years  . E. coli is a commensal of gut and as many orthopaedic patients are bedridden for prolonged periods, contamination of wounds, dressing  linen, clothes and even hands during perineal hygiene plays a major role in increasing transmission of infections. S. aureus was isolated most commonly from SSIs (7 of 9 isolates of S. aureus) followed by UTI (2 of 9 isolates). Similar results have been reported by Onche et al.¹³ About 10-30% of healthy people carry this organism in their nares. Infections by these organisms can also be caused by patients themselves. Bedsheets, instruments and dressing have also been found to act as reservoirs of S. aureus.

Antimicrobial resistance pattern of gram-negative bacilli showed high frequency of resistance to amoxicillin (75-100%), cephalexin (100%), ceftazidime (62.5-100%), cefepime (71.4-100%), ciprofloxacin (50-100%), gatifloxacin (62.5‑100%). Resistance to piperacillin / tazobactam and amoxicillin /clavulanic acid was (75-100%) each. Carbapenems were found to be most sensitive drug. The resistance rates as observed in the current study are similar to those reported by Akbas et al.¹¹  All the strains of P.aeruginosa were resistant to most of the antibiotics tested. Only 50% of the strains showed sensitivity to imipenem and piperacillin/tazobactam. High level of resistance, as observed in the present study, among the isolates from SSIs may be due to horizontal spread of these organisms among the patients which may be related to overcrowding in wards, poor socio economic status, and lack of hygiene.

 It is apparent from the results of antibiograms that orthopaedics wards and OTs could be a potential reservoir of nosocomial pathogens. . To control these infections and to prevent antibiotic resistance, it is suggested that the committee for controlling infections should be more active and new antimicrobials should be used with more caution and their long term use should be discouraged whenever possible.

Summary:

This study has highlighted three main issues in microbiology of infections in orthopaedic patients. Firstly , the SSIs are the most important infections in orthopaedic patients, that also associated with multiple and open fractures. Secondly, gram negative pathogens dominated in our study. Thirdly , resistant strains especially among gram negative pathogens have emerged and that creates problem not only in prescribing post operative treatment but also in deciding preoperative prophylaxis for such patients.

Reference :

1. Lynch P. Infection Prevention with Limited Resources. ETNA Communications: Chicago                          

2.   Agrawal AC, Jain S, Jain RK, Raza HKT. Pathogenic bacteria in an orthopaedic hospital in India. J Infect Developing Countries 2008;2:120-123.

3. Schatzker J. Principles of stable internal fixation. In: Schatzker J, Tile M (ed). The rationale of operative fracture care. Spinger-Verlag, Berlin 1996:10-11.

4. Sisk DT. General principles of fracture treatment. In: Crenshaw AH (ed). Campbell's operative orthopaedics. Mosby, Missouri 1987:1551-61.

5. Khosravi AD, Ahmadi F, Salmanzadeh S, Dashtbozorg A, Montazeri EA. Study of bacteria isolated from orthopedic implant infections and their antimicrobial susceptibility pattern. 2009;4:158-63.

6. Mbamali EI. Internal fixation of femoral shaft fractures at the Ahmadu Bello University Teaching Hospital Zaria. Nigerian Medical Practitioner 1981;2:81-5.

7. Oguachuba HN. Wound infection in the orthopaedic-traumatology department of Jos University Teaching Hospital, Jos, Nigeria. Nigerian Med J 1987;17:147-51.

8. Classen DC, Evans SR, Pestotnik SL. The timing of prophylactic administration of antibiotics and the risk of surgical wound infection. N Engl J Med 1992;326:281-5.

9. Collee JG, Miles RS, Watt B. Tests for identification of bacteria. In: Collee JG, Fraser AG, Marmion BP, Simmons A, ed. Mackie and McCartney Practical Medical Microbiology. 14^th ed. New York: Churchill Livingstone 1996.p.131-49,166-167.

10. Bauer AW, Kirby WMM, Sherris JC, Turck M. Antibiotic susceptibility testing by a standardized single disk method. Am J Clin Pathol 1966;45:493-6.

11. Akbas A, Bakir M, Savk SO. The examination of nosocomial infections that develop in the orthopedics clinic. Acta Orthop Traumatol Turc 1994;28:

12. Mohanty S, Dhawan B, Das BK, Kapil A. Bacteriology of orthopaedic wound infections in an Indian tertiary care hospital. Ind J Med Res 2005;121:784-5.

13. Onche II. Post-operative wound infection in implant surgery. Dissertation submitted to the National Post graduate Medical Collage of Nigeria. Lagos 2000.

14. Maksimovic J, Markovic-Denic L, Bumbasirevic M, Marinkovic J, Vlajinac H. Surgical site infections in orthopedic patients: prospective cohort study. Croat Med J 2008;49:58-65.

This is a peer reviewed paper 

Please cite as: Rama Sikka: Prevalence and antibiotic sensitivity pattern of bacteria isolated from nosocomial infections in orthopaedic patients

J.Orthopaedics 2010;7(2)e3

URL: http://www.jortho.org/2010/7/2/e3

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