Orthopedic implant surgeries, such as fracture fixations, joint replacements, and spinal instrumentation, have revolutionized the management of musculoskeletal disorders. However, these procedures are increasingly associated with a major complication—orthopedic implant-associated infections (OIAIs). These infections can lead to significant morbidity, repeated surgical interventions, implant failure, and substantial economic burden. Despite advances in surgical techniques, prophylactic antibiotic use, and sterilization protocols, the incidence of implant-related infections remains a significant clinical challenge [1-3].

Among the microorganisms responsible for these infections, Staphylococcus aureus is recognized as the most common pathogen. Its capacity to adhere to biomaterials, form biofilms, and evade host immune responses makes it particularly virulent in the setting of implant-associated infections. A critical concern in recent decades is the emergence and global spread of methicillin-resistant Staphylococcus aureus (MRSA), which complicates the management of infections due to its resistance to beta-lactam antibiotics and often, to multiple other antimicrobial agents [4-6].

MRSA infections are associated with poorer clinical outcomes, including increased risk of treatment failure, need for implant removal, prolonged antibiotic therapy, and extended hospitalization. The presence of methicillin resistance also limits the choice of effective antibiotics, often necessitating the use of last-resort agents such as vancomycin and linezolid. Studies have shown that MRSA strains are frequently associated with healthcare-associated risk factors, such as previous hospitalization, prior antibiotic use, presence of comorbidities like diabetes, and long surgical durations [7-9].

Although the burden of MRSA in orthopedic implant infections is well-documented in some regions, there is considerable geographic variation in its prevalence, and there remains a need for local surveillance data to guide empirical therapy and infection control practices. Furthermore, early identification of MRSA infections is crucial for optimizing antimicrobial regimens and improving patient outcomes [10, 11].

The present clinical study was designed to determine the prevalence of MRSA among patients with orthopedic implant infections in a tertiary care hospital setting. In addition, the study aimed to examine the clinical characteristics of MRSA-infected patients, analyze the antimicrobial susceptibility profiles of the isolates, and evaluate the implications of methicillin resistance on patient outcomes.

This prospective clinical study was conducted in the Departments of Orthopedics and Microbiology at a tertiary care hospital over a period of 12 months. This study was conducted at the Department of Orthopaedics, Kamineni Institute of Medical Sciences, Narketpalle, Telangana, India from February 2009 to January 2010. A total of 60 patients with suspected orthopedic implant-associated infections were enrolled after obtaining written informed consent. Ethical approval for the study was obtained from the Institutional Ethics Committee prior to commencement.

Inclusion Criteria:

• Patients of any age and gender with clinical and/or radiological evidence of infection at the site of an orthopedic implant.
• Patients undergoing revision surgery, debridement, or implant removal due to suspected infection.
• Availability of intraoperative specimens for microbiological evaluation.
• Patients who consented to participate in the study and were available for follow-up.

Exclusion Criteria:

• Patients with superficial surgical site infections not involving the implant.
• Patients with infections of traumatic wounds
• Cases where adequate clinical specimens could not be obtained for culture.
• Patients who received prolonged antibiotic therapy prior to sample collection, which may interfere with culture results.
• Patients with incomplete clinical data

Sample Collection and Microbiological Processing:

Intraoperative specimens were collected aseptically from the infected site, including deep tissue, synovial fluid, pus, or implant surface swabs. All samples were transported immediately to the microbiology laboratory for processing. Samples were cultured on blood agar and MacConkey agar and incubated aerobically at 37°C for 24–48 hours. Bacterial identification was performed based on colony morphology, Gram staining, and standard biochemical tests.

Antibiotic Susceptibility Testing and MRSA Detection:

Staphylococcus aureus isolates were identified and tested for methicillin resistance using the cefoxitin (30 µg) disk diffusion method, in accordance with Clinical and Laboratory Standards Institute (CLSI) guidelines. Zone diameters were interpreted to categorize isolates as methicillin-resistant (MRSA) or methicillin-sensitive (MSSA). Antibiotic susceptibility testing for other agents, including vancomycin, linezolid, clindamycin, and ciprofloxacin, was also performed using the Kirby-Bauer disk diffusion method.

Data Collection and Analysis:

Clinical data including patient age, sex, type of implant, site of infection, comorbidities (e.g., diabetes, immunosuppression), and history of prior antibiotic use or hospitalization, and treatment outcomes were recorded. Statistical analysis was conducted using SPSS software. Categorical variables were analyzed using Chi-square or Fisher’s exact test, and p-values <0.05 were considered statistically significant.

A total of 60 patients with suspected orthopedic implant-associated infections were included in the study. Of these, 44 (73.3%) were culture-positive, with Staphylococcus aureus identified in more than half of the cases. The prevalence of MRSA among S. aureus isolates, patient demographics, clinical factors, antibiotic susceptibility, and patient outcomes are presented in the tables below.

Table 1: Demographic and Clinical Characteristics of Study Population

This table 1 summarizes demographic and clinical data. The majority of patients were between 41–60 years of age, with a higher male predominance. Fracture fixation devices were the most common implant type. Diabetes was the leading comorbidity among infected patients.

Table 2: Distribution of Microbial Isolates in Culture-Positive Cases

This table 2 outlines the microbiological profile. S. aureus was the most prevalent organism. Over half of these were methicillin-resistant, emphasizing the significance of MRSA in implant infections.

Table 3: Risk Factors Associated with MRSA Infections

*Significant at p < 0.05

This table 3 analyzes risk factors among patients infected with S. aureus. Prior antibiotic use and recent hospitalization were significantly associated with MRSA, underscoring the role of healthcare exposure in methicillin resistance.

Table 4: Antibiotic Susceptibility Profile of S. aureus Isolates

This table 4 presents the antibiotic resistance patterns. All MRSA and MSSA isolates were sensitive to vancomycin and linezolid. However, resistance to ciprofloxacin and erythromycin was notably higher in MRSA strains.

Table 5: Clinical Outcomes in MRSA vs. MSSA Infections

*Significant at p < 0.05

This table 5 highlights clinical outcomes. MRSA-infected patients required longer intravenous therapy and more frequently underwent implant removal, with a lower recovery rate at 3 months compared to MSSA-infected patients.

Orthopedic implant-associated infections (OIAIs) remain a significant complication in orthopedic surgery, often resulting in prolonged morbidity, repeated surgeries, and substantial healthcare costs. Among the pathogens responsible, Staphylococcus aureus is the most frequently isolated organism, with methicillin-resistant Staphylococcus aureus (MRSA) posing a serious therapeutic challenge due to its multidrug resistance and association with poor outcomes reported by the Gristina et al., 1987; Zimmerli et al., (2004) [12, 13].

In our study, S. aureus accounted for over half of the culture-positive isolates (56.8%), of which 56% were identified as MRSA. This finding is in line with reports from Zimmerli et al., (2004) and Trampuz et al., (2006), who also found a high prevalence of S. aureus and MRSA in implant-related infections. MRSA’s ability to form biofilms enhances its capacity for surface colonization and evasion from host immune responses and antibiotics given by Costerton et al., (1999), thus complicating treatment [14-16].

We observed that MRSA-infected patients had significantly worse outcomes than those infected with methicillin-sensitive S. aureus (MSSA), including a higher requirement for implant removal and longer durations of intravenous antibiotic therapy. These findings mirror those of Parvizi et al., (2009), who noted that MRSA infections were more likely to result in treatment failure and recurrent infection. The lower recovery rate at 3 months among MRSA patients in our study further supports the virulence of these strains [17].

Additionally, prior hospitalization and previous antibiotic exposure were significantly associated with MRSA infections. These risk factors have been identified in earlier studies as important contributors to the emergence of resistant strains in postoperative settings reported by Weigelt et al., 2005; Huang et al., (2006). The findings underscore the role of healthcare-associated exposures in MRSA colonization and subsequent infection in orthopedic patients [18-20].

Antibiotic susceptibility testing revealed that all MRSA and MSSA isolates were sensitive to vancomycin and linezolid, consistent with global trends reported in the early 2000s given by Rybak et al., (1998); Soriano et al., (2006). However, a high level of resistance to clindamycin and fluoroquinolones among MRSA isolates was noted, reflecting the need for judicious use of these agents and the importance of sensitivity-guided therapy. The study reinforces the need for strict infection control practices, early microbiological diagnosis, and MRSA-targeted treatment regimens. While our findings provide valuable local data, limitations include the moderate sample size and lack of molecular typing to characterize the MRSA strains [21-23].

This study highlights the significant prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in orthopedic implant-associated infections. Over half of the S. aureus isolates were found to be methicillin-resistant, underscoring MRSA as a major pathogen in implant-related infections. Patients with MRSA exhibited poorer clinical outcomes, including longer durations of antibiotic therapy, increased need for implant removal, and delayed recovery, compared to those with methicillin-sensitive strains. Further multicenter and molecular-based studies are recommended to better understand MRSA epidemiology and to develop more effective prevention and treatment strategies for implant-associated infections.

Funding support:

Nil

Conflict of interest:

None

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