A study of nasal carriage of methicillin-resistant staphylococcus aureus in patients undergoing hemodialysis in a tertiary care hospital of Punjab

INTRODUCTION

Infection is a major cause of morbidity and mortality among patients undergoing hemodialysis for chronic renal failure.^1-4 Dialysis therapy including hemodialysis results in frequent contact with the hospital environment. The major pathogen in this group is Staphylococcus aureus and colonization of S. aureus is associated with a fourfold higher risk of bloodstream infection.^5-10 The predominance of this pathogen is because of the virulence factors permitting rapid tissue invasion, dissemination throughout the body, genetic plasticity permitting constant adaptation.¹¹

Carriage of nasal S. aureus has been reported as a significant risk factor for septicemia and infections due to S. aureus in hemodialysis patients.^4,12,13 Patients on hemodialysis are at more risk to Staphylococcal infections because of their low immunity, increased skin colonization by Staphylococci, multiple needle punctures required for dialysis, and also, because they are repeatedly exposed to the healthcare environment and often due to receiving prolonged courses of antibiotics, even besides being immunocompromised.^14,15

There are various reports of rapidly increasing resistance to multiple antibiotics, and the consequences of methicillin resistance for the outcomes of S. aureus infections are drastic.^16-26 Studies have found that nasal colonization with methicillin-resistant Staphylococcus aureus poses an increased risk of infection.²⁷

The present study was therefore conducted to evaluate the nasal carriage of MRSA in patients undergoing hemodialysis and the pattern of their antimicrobial resistance.

METHODS

The study was conducted on 100 patients undergoing hemodialysis in our institute.

Collection of specimens²⁸

Two sterile pre-moistened cotton-tipped swabs were used to collect specimens from anterior nares of patients at the hemodialysis unit after taking informed consent. Two swabs were rotated five times over the inner wall of the ala and septum of nose and were immediately transferred to microbiology laboratory for processing as per the standard microbiological protocol. Isolated strains were subjected to antimicrobial susceptibility testing using Kirby-Bauer disc diffusion.

The antibiotics used were, ampicillin (10 µg/disc), erythromycin (15 µg/disc), clindamycin (2 µg/disc), ciprofloxacin (5 µg/disc), amikacin (30 µg/disc), cotrimoxazole (25 µg/disc) and linezolid (30 µg/disc).

Methicillin resistance was detected by disc diffusion test using cefoxitin disc (30 µg) which is a surrogate marker for methicillin. Zone diameters were then measured as per CLSI criteria.

Vancomycin screen agar test^29,30

In-house prepared brain heart infusion agar plates containing 6µg/ml of vancomycin were used for vancomycin screen agar. The plates were inoculated with the test strain from the standard inoculum and incubated at 35°C for 24 hours. Any visible growth indicated reduced susceptibility to vancomycin. S. aureus ATCC 29213 was used as a reference strain.

Results have been shown in Tables 1, 2, and 3.

RESULTS

In our study, males (78%) outnumbered females (22%).

The majority (38%) of the patients were in the age group 41-60 years followed by 61-80 years (28%). A minimum number of patients were of age more than 80 years.

A significant correlation was found regarding the nasal carriage of S. aureus and hemodialysis duration.

Statistically analytic (Pearson’s Chi square test). χ² = 3.885, df = 1, p value =0.048 (statistically significant)

It was observed that 38% of the patients were carriers of S. aureus followed by CoNS, followed by aerobic spore bearers (Table 1).

Of the total 100 patients in a study, S. aureus was isolated in 38 (38%) patients and all the S. aureus isolates (100%, 38/38) were resistant to cefoxitin i.e., methicillin-resistant Staphylococcus aureus (MRSA).

All these MRSA isolates (38) in our study were found to be susceptible to vancomycin.

Antimicrobial susceptibility testing of all the MRSA isolates showed that they had high resistance to multiple classes of antibiotics. The maximum resistance was observed against ampicillin (100%), followed by ciprofloxacin (100%), erythromycin (84.21%), amikacin (78.94%), and cotrimoxazole (68.42%), and clindamycin (63.15%) (Table 3).

24 isolates were D-test positive out of the 38 MRSA (Figure 1).

Of these 38 MRSA isolates, 26 were isolated from patients on hemodialysis for more than 6 months duration while 12 from the patients on hemodialysis were of less than 6 months and the difference in the distribution of MRSA isolates between less than 6 months and more than 6 months was statistically significant (Table 2).

DISCUSSION

The nasal carriage of S. aureus plays a major role in the epidemiology and pathogenesis of staphylococcal infections. S. aureus nasal carriage has shown to be more common in long-term hemodialysis patients than in the general population.¹⁰ Several studies reported an increased risk for colonization and infection with MRSA in patients with end-stage renal disease.^{9,14,23,27,31}

In our study, males (78%) outnumbered females (22%) which are in accordance with the many other studies. A study conducted by Sathish et al, had 37 males (74%) and 13 females (26%) out of 50 patients enrolled.¹⁶ A study by Ghasemian et al, enrolled patients having most of the males (53.5%) than females (46.4%).¹⁸ However, in the studies conducted by Anil et al, Celik et al, and Chun Fu Lai et al, females were more in number as compared to males.^19,20,22

In the present study, the majority (38%) of the patients were in the age group 41-60 years followed by 61-80 years (28%). A minimum number of patients were of age more than 80 years.

A significant correlation was found regarding the nasal carriage of S. aureus and hemodialysis duration. Publications differ on this issue; some authors had not found hemodialysis duration as a risk factor while others have found it as a risk factor.^16,18

It was observed that 38% of the patients were carriers of S. aureus followed by CoNS, followed by aerobic spore bearers (Table 1). Montewka et al, have also reported the isolation of S. aureus and CoNS from nasal swabs obtained from the hemodialysis patients.¹⁷

Of the total 100 patients in a study, S. aureus was isolated in 38 (38%) patients. Many authors have reported similar isolation rates in their studies.¹⁹ However, a study conducted by Sathish et al, had reported an S. aureus nasal carriage rate of 62% among their study population.¹⁶ On contrary, a study conducted by Celik et al, reported 28.3% of their patients undergoing hemodialysis were nasal carriers of S. aureus.²⁰

All the S. aureus isolates (100%, 38/38) in our study were resistant to cefoxitin i.e., methicillin-resistant Staphylococcus aureus (MRSA). A study conducted by Deepika et al., has also reported similar findings.²¹ This poses a significant risk of transmitting MRSA from person to person directly or indirectly among hemodialysis patients and to other healthcare workers. Different studies had reported different rates of nasal carriage of MRSA among hemodialysis patients.^16-21

Of these 38 MRSA isolates, 26 were isolated from patients on hemodialysis for more than 6 months duration while 12 from the patients on hemodialysis were of less than 6 months and the difference in the distribution of MRSA isolates between less than 6 months and more than 6 months was statistically significant (Table 2).

Antimicrobial susceptibility testing of all the MRSA isolates showed that they had high resistance to multiple classes of antibiotics. The maximum resistance was observed against ampicillin (100%), followed by ciprofloxacin (100%), erythromycin (84.21%), amikacin (78.94%), and cotrimoxazole (68.42%), and clindamycin (63.15%) (Table 3).

24 isolates were D-test positive out of the 38 MRSA (Figure 1).

Other studies have also reported high resistance to various classes of antibiotics amongst MRSA isolates. All these MRSA isolates (38) in our study were found to be susceptible to vancomycin which correlates with the findings of other authors.^16-21 A hundred percent susceptibility to vancomycin in our study may be because this 6 lycopeptides is not being regularly used to treat staphylococcal infections in our setup. This reduces the selective pressure for the development of resistance to vancomycin.

CONCLUSION

Adequate establishment of Staphylococcal nasal carrier status in hemodialysis patients accompanied by antibiotic susceptibility testing should be done in routine as it is crucial to reduce associated morbidity and mortality. Robust infection control practices should be followed to prevent the transmission of MRSA among chronic hemodialysis patients.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee BFUHS/2K19P-TH/8907

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