Methicillin-resistant Staphylococcus aureus (MRSA) carriage among the critical care personnel in a tertiary care hospital in Sikkim: An observational study

Materials & Methods

This is a hospital based observational study conducted among all the healthcare workers posted in various critical care units [medicine Intensive Care Unit (ICU), surgical ICU, neonatal and paediatric ICU, cardiac care units, neurosurgical ICU, and post operative wards, Intensive trauma unit] of a Central Referral Hospital, Gangtok, Sikkim from July 2022 – June 2023. Approval was taken from the Institutional Ethics Committee prior to the start of the study. A written informed consent was taken from the participants.

All eligible candidates were provided with a questionnaire (which was developed in-house and validated) for the assessment of various risk factors like proper hand hygiene, history of close contact with any patient, history of hospitalisation or any chronic illness, etc.

Results

Out of the 300 participants, 70 (23.22%) were males, and 230 (76.66%) were females. Maximum participants, 202 (67.33%), belonged to the age group of 25-35 yr, the rest were (18.33%) between 36 and 45 yr. The age of the participants ranged from 23-58 yr (mean=31.94, SD=7.222). Among the participants, 44.66 per cent were staff nurses, 27 per cent were doctors, 13 per cent were attendants, seven per cent were housekeeping staff, and 6.33 per cent were physiotherapists and OT technicians. Most participants (51.6%) had 1-5 yr experience in critical care, 21.33 per cent had 6-10 yr, 11.66 per cent had 11-20 yr, and 1.33 per cent had 21-40 yr. Educationally, 27 per cent were graduates, 23.33 per cent were postgraduates, and 3.33 per cent had only primary education (Table I).

The most predominant organism isolated was coagulase-negative Staphylococci, 194 (64.7%). A total of 79 (26.3%) S. aureus colonies were isolated, among which 19 (24.05%) were methicillin-resistant. Nineteen (6.3%) nasal swabs processed showed no growth, and 4 (1.3%) swabs each showed growth of other organisms (namely gram-negative bacilli, micrococci, and candida species).

Of all the HCWs screened from critical care units, 19 were identified as MRSA carriers with nasal colonisation, while 281 were non-carriers. This study found a 6.33 per cent prevalence of MRSA nasal carriage in HCWs working in critical units.

Among the 230 female participants screened, 5.65 per cent were MRSA nasal carriers, compared with 10 per cent in the 70 male participants. Educationally, 26.67 per cent of MRSA carriers had completed Higher Secondary School, 6.44 per cent were graduates, 5.89 per cent had secondary education, and 5.72 per cent were postgraduates. The highest MRSA prevalence of 9.52 per cent was among attendants, followed by 7.69 per cent of housekeeping staff, 6.17 per cent doctors, and 6.42 per cent staff nurses. No MRSA carriers were reported among physiotherapists and OT technicians (Table II).

MRSA carriers were distributed across various critical care units: 16.66 per cent in the neurosurgical ICU, 12.12 per cent in the orthopaedic ITU, 10.86 per cent in the surgical ICU, 6.81 per cent in the post-operative OT, and 2.56 per cent in the medicine ICU. No MRSA carriers were reported from the paediatric ICU, neonatal ICU, post-operative OBG unit, or cardiac care units (Table III).

Antibiotic susceptibility test

All the MSSA isolates were 90 per cent sensitive to gentamicin, 85 per cent to tetracycline, and 60 per cent to trimethoprim/sulfamethoxazole. MSSA isolates showed 40 per cent sensitivity to erythromycin and 14 per cent sensitivity to ciprofloxacin. All the MSSA isolates showed 100 per cent susceptibility to linezolid and rifampicin. All the MSSA isolates were resistant to penicillin (Fig. 1).

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Fig. 1.

Antibiotic susceptibility pattern of MSSA.

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All the isolates of MRSA showed 100 per cent sensitivity to linezolid, 94.73 per cent to rifampicin, 84.21 per cent to tetracycline, 78.94 per cent to trimethoprim sulfamethoxazole and 73.68 per cent to gentamicin. While MRSA isolates were 47.36 per cent sensitive to clindamycin, 42.1 per cent sensitive to erythromycin and 10.52 per cent to ciprofloxacin (Fig. 2).

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Fig. 2.

Antibiotic susceptibility pattern of MRSA isolates.

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Discussion

It is essential to identify the carriers of MRSA among HCWs within hospital settings, specifically those employed in critical care units, as they serve as potential conduits for the spread of nosocomial illnesses, which prolong hospital stays.

In this study, 300 nasal swabs from HCWs in critical care units identified a 6.33 per cent MRSA carriage rate, which was comparable to previous studies conducted by Goyal et al¹⁶ in Delhi (6.6%), a study from Mysore (6.5%)¹⁷, Latha et al¹⁸ in Manipal (6.4%), and Singh et al¹⁹ in Bhubaneswar (7.5%)^16-19. Contrary to our findings, other studies have reported varying MRSA colonisation rates among HCWs. Another study from Mangalore, Karnataka²⁰ documented a 2.5 per cent prevalence in Mangalore, while Sridharan et al²¹ reported an 11.5 per cent carriage rate in Meerut.

A global study by Albrich and Harbarth, involving a literature review of 33,318 HCWs screened from January 1980 to March 2006, found a 4.6 per cent MRSA infection or colonisation rate¹⁰. Additionally, a systematic review and meta-analysis by Latha et al⁵ reported a pooled MRSA nasal carriage prevalence of 11 per cent among Indian HCWs.

This disparity can be attributed to differences in study design, including variations in sample size, methodologies, and detection techniques. Additionally, geographical regions and institutions may exhibit different MRSA prevalence rates.

In our study, 8.57 per cent (6) of the total MRSA carriers were males, and 5.65 per cent (13) were females. Similar results were seen in a study conducted by Singh et al¹⁹ where the carriage rate of MRSA among males was 9.1 per cent and 6.5 per cent among females. Giri et al²² from Nepal also reported a higher prevalence among males (8.7%) than females.

In this study, MRSA prevalence was highest among attendants (9.52%), followed by housekeeping staff (7.69%), staff nurses (6.42%), and doctors (6.17%). This contrasts with a study¹⁷ in Mysore, where the highest prevalence was among doctors (28.4%) and nursing interns (21.1%)¹⁷. Other Indian studies like the one by Singh et al¹⁹ have also reported a higher MRSA carriage prevalence among the staff nurses (22.1%), which is in contrast to this study.

The mechanism underlying MRSA nasal carriage is complex and not fully understood. The increased rate among nurses presents a notable epidemiological concern, as their frequent patient interactions make them potential reservoirs for infection, thereby perpetuating MRSA within the hospital setting.

This study reports the highest MRSA nasal carriage prevalence among HCWs in the neurosurgical ICU (16.66%), followed by the orthopedics ITU (12.12%), surgical ICU (10.86%), post-operative OT (6.81%), and medicine ICU (2.56%). Similarly, Khanal et al²³ found a high frequency of MRSA carriers in the surgical ICU and post-operative ward (28.6%). This may be due to high workload, overcrowding, and frequent wound care in these units, increasing MRSA transmission²³.

MRSA is associated with adverse clinical outcomes in ICUs and poses a significant challenge to hospital infection control. ICUs play a critical role in the widespread dissemination of MRSA, as individuals frequently move between various healthcare settings, including hospital wards and other medical facilities¹⁹. A significant association between MRSA carriage and educational qualification was seen in this study (P=0.041). This aligns with the study by Maroof et al²⁴ from Srinagar, which also found a higher prevalence among graduates.

The main obstacle to effective infection control protocols is rigorous adherence. Regular education and skill development for new HCWs, with active participation, can be a straightforward and efficient strategy to prevent the transmission of antibiotic-resistant bacteria like MRSA.

In this study, S. aureus isolates exhibited 100 per cent resistance to penicillin, consistent with findings by Bala et al²⁵ and Goyal et al¹⁶, though Kausalya et al²⁶. and Rahman et al²⁷ reported 71.5 per cent and 75 per cent resistance, respectively. Resistance to ciprofloxacin was 86 per cent, aligning with Ramakrishnan et al²⁰ and Singh et al¹⁹ (80 per cent), while Rahman et al²⁷ and Agarwal et al²⁸ reported lower resistance rates of 47.5 per cent and 50 per cent, respectively^27,28. Resistance rates in our study were 60 per cent for erythromycin, 58 per cent for clindamycin, and 40 per cent for trimethoprim/sulfamethoxazole, similar to Singh et al¹⁹ (58% for erythromycin) and Ramakrishnan et al²⁰ (60%). Lower clindamycin resistance was reported in Singh et al¹⁹ (20%) and Rahman et al²⁷ (15.91%) as compared to the present study. Gentamicin and tetracycline susceptibility were 90 per cent and 85 per cent, respectively, similar to Aila et al²⁹ (96.8% and 85.8%) and Giri et al²² (100% and 90.9%). Linezolid and rifampicin susceptibility was 100 per cent, consistent with Bala et al²⁵, and Giri et al²².

Among MRSA isolates, 100 per cent resistance to penicillin was observed, consistent with Bala et al²⁵ and Goyal et al¹⁶. Resistance rates were 89.47 per cent for ciprofloxacin, 57.89 per cent for erythromycin, and 52.63 per cent for trimethoprim/sulfamethoxazole. MRSA strains showed 100 per cent susceptibility to linezolid and high sensitivity to rifampicin (94.73%), tetracycline (84.21%), trimethoprim/sulfamethoxazole (78.94%), and Gentamicin (73.68%). This aligns with Aila et al²⁹, who reported 88.2 per cent sensitivity to rifampicin, 86.3 per cent to tetracycline, and 92.2 per cent to gentamicin. In contrast, Khanal et al²³ reported higher resistance to gentamicin (42.9%) and lower resistance to ciprofloxacin (14.3%) and trimethoprim/sulfamethoxazole (28.6%)²³. Clindamycin resistance in the present study was 52.63 per cent, similar to Singh et al¹⁹ (50%) and Maroof et al²⁴ (62.5%), but contrasting with Giri et al²², who reported high sensitivity (83.3%).

The variability in resistance rates among different antimicrobial agents reflects factors such as regional prescribing practices, patient demographics, and microbial characteristics. Antibiotic resistance in hospitals is primarily driven by the overuse, misuse, and inappropriate prescription of antibiotics for both community-acquired and hospital-acquired infections. Routine in vitro susceptibility testing for clindamycin is not reliable for identifying inducible resistance mediated by the erm gene, leading to treatment failure. This can be avoided by implementing a simple D-test for routine diagnostic procedure for accurate detection of inducible clindamycin resistance³⁰. The absence of strict regulations on antibiotic prescriptions, coupled with the accessibility of over-the-counter antibiotics, further aggravates this problem. Consequently, treating S. aureus infections in hospitals with these antibiotics may be ineffective due to high resistance rates.

Our study identified significant risk factors for MRSA colonisation, including non-adherence to hand hygiene practices (P<0.05), recent close interactions with patients (P=0.007), and proximity to MRSA carriers (P<0.05). However, antibiotic use, hospitalisation, and chronic medical conditions did not show a statistically significant association with MRSA carriage. The Healthcare Infection Control Practices Advisory Committee emphasises that the absence of an outbreak does not eliminate transmission risk³¹. Therefore, healthcare institutions should implement regular screening protocols for healthcare personnel, both during recruitment and periodically thereafter.

Some limitations of this study only include that it focussed on the HCPs posted in critical care units. Also, follow up of the identified carriers was not done. Inducible clindamycin resistance test (D test) was not done for the isolates as this study was for screening of nasal carriers and not patients. Furthermore, the absence of comparison with genotypic methods to ascertain the presence of resistance genes represents another notable limitation due to constraints pertaining to time, funding, and the availability of laboratory infrastructure.

Overall, this study found an MRSA nasal carriage rate of 6.33 per cent among HCWs in critical care units, with the highest prevalence among attendants and housekeeping staff. This highlights the need for targeted education and training to enhance infection control practices in these groups. Asymptomatic MRSA carriers among HCPs are of significance due to their potential to transmit the pathogen, increasing patient morbidity, mortality, and healthcare costs. Therefore, strict enforcement of infection control measures is crucial to reduce MRSA carriage and transmission in hospital settings.