Article Text
Abstract
Objective We sought to determine the prevalence and antimicrobial susceptibility pattern of methicillin-resistant Staphylococcus aureus (MRSA) isolated from the clinical samples at a tertiary care hospital in Nepal.
Methods Cross-sectional, observational study design.
Study setting The study was carried out at a tertiary care facility, the largest public hospital, Tribhuvan University Teaching Hospital (TUTH), Nepal.
Participants A total of 7433 clinical samples from hospital inpatients and outpatients available in the TUTH microbiology laboratory were examined. The study included clinical samples from the patients of either sex and across all age groups that had been clinically determined to have S. aureus infections.
Results Of 7433 clinical samples analysed, S. aureus was recovered from 499 (6.71%). The prevalence of MRSA was discovered to be 26.4% (95% CI 21.6% to 30.4%). The major sources of MRSA were pus, 71 (18.5%). MRSA isolates encountered 100% resistance to penicillin and cloxacillin, followed by ciprofloxacin (80.5%), erythromycin (79.8%), cephalexin (64.9%), cotrimoxazole (61.1%) and clindamycin (58.5%). Chloramphenicol (17.9%), and gentamicin (27.4%), on the other hand, exhibited minimal resistance. None of the isolates were resistant to vancomycin (0.0%). Prevalence of multidrug resistance (MDR) was markedly higher in MRSA, 94.05% (95% CI 89.4% to 98.6%), compared with methicillin-sensitive S. aureus, 52.12% (95% CI 46.2% to 57.8%).
Conclusion Our study indicated a high rate of MRSA and MDR-SA (Multidrug-resistant Staphylococcus aureus) prevalence in a Nepalese tertiary care hospital. Therefore, given the widespread burden of MRSA and the threat of the emergence of resistance to commonly used antibiotics, there is a need for the development, adoption and enforcement of appropriate control policies in these hospital settings. Regular surveillance, reporting mechanism as well as prudent use of antimicrobial agents are crucial to combating the progression of MDR-MRSA prevalence and antibiotic resistance.
- EPIDEMIOLOGY
- INFECTIOUS DISEASES
- Epidemiology
- Public health
- BACTERIOLOGY
Data availability statement
Data are available upon reasonable request.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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STRENGTH AND LIMITATIONS OF THIS STUDY
This retrospective, cross-sectional study was carried out in the country’s largest public tertiary care hospital using a large sample size, ensuring high external validity.
The comparison between hospital-acquired and community-acquired methicillin-resistant Staphylococcus aureus (MRSA) was not made.
Retrospective data were gathered for only 1 year to estimate the prevalence of MRSA; as a result, a longer period of time has not been used to track the trend of MRSA isolates and their antimicrobial resistance.
Given the cross-sectional nature of the evaluation, it did not allow any differentiation between transient and persistent isolates.
Introduction
Methicillin-resistant Staphylococcus aureus (MRSA) has become commonplace globally since it was initially recognised in a UK hospital in 1961,1–4 and poses a global threat causing serious infections in health facilities and the community, contributing 60% more deaths than the non-resistant form of the infections.5 Recent developments in new antimicrobials against MRSA include ceftaroline, ceftobiprole, dalbavancin, oritavancin, iclaprim and delafloxacin, all of which are in various phases of clinical studies.6–9 Despite ongoing development of new treatments, active surveillance efforts, and advancements in infection control, the incidence of MRSA has emerged as a major source of morbidity, higher costs of healthcare delivery services, and increased mortality in hospitals over the past decades.10–12 Clinical outcomes from MRSA infections are rather worse than those from methicillin-sensitive S. aureus (MSSA) infections.13 It often causes disseminated infections including infective endocarditis,14 septic arthritis15 and osteomyelitis.16 According to a Centers for Disease Control and Prevention report, estimated hospitalisation cases due to MRSA were 323 700 in 2017, resulting in 10 600 mortalities in one year.17
Public health is seriously threatened by the pathogen’s prevalence in many nations today, with isolates' resistance to the majority of antistaphylococcal antibiotics including penicillin, gentamicin, erythromycin, ciprofloxacin, rifampin, cotrimoxazole, chloramphenicol, norfloxacin and tetracycline.18 19 Moreover, once established, MRSA is frequently difficult to eradicate because it spreads more quickly than the other varieties when brought into hospitals.20 The prevalence of MRSA varies greatly between nations, as well as from one hospital to another within a single nation.21 The most recent data from the WHO on MRSA incidence showed rates surpassing 20% in all WHO regions and even as high as 80% in some countries.22 In Nepal, MRSA prevalence rates differ substantially from institution to institution, ranging from 26.1% to 70.6%.23 24
On the other hand, predominance of MRSA is a significant therapeutic issue in numerous hospitals and places around the world. It has been linked to multiple antibiotic resistance, including the commonly used drugs oxacillin, erythromycin or even vancomycin, the last medication for treating MRSA infection, stressing the need for precision and promptness in MRSA identification in the clinical setting for the timely management of infections brought on by this superbug.25–27 Given the significance of MRSA infections for public health, it is essential to track the present scenario of MRSA prevalence, as part of antimicrobial resistance (AMR) surveillance, across a variety of settings, especially in a resource-limited country like Nepal. In this study, we conducted a hospital-based study at the Department of Microbiology, Tribhuvan University Teaching Hospital (TUTH), a large tertiary care hospital in Kathmandu, Nepal, to determine the prevalence of MRSA among S. aureus isolates including their antimicrobial susceptibility patterns and multidrug resistance (MDR) to commonly used antibiotics.
Methods
Study design and setting
This observational and cross-sectional study was conducted at the Department of Microbiology, TUTH, during a 1 year period, from 1 January 2020 to 31 December 2020.
Study site and justification
This study was conducted at the Department of Microbiology, TUTH, Maharjgunj, Kathmandu, Nepal. This is the largest tertiary care public hospital located in the capital of Nepal. It is a hospital that provides medical education, research and patient care in a unique environment. It offers curative, rehabilitative, promotional and preventive healthcare services to all kinds of patients across the country.
Sample size and sampling technique
A non-probability, purposive sampling in consecutive 7433 clinical samples that satisfied the inclusion criteria for the study, and were accessible over the course of a 1 year period, was employed in the study.
Study population and selection criteria
This study included all the clinical specimens received at the Department of Microbiology, TUTH during the duration of the study, that is, a total of 7433 clinical specimens from inpatient as well as outpatient departments during 1 year (1 January 2020 to 31 December 2020). The study included clinical samples from all age groups that had been clinically determined to have S. aureus infections. Only one isolate of S.aureus was considered per patient.
Variables of interest
The outcome variables used in the study were S. aureus (MRSA and MSSA), whereas age, gender, specimen type and antibiotic sensitivity outcomes were used as predictor variables.
Specimen collection, isolation and identification
Required data were collected retrospectively from the records of the Department of Microbiology, TUTH. These records were the result of microbiological procedures as follows: the collection of the specimens, followed by inoculation in culture media and aerobic incubation at 37°C were done in accordance with the standard microbiological procedure following the American Society of Microbiology (ASM).28 Significant bacterial growth on culture of the specimens was processed for identification of S. aureus on the basis of colony morphology, Gram staining, catalase test and coagulase test. Catalase-positive and coagulase-positive Gram-positive cocci, predominantly arranged in clusters, were identified as S. aureus. Antimicrobial susceptibility test (AST) was done by the Kirby-Bauer disk diffusion method. Clinical Laboratories and Standard Institute (CLSI) guideline was followed to identify MRSA isolates using cefoxitin disk (30 µg) and to determine the antimicrobial agents to test in the AST. Zone of inhibition around each antimicrobial disk was measured and interpreted using the interpretation chart of CLSI to determine the AMR pattern of the S. aureus isolate. Isolates with a zone of inhibition ≤21 mm around the cefoxitin disk were identified as MRSA isolates.
Multidrug resistance
Isolates were considered MDR if they were resistant to at least three classes of first-line antimicrobial drugs.29
Quality assurance, data processing and statistical analysis
The reliability of the study findings was ensured by implementing standard microbiological procedures guided by ASM28 and CLSI. For quality control, S. aureus ATCC 25923 was employed.
Data were coded, entered and analysed using Statistical Package for Social Sciences (SPSS) software V.26 (SPSS, Chicago, Illinois, USA). Descriptive data were presented as frequency and percentage. Continuous data were presented as mean±SD, and frequency (%) tables were generated for categorical variables. The χ2 test and Fisher’s exact test, where necessary, were performed for comparison of categorical variables. All the data were analysed at 95% CI, and their corresponding 5% margin of error with a value of p<0.05 was considered to be statistically significant for all analyses.
Ethical issues
Data were anonymised to ensure the confidentiality of the patients.
Patient and public involvement
No patients were directly involved in this retrospective study, and the secondary data were analysed based on routine microbiological analysis.
Results
Demographic characteristics of the study population are presented in table 1. Among the total of 7433 clinical specimens, 499 (6.71%) S. aureus were isolated. Among these 499 S. aureus isolates, 267 (53.5%) were from men and 232 (46.5%) were from women, with a sex ratio of 1.14:1. The ages of the study subjects ranged from 5 days to 93 years with a mean age of 29.17±2.04 years and median age 26.00 (IQR:14–40) years. The rate of isolation for S. aureus was highest from pus/swab samples (74.0%) followed by blood (10.4%), body fluid (6.0%), sputum (5.2%) and urine (4.4%).
Table 2 depicts the prevalence rate of MRSA isolates. The estimated prevalence rate of MRSA was found to be 26.4% (95%CI 21.6% to 30.4%).
Table 3 demonstrates the association between MRSA isolation and various demographic and clinical specimens. Relatively a higher number of MRSA was isolated in men (53, 13.9 %) compared with women (48, 12.6 %) and the highest number of MRSA was detected in the age group 25–34 years (29, 7.9 %), followed by age groups 1–14 years (16, 4.4 %), 15–24 years (14, 3.8%), 45–64 years (14, 3.8 %), over 65 years (11, 3%), 35–44 years (9, 2.5%), and under age 1 year (5, 1.4%). The isolation rate of MRSA was not significantly associated with gender (p=0.53) as well as any of the age groups (p>0.05).
The major sources of MRSA were pus/swab (71, 18.5%), followed by blood (12, 3.1%), sputum (8, 2.1%), body fluid (7, 1.8%) and urine (3, 0.8%). The isolation rates of MRSA did not statistically correlate with any of the clinical samples (p>0.05).
S. aureus isolated in this study were highly resistant to penicillin (91.6%), followed by ciprofloxacin (63.2%), erythromycin (59.1%), clindamycin (39.9%), cotrimoxazole (39.5%) and doxycycline (28.8%). Chloramphenicol (10.7%), gentamicin (13.3%) and cephalexin (20.3%), on the other hand, showed less resistance. Vancomycin was the sole drug that exhibited 100% sensitivity to this pathogen (table 4).
Table 5 illustrates the antibiogram of MRSA and MSSA to different antimicrobial agents. All isolates were resistant to at least one antimicrobial agent. MRSA showed a higher degree of resistance to many drugs. MRSA isolates were 100% resistant to penicillin and cloxacillin, followed by 80.5% resistant to ciprofloxacin, 79.8% resistant to erythromycin, 64.9% resistant to cephalexin, 61.1% resistant to cotrimoxazole, 58.5% resistant to clindamycin and 57.1% to doxycycline. Vancomycin showed no resistance (0.0%), whereas chloramphenicol (17.9%) and gentamicin (27.4%) showed the least resistance. On the other hand, 91.1% of MSSA were resistant to penicillin. The likelihood of being resistant to or susceptible to methicillin was significantly associated with penicillin (p=0.002), cloxacillin (p<0.05), cephalexin (p=0.05), cotrimoxazole (p<0.05), ciprofloxacin (p<0.05), gentamicin (p<0.05), clindamycin (p<0.05) and erythromycin (p<0.05).
The status of MDR in relation to prevalence and its frequency (%) of resistant drugs is depicted in table 6. MDR prevalence in MRSA was notably higher, at 94.05% (95% CI 89.4% to 98.6%), compared with S. aureus 60.02% (95% CI 55.7% to 64.3%) and MSSA 52.12 (95% CI 46.2% to 57.8%). An increasing trend in the frequency (%) of drug resistance in MRSA was observed: around 26%, 28% and 41% of MDR comprised of at least three-drug resistant, four-drug resistant and more than four-drug resistant, respectively.
Discussion
The study examined the prevalence of MRSA using clinical samples of the bacteria from TUTH, Nepal, the country’s largest tertiary care facility. A total of 499 clinically significant S. aureus isolates from 7433 samples from patients that were admitted to the hospital over the course of the study were isolated. A total of 383 strains of S. aureus met the criteria for inclusion in a subsequent assessment of MRSA prevalence.
Available studies suggest that the prevalence rate of MRSA over different parts of Nepal and other regions of the country is not uniform, and a significant variation in its prevalence has been documented at different settings in Nepal and throughout the world.
The present study revealed a prevalence of 26.4% MRSA, which is comparable to the studies conducted in other regions of Nepal, including 26.14% in eastern Nepal,24 and 25.1%30 to 27.1%31 in the central part of Nepal. However, several investigations carried out in Nepal32–35 and elsewhere in the world26 36 37 reported a greater prevalence of MRSA. Although it is quite challenging to reconcile these contradictory data with respect to both time and location, these variations could be due to variances in the circulating clones, infection control procedures and trends for antibiotic prescription in various hospital settings. Additionally, the decline in prevalence in this study might be brought on by a reduction in hospital visits and less exposure to S. aureus infections as a result of COVID-19-induced travel restrictions.
In this study, men had a greater isolation rate of S. aureus than women. S. aureus isolation rates were higher among people aged 25–34 years. However, the prevalence of MRSA in the current investigation did not differ significantly by gender or age group, which corresponds well with earlier studies by Dilnessa et al,38 indicating that gender and age are not risk factors for the acquisition or colonisation of MRSA.
The present investigation depicted that the prevalence of MRSA and MSSA isolated from pus was the highest in comparison to other clinical samples, despite the fact that there was no statistical correlation between the isolation rates of MRSA and MSSA with any of the analysed clinical samples . This result is in line with the findings from various study settings in Nepal: Khanal et al,39 Pradhan et al,33 Sapkota et al23 and many similar studies in other countries: Akpaka et al40 and Kaleem et al.41 The highest isolation rate of S. aureus and MRSA in pus in our study could be partly due to the fact that wound samples came from the burn unit and surgical wards of the hospital. MRSA is increasingly prevalent in surgical wards, particularly in seriously ill patients who have spent a lot of time in intensive care units.42
AST of all 499 S. aureus isolates against 11 commonly used antibiotics showed that the overall resistance to antibiotics was alarmingly higher in penicillin (91.6%), followed by ciprofloxacin (63.2%) and erythromycin (59.1%). A moderate resistance against this pathogen was found in clindamycin (39.9%) and cotrimoxazole (39.5%). The higher rate of resistance observed in penicillin (91.6%) is in line with the results in the studies by Shrestha et al (91.94%),43 Ansari et al (94.7%)44 and Belbase et al (97.4%).45 The finding in the study by Kumari et al,24 in a tertiary care hospital in eastern Nepal that the drug was 100% resistant against this pathogen is corroborated by a study elsewhere in the world.46
The resistance to ciprofloxacin was 63.2%, which is lower than that reported by Belbase et al (61.74%),45 but well in line with prior investigations conducted in Nepal by Shrestha et al (61.74%)43and Ansari et al (63.7%).44 This is probably due to the indiscriminate and empirical use of these drugs. Further, quinolones are relatively cheaper and easily available as over-the-counter drugs in Nepal. Moreover, Nepal is a resource-limited nation with the majority of its citizens living below the poverty line, and owing to economic constraints, lack of health facilities and lack of awareness towards the drug resistance, this drug has been largely used as an over-the-counter drug, often without an antibiotic susceptibility test, consequently leading to drug resistance.
Further, a higher rate of resistance to erythromycin (59.1%) noted in this study was also supported by Belbase et al (55.3%)45 and Shrestha et al (52.94%)43 in contrast to 32.7% by Ansari et al.44 In addition, resistance to cotrimoxazole was 39.5% in comparison to 63.2% noted in a previous study by Belbase et al,45 81.7% by Ansari et al44 and 57.04% by Shrestha et al.43 On the contrary, lower resistance was manifested by vancomycin (1.7%), chloramphenicol (10.7%), gentamicin (13.3%) and cephalexin (20.3%).
With regard to chloramphenicol, which appeared to have a lower resistance rate (10.7%) towards this pathogen, it is higher than seen in a previous study by Shrestha et al,43 where 7.93% of isolates were resistant. Thus, wise use of this drug is crucial to limit the further emergence of resistance.
The growing resistance of MRSA to existing antibiotics is worrisome. All MRSA isolates found in this study were found to be entirely resistant (100%) to penicillin. Similar results were noted for penicillin among MRSA strains in different study settings in Nepal,45 47 and in other parts of the world.40 The prevalence of MRSA strains, which have been shown to be resistant to vancomycin in earlier investigations, varies substantially depending on the study location, from none (0.0 %)34 43 in different parts of Nepal to 0.33%48 in India, and alarmingly higher (29.4%) in Ethiopia38 and 62.5% in south-west Nigeria (62.5%).49 It is worth noting that none of the isolates in this study were resistant to vancomycin, which corroborates well with the study noted in different parts of Nepal.24 43 This lack of resistance depicted in our study is encouraging because vancomycin is the treatment of choice for MDR MRSA infections and should only be used as a last resort for MRSA infections that have proven resistant to other classes of antibiotics, in view of the possibility of resistance emergence. Prudent use and ongoing surveillance susceptibility testing of MRSA against vancomycin have been reported as a remedy to control reduced susceptibility of staphylococci to vancomycin.50–52
There was a significant difference in the resistance of MRSA and MSSA to medications such as penicillin, cloxacillin, cephalexin, ciprofloxacin, erythromycin, clindamycin, gentamicin, cotrimoxazole and doxycycline. However, MRSA and MSSA did not differ significantly in their susceptibility to chloramphenicol.
In a previous study conducted in Nepal by Adhikari et al,30 a significant difference in antibiotic resistance between MRSA and MSSA was observed in the case of ciprofloxacin, gentamycin and erythromycin. Similarly to this, Shrestha et al43 noted that there was a substantial difference in the resistance of MRSA and MSSA isolates to penicillin, fluoroquinolone, erythromycin, gentamicin, cotrimoxazole and tetracycline.
Given the fact that staphylococci can be transmitted from one person to another by direct or indirect contact, the rising prevalence of MRSA that is MDR is becoming a grave issue in the current state of medical care. Our study revealed an alarmingly high rate (94.05%) of MDR MRSA, with 26 being more than three, 28 being at least four and 41 being more than four antimicrobial drug resistant. Epidemiological studies have indicated a varying rate of MDR in MRSA in Nepal and elsewhere in the world. For instance, in western Nepal, Bhatta et al47 noted that a majority of MRSA (73.38%) isolates were MDR. Belbase et al, from a pus/wound swab sample in a tertiary care hospital Nepal,45 showed that 68.6% of the isolates were MDR. Lower respiratory tract MRSA isolates were reported to have MDR in the USA in 67.8% (for inpatients) and 65% (for outpatients) of the cases.53 In various contexts in India, up to 72.1% of MDR MRSA has been documented.37 48 It is very evident from this that stringent drug laws and MRSA surveillance are absolutely necessary to prevent the threat from growing.
Notably, MDR patterns were more prevalent in MRSA (94.05%) than in MSSA (52.12%). Cephalexin, clindamycin, erythromycin, ciprofloxacin, doxycycline and cotrimoxazole were all less than 50% effective against MRSA. Similarly, MRSA showed higher levels of resistance to various antibiotics than MSSA. The results of this study correspond with those of investigations carried out in other regions of Nepal.24
Limitations
There are major limitations in this study that could be addressed in future investigations. Due to the retrospective nature of the investigation, we discovered some missing data and only 383 of the 499 samples were analysed for a thorough examination of MRSA prevalence. The classification of MRSA as hospital-acquired and community-acquired would have reinforced the study’s conclusions. Nevertheless, the results of this study can help determine the best course of antimicrobial treatment action for a wide range of Staphylococcus infections. The study duration encompasses only a year. A longer study duration could have been helpful to determine the trend of MRSA over the years.
Conclusion
Our study indicates that S. aureus has grown to be a major public health issue in Nepalese tertiary care hospital settings. The prevalence of S. aureus varies noticeably based on the type of clinical samples. In hospitals, pus served as the primary potential source for S. aureus and MRSA. The prevalence of MRSA strains was slightly lower when compared with other studies conducted in Nepal; however, in contrast to previous studies carried out elsewhere, the prevalence rate was notably high. It is noteworthy that MDR patterns were more prevalent in MRSA than in MSSA, and penicillin, ciprofloxacin, cephalexin, erythromycin and cotrimoxazole were discovered to be the least effective drugs, whereas MRSA isolates exhibited higher susceptibility to vancomycin, chloramphenicol and gentamicin, and still the drug of choice for treating MDR MRSA infections. Therefore, given the widespread burden of MRSA and the threat of the emergence of resistance to commonly used antibiotics, there is a need for the development, adoption and enforcement of appropriate control policies in these hospital settings. Health education, mandatory antibiotic susceptibility test before antibiotic prescription, regular surveillance and reporting systems as well as careful use of antimicrobial agents are crucial to combat the progression of MRSA prevalence and antibiotic resistance. Importantly, vancomycin should only be used as a last resort for MRSA patients, even though just a few isolates in this study showed resistance to it. In addition, screening tests and MIC determination are strongly encouraged for monitoring the effectiveness of medication and for early detection of resistance among local strains. Further, genotypical studies to monitor the epidemiology of resistant strains of S. aureus are highly recommended.
Data availability statement
Data are available upon reasonable request.
Ethics statements
Patient consent for publication
Ethics approval
This study was conducted after obtaining ethical approval from the Institute of Medicine-Institutional Review Committee (IOM-IRC)- (Reference No. 272 E2078/79).
Acknowledgments
The authors thank the Department of Microbiology for generation and provision of data for this study. The authors also thank IOM-IRC for its support and approval of this study.
References
Footnotes
Collaborators None.
Contributors PA conceptualised the manuscript, helped with data collection, guided data analysis, and contributed to manuscript writing and data interpretation. DB, JRR, LB and AB helped with data collection, ensured database quality and helped with data integration, and contributed to data interpretation and manuscript writing. SKS conceptualised the manuscript, analysed the data, wrote the manuscript, and interpreted the data critically. All authors have read and approved the manuscript. SKS is responsible for the overall content as the guarantor.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.