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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 5  |  Issue : 1  |  Page : 30-34

Higher rate of methicillin-resistant Staphylococcus aureus carriage amongst hospitalised patients in rural South India


1 Undergraduate Medical Students, Faculty of Medicine, Government Theni Medical College, The Tamil Nadu Dr. M.G.R. Medical University, Theni, Tamil Nadu, India
2 Department of Microbiology, Faculty of Medicine, Government Theni Medical College, The Tamil Nadu Dr. M.G.R. Medical University, Theni, Tamil Nadu, India

Date of Web Publication18-Aug-2017

Correspondence Address:
Ramalingam Sekar
Department of Microbiology, Faculty of Medicine, Government Theni Medical College, The Tamil Nadu Dr. M.G.R. Medical University, Theni - 625 512, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jpsic.jpsic_3_17

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  Abstract 


Introduction: The carriage of Staphylococcus aureus is often considered an important issue in terms of infection control. The present study is aimed to determine the carriage rate of S. aureus and methicillin-resistant S. aureus (MRSA) amongst hospitalised patients in comparison to community population and healthcare workers in rural South India.
Methods: A cross-sectional prospective study was conducted amongst adult participants from three different groups – healthy community population, healthcare worker (staff nurses) and hospitalised patient. Finger, nose and throat of all study participants were examined for the carriage of S. aureus and MRSA by microbiological culture, identification and susceptibility testing to oxacillin.
Results: The carriage rate of S. aureus was 47.2', 55.6' and 77.8', respectively, in the community, hospitalised and healthcare workers; similarly MRSA carriers were 16.6', 47.2' and 22.2', respectively. S. aureus carriage rate was higher amongst healthcare workers, and MRSA carrier rate was higher amongst hospitalised patients. The MRSA carriage rate amongst hospitalised patients was 7-fold higher than the community population and 2-fold higher than the healthcare workers.
Conclusion: Hospitalised patients tend to carry the higher rate of MRSA and are at high risk of developing invasive infections. Hence, screening/decolonization for MRSA at the time of hospitalisation and prudent infection control measures is necessary to combat this pathogen.

Keywords: Colonization, healthcare worker, infection control, nosocomial, patient safety


How to cite this article:
Manthreshwar P, Sekar R, Narendran S, Amudhan M, Mythreyee M. Higher rate of methicillin-resistant Staphylococcus aureus carriage amongst hospitalised patients in rural South India. J Patient Saf Infect Control 2017;5:30-4

How to cite this URL:
Manthreshwar P, Sekar R, Narendran S, Amudhan M, Mythreyee M. Higher rate of methicillin-resistant Staphylococcus aureus carriage amongst hospitalised patients in rural South India. J Patient Saf Infect Control [serial online] 2017 [cited 2019 Jun 18];5:30-4. Available from: http://www.jpsiconline.com/text.asp?2017/5/1/30/213284




  Introduction Top


Staphylococcus aureus is one of the most common pathogens that has been known to cause a wide range of infections from asymptomatic colonization to life-threatening sepsis.[1],[2] A fundamental biological property of S. aureus is the ability to asymptomatically colonise normal people more commonly at anterior nares. Reportedly, about 27% of healthy adults are asymptomatic nasal carriers of S. aureus.[3] Therefore, healthy individuals could become carriers of this organism and have a risk of contracting an invasive infection.[4] However, when the carrier is a healthcare worker, they serve as a reservoir of S. aureus and possibly transmit the organism to the patients who are handled by them; further, if the organism was carried by a hospitalised patient, which possess the greatest risk of developing invasive infections.[5],[6] The primary mode of transmission of S. aureus is usually skin-to-skin contact followed by respiratory droplet from a colonised or infected individual.[6],[7]

Importantly, S. aureus is notorious for its ability to develop resistance to antibiotics. More specifically, methicillin-resistant S. aureus (MRSA) is the most concerned form of resistant phenotype, which is resistant to multiple drugs and eliminates most of the available treatment options.[8] Historically, MRSA strains were restricted to healthcare settings and are called healthcare-associated MRSA, but in the recent past, it was recognised as a widespread cause of community infections and are called community-associated MRSA, which spreads rapidly amongst healthy individuals within the community population.[9] Although the burden of MRSA infections is getting decreased in many countries when compared to Gram-negative resistant pathogens, it still has great significance in both community as well as healthcare-associated infections.[10],[11]

Infections caused by MRSA increase the length of hospital stay, responsible for increasing healthcare costs and have a high attributable mortality.[12],[13] Hence, screening for the carriage of MRSA is fundamental to nosocomial infection control, both for epidemiologic investigation and for day-to-day decision in isolation or barrier precautions.

Studies on the MRSA colonization were limited in developing countries, especially in rural areas. The limited data on MRSA limit the ability of the clinician to determine the need for empirical therapy for MRSA infection. Therefore, the present study was aimed to investigate the carriage rate of S. aureus and MRSA in our regional rural population and to analyse the carriage rate amongst hospitalised patients and healthcare workers in comparison with general community population.


  Methods Top


Study groups and participants

We conducted a cross-sectional prospective study on the carriage rate of MRSA amongst the adult participants from the rural population of Theni district (a remote district in South India), during the period from April 2012 to October 2012. The study participants were divided into three groups – general community population, healthcare workers and hospitalised patients – all participants were enrolled from the residents of rural set-up of Theni district, Tamil Nadu, South India. The community participants were enrolled from the general population of Theni district (control group), and healthcare workers (staff nurses) were enrolled from the Government Theni Medical College (GTMC) Hospital. Persons who have taken antibiotic in the past 1 month, history of hospitalisation for the past 1 year or having any other acute/chronic illnesses were excluded from these groups. Then, the third group of hospitalised patients was enrolled from septic, ortho and post-natal wards with an inclusion criterion of >1 week and <3 months hospitalisation.

Specimen collection and processing

Pre-moistened culture swabs were collected from the nose (swabbed in both nares) and throat from all the study participants and immediately inoculated on mannitol salt agar (MSA) (HiMedia, Mumbai). Further, finger impressions of study participants were directly collected on MSA.[14] After overnight incubation at 37°C, samples were examined for mannitol fermentation on MSA. Then, the mannitol-positive isolates were presumptively identified as S. aureus and are subjected to Gram's staining, catalase and coagulase test for confirmation.[15]

Then, the isolates of S. aureus were tested for methicillin resistance by a standard oxacillin salt agar (OSA) i.e., Mueller-Hinton Agar (HiMedia, Mumbai) with 6 μg/mL oxacillin (HiMedia, Mumbai) and 4% NaCl along with positive and negative controls. For susceptibility testing, all isolates of S. aureus were adjusted to 0.5 McFarland turbidity by direct colony suspension and approximately 1 μl was spot inoculated on OSA. Then, the culture plate was examined under transmitted light for the presence of >1 colony-forming unit after the incubation of 24 h at 35°C.[16]

Statistical analysis

Study results were analysed with GraphPad Prism version 5.3 (GraphPad Software Inc., California, USA)by Fisher's exact test, and the statistical significance was set at P ≤ 0.05. Confidence intervals (CIs) were calculated using the binomial distribution.

Ethical considerations

The study protocol was reviewed and approved by the Institutional Human Ethics Committee of GTMC (GTMC/2443/PandD/2011 dated September 27, 2011), and the confidentiality of the study participants was strictly maintained.


  Results Top


Amongst the 36 participants enrolled in each study group, the carriage rate of S. aureus (Finger [F] or Nose [N] or Throat [T]) was identified to be 47.2% (17/36), 55.6% (20/36) and 77.8% (28/36), respectively, in the community, hospitalised and healthcare workers; similarly, the MRSA carrier rate (F/N/T) was 16.6% (6/36), 47.2% (17/36) and 22.2% (8/36), respectively. More specifically the carrier rate (S. aureus and MRSA) was higher in the finger when compared to the nose and throat in all the study groups while the throat was found to be an uncommon site for MRSA carriage [Table 1].
Table 1: Carriage rate of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus amongst the different study groups

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Intriguingly, the S. aureus carrier (F/N/T) rate was higher amongst healthcare workers (77.8%) when compared with the general community (47.2%; P = 0.01), whereas the MRSA carriage was found to be slightly higher than the community population [Table 2]. More specifically, the carriage rate of S. aureus in the throat was significantly higher (P < 0.01) amongst healthcare workers (27.7% vs. 2.7%, respectively; odds ratio [OR] 13.5; 95% CI 1.6–111.9) while the MRSA carriage was not detected.
Table 2: Carrier rate of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus amongst hospitalised patients and healthcare workers in comparison to general community population

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Importantly, amongst the 36 hospitalised patients, 20 carried S. aureus, out of which 17 (17/36; 47.2%) were identified as MRSA (proportion – 17/20; 85%). Notably, this group was found to have 7-fold higher rate of MRSA carriage when compared to community population (19.4% vs. 2.7%, respectively; OR 8.5; 95%; CI 1.0–72.2) and 2-fold higher carriage rate when compared with healthcare workers (19.4% vs. 8.3%, respectively; OR 2.7; 95% CI 0.6–11.2).

Amongst the 36 study participants from the hospitalised patients, 10 (27.7%) were found to carry MRSA in their fingers. It is interesting to note that the 10/14 (71%) isolates of S. aureus were MRSA. Similarly, 7/8 (88%) nasal isolates and 2/4 (50%) throat isolates of S. aureus were resistant to oxacillin. It is also interesting to note that the MRSA from throat swab (2/36; 5.6%) was only detected from hospitalised patients. Thus, the MRSA carriage rate amongst hospitalised patients was always higher than other study groups irrespective of specimen site [Table 2].


  Discussion Top


In the present study, MRSA carriage rate was higher in the finger when compared with nose and throat; this suggests that the inclusion of finger/hand screening could improve the sensitivity of MRSA detection. However, most of the earlier studies conducted on MRSA colonization has not evaluated finger/hand as one of the colonization sites [9],[17],[18],[19],[20],[21],[22] and many of them reported nose as the most common site for MRSA colonization.[21],[22] However, a recent study demonstrated hand carriage of MRSA without nasal carriage amongst the considerable proportion of study participants.[14]

According to the recent study conducted amongst the children in North India, the nasal carriage of S. aureus and MRSA was 52.3% and 3.9%, respectively,[23] whereas the current study revealed the carriage rate of 22.2% and 2.7%, respectively, in the adult community population. A recent report from Madurai, stating that the nasal carriage of S. aureus and MRSA amongst the healthcare workers was 13% and 2%, respectively;[24] and the present study has shown 27.7% and 8.3%, respectively. According to Bartoloni et al.,[25] the carriage rate for S. aureus and MRSA amongst the hospitalised patients was 14.6% and 1.8%, respectively, in Bolivia. Although India is endemic to MRSA infection with about 30%–50% prevalence, the carriage rates were reportedly lower (15.6%).[26] However, recently Datta et al.[27] reported 22.5% carriage rate amongst intensive care unit patients from the urban medical centre in North India, and the present study documented a high proportion of 47.2% amongst hospitalised inpatients.

According to the review of Kluytmans et al.,[28] the prevalence of nasal carriage of S. aureus in the general population, healthcare workers and hospitalised patients was 37.2% (range: 19%–55.1%), 26.6% (range: 16.8%–56.1%) and 29.8% (range: 14.3%–52.5%), respectively. The present study findings corroborate well with this report.

Hospital-acquired infections are often transmitted by contact, primarily through the hands of healthcare workers,[6],[8] especially where the hand hygiene is poor.[29] The present study exposed finger as the most common site of S. aureus carriage, especially amongst the healthcare workers when compared with other sites and groups investigated. In contrast to earlier studies,[3] the present study documented the higher rate of S. aureus carriage in fingers, suggesting the poor hand hygiene amongst our rural population. Importantly, the carriage rate was higher amongst healthcare workers presumably because of the exposure to the contaminated hospital environment, which necessitates appropriate implementation of environmental cleaning and handwashing program as an infection control measure. Therefore, handwashing remains the single most important means to prevent the transmission of nosocomial pathogens, especially MRSA.[30]

The present study results documented the carriage rate of MRSA in rural South India with some limitations. The major limitation of our study is low sample size. Although we could not achieve statistical significance in our analysis, notable differences exist in MRSA carriage rate amongst the study groups investigated. Then, our study was conducted in the single institution; hence, the findings could not be generalised to other institutions where the circulating strain and patient exposure level differs. Further, we did not culture samples from other common sites of MRSA colonization such as axilla and groin, and we did not perform complete hand imprint as our Petri plate diameter is limited to 90 mm; thus, finger imprint was taken and is extrapolated for hand hygiene.[19],[22] Another limitation of our study was that the specimen collection from the general community participants (control group) was done at hospital laboratory instead of field visit to the community. Although they are healthy and representative of the general population, they have been entered into hospital setting at the time of specimen collection. Therefore, they might have contracted the MRSA from the hospital environment, and thus, there is some bias in sampling the community population. Moreover, this could be a possible reason for the higher carriage rate of MRSA in fingers of community population i.e., equal to that of healthcare workers, and this necessitates the screening of MRSA in environmental samples from the hospital setting.


  Conclusion Top


The MRSA carriage was significantly higher amongst hospitalised patients and is at high risk for developing invasive infections with this difficult to treat pathogen.[25],[31] Thus, identification and elimination of MRSA carrier state amongst the hospitalised patients is an important issue in patient safety and infection control policy of healthcare setting.

Acknowledgements

The authors would like to thank Indian Council of Medical Research for offering short-term studentship – 2012 for the first author of this paper, and the study was conducted as a short-term project for STS.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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