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S aureus and MRSA Nasal Carriage in dental HCPs.

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Staphylococcus aureus and MRSA Nasal Carriage Rates are Equivalent Amongst Dental Healthcare Providers and Hospital Healthcare Providers

Abstract
Background: Staphylococcus aureus (S. aureus) is a common cause of community and hospital acquired infections. Nosocomial acquisition of S. aureus and its methicillin resistant strain (MRSA) can be influenced by the extent of nasal carriage amongst healthcare workers. Given the close proximity with which dental care providers interact with patients, higher nasal carriage of S. aureus or MRSA by dental professionals would suggest a greater likelihood of nosocomial transfer of these microbes in this setting.
Objective: Assess whether or not dental healthcare providers are colonized to a greater extent than the published rates for healthcare providers working in a hospital setting.
Methods: Using a prospective trial design and published carriage rates for S. aureus (26.2%) and MRSA (4.6%) for medical healthcare providers, it was determined 49 dental providers were required to adequately test whether or not nasal carriage amongst this class of caregiver is significantly different than other providers. Upon consent, two nasal swabs were collected from the anterior nares of both nostrils from subjects randomly selected from clinic personnel from the MUSC-CDM. One swab was used to inoculate Mannitol Salts Agar (MSA) and the other CHROMagar® MRSAII. Media were incubated and scored according to the manufacturers’ specifications.
Results: 3 of the 49 subjects tested positive for MRSA nasal carriage (6.12%). 22 of the 49 subjects tested positive for S. aureus nasal carriage (44.9%), with a 2:1 predilection observed in male participants.
Conclusions: MUSC dental healthcare providers are not at a higher risk for MRSA and/or S. aureus nasal carriage than hospital healthcare providers. MUSC dental healthcare providers were at a higher risk of MRSA and/or S. aureus nasal carriage than the general population.
Acknowledgments: Appreciation is extended to Linda Formby, Lynn West, and Dr. Schmidt’s lab staff for all their help in obtaining and testing samples. 

Introduction
Staphylococcus aureus (S. aureus) is a common cause of community and hospital acquired infections. Nosocomial acquisition of S. aureus and its methicillin resistant strain (MRSA) can be influenced by the extent of nasal carriage amongst healthcare workers. Given the close proximity with which dental healthcare providers interact with patients and the frequent use of aerosolized handpieces, higher nasal carriage of S. aureus and MRSA by dental providers would suggest a greater likelihood of developing S. aureus and MRSA skin infections.3 Furthermore, a higher nasal carriage of S. aureus and MRSA could suggest a greater likelihood of nosocomial transfer of these microbes to patients and even family members of dental healthcare providers.

Objective
Assess whether or not dental healthcare providers are colonized to a greater extent than the published rates for healthcare providers working in a hospital setting.

Methods
Using a sample size calculation of our inclusion criteria, 49 subjects were determined to be adequate for acquisition of data. The subjects provided informed consent, HIPPA authorization, and 2 nasal swabs. The nasal swabs were acquired from the anterior nares of both nostrils in each subject. One swab was plated on to CHROMagar to test for MRSA. The other swab was plated on to Mannitol-Salt Agar to test for Staphylococcus aureus. The CHROMagar and Mannitol-Salt Agar plates were placed in an incubator at 37OC for 24 hours. The CHROMagar plates were read once at 24 hours and the positive MRSA plates were recorded. The Mannitol-Salt Agar plates were read once at 24 hours and a second time at 48 hours, and the positive S. aureus plates were recorded. To confirm the MRSA colonies on the CHROMagar plates, the colonies must test positive for the enzymes coagulase and catalase:
     To test for the coagulase enzyme, one drop of test latex reagent and two isolated colonies of the test isolate are mixed together on a test circle card.      
     Agglutination is observed for up to 20 seconds in a coagulase-positive isolate.
     To test for the catalase enzyme, one drop of 3% hydrogen peroxide and two isolated colonies of the test isolate are mixed together on a microscope slide.
     Bubbles and/or froth is observed in a catalase-positive isolate.

Results
3 of the 49 subjects swabbed tested positive for MRSA nasal carriage (6.12%).
All 3 MRSA positive isolates tested positive for coagulase and catalase.
22 of the 49 subjects swabbed tested positive for Staphylococcus aureus nasal carriage (44.9%).
9 of the 22 Staphylococcus aureus positive subjects were female.
13 of the 22 Staphylococcus aureus positive subjects were male.

Discussion
Healthcare providers and DHCPs are more likely to have nasal colonization of MRSA and S. aureus than the general public. This is consistent with published reports by the CDC and other publications that healthcare workers are more likely to be colonized than the community.

Nasal carriage of S. aureus showed a male predilection amongst MUSC DHCPs. According to published findings, demographic groups at greatest risk for skin and soft tissue infections likely caused by S. aureus are patients who are male, reside in the South or West, and receive Medicaid.

Older DHCPs were less likely to be colonized by S. aureus. According to published findings, in contrast to the age groups affected by most health conditions, the older the age group, the less at risk they are for developing S. aureus infections.

The number of years DHCPs have been providing clinical service FAILED to show an increased risk of nasal colonization for MRSA and S. aureus. Evidence has yet to demonstrate that healthcare workers with more years of clinical service show a greater risk of MRSA and/or S. aureus colonization.

Conclusion
DHCPs ARE NOT at a higher risk of nasal carriage of MRSA and/or Staphylococcus aureus than other healthcare professionals.

DHCPs ARE at a higher risk of nasal carriage of MRSA and/or Staphylococcus aureus than the general population.

The number of years of clinical service FAILED TO correlate with an increased risk of Staphylococcus aureus nasal carriage.
Male DHCPs are twice as likely to be Staphylococcus aureus nasal carriers.

With an increase in age, one is less likely to be colonized with Staphylococcus aureus.

SIGNIFICANCE OF FINDINGS
      Younger DHCPs, who are male, should be aware that they are at a greater risk for nasal colonization by Staphylococcus aureus and should strictly adhere to
      the following to mitigate the risk of nasal carriage
      Hand Hygiene Recommendations for DHCPs
      PPE Recommendations for DHCPs

References
1. Albrich WC, Harbarth S. Health-care workers: source, vector, or victim of MRSA? Lancet Infect Dis. 2008;8(5):289-301.
2. "MRSA and the Workplace." Centers for Disease Control and Prevention. DHHS (NIOSH), 1 Jan. 2013. Web. www.cdc.gov/niosh/topics/mrsa.
3. Olsen, K., M. Sangvik, GS Simonsen, JU Sollid, A. Sundsfjord, I. Thune, and JS Furberg. "Prevalence and Population Structure of Staphylococcus aureus Nasal Carriage in Healthcare Workers in a General Population. The Tromsø Staph and Skin Study."Epidemiology and Infection 141.1 (2013): 143- 52. PubMed. Cambridge University Press. www.ncbi.nlm.nih.gov/pmc/articles/PMC3518280
4. McCaig, Linda, L. Clifford McDonald, Sanjay Mandal, and Daniel Jernigan. "Staphylococcus aureus–associated Skin and Soft Tissue Infections in Ambulatory Care." Emerging Infectious Diseases 12.11 (2006): 1715-723. Centers for Disease Control and Prevention. Web. http://wwwnc.cdc.gov/eid/article/12/11/pdfs/06-0190.pdf.
5. Heiman, F., L. Wertheim, Damian Melles, Margreet Vos, Willem Van Leeuwen, Alex Van Belkum, Henri Verbrugh, and Jan Nouwen. "The Role of Nasal Carriage in Staphylococcus aureus Infections." The Lancet Infectious Diseases 5 (2005): 751-62 

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