INTRODUCTION

In 1882,Ogston introduced the clustered micrococci as "staphylococci," from the Greek staphyle, meaning bunch of grapes. In 1884 Anton J. Rosenbach (1842-1923), a German surgeon, isolated two strains of staphylococci, and named for the pigmented appearance as Staphylococcus aureus, (Latin aurum -gold), and Staphylococcus albus (now called epidermidis), (Latin albus- white).[1]

S. aureus are known for their drug resistance. They exhibit plasmid bound resistance to erythromycin, tetracyclines, amino glycosides and almost all clinically useful antibiotics except vancomycin. S. aureus were uniformly sensitive to penicillin originally, through occasional strains from the pre antibiotic era have been found to be capable of producing penicillinase. Some of these strains may show resistance to other antibiotics and heavy metals and cause outbreaks of hospital infections. These strains have been called "epidemic methicillin resistant Staphylococcus aureus" or EMRSA. Development of tolerance to penicillin, by which the bacterium is only inhibited but not killed.[2]3

Staphylococcus aureus nasal carriage in health care workers increases patient’s risk for developing infection after cardiac surgery, orthopedic surgery and in peritoneal dialysis. [3] This type of infections may also occur in dental clinics. Because, in dental clinics, minor surgical procedures such as extractions are done. The infection may occur in those extracted sites due to the exposure by this bacteria. As these bacteria have multiple drug resistance, the pathogens may cause post operative complications and wound healing, etc. This may spread due to sneezing or coughing.

In vascular surgery, the relation between nasal carriage of S. aureus and surgical site infections (SSI) is known. For this reason, a prospective analysis of S. aureus nasal carriage in patients undergoing vascular surgery was conducted. The incidence of surgical site infections in nasal carriers of S. aureus is 4 out of 55 (7.3%), whereas the incidence in non-carriers is 6 out of 159 (3.8%).[3] The SSI which occurred in the non-carriers of S. aureus may be from the operator. The same way, in dental procedures SSI may occur In Canada, this proportion increased from 1.6% in 1995-1999 to 7.0% in 2000–2004^[7]. Increased resistance to mupirocin is associated with decolonization failure.[8,9] Nasal swabs are commonly used to detect the presence of Staphylococcus aureus. A patient becomes clinically infected if this bacteria invades the skin or deeper tissues and multiplies.[4]So, screening is done for dentists to check the prevalence of nasal carriers of S. aureus. Nasal swabs were taken from the dentists and they were cultured using blood agar to check the viability of S. aureus. Those plates are checked for beta -hemolysis and then sub-cultured to confirm the viability.

MATERIALS AND METHODS:

This study was conducted among the students and staff in a dental hospital in Chennai. Many procedures including major and minor surgeries are performed daily. Hence, there is a high risk for S. aureus infections. Some of the operators might be a nasal carrier of this bacteria. So that they can pave way for infections for the patients in their surgical site. Nasal swabs were obtained and cultured.

The procedure for obtaining nasal swab are as follows.[5]

1. The subject was informed about the procedure. Any questions and allay any anxieties that the subject may have was investigated.

2. Hands were thoroughly washed and gloved

3. Swab packaging was opened after checking the expiry date

4. The swab stick was moistened with sterile water to prevent any discomfort to the patient.[6]

5. The swab was introduced into the anterior Nose and Sweeped upwards towards the top of the nare.

6. The procedure was repeated with the same swab in the other nare.

7. Without contaminating swab, it was placed into a sterile test tube and The subject was provided with tissues as required.

8. The wastes and gloves were disposed and the hands were washed.

Figure 1

Figure 2

Figure 3

Blood agar plates were dried in hot air oven at 45°C for 10-15 minutes. The swab collected were inoculated and spread uniformly on the surface using inoculation loop for isolation and identification. The plates were Incubated at 37°C for 24 hours aerobically. Then the plates were observed for the presence of beta-hemolytic colony with golden yellow pigmentation.(Figure-1).

The colonies with beta-hemolysis and golden yellow pigmentation were sub cultured on nutrient agar (Figure-2) for identification and further confirmation. Then the colonies were identified by the standard methods of biochemical tests and coagulase test. Further, to identify the prevalence of MRSA strains, the isolates were subjected to their susceptibility to Cefoxitin.(Figure-3).

RESULTS:

Table-1

Sl. no	No. of People Screened	S. aureus Positive	No. of MRSA
1	50	2	2

Table-1 shows the no. of people screened, positive and the results of MRSA.

Figure 4

DISCUSSION:

Out of 50 people, 12 swabs were observed with beta-hemolysis. They were sub-cultured and after confirmatory tests, only 2 swabs were confirmed to be S. aureus. Figure-4 represents the carriers and non-carriers of S. aureus among the dentists screened. Treatment in dentistry involves oral cavity in the hard and soft tissue. Aspiration from the nose will draw the bacteria from the nasal cavity to mouth. This and the bacteria spread from other sources will act as a risk factor in the colonization of the traumatized sites in the oral cavity. So identification of the nasopharyngeal carrier in the health care set up should be done periodically. It will improve the post operative care and increase the success of the treatment MRSA is especially troublesome in hospitals, prisons, and nursing homes, where patients with open wounds, invasive devices, and weakened immune systems are at greater risk of nosocomial infection than the general public.

CONCLUSION:

Even presence of one nasal carrier of S. aureus in a hospital may lead to an outbreak of SSI. Out of 50 people included in our study, 2(4%) of them were found to be nasal carriers of this bacteria. The incidence may be high if more people are included. A periodic screening activity will identify the carrier rate among the hospital personnel. Studies which includes the other hospital personnel including the staff, clinical assistants have more number of nasal carriers. S. aureus eradication therapy is advised for all nasal carriers of this bacteria. Proper protection measures such as masks, gloves should be used by the operator so that, even if any cough, can prevent the bacteria from spreading. Administration of mupirocin can reduce the risk of nasal carriage of S. aureus. [7] But, Mupirocin resistance of MRSA is increasing. This prevents the surgical site infections.

REFERENCES:

1. Rosenbach, AJ. Mikro-Qrganismenbei den Wound-Infections-Krankheiten des Menschen. Wiesbaden, J.F. Bergmann, 1884. p.18

2. Textbook of Microbiology, Ananthanarayan and Paniker, Medical Colleges Calicut, Kerela.

3. Donker JMW, van derLaan L, Hendriks YJAM, Kluytmans JAJW (2012) Evaluation of Staphylococcus aureus Nasal Carriage Screening before Vascular Surgery. PLoS ONE 7(6): e38127. doi:10.1371/journal.pone.0038127

4. RCN (2005a) Good Practice in Infection Prevention and Control: Guidance for Nursing Staff. London: RCN.

5. Dan Higgins, RGN, ENB 100, ENB 998, is senior charge nurse in critical care, University Hospital Birmingham.

6. Dougherty, L., Lister, S. (2004) The Royal Marsden Hospital Manual of Clinical Nursing Procedures (6th ed). Oxford: Black-well Publishing.

7. Simor AE, Stuart TL, Louie L, et al. Mupirocin- resistant, methi -cillinresistant Staphylococcus-aureus strains in Canadian hospitals. Antimicrob Agents Chemother 2007 ; 51 : 3880 – 3886.

8. Simor AE, Phillips E, McGeer A, et al. Randomized controlled trial of chlorhexidine gluconate for washing, intranasal mupirocin, and rifampin and doxycycline versus no treatment for the eradication of methicillin-resistant Staphylococcus aureus colonization. Clin Infect Dis 2007;44:178–185.

9. Robicsek A, Beaumont JL, Paule SM, et al.Universal Surveillance for methicillin - resistant Staphylococcus aureus in 3 affiliated hospitals. Ann Intern Med 2008;148:409–418.

Received on 06.07.2016 Modified on 20.07.2016

Research J. Pharm. and Tech 2016; 9(10):1650-1652.

DOI: 10.5958/0974-360X.2016.00332.2