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Table of Contents   
ORIGINAL RESEARCH  
Year : 2020  |  Volume : 31  |  Issue : 3  |  Page : 465-469
A study to assess the microbial profile and index of microbial air contamination in dental operatories


Department of Microbiology, Faculty of Dentistry, MAHER Meenakshi Ammal Dental College, Maduravoyal, Chennai, Tamil Nadu, India

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Date of Submission14-Sep-2018
Date of Decision08-Oct-2018
Date of Acceptance07-Jan-2019
Date of Web Publication06-Aug-2020
 

   Abstract 


Background: Microbial contamination of air in dental operatory is an important source of infection. In this study, passive air sampling using settle plates was used as an effective method to assess the microbial profile and index of microbial air contamination (IMA) in dental operatories. Aim: To assess the microbial profile and index of microbial air contamination (IMA) in dental operatories. Setting and Design: This study design was a experimental cum diagnosis study and was conducted in four outpatient dental operatories in a self-financing dental college using stratified random sampling technique. Materials and Methods: Twenty air samples were collected by leaving blood agar plates open for 1 h, 1 m above the floor and 1 m from the wall. After incubation at 37°C for 48 h, colonies were counted to assess the number of colony-forming units (CFUs) per plate. The number of CFU is the IMA. The evaluation of aerobic bacterial and fungal profiles of representative colonies was done by standard microbiological methods. Results: Independent sample 't' test was applied for this study. All air samples collected near the dental treatment unit showed more contamination than the ambient air. As per the IMA classes, the IMA near the dental treatment unit ranged from fair to poor. IMA of ambient air in all the four operatories was within the acceptable values. The most common microorganism isolated was Staphylococcus species. Conclusion: Passive air sampling is one of the effective ways of quantifying airborne bacteria as used in the present study. Air microbial level evaluation is a step towards cross-infection prevention.

Keywords: Colony-forming units, cross-infection, dental operatory, index of microbial air contamination, infection control, passive air sampling

How to cite this article:
Shanmugaraj GB, Rao AK. A study to assess the microbial profile and index of microbial air contamination in dental operatories. Indian J Dent Res 2020;31:465-9

How to cite this URL:
Shanmugaraj GB, Rao AK. A study to assess the microbial profile and index of microbial air contamination in dental operatories. Indian J Dent Res [serial online] 2020 [cited 2020 Sep 23];31:465-9. Available from: http://www.ijdr.in/text.asp?2020/31/3/465/291494



   Introduction Top


Air plays a vital role as a reservoir for both pathogenic and non-pathogenic living organisms. Microbial contamination of air in a health care setting is an important source of infection. In a dental operatory, air may contain particles derived from saliva, blood, dental plaque, tooth debris, or dental filling materials. Also, the oral cavity is a natural habitat for a large number of microorganisms. Most dental procedures that use handpieces, turbines, ultrasonic scalers, air polishers, and abrasion units have the potential for creating contaminated aerosols and splatter, thereby serving as a source of air contamination.[1] Therefore, recognition, monitoring, and control of air microbial contamination in dental operatories become essential and can be done routinely by microbiological sampling.

Air samples can be collected in two ways: by active air sampling using air samplers or by passive air sampling using the settle plates.[2] The standard for the measurement of microbial air contamination in environments is the index of microbial air contamination (IMA).[2] IMA measurement by settle plates is related to the level of the microbial contamination of the surrounding atmosphere and also gives an objective and accurate representation of both the extent of air contamination and the number of micro-organisms falling out in the area at risk.

Hence, in our study, passive air sampling using settle plates was used as an effective method to assess the microbial profile and IMA in dental operatories.


   Aim of the Study Top


To assess the microbial profile and IMA in dental operatories.


   Materials and Methods Top


The study design was experimental cum diagnosis study and was conducted in four outpatient dental operatories in a self-financing dental college using stratified random sampling technique. Four departments, pedodontics, oral and maxillofacial surgery, periodontology, and endodontic, where there was maximum use of drill, handpieces, scalers, and rotors for treatment were chosen for the study. As the aim of the study was to assess the air microbial contamination, the other departments where there was limited use of drill and aerosol production were not included in the study.

During the study, the dentists were performing treatments depending on the patient needs. A total of 20 air samples were collected during one working day. Blood agar plates of 90-mm diameter were used. For each department, three plates were kept in the active dental operation area close to the dental unit, at a distance of approximately 60 cm and two plates were kept in a corner of the practice room approximately 2.5 m from the dental unit to measure the microbial count of the ambient air.[3],[4] The  Petri dish More Details was left open to the air for 60 min, 1 m above the floor and 1 m from the wall. The microbial aerosols were allowed to settle under gravity.

The Petri dishes were incubated at 37°C for 1–2 days. After this period, colonies were counted to assess the number of colony-forming units (CFUs) per plate. The number of CFUs is the IMA.[2] The evaluation of aerobic bacterial and fungal profiles of representative colonies was done by standard microbiological methods.

The IMA performance of different dental operatories were assessed according to Pasquarella et al.,[2] who have described the IMA, classes of contamination, and maximum acceptable levels of IMA in different environments.





Environment at very high risk includes ultra clean rooms like reverse isolation rooms, operating room for joint replacement, and some procedures of the electronics and pharmaceutical industries. High-risk environment includes clean rooms like conventional operating theatres, continuous care units, and dialysis unit; medium risk environment includes day hospital, hospital wards, food industries, and kitchens, and low risk environment includes facilities.[2]


   Results Top


The mean CFU/plate of passive air sampling near the treatment unit and in ambient air in four dental operatories is given in [Table 1]. Results of 't' test indicated that all air samples collected near the dental treatment unit showed more contamination with microorganisms than the ambient air [Figure 1], [Figure 2], [Figure 3].
Table 1: Mean CFU/plate of passive air sampling in dental operatories

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Figure 1: Passive air sampling by settle plate showing contamination near dental treatment unit

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Figure 2: Passive air sampling by second settle plate showing contamination near the dental treatment unit

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Figure 3: Passive air sampling by settle plate showing less contamination in the ambient air

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In the present study, the most common microorganisms isolated were coagulase-negative Staphylococcus (CoNS) species, Staphylococcus aureus, followed by Micrococcus species [Table 2]. The presence of fungi in our study was found to be low.
Table 2: Profile of aerobic microorganisms isolated in passive air sampling

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As per the IMA classes in our study, the IMA near the dental treatment unit in two dental operatories was fair, as their IMA was within 26–50 CFU and performance of two of the operatories near the dental treatment unit was poor as the IMA was between 51 and 75 [Table 3]. As per the IMA classes in our study, the IMA of ambient air in all the four operatories was fair to good [Table 4] and within the acceptable values for the air microbial counts as the bacteria levels registered were lower than the maximum acceptable level of IMA (50 CFU) for hospital clinics.
Table 3: Performance IMA near the treatment unit in dental operatories

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Table 4: Performance IMA of ambient air in dental operatories

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   Discussion Top


In dental operatories, dental health care personnel and patients are daily exposed to a great variety of microorganisms both pathogenic and non-pathogenic. These are transported by aerosols and droplets produced during dental treatment procedures, promoting an increased risk of cross-infection.[5],[6],[7]

Most dental treatment procedures have the potential for creating contaminated aerosols and splatter. An aerosol can be defined as a suspension of microscopic solid or liquid particles in air for an appreciable period of time. Biological aerosols include bacteria, yeasts, molds, spores of bacteria and molds, and viruses.[2] As 75% of these particles drop on a desktop with a diameter of 2 m from the patient position, the environment plays an important role in this context.[8] Many dental procedures involve use of handpieces, turbines, ultrasonic scalers, air polishers, and abrasion units to remove material from the oral cavity and produce aerosols. The aerosols generated are usually ≥50 μm in diameter that may remain suspended in the air for longer time. Studies have demonstrated that dental drilling procedures create aerosols of saliva and products of drilling, producing particles of both small (<0.5 μm) and large (>0.5 μm) sizes. The aerosol may also contain airborne particles >50–100 μm in diameter that are defined as splatter droplets.[1]

Air microbial level evaluation, hence, becomes an important part in infection prevention. Thus, the main aim of our study was to assess the IMA, according to dental aerosols bacterial counts, in the dental operatories and to identify the representative aerobic microbial colonies. But counting microbes in the air is not an easy work. Even though many different methods are in use for quantifying air microbial contamination, it is limited to the count of CFUs. The CFU count is the most important parameter as it measures the live microorganisms which can multiply.[2]

Credibility of assessing microbial count is that the IMA is a reliable tool for monitoring the microbial surface contamination settling from the air. The concentration and quality of organisms found in the air can have a bearing on the patient's health and on the hospital employees. This can occur from the suspended aerosols in the air which may infect other patients, cross-contaminations from equipment used, and also from the clinician to the patients. Thus, estimating the microbial load in the air will enable the hospital infection control committee to implement infection control measures and maintain the aerosol suspension in the atmosphere to the minimum standards prescribed.

Air samples can be collected in two ways: by active air samplers or by passive air sampling using the settle plates. Both methods are widely used. But according to many studies, the settle plate method is still widely used as a simple and inexpensive way to qualitatively and quantitatively assess the environments over prolonged exposure times. Settle plate method is more advantageous as settle plates are sterile, economical, and readily available. The results obtained are reproducible and reliable. The schedule 1/1/1 was devised as a standard for measuring the microbial air contamination in hospital environments at bio-risk: the Petri dish must be left open to the air for 1 h, 1 m above the floor and 1 m from the wall.[2]

The standard for the measurement of microbial air contamination in environments is the IMA. This method quantifies the microbial flow directly related to the contamination of surfaces coming from microbes that reach critical points by falling on to them. The IMA is based on the count of the microbial fallout on to Petri dishes left open to the air according to the 1/1/1 scheme. It has proved to be a reliable and useful tool for monitoring the microbial surface contamination settling from the air in any environment.[9],[10]

The method for measuring the IMA is that a standard Petri dish 9 cm in diameter is left open to air according to the 1/1/1 scheme, for 1 h, 1 m from the floor, at least 1 m away from walls or any relevant physical obstacle. After 48 h incubation at 37°C, the CFUs are counted. The number of CFUs is the IMA.[2] Hence, in our study, colonies were counted to assess the number of CFUs per plate. The number of CFUs is the IMA. The evaluation of aerobic bacterial and fungal profiles of representative colonies was done by standard microbiological methods.

The mean CFU/plate of passive air sampling near treatment unit and in ambient air in four dental operatories is given in [Table 1]. Results indicated that all air samples collected near the treatment unit showed more contamination with microorganisms than in the ambient air. This is similar to the study by Lucia Bârlean et al.,[1] where the results of the study confirmed high levels of microbial air contamination during dental treatment. The study by Mutters et al.[11] confirmed the contamination of the workplace with bacteria in an area of diameter of 0.75 m. In the study by Manarte-Monteiro et al., the CFU counts were significantly higher at 0.5 m than at 2 m.[8]

However, in the current study, the level of dental operatory air contamination was lower than that found in previous studies and the IMA was within the maximum acceptable limits. A study published in 1995 reported a level of contamination of 216 CFU/m3 for ultrasonic scaling treatments[12] and 75 CFU/m3 for operative treatments and a more recent study found 120–280 CFU/m3 in the air in dental surgeries.[4]

In the present study, the most common microorganisms isolated were CoNS species, Staphylococcus aureus, followed by Micrococcus species. The presence of fungi in our study was found to be low. This is similar to the study by Manarte-Monteiro et al.,[8] in which the most common microorganisms isolated were Micrococcus sp., Streptococcus sp., and Staphylococcus sp. Rautemaa et al.[13] evaluated samples taken from personnel facial masks and surfaces in dental rooms where treatments were performed using high-speed rotating instruments, and registered Gram-positive cocci, namely Streptococcus viridans (Streptococcus genus) and Staphylococcus, as the most common bacterial findings. In the study by Mutters et al.,[11]CoNS followed by Micrococcus were the most predominant bacteria isolated. Staphylococcus aureus was the least isolated.

Staphylococcus is a normal commensal on the skin surface and anterior nares. It can cause a wide variety of diseases in humans through either toxin production or invasion. Staphylococcus aureus is an important pathogen that causes wound and human skin infections, and nosocomial infections. CoNS are the characteristic opportunistic pathogens that may cause catheter-related sepsis and infection of prosthetic joints. Micrococcus frequently present on the normal skin is mostly nonpathogenic.

As per the IMA classes, in our study, the IMA of ambient air in two dental operatories was fair, as their IMA was within 26–50 CFU and performance of two of the operatories near the treatment unit was poor as the IMA was between 51 and 75. As per the IMA classes, in our study, the IMA of ambient air in all the four operatories was fair to good and within the acceptable values for the air microbial counts because the bacteria levels registered were lower than the maximum acceptable level of IMA (50 CFU) for hospital clinics. The lower level of dental operatory air contamination could be because of the preventive measures adopted to control dental office air contamination as per CDC Guidelines for Infection Control in Dental Health-Care Settings.[14]

The aerosols and splatters produced during dental procedures have the potential to spread infection to dental and other people in the dental operatory. It is difficult to completely eliminate the risk posed by dental aerosols. It is possible to minimize the risk with relatively simple and inexpensive precautions such as personal barrier protection and universal precaution by dental staff, preprocedural mouth rinse with an antimicrobial mouth products before treatment, use of high-volume suction apparatus and operatory isolation (rubber dam) where applicable, better ventilation and air conditioning systems, and microbial controls for instruments and surfaces. The use of these precautions will reduce the aerosolized spread infections to a minimal level.[15]

The limitation of this study presented is that anaerobic microbial contamination was not determined because of the lack of appropriate facilities.


   Conclusion Top


According to this study, the air samples collected near the dental treatment unit showed more contamination with microorganisms than the ambient air, though the level of dental operatory air contamination and the IMA were within the maximum acceptable limits. Thus, the results of the present study highlight the need to assess the microbial profile and IMA in dental operatories as a step towards cross-infection prevention. Passive air sampling is one of the effective ways of quantifying airborne microorganisms as used in the present study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Bârlean L, Iancu LS, Minea ML, Dãnilã I, Baciu D. Airborne microbial contamination in dental practices in Iasi, Romania. OHDMBSCMarch 2010;IX: 16-20.  Back to cited text no. 1
    
2.
Pasquarella C, Pitzurra O, Savino A. The index of microbial air contamination. J Hosp Infect 2000;46:241-56.  Back to cited text no. 2
    
3.
Pina-Vaz I, Pina-Vaz C, Fontes de Carvalho M, Azevedo Á. Evaluating spatter and aerosol contamination during opening of access cavities in endodontics. Revista de Clínica e Pesquisa Odontologica 2008;4:77-83.  Back to cited text no. 3
    
4.
Azari MR, Ghadjari A, Nejad MRM, Nasiree NF. Airborne microbial contamination of dental units. Tanaffos 2008;7:54-7.  Back to cited text no. 4
    
5.
Castiglia P, Liguori G, Montagna MT, Napoli C, Pasquarella C, Bergomi M. Italian multicenter study on infection hazards during dental practice: Control of environmental microbial contamination in public dental surgeries. BMC Public Health 2008;8:187-94.  Back to cited text no. 5
    
6.
Szymańska J. Dental bioaerosol as an occupational hazard in a dentist's workplace. Ann Agric Environ Med 2007;14:203-7.  Back to cited text no. 6
    
7.
Micik RE, Miller RL, Mazzarella MA, Ryge G. Studies on dental aerobiology. I. Bacterial aerosols generated during dental procedures. J Dent Res 1969;48:49-56.  Back to cited text no. 7
    
8.
Manarte-Monteiroa P, Carvalhoa A, Pinab C, Oliveiraa H, Mansoc MC. Air quality assessment during dental practice: Aerosols bacterial counts in an universitary clinic. Rev Port Estamatol Med Dent Cir Maxilofac 2013;54:2-7.  Back to cited text no. 8
    
9.
Pasquarella C, Sansebastiano GE, Ferretti S, Saccani E, Fanti M, Moscato U. A mobile laminar airflow unit to reduce air bacterial contamination at surgical area in a conventionally ventilated operating theatre. J Hosp Infect 2007;66:313-9.  Back to cited text no. 9
    
10.
Monarca S, Grottolo M, Renzi D, Paganelli C, Sapelli P, Zerbini I. Evaluation of environmental bacterial contamination and procedures to control cross infection in a sample of Italian dental surgeries. Occup Environ Med 2000;57:721-6.  Back to cited text no. 10
    
11.
Mutters NT, Hägele U, Hagenfeld D, Hellwig E, Frank U. Compliance with infection control practices in an university hospital dental clinic. GMS Hyg Infect Control 2014;9. doi: 10.3205/dgkh000238  Back to cited text no. 11
    
12.
Grenier D. Quantitative analysis of bacterial aerosols in two different dental clinic environments. Appl Environ Microbiol 1995;61:3165-8.  Back to cited text no. 12
    
13.
Rautemaa R, Nordberg A, Wuolijoki-Saaristo K, Meurman JH. Bacterial aerosols in dental practice – A potential hospital infection problem? J Hosp Infect 2006;64:76-81.  Back to cited text no. 13
    
14.
Centres for Disease Control and Prevention. Summary of Infection Prevention Practices in Dental Settings: Basic Expectations for Safe Care. Atlanta, GA: Centres for Disease Control and Prevention, US Dept of Health and Human Services; 2016.  Back to cited text no. 14
    
15.
Singh A, Shiva Manjunath RG, Singla D, Bhattacharya HS, Sarkar A, Chandra N. Aerosol, a health hazard during ultrasonic scaling: A clinico-microbiological study. Indian J Dent Res 2016;27:160-2.  Back to cited text no. 15
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Correspondence Address:
Dr. Arthi Krishna Rao
Meenakshi Ammal Dental College, Alappakkam Main Road, Janaki Nagar, Maduravoyal, Chennai - 600 095, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.IJDR_707_18

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