Introduction
Exposure to microorganisms suspended in the air of both occupational and residential indoor environments is associated with a wide range of adverse health effects with major public health impacts. The quality of indoor air is one of the most significant factors affecting the health and well being of people.2, 1
The air inhaled by people is abundantly populated with microorganisms which are also called bioaerosols. Bio-aerosols are airborne particles that are living (bacteria, viruses and fungi) or originate from living organisms.2, 1
Bioaerosols are ubiquitous, highly variable, complex, natural or man-made in origin. The sampling and analysis of airborne microorganisms has received attention in recent years due to concerns with mould contamination in indoor environments, the threat of bioterrorism and the occurrence of associated health effects, including infectious diseases, acute toxic effects, allergies and cancer.3, 2, 1
In many environments such as hospitals, the presence of bio aerosols can compromise normal activities. Infectious aerosols tend to be extremely small (<5 μm) and can, therefore, remain suspended and viable in the air stream over long periods of time, resulting in extremely high risk of airborne infection in confined places.6, 5, 4
Nosocomial infection is a serious and widespread problem with many of the infections associated with person to person contact with an estimated 1 in 10 patients acquiring an infection during a hospital stay. While many of these infections are associated with person-to-person contact, there is increasing evidence that some infections are transmitted by the airborne route.6, 4
It has been calculated that the airborne route of transmission may account for as much as10–20 % of all endemic nosocomial infections. Supervision on biological bio-aerosol in hospitals can provide information for epidemiological investigation of hospital infections, research on microorganisms present in the air, development and qualitative control, as well as information about their current status.9, 8, 7
Quantitative and qualitative estimations of levels of microorganisms in the air reveal its value as an index for environmental hygiene and as an index related to human health. In hospitals, the problem of Staphylococcus aureus and pseudomonas aeruginosa and candida spp is a global public health problem, but it is particularly serious in resource limited countries.12, 11, 10 For the present study, we used settle plates technique10, 8, 5 to estimate bacterial load in the indoor air of wards.
Passive air sampling uses “settle plates”, which are standard Petridishes containing culture media, which are exposed to the air for a given time in order to collect biological particles which“sediment” out and are then incubated.11, 10
According to some authors,14, 13, 12 passive sampling provides a valid risk assessment as it measures the harmful part of the airborne population which falls on to a critical surface, such as in the surgical cut or on the instruments in operating theatres.
In addition, active air sampling is applicable when the concentration of microorganisms is not very high. However, where the building and environmental conditions of the hospital are very poor; we suspect that there will be very high concentration of microorganisms.16, 15, 14, 13
So the present study was conducted to assess bacteriological and fungal concentration of the indoor air of a teaching tertiary care institute hospital.
Both quantitative and qualitative analyses was conducted. The quantitative analysis was mainly conducted to determine bacterial/fungal load or number of bacteria/fungi in the indoor air. Qualitative analysis was conducted to identify specific species of bacteria.
Material and Methods
Study design
Cross-sectional study was conducted to assess the bacteriological/fungal concentration and to identify specific species of bacteria in the indoor air of tertiary care teaching hospital.
Sampling procedures20, 19, 18, 17, 10
Air sampling was performed with passive air sampling (settle plate’s methods) according to the 1/1/1 scheme (a Petri dish with a diameter of 9 cm was placed for 1 hour, 1 meter above the floor, and about 1 meter away from the walls or any major obstacles).
Air samples were taken from various randomly selected wards of the hospital, namely surgery, emergency, orthopedic, general ward, obstetric, medical ward, TB ward, etc which provides patient care services at the time of data collection.
In each ward Petri dishes was exposed for 60 min in the morning and afternoon. To minimize dilution of air contaminants, openings like doors and windows were closed including the mechanical ventilators during sampling. In addition, the movement of people during sampling was restricted to avoid air disturbance and newly emitted microorganisms.
Bacteria and fungi was collected on nutrient Agar, Blood Agar and Sabouraud Dextrose Agar(SDA).
To obtain the appropriate surface density for counting and to determine the load with respect to time of exposure, the sampling times were set at 60 min in the morning (at 10.00-11.00 AM) and afternoon (2:00-3.00 PM).
Air sample analysis
Both quantitative and qualitative analyses was conducted.
The quantitative analysis was mainly conducted to determine bacterial/fungal load or number of bacteria/fungi in the indoor air.
To determine the load, exposed culture medias/ air samples were taken to the laboratory and incubated at 37 °C for 24 h. After 24 h incubation period, bacterial and fungal load was enumerated as colony forming units (CFU) and CFU/m3 was determined by the formula N=5a*104(bt)-1 19, 18, 17 where 3 of indoor air;2); and
Qualitative analysis was conducted to identify specific species of bacteria and fungi by standard microbiological techniques.
Table 1
Bacteriological concentration of indoor air
Table 2
Fungal concentration of indoor air
Table 3
Microbiological profile
Observation and Results
The present cross-sectional study was conducted to assess the bacteriological/fungal concentration and to identify specific species of bacteria in the indoor air from a tertiary care teaching hospital for period of 3 months (June 2018 to August 2018)
Quantitative Analysis of Bioaerosal Concentration (load)
Bacterial load
The results indicate that the highest bacterial CFU/m3 air has been recorded at 10.00 am in TB chest ward which is 1179 CFU/ m3 at 60 min exposure, while the lowest bacterial CFU/m3 air has been recorded at 10.00 am in Nephrology ward which is 65.52 CFU/ m3 at 60 min exposure. Details of bacterial load CFU/m3 air for different health care wards are shown in Table 1.
Fungal load
The results indicate that the highest Fungal CFU/m3 air has been recorded at 10.00 am in casualty which is 262 CFU/ m3 at 60 min exposure, while no fungal growth CFU/m3 air has been recorded at Nephrology, Surgery (male), ENT, & Obstetric wards.
Details of fungal load CFU/m3 air for different health care wards are shown in Table 2.
In present study, air in the critical area of operating rooms were free of bioaerosals highlighting proper ventilation, fumigation and disinfectants in such areas.
Qualitative analysis of Bioaerosal (Microbiological Profile)
In the present study, hospital indoor air contains diverse range of microrganisms. Loads of Gram Positive Bacteria were higher than Gram Negative Bacteria. Amongst all bacterial isolates Staphylococcus aureus was identified in almost all health care wards except for Medicine (Male) ward. Whereas Candida spp was predominant fungal isolate identified in almost all health care wards except for NICU, surgery (Male), ENT and nephrology wards respectively.
The microbiological profile in the health care facility showed variety of pathogenic micro-organisms with the following allocation.
Gram positive cocci (Staphylococcus aureus predominant followed by coagulase negative staphylooccus)
Gram negative bacilli (Klebsiella spp, Ecoli and Pseudomonas aeruginosa)
Fungus (Candida spp predominant followed by Aspergillus spp)
Details of microbiological results from settle plates is shown in Table 3.
Discussion
Microbiological quality assessment of indoor air study is one the most important investigation to evaluate and determine microbial indoor air contamination. The information on the indoor microbial concentration of airborne bacteria and fungi is necessary to measure indoor air quality control and health hazards associated with it.
The bioaerosal concentration in the indoor environment of our tertiary care hospital, is estimated with the use of settle plate technique was ranged between 23-1179 CFU/m3. This range of bioaerosal load is much lesser than that reported from JIMA20 university specialized hospital and Gondar teaching hospital, northwest Ethiopia21 in which it was estimated between 2123-9733CFU/m3 & 480-1468CFU/m3 respectively. According to these standards, the microbiological load of our tertiary care teaching hospital is considered as ‘low’.
Though there is no standard uniform international estimation is available on the levels and acceptable microbial load in indoor air, the work conducted by WHO22 expert group on assessment of health risk of biological agents in indoor environment suggested that total microbial load should not exceed 1000CFU/m3. Whereas study conducted by sanitary standard of European commission23 suggested that 50 CFU/m3 as ‘very low’, 100CFU/m3 as ‘low’ and range 200-500 CFU/m3as ‘high’ and above 2000 CFU/m3 as ‘very high load’, considering this standards microbial load of our study is considered as ‘high’.
Hospital indoor air contains a diverse range of microorganisms, airborne microbes were detected in hospitals by various workers.23, 21, 16, 15 In study carried out by Jaffal et al,24 Staphylococcus aurues, coagulase negative Staphylococci, Micrococci, Diptheriods, Gram Negative Bacilli, and Bacillus spp were the isolates identified from different wards of hospital similar results were obtained in our present study.
A study conducted by Sudharsanam et al25 & Qudiesat et al26 found high concentration of Gram Positive Cocci then Gram Negative Bacteria, our study also highlights the same findings as Gram Positive Bacteria were isolated more than Gram Negative Bacteria with predominance of Staphylococcus auerus. High concentration of Gram Positive Cocci in our study may attribute to their lower susceptibility to environmental stress as pointed out in study conducted by Borriello et al.27 and to other factors such as improper ventilation and presence of increased number of occupants beyond room capacities.28, 27, 26
In the present study, isolation of Gram Negative Bacteria was occasional and in lower concentration. One of the reasons may be their susceptibility to environmental stress.28 Klebsiella spp was isolated in two wards, E.coli and Pseudomonas aeruginosa were isolated in one ward each and none, similar findings were seen in studies carried out by other researchers.28, 27
In our present study the fungal isolates includes dominance of Candida spp followed by Aspergillus spp. A study conducted by Sautour et al,29 they found that most frequently detected airborne fungi were Penicillium spp & Aspergillus spp. A investigation carried out by Gorny et al,30 the commonest fungal agents contaminating hospital rooms were found to be Aspergillus spp followed by Penicillium spp. Our study showed that there is higher incidence of isolation of Candida spp one of the reason of increased isolation of Candida spp in our study is due to overcrowding of patients and large numbers of visitors as pointed out in studies conducted by Sautour et al29 & Gorny et al.30
Conclusion and Recommendations
An assessment of airborne bacteria and fungi in indoor environment of hospital were experimentally investigated. Types and numbers of airborne micro-organisms were carried out at different hospital wards. The following conclusion & recommendations can be made:
Bacteria show higher growth comparing to fungi.
There is predominance of Gram Positive Cocci as compared to Gram Negative Bacilli.
This study revealed that hospital buildings were being ventilated by the aid of natural ventilation system which may increase the possibility of entrance of pollutants from unhygienic external environment. Many studies have indicated that insufficient ventilation system contributes to microbial loads of the wards.
Toilets and waste disposal sites should be located at significant distance away from hospital wards as they can act as potential source of infection. The study reveals that the microbial load in the hospital wards may be due to the presence of attached unhygienic toilets and poor waste management system.
Presence of increased incidence of Staphylococcus aureus and Candida spp in our hospital is a cause of concern as it is associated with increase incidences of noscomial infection in immune-compromised patients and children either as primary or secondary infections.
Apart from these infections, allergic reactions have also been reported following inhalation of fungal spores making it essential to pay attention to their presence in hospital air.
In present study, air in the critical area of operating rooms were free of any kind of bioaerosals, highlighting proper ventilation, fumigation and disinfectants in such areas.
Housekeeping activities (such as sweeping, using dry mops or clothes or shaking linen) can aerolise dust particles that may contain micro-organisms. Therefore, wet mopping should be preferred and recommended.
Fumigation at weekly intervals in hospital rooms may reduce load of airborne microbes. Bacillocid a commercially available surface and environmental disinfectant that has good cleaning properties along with bactericidal, viricidal, sporicidal and fungicidal activity, should be sprayed or use in mopping in hospitals.
Given the cost constraints, settle plate technique (passive air sampling) can be used in hospitals with fewer technical facilities for preliminary assessment of indoor air quality. Further more, exposed plate method was found to capture microorganisms efficiently with little variation in duplicates samples, thereby suggesting its use in hospitals for preliminary assessment of indoor air quality and determine pathogenic microorganisms which can cause noscomial infections.
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