Patients are primarily admitted into hospital wards for adequate management of their illnesses, although some patients experience illness progression while there [1]. These authors reported further that these illnesses are known as hospital-related illnesses (nosocomial infections), and they can be brought on by direct or indirect contact with a carrier through the use of inanimate objects or the air. Since most individuals spend 90% of their time indoors, either at home or at work, indoor environmental factors have a significant impact on human well-being [2]. They also stated that indoor air pollution is typically a complicated mixture of particles and other gaseous elements. Factors that affect indoor air quality in terms of microbial contamination in a given space at a given time include the quality of air entering the space, the number of occupants, their physical activity and associated aerosol production, human traffic, and the degree of ventilation [3].

Hospital-acquired illnesses can be caused by harmful bacteria that can be found in healthcare facilities [4]. Hospital-acquired infections are contracted by over 1.7 million hospitalized patients each year while receiving treatment for other medical conditions, and more than 98,000 people (1 in 17) pass away as a result of these infections, according to [5]. Bacteria have been implicated in causing 90% of the illnesses associated with hospital-acquired infections [6]. The level of bacteria in the interior air shows the cleanliness of the medical facility. On the ventilation system's pans as well as on the moist ceiling and floor, bacteria, mildew, and viruses can grow [7]. The majority of bacteria have an effect on patient health because they can survive on dry surfaces for months and are resistant to disinfectants [8].

Humans may come into contact with airborne bacteria in both household and hospital indoor settings [9]. Patients, employees, visitors, ventilation, and the outside could all introduce a significant quantity of disease-causing microorganisms into the hospital's interior air [5]. Hospitalized patients are more susceptible to infection because of the close quarters, increased patient traffic, and lax infection control procedures that can build up and foster the development and proliferation of bacteria [10]. In addition, it is thought to be crucial to create monitoring systems for determining indoor pollutant concentrations as well as important methods for enhancing and controlling indoor air quality [2]. Identifying the sources of air pollution is crucial for efficient indoor air quality monitoring. Therefore, this study was conducted to assess the bacteriological indoor air quality of three private hospitals in Dutse, in northwest Nigeria.

Study Area

This study was conducted in three (3) different private hospitals in Dutse. Dutse, which has undulant relief, is the capital of Jigawa State and is characterized by the Sudan Savanna agro-ecological zone [11]. Geographically, it lies at a latitude of 11^o42’8.46” N and a longitude of 9^o20’2.46” E (Figure 1). It is home to the Federal University of Dutse, which was established in November 2011.

Figure 1: A map showing the three private hospitals in the study area.

Brief Description of the Private Hospitals

In the Peace Clinic's reception area, which contains three fans and three patients, a bacteriological air quality check was done. Additionally, it was conducted in the female ward, which has two windows and one fan, and finally in the male ward, which likewise has two windows and one fan. In the male ward of the Dr. Bashir hospital, where there were four patients and three relatives of the patients, and in the reception area, which has two fans and six patients and five relatives of the patients, a bacteriological air quality assessment was done. The female ward, which has four windows and two fans, underwent air sampling in the same way. During the air sampling, there were three patients and ten family members of the patients. The Alkhari Clinic's ward one, which has two fans, two windows, and two patients and one relative of each patient, was used for bacteriological air quality assessment, while wards two and three each had one fan, two windows, and three patients and two relatives of each patient.

Sampling Technique and Data Collection

Three (3) private hospitals that consented to the conduct of this study were purposively selected for air sampling. Twenty-seven (27) air samples were collected from each selected private hospital ward, thereby leading to the collection of eighty-one (81) air samples. Air sampling was done using settle plate methods [12]. A sensitive weighing balance machine was used to measure 64.8 g of Trypticase Soy Agar (TSA) into a conical flask and then dissolve it in distilled water (1620 mL) according to the manufacturer’s instructions. Clotrimazole (0.016 g) was added to the agar to inhibit the growth of fungi during incubation [13]. The media was autoclaved and poured into eighty-one (81) sterilized petri dishes. Petri dishes containing TSA were transported to the hospitals in sealed plastic bags, as done by [14]. Each plate was labeled with a sample number, and time samples were collected. The plates were placed in the hospital wards at about one (1) meter above the ground, representing the human breathing zone [15]. Each plate was exposed for ten (10) minutes. After this exposure, the agar plates were covered and immediately taken back to the laboratory in sealed plastic bags. The agar plates were subsequently incubated for 24 hours at 37 °C [13]. The results were expressed as colony-forming units in a cubic meter of air (CFU/m³). A pure colony of each bacterial isolate was obtained following the procedure reported by [16].

Gram staining and Identification of the Bacterial Isolates

The Gram staining technique adapted by [17] was used in the microscopic identification of bacterial isolates. For each of the bacterial colonies derived, a drop of distilled water was applied at the center of a clean, grease-free glass slide. Then, a thin smear was created using a loopful of the pure colony and the distilled water. The smear was heat-fixed by passing it three (3) times over a spirit lamp after being allowed to air dry. The staining rack was positioned over the smear. Crystal violet was applied to the smear, and it was left there for 60 seconds. Water under pressure was used to rinse the crystals. The smear was then covered in Gram's iodine, left to sit on the slide for 60 seconds, and then washed with tap water. A solution of 75% alcohol and 5% acetone was used to decolorize the glass slide until the solvent was completely removed from the slide. It was instantly rinsed under running water, stained with safranin for 60 seconds, rinsed again under running water, and then left to air dry. Subsequent views of the glass slide were made using an oil immersion microscope (x100). The methodologies outlined by [18] had an impact on the decisions taken about the biochemical characterization tests carried out with the intention of identifying the bacterial isolates. According to the protocols described by [19], biochemical characterization tests such as the catalase test, coagulate test, citrate utilization test, indole test, motility test, methyl red test, and Voges-Proskauer test were carried out.

Enumeration and Identification of Bacterial Isolates

The enumeration of the bacterial colonies was done with an electric colony counter, leading to the generation of bacterial colony-forming units (CFU). Afterwards, the CFU per cubic meter (CFU/m³) of the bacterial isolates in the plates were determined using the equation reported by [13,20].

                 N = 5a x 104 (bt)^-1

     Where N= microbial CFU/m³ of indoor air

                       A= number of colonies per Petri dish

   b= dish surface area, cm²

                                        t= exposure time of the petri dish (in minutes)

Results obtained on the bacterial loads across hospitals and varying sample collection periods were subjected to analysis of variance (c) using Proc. GLM of GenStat version 17, and the means were separated using the Duncan Multiple Range Test (DMRT). However, the mean bacterial loads in the indoor air of the hospitals were used to determine whether they were within a range, indicating the level of contamination reported by [21].

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