MICROORGANISMS FOUND IN AIR-CONDITIONED BUILDINGS

ABSTRACT

Air-conditioners are temperature cooling equipment used in modifying air temperature of homes, offices, and industries for various reasons. Nevertheless, such artificial environment may be favourable to bacteria and fungi which may bring health risks to users, either by hypersensitivity or infections. The microorganisms found in air-conditioned buildings were examined in Umuahia, Abia State, Nigeria using the sedimentation technique. Five bacterial species were isolated and they include Staphylococcus aureus (24%), Klebsiella spp (24%), Micrococcus spp (12%), Bacillus spp (16%) and Escherichia coli (24%). Also, four fungal species were isolated and they include Aspergillus niger (31.25%), Aspergillus flavus (31.25%), Rhizopus stolonizer (31.25%), and Rhodotorula spp (6.25%). Staphylococcus aureus, Escherichia coli, and Klebsiella spp were predominant and the most frequently encountered bacteria having the highest percentage of occurrence while Aspergillus niger, Aspergillus flavus, and Rhizopus stolonizer were the most frequently encountered fungi with the highest percentage of occurrence. The results from the statistical analysis showed significant differences (P < 0.05). Ability of the isolates to access and inhabit air-conditioned buildings call for frequent cleaning of air-conditioners to guarantee their safe use as a means of achieving air quality.

TABLE OF CONTENTS

Title Page i

Certification ii

Dedication iii

Acknowledgement            iv

Table of Contents v

List of Tables vii

Abstract viii

CHAPTER ONE

1.0 Introduction 1

1.1 Time of the year when air-conditioners are used in Nigeria 2

1.2 Aim and Objectives 3

CHAPTER TWO

2.0 Literature Review 4

2.1 Advantages of air-conditioners 7

2.2 Disadvantages of air-conditioners 8

2.3 Microorganisms found in air-conditioned buildings 8

2.3.1 Fungi 8

2.3.2 Bacteria 9

2.4 Health implication of air-conditioned building 9

2.4.1 Hypersensitivity Diseases 10

2.4.2 Infectious Diseases 11

CHAPTER THREE

3.0 Material and methods 12

3.1 Study area 12

3.2 Sample collection 12

3.3 Media preparation 13

3.3.1 Nutrient agar 13

3.3.2 Mannitol salt agar 13

3.3.3 MacConkey agar 14

3.3.4 Potato dextrose agar 14

3.4 Sterilization of materials 14

3.5 Isolation and morphological study of bacteria 14

3.6 Isolation and taxonomic study of fungi 15

3.7 Bacterial identification 15

3.7.1 Gram Staining 15

3.7.2 Biochemical characterization of bacteria 16

3.7.2.1 Indole production test 16

3.7.2.2 Catalase test 16

3.7.2.3 Oxidase test 17

3.7.2.4 Methyl red test 17

3.7.2.5 Voges Proskauer test 17

3.7.2.6 Coagulase test 18

3.7.2.7 Motility test 18

3.8 Fungal identification 18

3.8.1 Cell morphology 18

3.8.2 Cultural morphology 19

3.9 Statistical analysis 19

CHAPTER FOUR

4.0 Results 20

CHAPTER FIVE

5.0 Discussion, Conclusion and Recommendations 28

5.1 Discussion 28

5.2 Conclusion 31

5.3 Recommendation 32

REFERENCES

APPENDIX I: Statistical table

APPENDIX II: Pictures of plates

LIST OF TABLES

1   Site characteristics of the various locations            22

2 Total viable count of isolated microorganisms      23

3 Identification and characterisation of bacterial isolates      24

4 Identification and characterisation of fungal isolates      25

5 Percentage of occurrence of bacteria found in air-conditioned buildings      26

6 Percentage of occurrence of fungi found in air-conditioned buildings      27

CHAPTER ONE

1.0 INTRODUCTION

The American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) has defined air-conditioning as the process of treating air to control simultaneously its temperature, humidity, cleanliness, quality and distribution to meet the requirements of the occupants, process or product in the conditioned space. An air-conditioner is the technical solution used to improve air quality and provide people with proper conditions or the simultaneous control of temperature, humidity and distribution of air for the purpose of human comfort or industrial utilization. Depending on the application, the sound level and pressure differential between the conditioned space and adjacent spaces are also controlled within prescribed limits (ASHRAE, 2006). An air-conditioning system consists of components and equipment arranged in sequential order to heat or cool, humidify or dehumidify, clean and purify, attenuate objectionable equipment noise, convey the conditioned outdoor air and return air to the conditioned space, and control and maintain an indoor or enclosed environment at optimum energy use (Wang and Lavan, 2002). Air-conditioner is usually used by the middle class and high class in Nigeria. The types of building served by air-conditioning systems include institutional, commercial, residential, and manufacturing buildings. In institutional, commercial and residential buildings, air-conditioning systems are designed principally to meet the health and comfort of the occupants. In manufacturing buildings, air-conditioning systems are provided to meet requirements for product processing or storage, or for the health and comfort of workers as well as processing in enclosed spaces. Historically, two types of air-conditioning systems have been observed to be used in Nigeria (Sanni, 2005). These are the room or window air conditioners and the central air-conditioning systems. The room air-conditioner is a factory-made encased assembly designed for delivery of conditioned air to an enclosed space without making use of ducts. It is usually installed through a wall enclosing the conditioned space. The central air-conditioning system is a system in which the air is treated in a central plant and carried to and from the conditioned space(s) by one or more fans and a system of ducts (Sanni, 2005).

1.1 TIME OF THE YEAR WHEN AIR-CONDITIONERS ARE USED IN NIGERIA

 Air-conditioning system consists of centralized equipment that provides an atmosphere with controlled temperature, humidity and purity at all times regardless of the weather conditions. Many of the air-conditioning units consist of merely a blower equipped with refrigerating unit that provides only the flow of cool filtered air. Air-conditioners are also temperature cooling equipment used in modifying indoor air temperature of homes, offices, cars and industries for various reasons hence they influence human health (Nester et al., 2006). In Nigeria, air temperatures are always on the high side except during the harmattan period. The air-conditioners are therefore used to modify the indoor air quality and are installed in homes, offices, vehicles and industries for various reasons including good operational output of equipment and comfort (Brown and wake, 2000). It was reported that most air-conditioners in used are operating outside their designed parameters due to inappropriate filters (Miller et al., 2007). Overuse has resulted in dust accumulations. The dust accumulation coupled with humidity especially at the downstream section of the cooling equipment lead to the proliferation of selected group of microorganisms capable of surviving the prevailing conditions (Nordell 2000). This situation has often resulted in what is referred to as “sick house syndrome” noticed only when users of such buildings spends considerable time in it and develop some form of allergic symptoms (Reponen et al., 2001). The sick house syndrome symptoms include headache, watery eyes, skin disorders and weakness. Organisms like Legionella pneumophilla, Streptococcus pneumoniae and Bacillus species have been reported in air conditioner filters (Nordell 2000; Kemp et al., 2000).

1.2 AIM AND OBJECTIVES

The aim of this study is to carry out investigation on microorganism found in air-conditioned buildings in Nigeria. In addition, to ascertain the role of microorganisms in air-conditioned buildings.

1.2.1 OBJECTIVES

1. To identify the bacterial load in air-conditioned building

2. To identify the fungal load in air-conditioned building

3. To identify the effect of air-conditioning on surfaces

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