CHAPTER ONE

INTRODUCTION

1.1 Background to the study    

Staphylococcus aureus is a bacterium that causes a wide range of infections, from superficial skin infections to severe, and potentially fatal, invasive disease [1]. Infections with this bacterium may be difficult to treat because some strains have developed mechanisms to resist the actions of drugs and are often resistant to one or more antibiotics including methicillin [1].

Methicillin resistant Staphylococcus aureus (MRSA) was first isolated in 1960 and over time MRSA infections have been largely attributed with hospital environments and are referred to as hospital-acquired MRSA (HA-MRSA) [2]. In the late 1990s, staphylococcal infections began to appear in healthy people who had known no risk factors for these infections or who have not been in the hospital and this was termed community acquired MRSA (CA-MRSA) [2]. The incidence of CA-MRSA has continued to increase in Cameroon [3]. Outbreaks of CA-MRSA have occurred among individuals sharing close contact with others in schools, prisons, and locker rooms, water sources also serve as possible environmental reservoir of CA-MRSA [3].

It is therefore important in identifying possible environmental reservoirs of MRSA in the community if the spread of CA-MRSA infections is to be controlled. Among other potential environmental reservoirs, wastewater has been identified as possible source of exposure to MRSA in the community [4]. Humans colonised with MRSA shed it from the nose, faeces, and skin. Therefore, MRSA can be spread to municipal wastewater, streams [5]. The strains causing health care‐associated MRSA infections (HA‐MRSA) has been distinguish from the strains causing community‐associated MRSA (CA‐MRSA) infections. HA‐MRSA typically are resistant to many classes of antibiotics and carry the methicillin resistance gene, mecA, on the staphylococcal cassette chromosome (SCC) of type II (SCCmec type II), while CA-MRSA tend to be resistant to fewer classes of antibiotics, carry the Panton‐Valentine leukocidin (PVL) genes responsible for the production of the PLV toxin, and carry SCCmec type IV. A third group known as livestock‐associated MRSA (LA‐MRSA), had recently been identified and has typically been associated with swine or cattle [6].

Bacteria have evolved with different mechanisms of resistance to antibiotics including enzymatic degradation of drugs, alteration of bacteria proteins that are antibiotics targets, changes in membrane permeability to antibiotics and the use of efflux pumps [7]. Mutation in the genes of bacteria is a major cause of antibiotic resistance (ABR) and the environment serve as a pool of antibiotic-resistant genes of which through the use of mobile genetic elements (MGEs) like plasmid, phage, transposons, integrons a bacterium can acquire the resistant genes from the environment using gene transfer mechanisms like transformation, transposition, and conjugation [8]. S. aureus has genes that are responsible in conferring resistance to antibiotics especially the mecA gene which is present in MRSA strains and provide a broad range of resistance to all beta-lactam antibiotics [9].

 In 2019 during the World Health Organization (WHO) AMR conference, Staphylococcus aureus was the second bacterium associated with high number of deaths due to antibiotic resistance after E. Coli. So, it is very important in identifying potential sources of antibiotic-resistant genes in the environment and their route of transmission to humans and animals [10].

1.2 Statement of The Problem

Access to good drinking water is still limited and unequally distributed in Cameroon [11]. The population of Akonolinga and Ayos depends on local water sources for drinking and other household activities with the river Nyong been the main source [12]. These municipalities are known to be endemic to Buruli ulcer disease (BUD) caused by the bacterium M. ulcerans and was linked to exposure to the river as a source of the infection as the population uses the river for fishing and bathing [13].

 During the One health water for Africa (OHWA) field school project last year November, most of the water sources used by the population tested positive for coliforms presence which shows that the water sources were contaminated. S. aureus can survive in water for 5-10 days though not still considered a waterborne bacterium, but it has been isolated from different water sources [14]. The river Nyong also served as a grazing site for cattle during the dry season and from previous study by [15], cattle rearing and other human activities led to contamination of the water sources with S. aureus.

Other household animals like pigs, fowls, dogs were not kept in protected fence and as such served as a source of contamination to the water source. Household latrines were open air latrines and not well protected from animals with most of the latrines not far from the water source. This served as a potential source of water contamination with S. aureus as reported by [16]

1.2 Rationale of the Study

MRSA is a bacterium of public health interest and was ranked 2^nd bacterium with a high number of deaths due to ABR just next to E. coli among the top 10 priority pathogens by WHO as it was associated with high death rate due to antibiotic resistance. It is considered a normal flora of the human body but the bacterium is an opportunistic and highly pathogenic microorganism causing severe infections in humans and animals when it enters in to the body especially through broken skin tissue or immune-compromised patients. With the emergence of MRSA strains, infections caused by this bacterium are now difficult and hard to treat leading to prolong illnesses, longer hospitalisation, high cost of treatment and consequently death. MRSA is able to persist not only in hospitals with high use of antimicrobial agents but also in the community with low level of antimicrobial agent use. It is now classified as HA-MRSA, CA-MRSA, LA-MRSA which is genetically different from each other. Most of the inhabitants in these localities are engaged in fishing in the river Nyong which has been identified as the main cause of the endemic Buruli ulcer disease (BUD) in Akonolinga and Ayos municipalities. A study by [17] documented the presence of Staph aureus as a secondary bacterium from BU patients with 33/52 (63.5%) of the BUD patients were infected with S. aureus even after treatment with rifampicin and streptomycin for 8 weeks and greatly impact the treatment of BUD by delaying the wound healing process. However, epidemiological data are very scanty which is a handicap to appreciate the actual burden of S. aureus and environmental determinants.

This study therefore seeks to identify sources of water that could serve as reservoir of S. aureus and their routes of transmission to humans and animals.

1.3  Research Questions

• What is the prevalence of aureus from water sources in Akonolinga and Ayos municipalities?
• What is the resistance pattern of isolated aureus from the water sources?
• What are the environmental factors exacerbating water contamination with aureus in aquatic environments?

1.4 Hypotheses

• aureus is present in water sources in Akonolinga and Ayos municipalities.
• aureus isolated from water sources in Akonolinga and Ayos municipalities are multi-drug resistant.
• Huaman behavioural risk factors contribute to water contamination with aureus.

1.5 Objectives

1.5.1 Main Objectives           

To determine the prevalence, characteristics and determinants of Staphylococcus aureus from water sources in Akonolinga and Ayos municipalities, centre region of Cameroon.

1.5.2 Specific Objectives

• To determine the prevalence of Staphylococcus aureus from water sources in Akonolinga and Ayos municipalities.
• To determine the resistant profile of isolated aureus from water sources in Akonolinga and Ayos municipalities.
• To identify human risk factors that could lead to contamination of water sources with aureus.