ABSTRACT
Methicillin resistance in Staphylococcus aureus (MRSA) is progressively increasing globally and has become a global health concern. Antibiotic susceptibility profile of Staphylococcus aureus was determined using disc diffusion method. A total of 21.9 % (73/360) from clinical and environmental samples tested positive for Staphylococcus aureus. The prevalence of Staphylococcus aureus in environmental samples was 24 % while it was 20.5 % in clinical samples. The age group 18 to 49 years had the highest prevalence of Staphylococcus aureus (74 %) followed by 0 to 17 years (42 %) while 50 to 70 years had the least (4 %). The prevalence of Staphylococcus aureus in female was 22.4 % while in male, it was 20 %. The resistance of Staphylococcus aureus to Oxacillin, Cefoxitin, Ampicillin, Vancomycin, Erythromycin, Norfloxacin, Rifampicin, Amoxacillin and Gentamycin were 88.60 %, 45.60 %, 34.20 %, 21.50 %, 18.90 %, 11.40 %, 8.90 %, 6.30 %, 5.10 % respectively. Septrin and Levofloxacin were 100 % active on all the 79 Staphylococcus aureus isolates. Methicillin (mecA) and Erythromycin (ermA and ermC) genes were molecularly identified from the isolates. These findings showed relatively high prevalence of Staphylococcus aureus from the samples and revealed poor personal hygienic practices amongst clinicians and patients.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the study
Staphylococcus aureus is a coagulase-positive, Gram-positive Coccus that forms clusters resembling grapes. Staphylococcus aureus is a bacterium that lives asymptomatically on healthy people, including their, mucous membranes, noses, guts, and skin glands (Sahreena and Kunyan, 2018).This ubiquitous bacterium is a major pathogen due to its combination of toxin-mediated virulence, invasiveness, and antibiotic resistance (Rachel et al., 2016; Sahreena and Kunyan, 2018).
This organism has been a leading cause of nosocomial and community-acquired infections. Staphylococcus aureus does not produce spores, it can contaminate food during preparation and processing. Staphylococcus aureus can thrive in a wide range of temperatures (7 to 48.5 degrees Celsius, optimum 30 to 37 degrees Celsius), pH (4.2 to 9.3, optimum 7 to 7.5), and sodium chloride concentrations up to 15%. Staphylococcus aureus is a desiccation-tolerant organism that can survive in potentially dry and stressful environments like the nose, skin, and inanimate surfaces like clothing, tables, and workbench surfaces (Rachel et al., 2016). Many food products benefit from these characteristics because they promote organisms growth and development (Rachel et al., 2016). After initial contact with S. aureus, it can survive about 48 hours on hands and environmental surfaces (Tong et al., 2015; Rachel et al., 2016).
About 30% of the global population have been colonized by S. aureus (Rachel et al., 2016). Bacteremia, infective endocarditis (IE), osteoarticular, skin, and soft tissue infections, pleuropulmonary and device-related infections are among the most common infections caused by Staphylococcus aureus (Tong et al., 2015; Rachel et al., 2016). The most well-known
Staphylococcus aureus infection is bacteremia. Numerous research on the prevalence, prognosis, and outcome of S. aureus have been reported. Infections caused by S aureus bacteremia (SAB) is a condition that mostly affects people in developed countries.. In addition, there is still a scarcity of high-quality evidence to direct SAB management (Tong et al., 2015). The pathogen’s propensity for acquiring antibiotic resistance makes treatment of these infections difficult. Community-acquired methicillin-resistant S. aureus (CA-MRSA) skin infections, in particular, are becoming more common in healthy people who have no known healthcare-related risk factors (Tattevin et al., 2012).
Resistance to commonly used antimicrobial drugs is frequently encountered in S. aureus. Some of the mechanisms of resistance include; inactivation of antibiotics by enzymes, decreased affinity for the antibiotics caused by alteration of the target, efflux pumps, and trapping of the antibiotic (Gitau et al., 2018).
Methicillin-resistant Staphylococcus aureus (MRSA) is defined as any strain of S. aureus that has acquired resistance to methicillin and other beta lactam antibiotics It is also responsible for a number of human infections that are difficult to treat (Brown et al., 2012; Dangler et al., 2013).
Staphylococcus aureus and MRSA are both shed by swimmers (Plano et al., 2011) and have been reported in seawater and beach sand(Plano et al., 2011; Goodwin et al., 2012). Staphylococcus aureus has a high resistance. The production of penicillin-binding protein 2a (PBP2a), which is encoded by the mecA gene on the mobile gene element (MGE) of the staphylococcal chromosome cassette mec (SCCmec), that has a low affinity for beta-lactam antibiotics, causes S. aureus to be resistant to methicillin (Akanbi et al., 2017).
The macrolide-lincosamide-streptogramin B resistance phenotype in Staphylococcus aureus includes erythromycin resistance. Chabbert was the first to identify this phenotype shortly after the use of erythromycin in clinical practice (Chabbert, 1956). Erythromycin was found to induce spiramycin in four clinical strains of S. aureus. This phenotype in S. aureus has been shown to be due to an erythromycin resistance mythylase (erm gene product) which renders newly synthesized ribosomes resistant to macrolide-lincosamide-streptogramin B antibiotics by methylating a specific adenosine residue of the 23S rRNA (Akanbi et al., 2017). In S. aureus, the genes encoding the methylase have been designated ermA, ermB, and ermC. ermA was first described by in 1969 in a clinical stain, designated 1206, with inducible resistance (Rahimi et al., 2016). Antimicrobials work by inhibiting key bacterial functions like cell walls synthesis (beta-lactams and glycopeptides), protein synthesis (aminoglycosides, tetracyclines, macrolides, lincosamides, chloramphenicol, mupirocin, and fusidic acid), nucleic acid synthesis (quinolones), RNA synthesis (rifampin), and metabolic pathways like folic acid metabolism (Rahimi et al., 2016). Antimicrobial resistance develops as a result of overuse, either by acquisition of foreign resistance genes or point mutations, resulting in a change in the antimicrobial target, degradation of the antimicrobial, or a decrease in the cell’s internal antimicrobial concentration (Rahimi et al., 2016;Bitrus et al., 2018).
Methicillin and erythromycin resistant S. aureus are also found to be resistant to other antibiotics such as oxacillin, amoxicillin and penicillin. These bacteria may also develop resistance to antibiotics such as clindamycin, cotrimoxazole, and gentamicin (Bale et al., 2018). The MecA gene, which codes for the penicillin-binding protein PBP 2A, is responsible for methicillin resistance (Cuny et al., 2015; Bitrus et al., 2017). Clinical isolates with the erm (A) and erm(C) genes, which code for rRNA methylases, are erythromycin resistant (Rahimi et al., 2016)
Healthy humans and animals have been found to have a new methicillin resistance gene called mecC (Harrison et al., 2013; Perrero et al., 2014). The mecC gene has been reported to be responsible for morbidity and mortality in different parts of the world (Persoons et al., 2013), and is referred to as community acquired methicillin-resistant S. aureus (CA-MRSA) (Perrero et al., 2014).
1.2 Statement of the Research Problem
Antibiotic-resistant bacteria have emerged as a major problem in antibiotic therapy. Methicillin resistant Staphylococcus aureus is a major cause of hospital and community acquired infections that are becoming increasingly difficult to combat because methicillin resistant S. aureus has the ability to develop resistance to any antibiotic to which it has been exposed (Bitrus et al., 2017; Cheunget al., 2021). Community acquired MRSA is the major cause of bacteremia and infective endocarditis (IE) as well as osteoarticular, skin and soft tissue infections (SSTIs), pleuropulmonary, and device related infections that has become increasingly problematic due to its high virulence and the ease with which they spread in the community (Reyes et al., 2011; Tacconelli and Magrini , 2017). Staphylococcus aureus was found in the majority of clinical trials involving Staphylococci. Some species are considered non-pathogenic, while S. aureus is considered a pathogen. Approximately 30% of the human population are colonized with S. aureus (Tong et al., 2015).
Here in Nigeria, some studies conducted across the country showed that methicillin resistant S. aureus has been isolated and is a common cause of hospital and community acquired infections with varying prevalence (Fayomi et al., 2011; Sina et al., 2011; Adeiza et al., 2020). Also, nasal carriage of S. aureus amongst students has been reported (Rasheed and Hussein, 2020).
1.3 Justification for the Study
Staphylococcus aureus is responsible for many human diseases with high morbidity and mortality rates. The increasing morbidity and mortality rate has been reported by various studies to be strongly linked to corresponding upsurge in the occurrence of resistant Staphylococcus aureus. Diseases caused by methicillin resistant Staphylococcus aureus and other non-methicillin resistant Staphylococcus aureus are challenging.
The prevalence of MRSA and non-MRSA in various clinical and environmental sources and their antibiotic profile will serve very useful purpose to clinicians for management of disease cases involving S. aureus. To the best of my knowledge the prevalence of antibiotic susceptibility profile of methicillin and erythromycin resistant S. aureus in clinical and environmental samples is yet to be documented for Minna Niger state. It is hoped that information from this research work will increase knowledge on the prevalence of methicillin and erythromycin resistant S. aureus and the most suitable antibiotics for managing such strains.
1.4 Aim and Objectives of the Study
The aim of this study was to identify and determine antibiotic susceptibility profile of methicillin and erythromycin resistant Staphylococcus aureus from clinical and environmental samples of Minna Nigeria.
The objectives of the study were to:
i. isolate Staphylococcus aureus from clinical and environmental sources in General Hospital Minna Niger State;
ii. determine antibiotic susceptibility profile of methicillin and non-methicillin resistant Staphylococcus aureus;
iii. detect the occurrence of methicillin and erythromycin resistant genes in the Staphylococcus aureus.
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IDENTIFICATION AND ANTIBIOTIC SUSCEPTIBILITY PROFILE OF METHICILLIN AND ERYTHROMYCIN RESISTANT Staphylococcus aureus FROM CLINICAL AND ENVIRONMENTAL SAMPLES IN MINNA NIGERIA
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