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  • PROJECT TITLE: PREVELENCE AND PLASMID PROFILING OF Pseudomonas aeruginosa AND Escherichia coli FROM CLINICAL AND ENVIRONMENTAL SAMPLES
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CHAPTER ONE

INTRODUCTION

1.1       Background of study

Human opportunistic pathogen like Pseudomonas aeruginosa and Escherichia coli are ubiquitous environmental bacterium that causes numerous opportunistic human infections. The emerging presence of multi-drug-resistant isolates to many antimicrobials used for hospital patients has attracted the attention of many researchers in recent decades (Gomez et al., 2012). A wide range of biochemical and physiological mechanisms may be responsible for resistance. The abuse of antibiotics in human medicines, animal treatment and agriculture combined with inadequate wastewater treatment has led to the presence of antibiotics and antibiotic resistant bacteria in the environment particularly in the surface waters (Ghafur, 2010; Baquero et al., 2008). Subsequently, it has led to the development of multiple drug resistance in many bacterial species (Nikaido et al., 2009).

Pseudomonas aeruginosa is a leading cause of hospital-acquired infections, giving rise to a wide range of opportunistic infections. Its high intrinsic resistance to antibiotics and ability to develop multidrug resistance pose serious therapeutic problems (Kohler et al., 1999). Pseudomonas aeruginosa is highly ubiquitous in water systems, and has intrinsic antimicrobial resistance due to low outer membrane permeability, as well as an extensive efflux pump system (Aeschlimann, 2003; Lister et al., 2009). Pseudomonas aeruginosa demonstrates resistance to multiple antibiotics, thereby rendering common antibiotic therapy ineffective (Bodey et al., 2008). The presence of multidrug-resistant Pseudomonas aeruginosa in an aquatic environment (milieu) may be important for immunosuppressed or other at-risk individuals, for whom treatment difficulties have greater implications (Obritsch et al., 2004).

Pseudomonas aeruginosa belongs to a vast genus of obligate aerobic, non‐fermenting, saprophytic, Gram‐negative bacilli widespread in nature, particularly in moist environments (Volk et al., 1991; DuBois et al., 2001). Naturally, this organism is endowed with weak pathogenic potentials. However, its profound ability to survive on inert materials, minimal nutritional requirement, tolerance to a wide variety of physical conditions and its relative resistance to several unrelated antimicrobial agents and antiseptics, contributes enormously to its ecological success and its role as an effective opportunistic pathogen (Gales et al., 2001). The organism is pathogenic when introduced into areas devoid of normal defences (Jawetz et al., 1991) and infections are both invasive and toxigenic (Todar, 2002).

The organism has been incriminated in cases of meningitis, septicaemia, pneumonia, ocular and burn infections, hot tubs and whirlpool‐associated folliculitis, osteomyelitis, cystic fibrosis‐related lung infection, malignant external otitis and urinary tract infections with colonized patients being an important reservoir (Hernandez et al., 1997). Cross‐transmission from patient to patient may occur via the hands of the health care staff or through contaminated materials and reagents (DuBois et al., 2001). However, it is believed that Pseudomonas aeruginosa is generally environmentally acquired and that person‐to‐person spread occurs only rarely (Harbour et al., 2002). As such, contaminated respiratory care equipment, irrigating solutions, catheters, infusions, cosmetics, dilute antiseptics, cleaning liquids, and even soaps have been reported as vehicles of transmission (Joklik et al., 1992; Berrouane et al., 2000; DuBois et al., 2001).

Escherichia coli is the most prevalent facultative anaerobic species in the gastrointestinal tract of human and animals, usually a harmless microbe, but it is also a medically important bacteria causing a number of significant illnesses(Friedman, et al., 2002). Vegetables may be contaminated through insufficiently-treated water and fertilizers or may be compromised by the use of biocides during cultivation (Beuchat, 1996). Similarly, animals can also become infected from water or food contaminated with wastes of human or animal origin or with human carrier workers. One of the possible ways of entry of various microbes could be the handling of meat and meat products by adopting improper hygienic measures during handling and processing (Kiranmayi et al., 2011).

Escherichia coli (E. coli) bacteria normally live in the intestines of people and animals. Most Escherichia coli are harmless and actually are an important part of a healthy human intestinal tract. However, some Escherichia coli are pathogenic, meaning they can cause illness, either diarrhea or illness outside of the intestinal tract. The types of Escherichia coli that can cause diarrhea can be transmitted through contaminated water or food, or through contact with animals or persons (CDC, 2003). 

Antibiotic resistance in Escherichia coli has been globally identified in isolates from environmental, animal and human sources (Dromigny, 2005).This is a consequence of the use of antimicrobials in medicine and their application in animal husbandry, which have brought about phenotypic changes, often due to chromosomal mutations (Erb et al., 2007) . Several studies have revealed that Escherichia coli is resistant to a number of antibiotics (Von and Reinhard, 2000; Gangoue et al., 2004 , Orrett and Shurl, 2001; Iqbal and Patel, 2002; Al-Tawfiq, 2006).Adding to the consequences of microbial resistance to antibiotics on human health, contamination of surface water bodies with resistant bacterial strains from human activities and livestock operations has also been reported (Iqbal and Patel, 2002).As a result of their clinical significance, many methods exist for the epidemiological investigation of infections caused by Pseudomonas aeruginosa and Escherichia coli. In different parts of the world, biotyping, serotyping, antibiogram, phage typing, bacteriocin typing, plasmid profile, and more recent techniques like pulsed‐field gel electrophoresis and random amplified polymorphic DNA analyses have been used in typing the organism (Hernande et al., 1997). However, most of these methods are not widely available in routine diagnostic laboratories in developing countries because of the technical difficulties and expenses they involve. It would therefore be an important advancement if a cheap, reliable and simplified scheme could be developed, especially for the developing countries.

1.1       Aims of study

The aim of this work is to determine the prevalence of Pseudomonas aeruginosa and Escherichia coli, and to study their antibiotic resistant characteristics property.

1.2       Specific objectives of study

This study was design to achieve the following specific objectives:       

1.      to isolate, characterize and identify Pseudomonas aeruginosa and Escherichia coli in clinical and environmental samples.

2.      to determine the prevalence of Pseudomonas aeruginosa and Escherichia coli from all collected samples.

3.      to evaluate the antibiotics sensitivity property of Pseudomonas aeruginosa and Escherichia coli.

4.      to determine the presence of plasmid carrying antibiotics resistance gene in both Pseudomonas aeruginosa and Escherichia coli.


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