Abstract
The emergence of multiple antibiotic resistance in bacteria and the indiscriminate use of antibiotics contribute to the dissemination of resistant pathogens in the environment which may cause problems in therapy and is a serious public health issue. This study was conducted to determine the incidence of Pseudomonas aeruginosa and E.coli isolates in certain clinical and environmental samples as well as to determine the susceptibility patterns of these isolates to some commonly used antibiotics. The organisms were isolated using standard microbiological techniques and the antibiotic susceptibility was determined using disc diffusion method while plasmid curing was done using sodium dodecyl sulphate (SDS). The result of this studies showed that most of the clinical and environmental isolates were more resistant to amoxacillin and augumentin but clinical isolates showed higher resistance. It was also observed that clinical isolates showed least resistance to gentamycin, ofloxacin, and ciprofloxacin; similar least resistance were observed in environmental samples with gentamycin and ciprofloxacin. There was a significant difference (P≥ 0.05) in the percentage resistance between the clinical and environmental isolates. Thirteen isolates that were resistant to more than seven antibiotics were subjected to plasmid curing using 1% and 5% SDS. It was observed that at treatment with 1% SDS some of the isolates became resistant to more than one antibiotic; when SDS was increased to 5%, some of the isolates that were resistant become completely sensitive to all the antibiotics used. However, one of the P.aeruginosa that was initially sensitive to chloramphenicol became completely resistant at 5% SDS and another isolate of P.aeruginosa that was initially sensitive to septrin, sparfloxacin and ciprofloxacin became completely resistant at 1% and 5% SDS. This study indicates that P.aeruginosa and E.coli isolated from clinical samples were more resistant to antibiotics than those isolated from environmental samples. It has as well shown that there may be a possible transfer of resistance from one strain to another.
CHAPTER ONE
- INTRODUCTION AND LITERATURE REVIEW
- Introduction
The discovery of antibacterial agents had a major impact on the rate of survival from infections. However, the changing patterns of antimicrobial resistance caused a demand for new antibacterial agents. Therefore, the emergence of bacterial resistance to most of the commonly used antibiotics is of considerable medical significance (Khan and Malik, 2001; Oteo et al., 2002).
Antibiotic resistance genes in most bacteria are frequently found in extra chromosomal elements known as R-plasmids. Pseudomonas aeruginosa is naturally resistant to many of the widely used antibiotics, so chemotherapy is often difficult (Dubois et al., 2001).
Resistance is due to a resistance transfer plasmid (R-plasmid) which is a plasmid carrying gene encoding proteins that detoxify various antibiotics (Poole, 2004). Antibiotic resistant bacteria are widespread. Several antibiotic resistant genes can be carried by a single R-plasmid or alternatively, a cell may contain several R plasmids. In either case, the result is multiple resistance (Madigan et al., 2009).
Escherichia coli is a Gram negative bacterium and the main aerobic commensal bacterial species (Alhaj et al., 2007; Von and Marre, 2005). The native habitat of Escherichia coli is the enteric tract of humans and other warm-blooded animals. Therefore, Escherichia coli is widely disseminated in the environment through the faeces of humans and other animals and its presence in water is generally considered to indicate faecal contamination and the possible presence of enteric pathogens. Esherichia coli is able to acquire antibiotic resistance easily. Antibiotic resistant Esherichia coli may pass on the genes responsible for antibiotic resistance to other species of bacteria, such as Staphylococcus aureus, through a
process called horizontal gene transfer (Dubois et al., 2001). Esherichia coli often carry
multidrug resistant plasmids and under stress readily transfer those plasmids to other species. Thus, Esherichia coli is an important reservoir of transferable antibiotic resistance (Salyers et al., 2004). It has been observed that antibiotic susceptibility of bacterial isolates is not constant but dynamic and varies with time and environment (Hassan, 1995).
Escherichia coli is an opportunistic pathogen in neonatal and immuno-compromised patients (Annette, 1998). Bacteremia, wound infections, urinary tract infection, and gastrointestinal infections are the diseases associated with Escherichia coli and are often fatal in newborns (Raina et al., 1999). The organism is of clinical importance due to its cosmopolitan nature and the ability to initiate, establish and cause various kinds of infections (Okeke et al., 2000; Olowe et al., 2003; Tobih et al., 2006). Infections with antibiotic resistant bacteria make the therapeutic options for infection treatment extremely difficult or virtually impossible in some instances (El-Astal, 2004). Therefore, the determination of antimicrobial susceptibility of clinical isolates is often crucial for optimum antimicrobial therapy of infected patients.
A high-density patients’ population in frequent contact with health care staff and the attendant risk of cross-infection contributes to the spread of antibiotic-resistant microorganisms in the environment (Bataineh et al., 2007). Occurrence and prevalence of these resistant strains in the environment is, therefore, a usual kind of thing in developing countries. The Gram negative bacterium Pesudomonas aeruginosa is a ubiquitous aerobe that is present in water, soil and on plants (Banerjee and Stableforth, 2000). 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 defenses (Jawetz et al., 1991) and infections are both invasive and toxigenic (Todar, 2002).
Pseudomonas aeruginosa 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).
Increase in antibiotic resistance level is now a global problem. Pseudomonas aeruginosa is naturally resistant to many of the widely used antibiotics, so chemotherapy is often difficult. Resistance is due to a resistance transfer plasmid (R-plasmid) which is a plasmid carrying genes encoding proteins that detoxify various antibiotics out of the cell. Low antibiotic susceptibility, which is a worrying characteristic, is attributable to a concerted action of multidrug efflux pumps with chromosomally-encoded antibiotic resistance genes
e.g. mexAB-oprM,mexXY, etc (Poole, 2004), and low permeability of the bacterial cellular envelopes. Besides intrinsic resistance, Pseudomonas aeruginosa easily develops acquired resistance either by mutation in chromosomally-encoded genes, or by the horizontal gene transfer of antibiotic resistance determinants. Development of multidrug resistance by Pseudomonas aeruginosa isolates requires several different mutations and/or horizontal
transfer of antibiotic resistance genes.
Hypermutation favours the selection of mutation-driven antibiotic resistance in Pseudomonas aeruginosa strains producing chronic infections, whereas the clustering of several different antibiotic resistance genes in integrons favours the concerted acquisition of antibiotic resistance determinants. Some recent studies have shown that phenotypic resistance associated with biofilm formation or to the emergence of small-colony-variants may be important in the response of Pseudomonas aeruginosa populations to antibiotic treatment (Cornelis, 2008).
- Statementof problem
Massive quantities of antibiotics are being prepared and used each day. As a result of this, an increasing number of diseases are resisting treatment due to the spread of drug resistance as a result of drug misuse. Patients with Pseudomonas aeruginosa and Escherichia coli infections may inherently develop resistant to many classes of antibiotics as a result of misuse and improper disposal of drug in the environment and this may cause difficulty in treatment and may lead to life-threatening diseases and possibly death.
