PREVALENCE OF INTEGRONS IN GRAM NEGATIVE BACTERIA
Integrons in Livestock, poultry and fish ponds
A study carried out by Barlow et al. , (2004), identified 86% of class 1 and 94% of class 2 integrase genes (intI1 and intI2) in mixed bacterial cultures from 50 bovine faecal samples in Australia. Class 1 integron was found in 19 out of 20 multi drug resistant Salmonella enterica isolated from different poultry farms in Egypt and they were found to harbor genes encoding resistant determinants to trimethoprim (dfrA1 and dfrA15), chloramphenicol (catB) and aminoglycoside (aadA1) (Orady et al. , 2017). Kang et al. , 2014 identified 42. 3% class 1 integrons and 0. 6% class 2 integrons from the large intestine of poultry and 18. 8% of class 1 integrons and 3. 0% of class 2 integrons in the large intestine of swine. Ho et al. , (2009) established that the prevalence of integrons in multi drug resistant E. coli strains derived from animal faecal samples were higher than in human strains. This result was in harmony with a previous study done by Nogrady et al. , (2006), where the variability of class 1 integrons was higher among commensal strains as compared to extraintestinal pathogens.
According to Alonso et al. , (2017), the resistant rate in African studies vary among regions and studied animal population but the highest resistant rate have been reported for tetracycline (10. 06-95%), ampicillin (6. 02-95. 7%) and trimethoprim/sulfamethoxazole (4. 49-80%) (Adelowo et al. , 2014; Adenipekum et al. , 2015). Class 1 integrons of 1. 6 and 1. 8 kb were detected in 22% of commensal E. coli isolates from farmed catfish, containing resistance gene cassettes dfrA12-aadA2 and dfrA17-aadA, beside the predominant tetracycline resistance genes tet(B) (77%) and tet(A) (25%) respectively (Nawaz et al. , 2009). Several studies have shown the prevalence of integrons in E. coli from poultry, poultry meat and cattle in Africa with a high prevalence among class 1 and class 2 integrons (Soufi et al. , 2009; Ben Slama et al. , 2010; Inwezerua et al. , 2014; Maamar et al. , 2016).
Implication of integrons in public health
Research has shown that food-borne infections are one of the leading causes of public health crisis and pathogens involved include Salmonella spp, E. coli, and Shigella which are responsible for 14 million illnesses and 60,000 hospitalizations and 1800 deaths annually. Food borne pathogens are present in food poisoning, in contaminated food samples such as milk, pork, chicken, veal, beef, turkey and lamb meat as well as in food production animals such as cattle, chickens, pigs and cows.
Antibiotic resistant food borne pathogens are considered to be a major contributor to both health-care associated and food-borne illnesses, carriage of such bacteria in a wide variety of food and food production animals are no longer limited solely to food hazards, but also poses a significant occupational risk for the industrial staff such as handlers, asymptomatic carriers and uncolonized individuals (Xu et al. , 2012). Yang et al. did a preliminary surveillance of antimicrobial resistance on food borne strains, phenotypic correlation existed among the aspects of antibiotic susceptibility. However, the occurrence and prevalence of integrons including class 1 integron and other classes of integrons as well as the role of such integrons play in the antimicrobial resistance in food safety require further investigation.
Chapter Three
Materials and Method
Sample collection
Waste water from the fish pond and faecal samples from the cow, goat and poultry birds will be collected aseptically from three different locations in each of the Southwestern State. The samples would be collected in sterile containers and would be transported to the laboratory in an icebox. Isolation of bacteriaOne gram of the fecal sample and 1 ml of the wastewater sample would be suspended in test tubes containing 9 ml of peptone water, then homogenized then cultured on MacConkey, and Centrimide plates. All suspected E. coli sample would be sub-cultured on Eosin Methylene blue agar for the production of green metallic sheen. Suspected Salmonella and Shigella samples would be cultured on Salmonella Shigella agar.
Preliminary Identification
Gram Staining
A drop of distilled water is placed on a slide and a minute amount of a colony from the sub-cultured plate will be transferred aseptically to the slide with an inoculation loop. The colony will be spread out with the loop to an even thin film over a circle of 1. 5cm in diameter. The smear is then air-dried and fixed over a gentle flame. The smear is flooded with crystal violet for one minute. Excess dye would be poured off and the slide is gently rinsed in water. The smear would be flooded with Lugol’s iodine for 30secs, then rinsed with water and drained carefully. It will be rinsed with 70% alcohol for 15 seconds. It would be rinsed with tap water at the end of the 15 seconds to stop the decolorization. The smear would then be counterstained with 0. 25% safranin for 60 seconds, rinsed with water and air dried. The cells are to be examined under the light microscope using x100 objective lens (oil immersion) for Gram’s reaction and cellular morphology (Fawole & Oso, 2004).
