Although many genes related to the pathogenicity of Campylobacter jejuni have been reported, the relationships between these genes and the sources of strains are not clear. In this study, the presence of 11 pathogenic genes responsible for the expression of adherence, invasion, colonization and cytotoxin production was examined in 111 C. jejuni isolated from human clinical samples, poultry meat, broiler faeces and bovine faeces. For most of the pathogenic genes, no difference in their presence in C. jejuni was found among the sources, but, for racR, wlaN and virB11, there were some variations among sources. The racR gene was present at rates of 98·2 (human clinical samples), 90·5 (poultry meat), 85·7 (broiler faeces) and 76·7 % (bovine faeces). Detection rates for the wlaN gene were 25·0, 23·8, 4·7 and 7·7 % and those for the virB11 gene were 10·7, 9·5, 9·5 and 15·4 % in human clinical samples, poultry meat, broiler faeces and bovine faeces, respectively. One hundred and seven of 111 strains (96·4 %) carried from eight to 10 of the pathogenic genes. These data did not show remarkable differences in the presence of pathogenic genes carried by C. jejuni from various sources. IntroductionCampylobacter jejuni is one of the most common causes of bacterial enteritis. Campylobacteriosis is mainly a foodborne infection, and poultry products may play an important role in transmission to humans (Park, 2002). C. jejuni contamination of poultry meat during processing has been reported (Kazwala et al., 1990;Chuma et al., 1994Chuma et al., , 1997Berrang et al., 2001;Hartnett et al., 2001). Adherence, invasion and cytotoxin production appear to be possible virulence factors. The clinical and epidemiological characteristics of the disease provide clues to the molecular mechanisms that play a role in C. jejuni infection. Recently, some genes have been recognized as responsible for the expression of pathogenicity. In this study, flaA (Nuijten et al., MethodsBacterial strains and growth conditions. One hundred and eleven strains in total were tested in this study, including 56 isolates from human clinical samples, 21 from poultry meat, 21 from broiler faeces and 13 from bovine faeces. All strains were incubated on Müller-Hinton agar (Oxoid) at 42 8C under microaerobic conditions (85 % N 2 , 5 % O 2 , 10 % CO 2 ) for 24 h.Preparation of DNA. Template DNAs for PCR were extracted by the conventional boiling method. Fresh cultures of C. jejuni were suspended in 300 ìl TE buffer and the suspensions were boiled at 95 8C for 10 min. After centrifugation at 15 000 r.p.m. for 2 min, the supernatants were stored at À20 8C and used as template DNA.PCR primer design and amplification.

ABSTRACT. The presence of 11 virulence-associated genes in Campylobacter jejuni isolated from chickens at different stages of their development was examined by PCR. Multiple groups of C. jejuni were colonized in one chicken at the same time. Two hundred thirty one C. jejuni in total were isolated from the same group at four different ages and 12 groups of C. jejuni possessing of 11 virilence-associated genes were observed. Eleven, eight, five and three groups of C. jejuni were detected at 21, 28, 42 and 56 days after hatching, respectively. The variation of Campylobacter groups was reduced as the chicken developed and one group of C. jejuni became predominant.

Oil spillage has become a global environmental problem. Natural bioremediation is the only ecofriendly solution to resist its devastating environmental and economic damage damage. In this investigation, petroleum tolerant and degrading bacteria were isolated from different oil-contaminated soil and water samples. Bushnell Haas media supplemented with petrol, kerosene, and diesel as sole carbon sources was used for isolation of bacteria capable of degrading these petroleum fractionates. From three soil samples and two water samples, a total of nine bacterial strains were isolated capable of degrading petrol, kerosene and diesel with varying tolerance capacities. The isolates were identified by using standard biochemical tests and morphological studies, and it was determined that these strains belong to six bacterial genera e.g., Staphylococcus, Micrococcus, Streptococcus, Bacillus, Klebsiella and Corynebacterium. The isolated Staphylococcus spp. were found to be the most tolerant isolate withstanding as high as 7% petroleum. The others also exhibit tolerance to varying concentrations of petroleum. All these isolates were able to degrade petroleum completely and produced CO 2 within 7 days, with a few exceptions for Bacillus sp. and Klebsiella sp. which required 15 days for complete degradation of kerosene. These isolates seemed to have potential for bioremediation of oil contaminated soil and water.

This project is by far the most significant accomplishment in my life and it would not have been impossible without people who supported me and believed in my caliber. I would like to extend my gratitude and sincere thanks to my honorable supervisor Dr. Surajit Das, Assistant Professor, Department of Life Science. He is not only a great lecturer with deep vision but also most importantly a kind person. I sincerely thank for his exemplary guidance and encouragement. His trust and support inspired me in the most important moments of making right decisions and I am glad to work under his supervision.

Hospitalizations due to urinary tract infections are among the most commonly observed condition throughout the world. The study conducted among a total of 200 positive urine samples comprising male and female patients of different age showed E. coli (120), Klebsiella spp. (56) and Proteus spp. (24). Based on antibiotic susceptibility testing, It was revealed that E. coli showed lowest resistance to cefotaxime (35%) and highest resistance to levofloxacin (60%), whereas, Klebsiella spp. showed resistance to ceftriaxone (30.59%) and amoxicillin (88.33%). Likewise, Proteus spp. observed to have 29.16% (azithromycin) and 70.83% (ciprofloxacin) resistance. Cefotaxime was found to be the best drug for the treatment of E. coli related infections with 66.67% sensitivity. Ceftriaxone (69.41%) sensitive) was also found to be the best drug for the treatment of Klebsiella spp., whereas Proteus spp. could be effectively treated by Azithromycin (70.83% sensitive). Thirty-six (36) Multi drug resistant (MDR) pathogens were found in the sample of the elder males, 29 MDR pathogens were found in the sample of young males, 39 MDR were found in the sample of young females, and 40 MDR were found in the sample of elder females. Sixty eight percent of the isolated strains were highly multidrug resistant. Overall, MDR prevalence was 72%, and E. coli exhibited 54.16% MDR prevalence among isolates. The results revealed a surge in MDR pathogens that could impose major threat among community health.