Post genome analysis of Campylobacter jejuni

Prevalence, associated risk factors and antimicrobial susceptibility pattern of Campylobacter species among under five diarrheic children at Gondar University Hospital, Northwest Ethiopia

BACKGROUND

Recent reports indicate that Campylobacter species are becoming one of the leading causes of bacterial diarrhoeal disease worldwide and most of the isolates are resistant to different antibiotics. This study aimed at determining the prevalence, associated risk factors and susceptibility pattern of Campylobacter species in under-five diarrheic children.

METHODS

A cross-sectional study was conducted from October 2011 to March 2012. Samples were collected from under five diarrhoeic children who visited University of Gondar Teaching Hospital and seeking medical services during the study period. Stool specimens were aseptically inoculated using selective media and species isolation was further processed following standard procedures. Antimicrobial susceptibility test for Campylobacter species was performed using the standard agar disc diffusion method. The data was entered and analyzed using SPSS version 16 packages. Odd ratio was used to see their association between variables and then logistic regression was used to measure strengths of association. P-values less than 0.05 were taken as statistically significant.

RESULT

A total of 285 under five children with diarrhoea were included in this study. Of these144 (50.5%) were males and 141(49.5%) were females with the age range of one month to five years and mean age of 2.26 years (25months). Among 285 stool specimens cultured, 44(15.4%) of them were positive for Campylobacter species. Culture positivity for Campylobacter was higher in children below 12 months of age. Latrine usage, water source, boiling drinking water, bottle feeding, nutritional status and exposure to domestic animals had statistically significant association. Highest drug resistance rate were found in ampicillin (68.2%), tetracycline (56.8%) and trimethoprim- sulfamethoxazole (54.5%).

CONCLUSION

Isolation rate of Campylobacter species were frequent among under five children. The frequency was higher in those children who were malnourished, drinking of unprotected water and direct contact with infected animals (especially cats, dogs, pigeons, hens and their products). The antimicrobial resistance patterns for some of the commonly prescribed antibiotics were high. Therefore, awareness of hand washing and proper boiling of drinking water are probably important in preventing infection with Campylobacter species and childhood diarrhea should not be underestimated and effectiveness of the drugs should be continuously monitored by doing antimicrobial susceptibility test.

Rapid construction of Campylobacter jejuni deletion mutants

AIMS

To develop a novel method for rapid construction of Campylobacter jejuni deletion mutants.

METHODS AND RESULTS

We used overlapping extension PCR protocol to amplify a target sequence region of Camp. jejuni genomic DNA in which an internal fragment, Cj0618 coding sequence, was replaced by a chloramphenicol resistance cassette. After the resulting PCR product was introduced into electrocompetent Camp. jejuni 81-176, chloramphenicol-resistant mutants in which the wild type allele has been replaced by the deletion cassette were selected. DNA sequencing confirmed precise deletion in the Cj0618 gene. As expected from the previously reported role of Cj0618 in chick colonization, the resulting deletion mutant showed a caecal colonization defect in chick infection.

CONCLUSIONS

This method can be used for rapid construction of Camp. jejuni deletion mutants.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of this method should facilitate functional characterization of various Camp. jejuni genes.

Comparative typing of Campylobacter jejuni by heat-stable serotyping and PCR-based restriction fragment length polymorphism analysis

Campylobacter jejuni has become the most common bacterial cause of human gastroenteritis worldwide. Rapid, discriminatory typing methods are required to identify potential clusters of infections. The major disadvantage of the well-evaluated and widely used Penner heat-stable serotyping method is the high level of nontypeability. The correlation of the types determined by the Penner heat-stable serotyping method and PCR-based restriction fragment length polymorphism (RFLP) analysis of the lipooligosaccharide (LOS) biosynthesis genes of C. jejuni was studied with 149 C. jejuni strains. Of these strains, 79 were patient strains belonging to 25 Penner serotypes, 60 were nontypeable patient strains, and 10 were reference strains. A 9.6-kb DNA fragment of the LOS gene cluster was amplified and digested with the restriction enzymes HhaI and DdeI. Altogether, 39 different RFLP types (including 30 HhaI profiles and 32 DdeI profiles) were identified. Type Hh1Dd1 was the most common type, with 36% of the strains and strains of 12 serotypes being of this type. A high level of discrimination was obtained, and a correlation between the Penner serotypes and the PCR-RFLP types could be seen. Also, variation in the LOS biosynthesis genes within a single Penner serotype was found. Although the PCR-RFLP method may not be sufficient to compensate for Penner serotyping, it can give valuable information about nontypeable strains and further characterize strains of common serotypes.

Oral immunization of chickens with avirulent Salmonella vaccine strain carrying C. jejuni 72Dz/92 cjaA gene elicits specific humoral immune response associated with protection against challenge with wild-type Campylobacter

It is well documented that poultry and poultry products are the major source of human campylobacteriosis and salmonellosis. This study examined the general efficacy of avirulent Salmonella vaccine strains expressing Campylobacter antigen as a bivalent chicken vaccine prototype. Three C. jejuni genes: cjaA (cj0982c), cjaC (cj0734c) and cjaD (cj0113) encoding highly immunogenic proteins which are conserved among different Campylobacter serotypes, were introduced into avirulent Salmonella enterica sv. Typhimurium (chi 4550 and chi 3987) strains of two different serotypes (UK-1 and SR). The high copy number plasmid pYA3341 Asd(+) was used as a cloning vector. The constitutive expression of all analysed genes as measured by Western immunoblot technique was independent of the particular host strain. Specific rabbit anti-rCjaA antibody reacted not only with CjaA but also with other solute-binding protein (family 3), component of the ABC transport system (CjaC protein), was chosen as the protective antigen for animal experiments. Chickens orally immunized with Salmonella expressing Campylobacter cjaA gene developed serum IgG and mucosal IgA antibody responses against Campylobacter membrane proteins and Salmonella OMPs, as measured by an ELISA test. Protection experiment showed that chicken immunization with avirulent Salmonella carrying Campylobacter cjaA gene greatly reduced the ability of heterologous wild type C. jejuni strain to colonize the bird cecum.

Human campylobacteriosis in developing countries

Campylobacteriosis is a collective description for infectious diseases caused by members of the bacterial genus Campylobacter. The only form of campylobacteriosis of major public health importance is Campylobacter enteritis due to C. jejuni and C. coli. Research and control efforts on the disease have been conducted more often in developed countries than developing countries. However, because of the increasing incidence, expanding spectrum of infections, potential of HIV-related deaths due to Campylobacter, and the availability of the complete genome sequence of C. jejuni NCTC 11168, interest in campylobacteriosis research and control in developing countries is growing. We present the distinguishing epidemiologic and clinical features of Campylobacter enteritis in developing countries relative to developed countries. National surveillance programs and international collaborations are needed to address the substantial gaps in the knowledge about the epidemiology of campylobacteriosis in developing countries.