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FP5

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Project ID: ICA4-CT-2001-10028
Finanziato nell'ambito di: FP5-INCO 2
Paese: Malaysia

Characterization and conjugation of chloramphenicol resistant gene

Resistance gene detection and horizontal transfer.

To increase the rapidity and accuracy of resistance testing, the use of PCR (a genotypic approach and DNA-based assay) for the detection of bacterial resistance was developed. This novel approach is a true revolution because it relies on a completely different concept; testing for resistance instead of testing for susceptibility. In our study, detection of the 136 chloramphenicol resistant isolates (32 for Cat I, 101 for Cat II and 3 for both Cat I and Cat II) using PCR targeting the Cat genes (genes responsible for chloramphenicol resistance) showed that PCR is a rapid, robust, cost-effective and sensitive method. Prior to amplification, crude genomic DNA of isolates was harvested using boiling method, which is a simple, safe and rapid way of DNA extraction. Biochemical Cat assay were carried out to analyze whether the mechanism of chloramphenicol resistant bacteria occurred by enzymatic or non-enzymatic resistance.

The isolates, which gave negative results for Cat genes detection, were analyzed for biochemical Cat assay. Resistance to antibiotics is usually a transferable factor and is important to the growth and spread of pathogenic bacteria. Out of 136 positive Cat genes isolates, only 56 were considered as potential donors because of their sensitivity to streptomycin, giving an inhibition zone of more than 6 mm. Antibiotic susceptibility testing showed that the donor transferred sulphonamide (S3 100) and chloramphenicol (C30) resistant genes to recipient and appears as transconjugant. This is evidence that chloramphenicol resistant bacteria detectable in aquaculture do participate in the molecular communication between bacteria of the aquaculture system.

The emergence of drug resistance in microorganisms is a serious problem, and several strategies have been proposed to try to overcome it. Prevention should be the ultimate solution, and vaccines have been suggested as a strategy that can be used to slow down the emergence of drug resistance by decreasing the infection rate and hence antibiotic usage. Broad surveillance programs and education of clinicians, pharmacists, veterinarians, drug company representatives, and the public about the spread of antimicrobial resistance and the consequences of antibiotic misuse should also have a significant impact.

Restrictive use of newer and broad-spectrum antibiotics has also been applied and advocated. Strict application of therapeutic guidelines might also be useful. Another strategy is the simultaneous rapid genotypic identification of bacteria and their antibiotic resistance genes will have a major impact on the treatment of infectious diseases while contributing to a better control of antimicrobial resistance.

Reported by

Aquatic Animal Health Unit
Faculty of Veterinary Medicine, Universiti Putra Malaysia
43400 Serdang
Malaysia