Two step PCR method to exchange the resistance cassette of a vector

For co-transformation of two plasmids, both have to possess different antibiotic selection markers. If that is not the case, normally the gene of interest (GOI) is subcloned into another vector. Here we introduce a fast and easy method to exchange the antibiotic resistance cassette (ARC) in only two PCR steps.Method SummaryTo shuttle the antibiotic resistance cassette (ARC) from one vector to another, one can amplify the ARC of interest and use the resulting PCR-product as a primer pair for the next amplification step. Simply remove parental DNA template by DpnI digestion, transform PCR product directly in E. coli cells, select transformants on an appropriate agar plate and isolate target vector by plasmid preparation.

Antibiotic Resistance Profile and association with Integron Type I among Salmonella Enterica Isolates in Thailand

Salmonella infection is the second most common cause of diarrhea in Thailand; however, the data on antimicrobial resistance is limited. There were137 Salmonella strains, isolated from patients and 126 strains isolated from chicken meat, collected from Nonthaburi, Thailand during 2002. The top five serotypes of patients isolates were Enteritidis (22%), Typhimurium (11%), Weltevreden (8.8%), Rissen (8%), and Choleraesuis (6.6%) while the top five serotypes of chicken meat isolates were found as follows: Schwarzengrund (11.91%), Hadar (11.11%), Rissen (8.73%), Amsterdam (7.94%), and Anatum (7.94%). Salmonella strains were most resistance to the class of antibiotics that act as inhibitor to nucleic acid synthesis such as antifolates group (Trimethoprim;SXT) and fluoroquinolones (Nalidixic acid; NA, Ciprofloxacin; CIP),while the β lactam antibiotic was more effective, i.e. the 3rd gen cephalosporin (Ceftazidime; CAZ, Cefotaxime ; CTX), Monobactam (Aztreonam; ATM) and carbapenams group (Imipenem; IMP, Meropenem; MEM). The role of class I integron element in transmission of the resistance gene was revealed by detection the gene cassette associated with a class 1 integron in plasmid preparation among 80% of the isolated strains. The gene cassettes containing resistant genes of dhfrA12 (resistant to trimethoprim) and aadA2 (resistant to streptomycin and spectinomycin), were detected more frequently in the resistant strains. These gene cassettes were likely to be transmitted via plasmid, as it could not be detected in genomic DNA.