RESUMO
Using a sucrose counter-selection strategy, we have constructed an unmarked aroC deletion mutant of B. pseudomallei strain A2 in order to investigate the possibility of an effective live-attenuated vaccine. The aroC deletion in the resultant mutant, designated A2DeltaaroC, was confirmed by PCR, Southern hybridization and failure of the mutant to grow in a defined medium without aromatic compounds. Compared to the parental wild type strain, A2DeltaaroC was highly attenuated for virulence following intraperitoneal introduction into BALB/c and C57BL/6 mice. BALB/c mice immunized intraperitoneally with A2DeltaaroC were not protected against a challenge dose of 500 cfu (25 x LD50) of the parental strain A2, whereas C57BL/6 mice similarly immunized intraperitoneally with A2DeltaaroC were significantly protected against a challenge dose of 6,000 cfu (20 x LD50).
RESUMO
This study presents updates on molecular epidemiology of extended-spectrum beta-lactamases (ESBLs) in clinical isolates of Enterobacteriaceae from Srinagarind Hospital, Khon Kaen University, Thailand. All isolates were screened for the presence of ESBL genes, bla(TEM), bla(SHV), bla(VEB) and bla(CTX-M), using PCR followed by nucleotide sequence determination. The results revealed that beta-lactamase genes among 48 isolates collected between 1998 and 1999 were bla(SHV) (79%), bla(CTX-M-9) (52%), bla(TEM-1) (48%) and bla(VEB) (33%), whereas those found in 52 isolates collected in 2003 were bla(TEM-1) (79%), bla(CTX-M-15) (44%), bla(SHV) (36%), bla(VEB) (36%), bla(CTX -M-14) (11%) and bla(CTX-M-9) (10%). In addition, 45 isolates carried at least two different ESBL genes. Using PCR, part of insertion sequence ISEcpl was found in the upstream regions of bla(CTX-M-14) and bla(CTX-M-15). ERIC-PCR analysis revealed that most ESBL-producing isolates were of different strains. This is the first report of CTX-M-9, CTX-M-14 and CTX-M-15 beta-lactamase genes in Enterobacteriaceae in Thailand.