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- Prevalence and Antibiotic Susceptibility of Vancomycin-Resistant Enterococci in Chicken Intestines and Fecal Samples from Healthy Young Children and Intensive Care Unit Patients
- Shin Moo Kim , Eun Sook Shim , Chi Nam Seong
- J. Microbiol. 2001;39(2):116-120.
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Abstract
- The prevalence, resistance genotype and antibiotic susceptibility of vancomycin-resistant enterococci (VRE) were determined. Prevalence of VRE in chickens, healthy children and intensive care unit (ICU) patients was 43.0%, 12.7% and 24.1%, respectively. Forty out of 56 isolates from chicken intestines were identified as Enterococcus faecium, and 12 were E. faecalis. All the isolates contained the vanA gene. Nine out of 13 VRE isolates from patients and two out of 21 from healthy young children were identified as E. faecium. The resistance types of E. faecium, E. gallinarium and E. casseliflavus were VanA, VanC1, and VanC2, respectively. The mimimum inhibitory concentrations (MICs) of E. faecium, E. gallinarium, and E. casseliflavus to vancomycin were 512, 8 and 4 g/ml, respectively. Specifically, E. faecium isolates were resistant to most of antibiotics except ampicillin and gentamicin. This is the first report of high VanA type VRE prevalence in nonhospitalized young children in Korea.
- Salmonella Invasion Gene Regulation: A Story of Environmental Awareness
- Bradley D. Jones
- J. Microbiol. 2005;43(1):110-117.
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Abstract
- Salmonella enterica serovar Typhimurium causes human gastroenteritis and a systemic typhoid-like infection in mice. A critical virulence determinant of Salmonella is the ability to invade mammalian cells. The expression of genes required for invasion is tightly regulated by environmental conditions and a variety of regulatory genes. The hilA regulator encodes an OmpR/ToxR family transcriptional regulator that activates the expression of invasion genes in response to both environmental and genetic regulatory factors. Work from several laboratories has highlighted that regulation of hilA expression is a key point for controlling expression of the invasive phenotype. A number of positive regulators of hilA expression have been identified including csrAB, sirA/barA, pstS, hilC/sirC/sprA, fis, and hilD. HilD, an AraC/XylS type transcriptional regulator, is of particular importance as a mutation in hilD results in a 14-fold decrease in chromosomal hilA::Tn5lacZY-080 expression and a 53-fold decrease in invasion of HEp-2 cells. It is believed that HilD directly regulates hilA expression as it has been shown to bind to hilA promoter sequences. In addition, our research group, and others, have identified genes (hilE, hha, pag, and lon) that negatively affect hilA transcription. HilE appears to be an important Salmonella-specific regulator that plays a critical role in inactivating hilA expression. Recent work in our lab has been directed at understanding how environmental signals that affect hilA expression may be processed through a hilE pathway to modulate expression of hilA and the invasive phenotype. The current understanding of this complex regulatory system is reviewed.
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