A nosocomial outbreak of fluoroquinolone-resistant salmonella infection.

BACKGROUND: Infection with fluoroquinolone-resistant strains of salmonella is rare, as is nosocomial salmonella infection. We describe the first recognized outbreak of fluoroquinolone-resistant salmonella infections in the United States, which occurred in two nursing homes and one hospital in Oregon. METHODS: We interviewed medical staff and reviewed patients' charts and death certificates. In Nursing Home A we conducted a case-control study. Patients were defined as residents of the nursing home from whom fluoroquinolone-resistant Salmonella enterica serotype Schwarzengrund was isolated between February 1996 and December 1998. Controls were residents with similar medical conditions whose cultures did not yield salmonella. We compared isolates using pulsed-field gel electrophoresis and sequence analysis. We reviewed pharmacy records to compare the use of fluoroquinolone among several nursing homes. RESULTS: Eleven patients with fluoroquinolone-resistant salmonellosis were identified at two nursing homes. The index patient had been hospitalized in the Philippines and had probably acquired the infection there. Transmission was probably direct (from patient to patient) or through contact with contaminated surfaces. Treatment with fluoroquinolones during the six months before a culture was obtained was associated with a significant risk of salmonella infection (4 of 5 patients had taken fluoroquinolones, as compared with 2 of 13 controls; odds ratio, 22.0; 95 percent confidence interval, 1.06 to 1177). The patients were not significantly more likely than the controls to have taken other antibiotics. More fluoroquinolones were used at Nursing Home A than at similar nursing homes in Oregon. The isolates from the outbreak had similar patterns on pulsed-field gel electrophoresis and the same gyrA mutations. The isolates from the outbreak were also similar to the only previous isolate of fluoroquinolone-resistant salmonella in the United States, which came from a patient in New York who had been transferred from a hospital in the Philippines. CONCLUSIONS: We describe a prolonged nosocomial outbreak of infection with fluoroquinolone-resistant S. enterica serotype Schwarzengrund. More such outbreaks are likely in institutional settings, particularly those in which there is heavy use of antimicrobial agents.

Pretreatment with urea-hydrochloric acid enhances the isolation of Helicobacter pylori from contaminated specimens.

Human saliva seeded with H. pylori was incubated in urea-HCl and then cultured on nonselective media. Pretreatment with 0.06 N HCl-0.08 M urea for 5 min at 37 degrees C resulted in reproducible isolation of H. pylori, even at low inocula (< or =10(2) CFU/ml of saliva), despite the presence of large numbers of contaminating organisms.

Characterization of gyrA mutations associated with fluoroquinolone resistance in Campylobacter coli by DNA sequence analysis and MAMA PCR.

Increasing numbers of fluoroquinolone-resistant Campylobacter coli isolates received at the Minnesota State Public Health Laboratory and at the Centers for Disease Control and Prevention have been a cause for concern. The gyrA quinolone resistance-determining regions of several fluoroquinolone-resistant isolates were sequenced to examine the mechanism of resistance. Ciprofloxacin-resistant C. coli isolates examined by DNA sequencing had a Thr-86 to Ile (ACT-->ATT) gyrA mutation, leading to resistance to fluoroquinolone antibiotics. A mismatch amplification mutation assay polymerase chain reaction protocol was developed to detect this gyrA mutation.

Ciprofloxacin resistance in Campylobacter jejuni isolates: detection of gyrA resistance mutations by mismatch amplification mutation assay PCR and DNA sequence analysis.

The gyrA quinolone resistance determining region was sequenced from 13 ciprofloxacin-resistant and 20 ciprofloxacin-susceptible Campylobacter jejuni isolates. All isolates resistant to ciprofloxacin had Thr-86-to-Ile mutations, a mutation frequently associated with the acquisition of resistance to fluoroquinolones. A mismatch amplification mutation assay (MAMA) PCR protocol was developed that detects this gyrA mutation in quinolone-resistant isolates. The MAMA PCR provides a means for routine detection of the gyrA mutation without the need for sequencing the gyrA gene.

Cloning and characterization of the galactokinase gene from Streptococcus thermophilus.

The objective of this research was to clone and characterize the galactokinase gene (galK) from Streptococcus thermophilus F410. Partially digested genomic DNA was cloned into pBR322 and transformed into galK Escherichia coli, and a galactose-fermenting transformant was isolated. Restriction analysis revealed that the transformant resulted from a Sau3A-HindIII 4.0-kb fragment. Galactokinase activity in the recombinant was 10 times that of the parent strain. Analysis of the DNA sequence showed the presence of a 1.3-kb open reading frame that had high homology with the galK gene from other organisms. A putative ribosome-binding site, start and stop codons, and -10 and -35 sequences were identified. The predicted protein had a molecular mass of 49 kDa, which corresponded to the estimated size of a band apparent by SDS-PAGE. Amino acid sequence homologies with other galactokinases ranged from 50 to 62% similarity. Northern blots were performed between the galK gene and mRNA from S. thermophilus. No hybridization signals were observed for cells grown in glucose, but cells grown in lactose or galactose gave moderate and strong signals. The results suggest that repression of the galK gene by glucose may be responsible for the galactose-releasing phenotype in these strains.

Sodium butyrate causes an increase in the block to transcriptional elongation in the c-myc gene in SW837 rectal carcinoma cells.

Elevated expression of the c-myc oncogene is a frequent finding in tumors and cell lines derived from carcinomas of the colon and rectum. In a previous study we demonstrated that the differentiation agent sodium butyrate causes a rapid reduction in the expression of c-myc RNA in the rectal carcinoma cell line SW837. This effect was blocked by inhibitors of protein synthesis, suggesting that butyrate causes the induction of an activity that has a negative effect on c-myc expression. In the present work we demonstrate that the rapid decrease in the level of c-myc RNA, upon treatment of SW837 cells with 2 mM butyrate, is followed by a slower decrease in the level of p53 RNA and an increase in the RNA levels for fibronectin and a placental type alkaline phosphatase. Using in vitro elongation of nascent transcripts to measure transcription and actinomycin D chase experiments to measure RNA stability, we show that the reduction in expression of c-myc RNA is due to an increase in the block to transcriptional elongation, rather than a decrease in transcriptional initiation or an increase in degradation of the RNA. We conclude that sodium butyrate induces an activity that increases the transcriptional block in SW837 cells, and that regulation of transcriptional elongation is an important mechanism for regulating c-myc expression in this cell type. A shift in relative usage of the two major promoters in the c-myc gene accompanies the reduction in expression. The potential significance of this finding with respect to transcriptional elongation is discussed. Mutations in the exon 1/intron 1 boundary region of the c-myc gene cause an increase in transcriptional elongation in Burkitt lymphoma. We sequenced this region in a series of cell lines derived from colorectal carcinomas, all of which had an elevated level of c-myc expression, to determine if a similar mutational mechanism is at work in this disease. All of the lines examined had a normal c-myc DNA sequence, suggesting that the deregulation of c-myc expression in colon cancer is not due to a cis mutation in this region.