A total of 6,226 fecal samples collected from 1980 to 1996 in the Australian states of Victoria, New South Wales, and Tasmania from individuals with gastroenteritis were tested for small round-structured viruses (SRSVs) and classical human caliciviruses (ClHuCVs) by electron microscopy. There were 223 samples positive for SRSVs, and nine positive for ClHuCVs. SRSVs were detected in individuals of all ages and were commonly associated with gastroenteritis outbreaks in nursing homes and hospitals. SRSVs were detected throughout the year, but were more common in the period from late winter to early summer in Australia (August to December). There were peaks of virus activity in the early 1980s and more recently in 1995 and 1996. Analyses by RT-PCR and sequencing of a segment of ORF1 encoding the putative RNA polymerase for SRSVs and ClHuCVs showed the presence of viruses belonging to several genogroups. Viruses of genogroup 1 (Norwalk/Southampton-like) and genogroup 3 (ClHuCVs) were relatively rare. Viruses of genogroup 2 (Snow Mountain-like) were common, and could be divided into two subgroups, one containing Toronto/Mexico-like viruses, the other Lordsdale/Camberwell-like viruses. The majority of viruses detected belonged to this latter subgroup.
In the gammaproteobacteria the RpoH regulon is often equated with the stress response, as the regulon contains many of the genes that encode what have been termed heat shock proteins that deal with the presence of damaged proteins. However, the betaproteobacteria primarily utilize the HrcA repressor protein to control genes involved in the stress response. We used genome-wide transcriptional profiling to compare the RpoH regulon and stress response of Neisseria gonorrhoeae, a member of the betaproteobacteria. To identify the members of the RpoH regulon, a plasmid-borne copy of the rpoH gene was overexpressed during exponential-phase growth at 37 degrees C. This resulted in increased expression of 12 genes, many of which encode proteins that are involved in the stress response in other species. The putative promoter regions of many of these up-regulated genes contain a consensus RpoH binding site similar to that of Escherichia coli. Thus, it appears that unlike other members of the betaproteobacteria, N. gonorrhoeae utilizes RpoH, and not an HrcA homolog, to regulate the stress response. In N. gonorrhoeae exposed to 42 degrees C for 10 min, we observed a much broader transcriptional response involving 37 differentially expressed genes. Genes that are apparently not part of the RpoH regulon showed increased transcription during heat shock. A total of 13 genes were also down-regulated. From these results we concluded that although RpoH acts as the major regulator of protein homeostasis, N. gonorrhoeae has additional means of responding to temperature stress.
A DNA microarray was used to identify genes transcribed in Neisseria gonorrhoeae using Ecf, an alternative sigma factor. No differences between the transcriptional profiles of strain FA1090 and a mutant where ecf had been inactivated could be detected when both were grown in vitro. We therefore constructed a gonococcal strain in which Ecf can be overexpressed. Some differentially expressed genes are clustered with ecf on the genome and appear to form a single transcriptional unit. Expression of the gene encoding MsrAB, which possesses methionine sulfoxide reductase activity, was also dependent on Ecf, suggesting that the regulon responds to oxidative damage. Western blotting confirmed that the increased level of MsrAB protein is dependent on the presence of Ecf.Bacterial sigma factors are essential components of the RNA polymerase holoenzyme and determine promoter selectivity and specificity. Bacteria usually contain at least one essential sigma factor, sigma-70, which is necessary for cell viability, as well as a number of accessory sigma factors that are often involved in responses to environmental stimuli or the phase of growth. The relative amount of RNA polymerase holoenzyme containing each sigma factor determines the amplitude of the expression of a specific collection of genes.We have searched the genome sequence of Neisseria gonorrhoeae strain FA1090 (GenBank accession number AE004969) for the presence of genes encoding sigma factors. As expected, there is a gene, rpoD, encoding sigma-70 (NGO0999). Only two intact genes encoding alternative sigma factors, rpoH (NGO0288) and ecf (NGO1944), were found. Laskos et al. (11) have shown that there is also an inactive RpoN-like sigma factor, RLS, although this sequence feature (NGO1766) has not been annotated as such in the publicly available annotations of the N. gonorrhoeae strain FA1090 genome sequence (GenBank accession number AE004969; annotations at www .stdgen.lanl.gov, cmr.tigr.org/tigr-scripts/CMR/CmrHomePage .cgi, and www.ncbi.nlm.nih.gov/genomes/lproks.cgi). The ecf gene encodes a member of the extracytoplasmic function (ECF) family of sigma factors. As the name suggests, ECF sigma factors from different bacterial species appear to respond specifically to a variety of extracytoplasmic stimuli. Characteristically, their activity is controlled by anti-sigma factors, and they control relatively small regulons (1). In most examples of this system investigated to date, the ECF sigma factors regulate not only their own expression but also that of the genes encoding the cognate anti-sigma factor, which are located in the same operon.We have used DNA microarrays to assess the role of the sigma factor Ecf in gonococci and show that it controls a small regulon which contains the msrAB gene, which encodes an unusual methionine sulfoxide reductase. MATERIALS AND METHODSBacterial strains, plasmids, and growth conditions. The bacterial strains and plasmids used in this study are listed in Table 1. Escherichia coli strain DH5␣ [F Ϫ endA1 thi-1 hsdR17 supE44 relA1 ⌬l...
We describe an outbreak of gastroenteritis in which the nucleic acid of three distinct noroviruses was amplified from the same fecal sample. To enable the separate amplification of each virus, an inclusion/exclusion RT-PCR primer design strategy was developed. This paired a virus-specific exclusion primer (designed with the exact sequence of one virus in a region displaying low conservation among the three viruses) with a virus-nonspecific inclusion primer (designed in a conserved region). Thus, in each reaction the exclusion primer provided specificity for a single virus, and the inclusion primer increased the sensitivity and allowed hybridization in a region of unknown sequence. Analysis of the partial genomic sequences of the three viruses (3.6-3.8 kb) indicated that each virus belonged to a separate genogroup II cluster, and each displayed evidence of a potential recombination event when the sequences were compared with other published norovirus sequences. Our results, which show a mixed norovirus infection in a single individual, confirm the need to be aware of the possibility of mixed norovirus infections, and of the possibility of genomic recombination causing anomalies in phylogenetic analyses in such instances.
An outbreak of gastroenteritis caused by Norwalk-like virus occurred in two areas of the hospital: area 1, consisting of three adjacent and interconnected wards, with mostly elderly patients; and area 22, an acute ward in a separate building with elderly patients. In area 1, 40 patients and 20 staff were affected; in area 2, 18 patients and 14 staff were affected. Infection control measures were instituted in consultation with the government health authority. These measures did not appear to affect the course of the outbreak, but may have prevented spreads to the other wards.
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