Our results indicate that the exoU genotype, which is associated with specific susceptibility profiles, is a relevant independent marker of early mortality in P. aeruginosa bacteremia.

BackgroundA livestock-associated clonal lineage (ST398) of methicillin-resistant Staphylococcus aureus (MRSA) has been identified causing colonization or infection in farm workers. The aim of the study was to analyze the prevalence of MRSA-ST398 colonization in pigs and in pig farmers in an area with a high pig population (Osona, Barcelona province, Catalonia, Spain).MethodsWe performed a cross-sectional prevalence study in Osona (Catalonia, Spain), from June 2014 to June 2015. All pig farm workers from 83 farms were studied. Twenty of these farms were randomly selected for the study of both pigs and farmers: 9 fattening and 11 farrow-to-finish farms. All workers over the age of 18 who agreed to participate were included. Samples were analyzed to identify MRSA-ST398 and their spa type.ResultsEighty-one of the 140 pig farm workers analyzed (57.9% (95% IC: 50.0–66.4%)) were MRSA-positive, all of them ST398. The mean number of years worked on farms was 17.5 ± 12.6 (range:1–50), without significant differences between positive and negative MRSA results (p = 0.763). Over 75% of MRSA-ST398 carriers worked on farms with more than 1250 pigs (p < 0.001). At least one worker tested positive for MRSA-ST398 on all 20 selected pig farms. Ninety-two (46.0% (95% IC: 39.0–53.0%)) of the nasal swabs from 200 pigs from these 20 farms were MRSA-positive, with 50.5% of sows and 41.4% of fattening pigs (p = 0.198) giving MRSA-positive results. All the isolates were tetracycline-resistant, and were identified as MRSA-ST398. The spa type identified most frequently was t011 (62%). Similar spa types and phenotypes of antibiotic resistance were identified in pigs and farmers of 19/20 tested farms.ConclusionsThe prevalence of MRSA-ST398 among pig farm workers and pigs on farms in the studied region is very high, and the size of the farm seems to correlate with the frequency of colonization of farmers. The similar spa-types and phenotypes of resistance detected in pigs and workers in most of the farms studied suggest animal-to-human transmission.

Mycobacteria are thought to have either one or two rRNA operons per genome. All mycobacteria investigated to date have an operon, designated rrnA, located downstream from the murA gene. We report that Mycobacteriun fortuitum has a second rrn operon, designated rrnB, which is located downstream from the tyrS gene; tyrS is very close to the 3 end of a gene (3-mag) coding for 3-methylpurine-DNA-glycosylase. The second rrn operon of Mycobacterium smegmatis was shown to have a similar organization, namely, 5 3-mag-tyrS-rrnB 3. The rrnB operon of M. fortuitum was found to have a single dedicated promoter. During exponential growth in a rich medium, the rrnB and rrnA operons were the major and minor contributors, respectively, to pre-rRNA synthesis. Genomic DNA was isolated from eight other fast-growing mycobacterial species. Samples were investigated by Southern blot analysis using probes for murA, tyrS, and 16S rRNA sequences. The results revealed that both rrnA and rrnB operons were present in each species. The results form the basis for a proposed new scheme for the classification of mycobacteria. The approach, which is phylogenetic in concept, is based on particular properties of the rrn operons of a cell, namely, the number per genome and a feature of 16S rRNA gene sequences.Mycobacterium tuberculosis and Mycobacterium leprae are major human pathogens which have the ability to grow slowly within host cells. The mechanisms used by these pathogens to control their growth rates is not well understood. Cell growth is dependent on protein biosynthesis, which, in turn, requires the synthesis of new ribosomes. The rate-determining step in ribosome synthesis is thought to be the rate of synthesis of rRNA (4,8). Therefore, there is a need to identify factors important to transcription of rRNA (rrn) operons (12,14) and the ways in which these transcripts are processed to form mature rRNA (16,17).Traditionally, mycobacteria are classified as either slow growers or fast growers according to the time taken (less than 7 days for fast growers, longer than 7 days for slow growers) for colonies to appear on a solid medium (15, 37). The slowgrowing pathogens M. tuberculosis (6,18,36) and M. leprae (20,21,32) have a single rrn operon per genome, whereas most fast growers have two rrn operons per genome (2, 9). The apparent correlation between growth rate and the number of rrn operons per genome provides a possible explanation for the division of mycobacteria into fast-and slow-growing species.However, slow-growing and fast-growing mycobacteria are all close relatives, as judged by the relatedness (95% or more) of their 16S rRNA sequences (26,29,35), so that comparative studies provide a way of identifying highly conserved sequence elements important to the synthesis of mature rRNA (13). Furthermore, it is valuable to identify the gene immediately upstream from the rrn operon under investigation (11, 13). First, this upstream gene serves to identify the operon. Second, upstream gene sequences may provide elements dedicated to the ex...

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