Epidemic Clostridium difficile (027/BI/NAP1) rapidly emerged in the past decade as the leading cause of antibiotic-associated diarrhea worldwide. However, the key moments in the evolutionary history leading to its emergence and subsequent patterns of global spread remain unknown. Here we define the global population structure of C. difficile 027/BI/NAP1 based on whole-genome sequencing and phylogenetic analysis. We demonstrate that two distinct epidemic lineages, FQR1 and FQR2, not one as previously thought, emerged in North America within a relatively short period after acquiring the same fluoroquinolone resistance mutation and a highly-related conjugative transposon. The two epidemic lineages displayed distinct patterns of global spread, and the FQR2 lineage spread more widely leading to healthcare outbreaks in the UK, continental Europe and Australia. Our analysis identifies key genetic changes linked to the rapid trans-continental dissemination of epidemic C. difficile 027/BI/NAP1 and highlights the routes by which it spreads through the global healthcare system.

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Background: Brain abscesses and ischaemic strokes complicate pulmonary arteriovenous malformations (PAVMs). At risk individuals are poorly recognised. Stroke/ abscess risk factors have not been defined. Methods: A cohort study of 323 consecutive individuals with PAVMs (n = 219) and/or the commonly associated condition hereditary haemorrhagic telangiectasia (HHT, n = 305) was performed. Most of the 201 individuals with PAVMs and HHT had no respiratory symptoms, and were unaware they had HHT. Anderson-Gill models assessed constant and time dependent potential predictive variables for stroke/abscess, and rate reduction by PAVM embolisation. Results: 57 individuals with PAVMs and HHT experienced brain abscess or ischaemic stroke, usually prior to the diagnosis of underlying PAVMs/HHT. The primary determinants of stroke and abscess risks were unrelated to severity of PAVMs. Males had higher brain abscess rates (hazard ratio 3.61 (95% CI 1.58, 8.25), p = 0.0024); interventional histories and bacteriological isolates suggested dental sources. Once adjusted for gender, there was a marginal association between brain abscess and low oxygen saturation. For ischaemic stroke, there was no association with any marker of PAVM severity, or with conventional neurovascular risk factors. Surprisingly, low mean pulmonary artery pressure was strongly associated with ischaemic stroke (hazard ratio 0.89 (95% CI 0.83, 0.95) per mm Hg increase; p = 6.2610 25 ). PAVM embolisation significantly reduced ischaemic stroke rate (p = 0.028); no strokes/abscesses occurred following obliteration of all angiographically visible PAVMs. The mean PAVM diagnosis-treatment interval was longer, however, when neurological risks were unrecognised. Conclusions: Ischaemic strokes and brain abscesses occur commonly in undiagnosed HHT patients with PAVMs. Risk reduction could be improved.Pulmonary arteriovenous malformations (PAVMs) are abnormal dilated vessels which provide a rightto-left (R-L) shunt between the pulmonary arterial and venous circulations.

The development of chronic and recurrent Staphylococcus aureus infections is associated with the emergence of slow-growing mutants known as small-colony variants (SCVs), which are highly tolerant of antibiotics and can survive inside host cells. However, the host and bacterial factors which underpin SCV emergence during infection are poorly understood. Here, we demonstrate that exposure of S. aureus to sublethal concentrations of H2O2 leads to a specific, dose-dependent increase in the population frequency of gentamicin-resistant SCVs. Time course analyses revealed that H2O2 exposure caused bacteriostasis in wild-type cells during which time SCVs appeared spontaneously within the S. aureus population. This occurred via a mutagenic DNA repair pathway that included DNA double-strand break repair proteins RexAB, recombinase A, and polymerase V. In addition to triggering SCV emergence by increasing the mutation rate, H2O2 also selected for the SCV phenotype, leading to increased phenotypic stability and further enhancing the size of the SCV subpopulation by reducing the rate of SCV reversion to the wild type. Subsequent analyses revealed that SCVs were significantly more resistant to the toxic effects of H2O2 than wild-type bacteria. With the exception of heme auxotrophs, gentamicin-resistant SCVs displayed greater catalase activity than wild-type bacteria, which contributed to their resistance to H2O2. Taken together, these data reveal a mechanism by which S. aureus adapts to oxidative stress via the production of a subpopulation of H2O2-resistant SCVs with enhanced catalase production.

Although a high prevalence of antibodies to Helicobacter pylori has been documented within families, culture and DNA typing of strains from infected children and their parents has not been evaluated. This study aimed to analyse H pylori infection within family groups. Endoscopy, gastric biopsy, and H pylori culture were performed on all eight parents of four children who presented with dyspepsia and who had a positive H pylori culture. All biopsy specimens were cultured on Columbia based blood agar under microaerophilic conditions for four days. The DNA from each strain was extracted and electrophoretic patterns were compared after digestion with restriction endonucleases Hae III or Hind III. Ribotyping using a biotinylated cDNA probe prepared from 16S and 23S rRNA of H pylon NCTC 11638 was also used. Seven of the parents were positive for H pylorn on urease testing, histology, and on culture. DNA typing showed the same or a similar strain to be present in at least two family members in three of the four family groups. In family 1, the mother, father, and child all had an identical strain; in family 2, father and son had a similar related strain; father and mother had the same strain in family 3; and all strains were unique in family 4. These data provide evidence for either intrafamilial cross infection or a common source of infection within family groups. (Gut 1993; 34: 1348-1350 Helicobacter pylon is recognised as a significant cause of chronic antral gastritis and important in the aetiology of peptic ulceration.' There is also evidence to support a role as a risk factor for gastric carcinoma.2 5 It is known that the prevalence increases with age6 and that while the incidence in children is lower than that in adults, intrafamilial clustering has been shown. DNA TYPING H pyloni isolates from four children and their parents, plus two isolates chosen randomly from unrelated individuals were incubated on brain heart infusion agar supplemented with 5% v/v horse blood and 1% v/v isovitalex (Oxoid) for 48 hours at 37%, under microaerophilic conditions (5% 02, 5% C02, 2% H2, 88% N2). Chromosomal DNA was isolated and purified from each isolate using the guanidium thiocyanate reagent method.'0 The purified DNA was incubated with the restriction endonuclease (Hae III) for four hours at 37°C and the digests were electrophoresed at 30 v for 16 hours in a horizontal agarose gel. After electrophoresis the gels were stained with ethidium bromide and photographed. Strain DNAs which did not cut with Hae III were subjected to Hind III digestion. For ribotyping, the gels were then transferred to nylon membranes by means of vacublotting. A biotinylated cDNA probe was prepared from 16S and 23S rRNA of H pylori NCTC 11638 using reverse transcriptase. Biotinylation was achieved by the incorporation of biotin-16-dUPT. The membranes were then hybridized by standard procedures for 16 hours at 42°C, using the biotinylated cDNA probe. Restriction digest patterns and ribopatterns were compared. Details of DNA typing methods have b...

This study suggests that a simple case definition for national and international neonatal BSI surveillance is provided by a blood culture yielding a recognised pathogen in pure culture, or a mixed growth or skin commensal plus > or =3 predefined clinical signs.

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Background-Management of dyspepsia remains a controversial area. Although the European Helicobacter pylori study group has advised empirical eradication therapy without oesophagogastroduodenoscopy (OGD) in young H pylori positive dyspeptic patients who do not exhibit alarm symptoms, this strategy has not been subjected to clinical trial. Aims-To compare a "test and treat" eradication policy against management by OGD. Patients-Consecutive subjects were prospectively recruited from open access OGD and outpatient referrals. Methods-H pylori status was assessed using the carbon-13 urea breath test. H pylori positive patients were randomised to either empirical eradication or OGD. Symptoms and quality of life scores were assessed at baseline and subsequent reviews over a 12 month period. Results-A total of 104 H pylori positive patients aged under 45 years were recruited. Fifty two were randomised to receive empirical eradication therapy and 52 to OGD. Results were analysed using an intention to treat policy. Dyspepsia scores significantly improved in both groups over 12 months compared with baseline; however, dyspepsia scores were significantly better in the empirical eradication group. Quality of life showed significant improvements in both groups at 12 months; however, physical role functioning was significantly improved in the empirical eradication group. Fourteen (27%) in the empirical eradication group subsequently proceeded to OGD because of no improvement in dyspepsia. Conclusions-This randomised study strongly supports the use of empirical H pylori eradication in patients referred to secondary practice; it is estimated that 73% of OGDs in this group would have been avoided with no detriment to clinical outcome. (Gut 1999;45:186-190)