High prevalence of Helicobacter pylori clarithromycin resistance mutations among Seattle patients measured by droplet digital PCR.

BACKGROUND: Treatment of Helicobacter pylori infection is often empiric; however, current guidelines for management of Helicobacter pylori infection advise against the use of standard triple therapy (clarithromycin, amoxicillin, and proton-pump inhibitor) when clarithromycin resistance exceeds 20%. We developed and tested a new culture-free assay to detect clarithromycin resistance-conferring mutations to determine the prevalence of H. pylori clarithromycin resistance in patients from the United States Pacific Northwest. MATERIALS AND METHODS: Droplet digital PCR (ddPCR) was used to detect the H. pylori 23S rRNA gene, and resistance-conferring mutations, in archived, formalin-fixed, paraffin-embedded (FFPE) gastric tissue and to retrospectively determine the prevalence of clarithromycin-resistant H. pylori among 110 patients at an academic medical center in the Northwest United States between 2012 and 2014. RESULTS: Of 102 patients with the H. pylori 23S rRNA gene detected by the ddPCR assay, 45 (44%) had clarithromycin resistance mutations. Thirty-three of the 45 patients with clarithromycin resistance mutations had a mix of wild-type and resistance alleles. Prevalence of clarithromycin resistance mutations differed among racial groups and was highest among Asians, with mutations detected in 14 (67%) of the 21 patient samples. CONCLUSIONS: The prevalence of clarithromycin resistance detected in this region exceeds 20%, indicating that standard triple therapy should not be the first-line antibiotic treatment for H. pylori infection. Culture-free assays for detecting clarithromycin resistance mutations can be performed on archived tissue samples and will aid in informing tailored treatment for effective H. pylori eradication.

Prospective assessment of consensus criteria for evaluation of patients with suspected choledocholithiasis.

BACKGROUND AND AIM: American Society for Gastrointestinal Endoscopy (ASGE) guidelines have proposed criteria to stratify patients into low, intermediate and high risk of choledocholithiasis. The criteria include variables that are readily available in clinical practice. The objective of the present study was to prospectively assess the accuracy of these criteria. METHODS: A prospective observational cohort study was conducted at Beth Israel Deaconess Medical Center. All adult patients referred for endoscopic retrograde cholangiopancreatography (ERCP) with suspected choledocholithiasis were considered for inclusion. ASGE criteria were applied, and each patient was categorized as high, intermediate or low risk for choledocholithiasis. Presence of stone at ERCP served as criteria standard. RESULTS: During the study period, 402 patients met study inclusion criteria and 336 were reported in the final analysis. Of the 244 patients in the high risk for choledocholithiasis group, 185 were found to have stones at ERCP (75.8%, 95% CI 70.2-80.1%). Of the 92 patients in the intermediate risk for choledocholithiasis group, 45 had stones at ERCP (48.9%, 95% CI 38.8-59.1%); P-value for difference between groups = 0.001. Diagnostic accuracy for choledocholithiasis in the high-risk group was 69.05%, and for the intermediate group was 39.95%. Presence of choledocholithiasis on pre-ERCP imaging (OR: 3.6; 95% CI 2.2-6.0; P < 0.01), and bilirubin >1.8 but <4 mg/dL (OR: 1.69; 95% CI 1.0-2.8; P < 0.04) were the strongest predictors of choledocholithiasis. No additional variable that improved accuracy of ASGE criteria was identified. CONCLUSION: ASGE criteria stratify patients by risk for choledocholithiasis and can be used in routine clinical practice.

The global regulator Ler is necessary for enteropathogenic Escherichia coli colonization of Caenorhabditis elegans.

Enteropathogenic Escherichia coli (EPEC) is an important cause of infant diarrhea in developing countries and is useful for general investigations of the bacterial infection process. However, the study of the molecular pathogenesis of EPEC has been hampered by the lack of genetically tractable, convenient animal models. We have therefore developed the use of the nematode Caenorhabditis elegans as a small animal model of infection for this diarrheal pathogen. We found that nematodes died faster on nematode growth medium in the presence of EPEC pathogens than in the presence of the laboratory control strain MG1655. Increased numbers of pathogens in the gut, determined by standard plate count assays and fluorescence microscopy using green fluorescent protein-expressing bacteria, correlated with killing. Deletion of the gene encoding the global regulator Ler severely reduced the ability of EPEC to colonize the nematode gut and could be complemented by providing the ler gene on a multicopy plasmid in trans. Neither the type III secretion system nor the type IV bundle-forming pilus was required for colonization. Combined, the similarities and distinct differences between EPEC infection of nematodes and that of humans offer a unique opportunity to study several stages of the infection process, namely, attachment, colonization, and persistence, in a genetically tractable, inexpensive, and convenient in vivo system.