National and Regional United States Antibiotic Resistance to Helicobacter pylori Resistance to Helicobacter pylori. Lessons from a Clinical Trial.

Corresponding author: David Y. Graham, M.D., Michael E. DeBakey Veterans Affairs Medical Center, RM 3A-318B (111D), 2002 Holcombe Boulevard, Houston, TX 77030 USA, Phone: 713-795-0232, FAX: 713-795-4471, dgraham@bcm.edu. Dr Hulten: study concept and design; acquisition of data; analysis and interpretation of data; drafting of the manuscript; critical revision of the manuscript for important intellectual content; statistical analysis; Dr Kalfus: study concept and design; acquisition of data; analysis and interpretation of data; drafting of the manuscript; critical revision of the manuscript for important intellectual content; statistical analysis; Dr. Graham: study concept and design; acquisition of data; analysis and interpretation of data; drafting of the manuscript; critical revision of the manuscript for important intellectual content; statistical analysis; Ms. Lamberth: technical material support, analysis and interpretation of data


Introduction
Although antimicrobial resistance to H. pylori has increased globally, resistance patterns have been shown to differ in relation to sex, age, ethnicity, life style habits, socioeconomic status, geographical distribution and particularly with national antibiotic consumption rates 1 . H. pylori is not yet included local, regional, and national susceptibility data. A 2015 study from the Houston VA Medical Center reported an increase of clarithromycin resistance among H. pylori from 9.1% in 2009-2010 to 24.2% in 2011-2013; 20.3% of the isolates were resistant to metronidazole. H. pylori resistance to tetracycline, amoxicillin, and rifabutin have remained historically low to absent in the US.
Here we report antimicrobial susceptibility from a randomized, double blind placebocontrolled U.S H. pylori eradication study conducted from 2017-2018 from clinical study sites across 20 states. The clinical results have previously been reported 2 . These data represent the largest survey of H. pylori antimicrobial susceptibility in more than 15 years.

Ethical Practices
The study protocol and all amendments were approved by the respective institutional review boards of participating institutions. All patients provided written informed consent before participating in the study.

Results
A total of 455 patients were enrolled in a double-blinded phase 3 clinical study which evaluated fixed dose triple therapy combination of amoxicillin-rifabutin-omeprazole vs. a fixed dose dual therapy comparator (amoxicillin -omeprazole). MICs were obtained for 345 clinical isolates recovered from treatment-naïve patients at 51 centers (20 states) across the US, representing 76% of the total number of patients enrolled in the study. The most common reason for failure of culture was improper storage or shipment of specimens. Additionally, a few isolates grew poorly on the Mueller-Hinton agar used for MIC determination, such that a reliable result could not be obtained.

Patients Demographics.
One hundred and thirty-one of 345 (38%) were male and the mean age of all patients was 46.4 ± 13 years (range 18-70 years). The majority of patients (263, 76.2%) were white, 71 (20.6%) were Black, and 11 (3.2%) were of other backgrounds (Asians were excluded from participation); overall, 208 (60.3%) identified as Hispanic. Enrollment was unevenly distributed across the different states.
In order to better describe the data from a geographic perspective, the US was divided into 3 regions East, Central and West to allow visualization and comparison across regions (Table  1). Clarithromycin resistance ranged from 11.1% in the Western US to 23.2% in the Eastern states (p=0.03). Metronidazole resistance was high in all regions ranging from 35.5%-49.7%. Amoxicillin resistance ranged from 5.3% to 8.3%. Because of the smaller numbers tested for resistance to levofloxacin or tetracycline it was not possible to detect whether there were significant regional differences.

Discussion
Overall, we found that the proportion of US isolates with resistance to clarithromycin (17.6%) metronidazole (43.6%), and levofloxacin (57.8%) were higher compared to previous reports. As noted above, this study showed high rates of metronidazole resistance across all regions. No isolate was resistant to rifabutin. Amoxicillin and tetracycline resistance were both observed albeit at low rates (amoxicillin resistance 6.4% and tetracycline resistance 2.8%).
In both treatment arms of the prior study amoxicillin resistance had a small but measurable effect on treatment outcome 2 . In contrast, resistance to clarithromycin, metronidazole, or levofloxacin is highly correlated with treatment failure when they are used in triple therapies. There was also a poor correlation between outcome (cure or failure) with individual isolates and the measured MIC resistance breakpoint for amoxicillin with the dual high dose PPI and amoxicillin treatment arm. Interpretation of the effect of amoxicillin resistance on outcome in the dual therapy are were further complicated by the fact that the cure rate with the dual therapy was low (i.e., 57.7%) which was however consistent with prior US studies of similar therapy [3][4][5] . Clarithromycin resistance differed significantly across the regions (P=0.03) with the greatest resistance observed in the East. Metronidazole resistance was high in all regions.
These results are consistent with the global increase in antimicrobial resistance and underscores the most recent H. pylori guidelines to no longer prescribe clarithromycin, metronidazole, or levofloxacin-containing triple therapies 6,7 . The general unavailability of readily accessible H. pylori culture and susceptibility testing requires treating physicians pay close attention to the results of testing for cure to alert them when therapies become ineffective 8 . The recently introduced rifabutin triple therapy (Talicia®) and bismuth quadruple therapy are the only currently available regimens in the U.S. for which H. pylori resistance is rare. The commercially available bismuth formulation, Pylera® is often inconvenient to prescribe as it is packaged for 10 day therapy whereas treatment guidelines recommend 14 day therapy for optimal effectiveness 8 . Local antimicrobial resistance rates are needed to allow for clinicians to reliably and successfully eradicate H. pylori infections. Hulten  Gastroenterology. Author manuscript; available in PMC 2021 July 09.