Comparison of Helicobacter pylori eradication rates between 7 and 14 days of tailored therapy according to clarithromycin resistance test: A randomized, multicenter, non-inferiority study.

BACKGROUND: Recently, a simple tailored therapy based on clarithromycin resistance has been implemented as Helicobacter pylori (H. pylori) eradication therapy. Nonetheless, despite the tailored therapy and frequent adverse events, studies on treatment period are lacking. This study aimed to compare the H. pylori eradication rates of 7-day and 14-day tailored therapy regimens according to clarithromycin resistance. MATERIALS AND METHODS: This multicenter, prospective, randomized, noninferiority trial enrolled H. pylori-positive patients who were randomly assigned to 7-day and 14-day regimen groups, depending on the presence or absence of clarithromycin resistance by 23S rRNA gene point mutations. Standard triple therapy (STT) (20 mg rabeprazole, 1 g amoxicillin, and 500 mg clarithromycin twice daily) or bismuth quadruple therapy (BQT) (20 mg rabeprazole twice daily, 500 mg metronidazole thrice daily, 120 mg bismuth four times daily, and 500 mg tetracycline four times daily) was assigned by clarithromycin resistance. Eradication rates and adverse events were evaluated. RESULTS: A total of 314 and 278 patients were included in the intention-to-treat (ITT) and per-protocol (PP) analyses, respectively; however, 31 patients were lost to follow-up, whereas five patients violated the protocol. Both the 7-day and 14-day regimens showed similar eradication rates in the ITT (7-day vs. 14-day: 78.3% vs. 78.3%, p > 0.99) and PP (87.9% vs. 89.1%, p = 0.851) analyses. Non-inferiority was confirmed (p < 0.025). A subgroup analysis according to clarithromycin resistance (clarithromycin resistance rate: 28.7%) revealed no significant difference in eradication rates between the 7-day and 14-day STT (90.0% vs. 90.1%, p > 0.99) and BQT (82.5% vs. 86.5%, p = 0.757). Furthermore, adverse events did not significantly differ between the two groups. CONCLUSIONS: The 7-day triple and quadruple therapy according to clarithromycin resistance showed similar eradication rates, as compared to the 14-day therapy.

In community-acquired pneumonia, adding oral clarithromycin to standard care increased early clinical response.

SOURCE CITATION: Giamarellos-Bourboulis EJ, Siampanos A, Bolanou A, et al. Clarithromycin for early anti-inflammatory responses in community-acquired pneumonia in Greece (ACCESS): a randomised, double-blind, placebo-controlled trial. Lancet Respir Med. 2024;12:294-304. 38184008.

Evidence of Helicobacter pylori heterogeneity in human stomachs by susceptibility testing and characterization of mutations in drug-resistant isolates.

Heterogeneity of Helicobacter pylori communities contributes to its pathogenicity and diverse clinical outcomes. We conducted drug-susceptibility tests using four antibiotics, clarithromycin (CLR), amoxicillin (AMX), metronidazole and sitafloxacin, to examine H. pylori population diversity. We also analyzed genes associated with resistance to CLR and AMX. We examined multiple isolates from 42 Japanese patients, including 28 patients in whom primary eradication with CLR and AMX had failed, and 14 treatment-naïve patients. We identified some patients with coexistence of drug resistant- and sensitive-isolates (drug-heteroR/S-patients). More than 60% of patients were drug-heteroR/S to all four drugs, indicating extensive heterogeneity. For the four drugs except AMX, the rates of drug-heteroR/S-patients were higher in treatment-naïve patients than in primary eradication-failure patients. In primary eradication-failure patients, isolates multi-resistant to all four drugs existed among other isolates. In primary eradication-failure drug-heteroR/S-patients, CLR- and AMX-resistant isolates were preferentially distributed to the corpus and antrum with different minimum inhibitory concentrations, respectively. We found two mutations in PBP1A, G591K and A480V, and analyzed these in recombinants to directly demonstrate their association with AMX resistance. Assessment of multiple isolates from different stomach regions will improve accurate assessment of H. pylori colonization status in the stomach.

Vonoprazan-based therapies versus PPI-based therapies in patients with H. pylori infection: Systematic review and meta-analyses of randomized controlled trials.

BACKGROUND: This study aims to evaluate the efficacy and safety of vonoprazan-amoxicillin (VA), vonoprazan-amoxicillin-clarithromycin (VAC), vonoprazan-based bismuth-containing quadruple therapy (VBQT), and PPI-based triple (PAC) or quadruple therapy (PBQT) for H. pylori infection with the consideration of duration of therapy and amoxicillin dose (H: high; L: low). MATERIALS AND METHODS: PubMed, Embase, and the Cochrane Central Register of Controlled Trials were searched for eligible randomized controlled trials (RCTs) up to December 15, 2023. The efficacy outcome was eradication rate, and safety outcomes included the rates of adverse events and treatment discontinuation. RESULTS: Twenty-seven RCTs were included. The pooled eradication rates were 82.8% for VA, 89.1% for VAC, and 91.8% for VBQT, which increased with the higher amoxicillin frequency of administration and extended duration of therapy within each regimen. There were no significant differences in eradication rate when comparing 7-VA versus 7-VAC and 14-VA versus 14-VAC. VA was at least comparable to PAC. The eradication rate did not differ significantly between 10-H-VA or 14-H-VA versus 14-PBQT. 7-L-VAC demonstrated higher eradication rate versus 7-PAC and comparable rate to 14-PAC. 14-VBQT showed higher eradication rates versus 14-PBQT. The adverse events rate was 19.3% for VA, 30.6% for VAC, and 38.4% for VBQT. VA had similar risk of adverse events versus VAC and significantly fewer adverse events compared to PBQT. The treatment discontinuation rate did not differ significantly between treatments. CONCLUSIONS: The eradication rate of VBQT was the highest at above 90% followed by VAC and VA. VA was as effective as VAC and superior to PPI-based therapies with favorable safety, highlighting the potential of VA therapy as a promising alternative to traditional PPI-based therapies. VPZ-based triple or quadruple therapies was more effective than PPI-based therapies. Further studies are needed to establish the optimal treatment regimen especially in the western countries.

Triple-drug combination therapy versus six-month proton pump inhibitor monotherapy in non-Helicobacter pylori Helicobacter eradication, and hyperacid environment preference of Helicobacter suis: a clinical study.

BACKGROUND: At present, eradication regimens for non-Helicobacter pylori Helicobacter (NHPH) have not been established yet. We investigated effectiveness of the standard triple-drug combination therapy for Helicobacter pylori eradication and of a proton pump inhibitor (PPI) monotherapy in eradication of NHPH. METHODS: Subjects were the patients who were diagnosed with NHPH-infected gastritis based on microscopic findings, helical-shaped organisms obviously larger than Helicobacter pylori, in the gastric mucosal specimens using Giemsa staining at Kenwakai Hospital between November 2010 and September 2021, whose NHPH species were identified by polymerase chain reaction (PCR) analysis of urease genes in endoscopically-biopsied samples, and who consented to NHPH eradication with either the triple-drug combination therapy for one week or a PPI monotherapy for six months. Six months after the completion of eradication, its result was determined with esophagogastroduodenoscopy, microscopic examination, and PCR analysis. In cases of unsuccessful eradication, a second eradication with the other therapy was suggested to the patient. RESULTS: PCR analysis detected NHPH in 38 patients: 36 as Helicobacter suis and two as Helicobacter heilmannii/Helicobacter ailurogastricus. Fourteen Helicobacter suis-infected and one Helicobacter heilmannii/Helicobacter ailurogastricus-infected patients requested eradication therapy. The triple-drug combination therapy succeeded in four of five patients, while the PPI monotherapy succeeded in five of 10 patients. Three of five patients who had been unsuccessful with the latter therapy requested the triple-drug combination therapy as the second eradication and all three were successful. In total, the triple-drug combination therapy succeeded in seven out of eight (87.5%) attempted cases, while the PPI monotherapy in five out of 10 (50%) attempted cases. CONCLUSIONS: In NHPH eradication, the triple-drug combination therapy was considered to be effective to some extent and to become the first-line therapy. While, although less successful, PPI monotherapy appeared to be a potentially promising option particularly for patients with allergy or resistance to antibiotics. Effectiveness of PPI monotherapy may be attributed to hyperacid environment preference of Helicobacter suis and PPI's acid-suppressive effect. Additionally, male predominance in NHPH-infected gastritis patients may be explained by gender difference in gastric acid secretory capacity. However, further evidence needs to be accumulated. STUDY REGISTRATION: This study was approved by the Research Ethics Committee of Kenwakai Hospital (No. 2,017,024).

A reconstructed genome-scale metabolic model of Helicobacter pylori for predicting putative drug targets in clarithromycin and rifampicin resistance conditions.

BACKGROUND: Helicobacter pylori is considered a true human pathogen for which rising drug resistance constitutes a drastic concern globally. The present study aimed to reconstruct a genome-scale metabolic model (GSMM) to decipher the metabolic capability of H. pylori strains in response to clarithromycin and rifampicin along with identification of novel drug targets. MATERIALS AND METHODS: The iIT341 model of H. pylori was updated based on genome annotation data, and biochemical knowledge from literature and databases. Context-specific models were generated by integrating the transcriptomic data of clarithromycin and rifampicin resistance into the model. Flux balance analysis was employed for identifying essential genes in each strain, which were further prioritized upon being nonhomologs to humans, virulence factor analysis, druggability, and broad-spectrum analysis. Additionally, metabolic differences between sensitive and resistant strains were also investigated based on flux variability analysis and pathway enrichment analysis of transcriptomic data. RESULTS: The reconstructed GSMM was named as HpM485 model. Pathway enrichment and flux variability analyses demonstrated reduced activity in the ribosomal pathway in both clarithromycin- and rifampicin-resistant strains. Also, a significant decrease was detected in the activity of metabolic pathways of clarithromycin-resistant strain. Moreover, 23 and 16 essential genes were exclusively detected in clarithromycin- and rifampicin-resistant strains, respectively. Based on prioritization analysis, cyclopropane fatty acid synthase and phosphoenolpyruvate synthase were identified as putative drug targets in clarithromycin- and rifampicin-resistant strains, respectively. CONCLUSIONS: We present a robust and reliable metabolic model of H. pylori. This model can predict novel drug targets to combat drug resistance and explore the metabolic capability of H. pylori in various conditions.

Continuing Medical Education Questions: April 2024.

Article Title: Effectiveness of Helicobacter pylori treatments according to antibiotic resistance.

Amoxicillin/clavulanate in combination with rifampicin/clarithromycin is bactericidal against Mycobacterium ulcerans.

BACKGROUND: Buruli ulcer (BU) is a skin neglected tropical disease (NTD) caused by Mycobacterium ulcerans. WHO-recommended treatment requires 8-weeks of daily rifampicin (RIF) and clarithromycin (CLA) with wound care. Treatment compliance may be challenging due to socioeconomic determinants. Previous minimum Inhibitory Concentration and checkerboard assays showed that amoxicillin/clavulanate (AMX/CLV) combined with RIF+CLA were synergistic against M. ulcerans. However, in vitro time kill assays (TKA) are a better approach to understand the antimicrobial activity of a drug over time. Colony forming units (CFU) enumeration is the in vitro reference method to measure bacterial load, although this is a time-consuming method due to the slow growth of M. ulcerans. The aim of this study was to assess the in vitro activity of RIF, CLA and AMX/CLV combinations against M. ulcerans clinical isolates by TKA, while comparing four methodologies: CFU enumeration, luminescence by relative light unit (RLU) and optical density (at 600 nm) measurements, and 16S rRNA/IS2404 genes quantification. METHODOLOGY/PRINCIPAL FINDINGS: TKA of RIF, CLA and AMX/CLV alone and in combination were performed against different M. ulcerans clinical isolates. Bacterial loads were quantified with different methodologies after 1, 3, 7, 10, 14, 21 and 28 days of treatment. RIF+AMX/CLV and the triple RIF+CLA+AMX/CLV combinations were bactericidal and more effective in vitro than the currently used RIF+CLA combination to treat BU. All methodologies except IS2404 quantitative PCR provided similar results with a good correlation with CFU enumeration. Measuring luminescence (RLU) was the most cost-effective methodology to quantify M. ulcerans bacterial loads in in vitro TKA. CONCLUSIONS/SIGNIFICANCE: Our study suggests that alternative and faster TKA methodologies can be used in BU research instead of the cumbersome CFU quantification method. These results provide an in vitro microbiological support to of the BLMs4BU clinical trial (NCT05169554, PACTR202209521256638) to shorten BU treatment.

Treatment of Helicobacter pylori with potassium competitive acid blockers: A systematic review and meta-analysis.

BACKGROUND: Helicobacter pylori (H. pylori) infects over half the global population, causing gastrointestinal diseases like dyspepsia, gastritis, duodenitis, peptic ulcers, G-MALT lymphoma, and gastric adenocarcinoma. Eradicating H. pylori is crucial for treating and preventing these conditions. While conventional proton pump inhibitor (PPI)-based triple therapy is effective, there's growing interest in longer acid suppression therapies. Potassium competitive acid blocker (P-CAB) triple and dual therapy are new regimens for H. pylori eradication. Initially used in Asian populations, vonoprazan (VPZ) has been recently Food and Drug Administration-approved for H. pylori eradication. AIM: To assess the efficacy of regimens containing P-CABs in eradicating H. pylori infection. METHODS: This study, following PRISMA 2020 guidelines, conducted a systematic review and meta-analysis by searching MEDLINE and Scopus libraries for randomized clinical trials (RCTs) or observational studies with the following command: [("Helicobacter pylori" OR "H pylori") AND ("Treatment" OR "Therapy" OR "Eradication") AND ("Vonaprazan" OR "Potassium-Competitive Acid Blocker" OR "P-CAB" OR "PCAB" OR "Revaprazan" OR "Linaprazan" OR "Soraprazan" OR "Tegoprazan")]. Studies comparing the efficacy of P-CABs-based treatment to classical PPIs in eradicating H. pylori were included. Exclusion criteria included case reports, case series, unpublished trials, or conference abstracts. Data variables encompassed age, diagnosis method, sample sizes, study duration, intervention and control, and H. pylori eradication method were gathered by two independent reviewers. Meta-analysis was performed in R software, and forest plots were generated. RESULTS: A total of 256 references were initially retrieved through the search command. Ultimately, fifteen studies (7 RCTs, 7 retrospective observational studies, and 1 comparative unique study) were included, comparing P-CAB triple therapy to PPI triple therapy. The intention-to-treat analysis involved 8049 patients, with 4471 in the P-CAB intervention group and 3578 in the PPI control group across these studies. The analysis revealed a significant difference in H. pylori eradication between VPZ triple therapy and PPI triple therapy in both RCTs and observational studies [risk ratio (RR) = 1.17, 95% confidence interval (CI): 1.11-1.22, P < 0.0001] and (RR = 1.13, 95%CI: 1.09-1.17, P < 0.0001], respectively. However, no significant difference was found between tegoprazan (TPZ) triple therapy and PPI triple therapy in both RCTs and observational studies (RR = 1.04, 95%CI: 0.93-1.16, P = 0.5) and (RR = 1.03, 95%CI: 0.97-1.10, P = 0.3), respectively. CONCLUSION: VPZ-based triple therapy outperformed conventional PPI-based triple therapy in eradicating H. pylori, positioning it as a highly effective first-line regimen. Additionally, TPZ-based triple therapy was non-inferior to classical PPI triple therapy.

Refractoriness to anti-Helicobacter pylori treatment attributed to phenotypic resistance patterns in patients with gastroduodenopathy in Guayaquil-Ecuador.

BACKGROUND: Treatment of Helicobacter pylori gastric infection is complex and associated with increased rates of therapeutic failure. This research aimed to characterize the H. pylori infection status, strain resistance to antimicrobial agents, and the predominant lesion pattern in the gastroduodenal mucosa of patients with clinical suspicion of refractoriness to first- and second-line treatment who were diagnosed and treated in a health center in Guayaquil, Ecuador. METHODS: A total of 374 patients with upper gastrointestinal symptoms and H. pylori infection were preselected and prescribed one of three triple therapy regimens for primary infection, as judged by the treating physician. Subsequently, 121 patients who returned to the follow-up visit with persistent symptoms after treatment were studied. RESULTS: All patients had H. pylori infection. Histopathological examination diagnosed chronic active gastritis in 91.7% of cases; premalignant lesions were observed in 15.8%. The three triple therapy schemes applied showed suboptimal efficacy (between 47.6% and 77.2%), with the best performance corresponding to the scheme consisting of a proton pump inhibitor + amoxicillin + levofloxacin. Bacterial strains showed very high phenotypic resistance to all five antimicrobials tested: clarithromycin, 82.9%; metronidazole, 69.7%; amoxicillin and levofloxacin, almost 50%; tetracycline, 38.2%. Concurrent resistance to clarithromycin-amoxicillin was 43.4%, to tetracycline-metronidazole 30.3%, to amoxicillin-levofloxacin 27.6%, and to clarithromycin-metronidazole 59.2%. CONCLUSIONS: In vitro testing revealed resistance to all five antibiotics, indicating that H. pylori exhibited resistance phenotypes to these antibiotics. Consequently, the effectiveness of triple treatments may be compromised, and further studies are needed to assess refractoriness in quadruple and concomitant therapies.

Effects of four antibiotics on the photosynthetic light reactions in the green alga Chlorella pyrenoidosa.

Antibiotics are ubiquitously present in aquatic environments, posing a serious ecological risk to aquatic ecosystems. However, the effects of antibiotics on the photosynthetic light reactions of freshwater algae and the underlying mechanisms are relatively less understood. In this study, the effects of 4 representative antibiotics (clarithromycin, enrofloxacin, tetracycline, and sulfamethazine) on a freshwater alga (Chlorella pyrenoidosa) and the associated mechanisms, primarily focusing on key regulators of the photosynthetic light reactions, were evaluated. Algae were exposed to different concentrations of clarithromycin (0.0-0.3 mg/L), enrofloxacin (0.0-30.0 mg/L), tetracycline (0.0-10.0 mg/L), and sulfamethazine (0.0-50.0 mg/L) for 7 days. The results showed that the 4 antibiotics inhibited the growth, the photosynthetic pigment contents, and the activity of antioxidant enzymes. In addition, exposure to clarithromycin caused a 118.4 % increase in malondialdehyde (MDA) levels at 0.3 mg/L. Furthermore, the transcripts of genes for the adenosine triphosphate (ATP) - dependent chloroplast proteases (ftsH and clpP), genes in photosystem II (psbA, psbB, and psbC), genes related to ATP synthase (atpA, atpB, and atpH), and petA (related to cytochrome b6/f complex) were altered by clarithromycin. This study contributes to a better understanding of the risk of antibiotics on primary producers in aquatic environment.

Pharmacokinetic Interactions Between Tegoprazan and the Combination of Clarithromycin, Amoxicillin and Bismuth in Healthy Chinese Subjects: An Open-Label, Single-Center, Multiple-Dosage, Self-Controlled, Phase I Trial.

BACKGROUND: Tegoprazan is a potassium-competitive acid blocker that inhibits gastric acid and which may be used for eradicating Helicobacter pylori. This study focuses on the pharmacokinetic interaction and safety between tegoprazan and the combination of clarithromycin, amoxicillin and bismuth in healthy Chinese subjects. METHODS: An open-label, three-period, single-center, multiple-dosage, single-sequence, phase I trial was conducted in 22 healthy subjects. In period 1, the subjects took tegoprazan 50 mg twice daily for 7 days, and in period 2 they were administered clarithromycin 500 mg, amoxicillin 1000 mg and bismuth potassium citrate 600 mg twice daily for 7 days (days 14-20). Tegoprazan, clarithromycin, amoxicillin and bismuth potassium citrate were then administered in combination for 7 days (days 21-27) in period 3. Blood samples were collected up to 12 h after the last dose of each period. Safety assessments were performed in each period. RESULTS: The geometric mean ratios (GMRs) [90% confidence interval (CI)] of maximum plasma concentration at steady state (Cmax,ss) and area under the plasma concentration-time curve over the dosing interval (AUCτ) at steady state were 195.93% (175.52-218.71%) and 287.54% (263.28-314.04%) for tegoprazan and 423.23% (382.57-468.22%) and 385.61% (354.62-419.30%) for tegoprazan metabolite M1, respectively. The GMRs (90% CI) of Cmax,ss and AUCτ were 83.69% (77.44-90.45%) and 110.30% (102.74-118.41%) for clarithromycin, 126.25% (114.73-138.93%) and 146.94% (135.33-159.55%) for 14-hydroxyclarithromycin, 75.89% (69.73-82.60%) and 94.34% (87.94-101.20%) for amoxicillin, and 158.43% (125.43-200.11%) and 183.63% (156.42-215.58%) for bismuth, respectively. All reported adverse events were mild. The frequency of adverse events during the coadministration stage was not higher than that during the single- or triple-drug administration stages. CONCLUSION: The plasma exposure of tegoprazan, M1, 14-hydroxyclarithromycin and bismuth was increased after the coadministration of tegoprazan, clarithromycin, amoxicillin and bismuth. The coadministration exhibited favorable safety and tolerability. CLINICAL TRIALS REGISTRATION: CTR20230643.

14-day tailored PCR-guided triple therapy versus 14-day non-Bismuth concomitant quadruple therapy for Helicobacter pylori eradication: A multicenter, open-label randomized noninferiority controlled trial.

BACKGROUND: The systematic use of susceptibility testing and tailored first-line treatment for Helicobacter pylori eradication has yet to be established. AIM: To compare 14-day tailored PCR-guided triple therapy to 14-day non-Bismuth concomitant quadruple therapy for first-line Helicobacter pylori eradication. PATIENTS AND METHODS: We performed a multicenter, parallel-group, randomized noninferiority controlled trial. Naive adult patients with Helicobacter pylori infection were treated with 14-day tailored PCR-guided triple therapy (esomeprazole 40 mg and amoxicillin 1000 mg b.d. plus clarithromycin 500 mg or levofloxacin 500 mg b.d. according to clarithromycin susceptibility) or 14-day non-Bismuth concomitant quadruple therapy (esomeprazole 40 mg, amoxicillin 1000 mg, clarithromycin 500 mg, and metronidazole 500 mg b.d.). The primary endpoint was H. pylori eradication. RESULTS: We screened 991 patients for eligibility and randomized 241 patients. The first-line eradication rate was 99.2% in the tailored PCR-guided group and 95.9% in the control group (ITT population; absolute difference of +3.30%, with a lower bound of CI at -0.68%). Both first-line therapies were well tolerated, with a formally significant difference in favor of the tailored PCR-guided group (61.4% vs. 41.2%, p = 0.003). Economic analyses revealed a lower cost of the tailored PCR-guided arm, with a 92% chance of being jointly more effective and less expensive than the control arm in the ITT population. CONCLUSION: In a country with a high level of clarithromycin resistance, the results of our study demonstrated the noninferiority of 14-day tailored PCR-guided triple therapy as a first-line H. pylori eradication therapy compared to 14-day non-Bismuth quadruple therapy (ClinicalTrials.gov NCT02576236).

Biofilm prevention concentration of clarithromycin against clinically relevant species of nontuberculous mycobacteria.

OBJECTIVE: Mycobacterium avium complex (MAC) and Mycobacterium abscessus are a group of nontuberculous mycobacteria (NTM) that have been described as human pathogens. Their ability to develop biofilms in tissues and medical devices is one of the most important pathogenicity factors, with important implications in diagnosis and treatment. Macrolides are usually considered one of the bases of this treatment. METHODS: Here we have studied the biofilm prevention concentration (BPC) of 16 strains (n=16) with clarithromycin to avoid the biofilm development by these NTM. RESULTS: In this study, all M. abscessus strains have similar BPC, while MAC strains showed different values. For MAC the concentrations ranged between 1-16 mg/L, while for M. abscessus the concentration was 32 mg/L for all strains except one that was 64 mg/L. CONCLUSIONS: These results open the possibility of using macrolides for the prevention of biofilm development in patients with a risk of developing NTM disease.

Effects of clarithromycin exposure on the growth of Microcystis aeruginosa and the production of algal dissolved organic matter.

Antibiotics are commonly found in the aquatic environment, which can affect microbial community compositions and activities, and even have potential adverse impacts on human and ecosystem health. The current understanding of the effects of antibiotics on microalgae growth and algal dissolved organic matter (DOM) remains indistinct. To understand the toxic effects of antibiotics on the microalgae, Microcystis aeruginosa was exposed to clarithromycin (CLA) in this study. Cell density determination, chlorophyll content determination, and organic spectrum analysis were conducted to show the effect of CLA exposure on the growth, photosynthetic activity, and organic metabolic processes of Microcystis aeruginosa. The findings revealed that the physiological status of algae could be significantly influenced by CLA exposure in aquatic environments. Specifically, exposure to 1 µg/L CLA stimulated the growth and photosynthetic activity of algal cells. Conversely, CLA above 10 µg/L led to the inhibition of algal cell growth and photosynthesis. Notably, the inhibitory effects intensified with the increasing concentration of CLA. The molecular weight of DOM produced by Microcystis aeruginosa increased when exposed to CLA. Under the exposure of 60 µg/L CLA, a large number of algal cells ruptured and died, and the intracellular organic matter was released into the algal liquid. This resulted in an increase in high molecular weight substances and soluble microbial-like products in the DOM. Exposure to 1 and 10 µg/L CLA stimulated Microcystis aeruginosa to produce more humic acid-like substances, which may be a defense mechanism against CLA. The results were useful for assessing the effects of antibiotic pollution on the stability of the microalgae population and endogenous DOM characteristics in aquatic ecosystems.

Successful management of Mycobacterium abscessus pneumonia in a 53-day-old immunocompetent infant.

Pulmonary infection due to Mycobacterium abscessus complex (MABC) usually occurs in children with underlying risk factors including cystic fibrosis (CF), chronic lung disease, and immunocompromised status, but rarely in immunocompetent children without underlying lung disease, especially in infants. We present a case of MABC pulmonary disease (MABC-PD) in an otherwise healthy 53-day-old male infant with one week of cough and respiratory distress. Computed tomography showed multiple masses across both lungs. Isolated mycobacteria from his bronchoalveolar lavage fluid were identified as MABC. We describe our complete evaluation, including immunodeficiency evaluation incorporating whole exome sequencing and our therapeutic process given complicated susceptibility pattern of the M. abscessus isolate, and review literature for MABC-PD in immunocompetent children. The infant was successfully treated through prolonged treatment with parenteral Amikacin, Cefoxitin, Linezolid, and Clarithromycin, combined with inhaled Amikacin.

Genetic basis of clarithromycin resistance in Bacillus anthracis.

The high-consequence pathogen Bacillus anthracis causes human anthrax and often results in lethal infections without the rapid administration of effective antimicrobial treatment. Antimicrobial resistance profiling is therefore critical to inform post-exposure prophylaxis and treatment decisions, especially during emergencies such as outbreaks or where intentional release is suspected. Whole-genome sequencing using a rapid long-read sequencer can uncover antimicrobial resistance patterns if genetic markers of resistance are known. To identify genomic markers associated with antimicrobial resistance, we isolated B. anthracis derived from the avirulent Sterne strain with elevated minimal inhibitory concentrations to clarithromycin. Mutants were characterized both phenotypically through broth microdilution susceptibility testing and observations during culturing, as well as genotypically with whole-genome sequencing. We identified two different in-frame insertions in the L22 ribosomal protein-encoding gene rplV, which were subsequently confirmed to be involved in clarithromycin resistance through the reversion of the mutant gene to the parent (drug-susceptible) sequence. Detection of the rplV insertions was possible with rapid long-read sequencing, with a time-to-answer within 3 h. The mutations associated with clarithromycin resistance described here will be used in conjunction with known genetic markers of resistance for other antimicrobials to strengthen the prediction of antimicrobial resistance in B. anthracis.IMPORTANCEThe disease anthrax, caused by the pathogen Bacillus anthracis, is extremely deadly if not treated quickly and appropriately. Clarithromycin is an antibiotic recommended for the treatment and post-exposure prophylaxis of anthrax by the Centers for Disease Control and Prevention; however, little is known about the ability of B. anthracis to develop resistance to clarithromycin or the mechanism of that resistance. The characterization of clarithromycin-resistant isolates presented here provides valuable information for researchers and clinicians in the event of a release of the resistant strain. Additionally, knowledge of the genetic basis of resistance provides a foundation for susceptibility prediction through rapid genome sequencing to inform timely treatment decisions.

Minimum inhibitory concentrations of azithromycin in clinical isolates of Mycobacterium avium complex in Japan.

The latest guidelines include azithromycin as a preferred regimen for treating Mycobacterium avium complex (MAC) pulmonary disease. However, serially collected susceptibility data on clinical MAC isolates are limited, and no breakpoints have been determined. We investigated the minimum inhibitory concentrations (MICs) of azithromycin and clarithromycin for all MAC strains isolated in 2021 from a single center in Japan, excluding duplicates. The MICs were determined using a panel based on the microbroth dilution method, according to the latest Clinical and Laboratory Standards Institute recommendations. The MICs were determined for 318 MAC strains. Although there was a significant positive correlation between the MICs of azithromycin and clarithromycin, the MICs of azithromycin tended to be higher than those of clarithromycin. Among the cases in which the strains were isolated, 18 patients initiated treatment, including azithromycin treatment, after sample collection. Some patients infected with stains with relatively high azithromycin MICs achieved a microbiological cure with azithromycin-containing regimens. This study revealed a higher MIC distribution for azithromycin than clarithromycin, raising questions about the current practice of estimating azithromycin susceptibility based on the clarithromycin susceptibility test result. However, this was a single-center study that included only a limited number of cases treated with azithromycin. Therefore, further multicenter studies that include a greater number of cases treated with azithromycin are warranted to verify the distribution of azithromycin MICs and examine the correlation between azithromycin MICs and treatment effectiveness.IMPORTANCEThe macrolides serve as key drugs in the treatment of pulmonary Mycobacterium avium complex infection, and the administration of macrolide should be guided by susceptibility test results. Azithromycin is recommended as a preferred choice among macrolides, surpassing clarithromycin; however, drug susceptibility testing is often not conducted, and clarithromycin susceptibility is used as a surrogate. This study represents the first investigation into the minimum inhibitory concentration of azithromycin on a scale of several hundred clinical isolates, revealing an overall tendency for higher minimum inhibitory concentrations compared with clarithromycin. The results raise questions about the appropriateness of using clarithromycin susceptibility test outcomes for determining the administration of azithromycin. This study highlights the need for future discussions on the clinical breakpoints of azithromycin, based on large-scale clinical research correlating azithromycin susceptibility with treatment outcomes.

Fourteen-day vonoprazan-based bismuth quadruple therapy for H. pylori eradication in an area with high clarithromycin and levofloxacin resistance: a prospective randomized study (VQ-HP trial).

Potassium-competitive acid blockers (P-CABs) provide potent acid inhibition, yet studies on P-CAB-based quadruple therapy for H. pylori eradication are limited. We theorized that integrating bismuth subsalicylate into a quadruple therapy regimen could enhance eradication rates. However, data on the efficacy of vonoprazan bismuth quadruple therapy are notably scarce. Therefore, the aim of this study was to evaluate the efficacy of vonoprazan-based bismuth quadruple therapy in areas with high clarithromycin and levofloxacin resistance. This was a prospective, single-center, randomized trial conducted to compare the efficacy of 7-day and 14-day vonoprazan-based bismuth quadruple therapy for H. pylori eradication between June 1, 2021, and March 31, 2022. Qualified patients were randomly assigned to the 7-day or 14-day regimen (1:1 ratio by computer-generated randomized list as follows: 51 patients for the 7-day regimen and 50 patients for the 14-day regimen). The regimens consisted of vonoprazan (20 mg) twice daily, bismuth subsalicylate (1024 mg) twice daily, metronidazole (400 mg) three times daily, and tetracycline (500 mg) four times daily. CYP3A4/5 genotyping and antibiotic susceptibility tests were also performed. Successful eradication was defined as 13negative C-UBTs 4 weeks after treatment. The primary endpoint was to compare the efficacy of 7-day and 14-day regimens as first-line treatments, which were assessed by intention-to-treat (ITT) and per-protocol (PP) analyses. The secondary endpoints included adverse effects. A total of 337 dyspeptic patients who underwent gastroscopy were included; 105 patients (31.1%) were diagnosed with H. pylori infection, and 101 patients were randomly assigned to each regimen. No dropouts were detected. The antibiotic resistance rate was 33.3% for clarithromycin, 29.4% for metronidazole, and 27.7% for levofloxacin. The CYP3A4 genotype was associated with 100% rapid metabolism. The H. pylori eradication rates for the 7-day and 14-day regimens were 84.4%, 95% CI 74.3-94.2 and 94%, 95% CI 87.4-100, respectively (RR difference 0.25, 95% CI 0.03-0.53, p value = 0.11). Interestingly, the 14-day regimen led to 100% eradication in the clarithromycin-resistant group. Among the patients in the 7-day regimen group, only two exhibited resistance to clarithromycin; unfortunately, neither of them achieved a cure from H. pylori infection. The incidence of adverse events was similar in both treatment groups, occurring in 29.4% (15/51) and 28% (14/50) of patients in the 7-day and 14-day regimens, respectively. No serious adverse reactions were reported. In conclusion, 14 days of vonoprazan-based bismuth quadruple therapy is highly effective for H. pylori eradication in areas with high levels of dual clarithromycin and levofloxacin resistance.

Study on Drug Resistance to Treatment for Ureaplasma Urealyticum Infections in the Female Genital Tract.

BACKGROUND: Ureaplasma urealyticum (U. urealyticum) commonly occurs in female genitourinary infections, and its different biovars and serotypes have varying degrees of resistance to different antibiotics. This study aimed to ex-plore the characteristics of U. urealyticum infection and drug-resistant profiles in Chinese females. METHODS: We included 1,045 females with genital tract infections who visited Tangshan Workers' Hospital and Tangshan Maternal and Child Health Center from September 2017 to December 2018. The bacteria were selectively cultured, and drug sensitivity experiments were conducted. Eight pairs of oligonucleotide primers were designed, and polymerase chain reaction (PCR) was performed to amplify specific DNA fragments to perform bacterial strain typing. RESULTS: Among the 1,045 participants included, 566 (54.11%) participants were positive for mycoplasma infection. There were 432 (41.34%) participants with U. urealyticum infection, accounting for 76.33% of the positive participants. The infection rate of U. urealyticum was the highest in females who were 21 - 30 years old, followed by those who were 31 - 40 years old. Ureaplasma urealyticum showed the highest sensitivity to tetracyclines and the greatest resistance to quinolones. The biovar 1 of U. urealyticum with the highest detection rate of serotype 4, accounted for 66.88%. The biovar 2 of U. urealyticum mainly showed mixed subtypes 2 and 3. Biovar 2 showed higher resistance to sparfloxacin, clarithromycin, josamycin, and doxycycline than biovar 1. CONCLUSIONS: Women might be more susceptible to U. urealyticum, especially if they are of childbearing age. Urea-plasma urealyticum is mainly caused by a single serotype 6 infection. The resistance of U. urealyticum to quinolone (e.g., norfloxacin) is a great concern. Sparfloxacin, clarithromycin, ciprofloxacin, and doxycycline might be more suitable for people with biovar 1 infection. Biotyping may facilitate clinical drug use and help avoid the emergence of drug-resistant strains.