Comparison of disc diffusion and epsilometer (E-test) testing techniques to determine antimicrobial susceptibiliy of Campylobacter isolates of food and human clinical origin

In vitro anti-bactrical activity and its preliminary mechanism of action of the non-medicinal parts of Sanguisorba officinalis L. against Helicobacter pylori infection

ETHNOPHARMACOLOGICAL RELEVANCE

Sanguisorba officinalis L. (S. officinalis L.), known as Di Yu (DY) in Traditional Chinese Medicine (TCM), are used to treat burns, vomiting of blood, asthma, intestinal infections, and dermatitis. It has been reported that the root of DY has a significant inhibitory effect on Helicobacter pylori (H. pylori). However, there is currently little research on the composition analysis and anti-H. pylori infection properties of the non-medicinal parts of DY, such as its stems, leaves, and flowers.

AIM OF STUDY

The commonly used eradication therapies for H. pylori infection are antibiotic-based therapies. With the increasing antibiotic resistance of H. pylori, it is urgent to find effective alternative therapies. To find alternative therapies and increase the utilization of DY, this study aims to investigate the phytochemistry profile, in vitro anti-H. pylori activity, and preliminary antibacterial mechanism of the non-medicinal parts of DY.

MATERIALS AND METHODS

The non-medicinal parts of DY extracts were obtained by using hot water reflux method. The chemical composition of these extracts was analyzed using colorimetric method, high-performance liquid chromatography (HPLC), and ultra-high-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS). The in vitro anti-H. pylori activity was investigated using broth microdilution method, checkerboard dilution method, time-kill curve, time-inhibition curve, scanning electron microscopy, and transmission electron microscopy. Transcriptional sequencing technology was used to study the effect of DY stems and flowers on the gene expression of H. pylori and explore possible antibacterial mechanisms.

RESULTS

The non-medicinal parts of DY contain abundant phytochemicals, such as total phenols and total flavonoids, and possess strong inhibitory and bactericidal activity against both standard and clinical strains of H. pylori in vitro. The MIC was 80-1280 μg/mL and the MBC was 80-2560 μg/mL, and the strength of the antibacterial effects was dependent on the concentration of phytochemicals (total polyphenols, gallic acid and ellagic acid). In addition, the combination of non-medicinal parts of DY with antibiotics, such as amoxicillin, metronidazole, levofloxacin, and clarithromycin, did not result in any antagonistic effects. All of them could disrupt the morphology, internal microscopic and cell wall structures of H. pylori thereby acting as an inhibitor. The mechanism of action was found to be the disruption of H. pylori morphology, internal microstructure, and cell wall. Transcriptomic analysis showed that the non-medicinal parts of DY significantly regulated the gene expression of H. pylori, especially the metabolic pathway.

CONCLUSIONS

This study analyzed the chemical composition of the non-medicinal parts of DY and confirmed its inhibitory and bactericidal activities against H. pylori, both standard and clinical strains. Additional, the mechanism of inhibition involves disrupting the structure of H. pylori cells, altering gene expression, and interfering with bacterial metabolic pathways. This study provides a reference for further resource utilization and the development of H. pylori drugs using the non-medicinal parts of DY.

Comparison of disk diffusion and broth microdilution methods for antimicrobial susceptibility testing of Campylobacter isolates of meat origin

The aim of this study was to compare the disk diffusion (DD) and the broth microdilution (BMD) methods in determining the antimicrobial susceptibility of 36 Campylobacter isolates of meat-origin to six antibacterial drugs (erythromycin, ciprofloxacin, tetracycline, streptomycin, gentamicin and nalidixic acid). All the available zone diameter and minimum inhibitory concentration (MIC) breakpoints of C. jejuni and C. coli as recommended by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) were utilized. In addition, the zone diameter breakpoints of Enterobacterales for nalidixic acid, gentamicin, and streptomycin, as recommended by the Clinical and Laboratory Standards Institute (CLSI), were applied. All Campylobacter isolates were categorised as susceptible to erythromycin and gentamicin by both methods indicating completely concordant classification results. The overall highest 'Very major error' (VME) and 'Major error' (ME) rates were detected for nalidixic acid (13.3%) and tetracycline (26.3%), respectively, whereas a 'Minor error' (mE) rate was detected only for ciprofloxacin (60.1%). However, the Cohen's kappa statistic indicated a substantial concordance between the DD and BMD classification results for tetracycline and streptomycin, and almost perfect agreement for nalidixic acid, with corresponding categorical agreement rates of over 86% and approximately up to 92%. The correlation between the complementary inhibition zones and MIC breakpoints was strong and statistically highly significant (p < 0.001) for ciprofloxacin, tetracycline, streptomycin, and nalidixic acid.

Antimicrobial Resistance of Campylobacter spp. Isolates from Broiler Chicken Meat Supply Chain in Maputo, Mozambique

The transfer of antimicrobial-resistant bacterial strains from poultry products to humans has become a public health issue, a possible cause being the indiscriminate antibiotics use in poultry production. Therefore, in this study we examined the susceptibility of 24 Campylobacter isolates from broiler chicken carcasses from supermarkets, informal markets, and a slaughterhouse in Maputo, Mozambique, to 13 antibiotics. The results of the study showed that the isolates were resistant to at least six antibiotics in four classes. Isolates from supermarkets were resistant to tetracycline, doxycycline, erythromycin, streptomycin, and cotrimoxazole (100%); penicillin (87.5%); and gentamycin and sulfamethoxazole (75%). Isolates from informal markets were resistant to tetracycline (100%); doxycycline and penicillin (87.5%); and erythromycin (75%), whereas isolates from the slaughterhouse were resistant to tetracycline, doxycycline, penicillin, and colistin (100%); erythromycin (87.5%); and streptomycin (75%). Overall, isolates from supermarkets showed higher resistance profiles (37.9%) than those from informal markets (31.5%) and slaughterhouses (30.6%); however, the difference was not significant (p > 0.05). The findings of the study showed that there is a high circulation of antimicrobial-resistant Campylobacter in the broiler meat supply chain of Maputo, Mozambique, representing sources for human infections and highlighting the need for measures regulating antibiotics use in livestock production.

Antimicrobial Resistance, FlaA Sequencing, and Phylogenetic Analysis of Campylobacter Isolates from Broiler Chicken Flocks in Greece

Human campylobacteriosis caused by thermophilic Campylobacter species is the most commonly reported foodborne zoonosis. Consumption of contaminated poultry meat is regarded as the main source of human infection. This study was undertaken to determine the antimicrobial susceptibility and the molecular epidemiology of 205 Campylobacter isolates derived from Greek flocks slaughtered in three different slaughterhouses over a 14-month period. A total of 98.5% of the isolates were resistant to at least one antimicrobial agent. In terms of multidrug resistance, 11.7% of isolates were resistant to three or more groups of antimicrobials. Extremely high resistance to fluoroquinolones (89%), very high resistance to tetracycline (69%), and low resistance to macrolides (7%) were detected. FlaA sequencing was performed for the subtyping of 64 C. jejuni and 58 C. coli isolates. No prevalence of a specific flaA type was observed, indicating the genetic diversity of the isolates, while some flaA types were found to share similar antimicrobial resistance patterns. Phylogenetic trees were constructed using the neighbor-joining method. Seven clusters of the C. jejuni phylogenetic tree and three clusters of the C. coli tree were considered significant with bootstrap values >75%. Some isolates clustered together were originated from the same or adjacent farms, indicating transmission via personnel or shared equipment. These results are important and help further the understanding of the molecular epidemiology and antimicrobial resistance of Campylobacter spp. derived from poultry in Greece.

Rapid Methods for Antimicrobial Resistance Diagnostics

Antimicrobial resistance (AMR) is one of the most challenging threats in public health; thus, there is a growing demand for methods and technologies that enable rapid antimicrobial susceptibility testing (AST). The conventional methods and technologies addressing AMR diagnostics and AST employed in clinical microbiology are tedious, with high turnaround times (TAT), and are usually expensive. As a result, empirical antimicrobial therapies are prescribed leading to AMR spread, which in turn causes higher mortality rates and increased healthcare costs. This review describes the developments in current cutting-edge methods and technologies, organized by key enabling research domains, towards fighting the looming AMR menace by employing recent advances in AMR diagnostic tools. First, we summarize the conventional methods addressing AMR detection, surveillance, and AST. Thereafter, we examine more recent non-conventional methods and the advancements in each field, including whole genome sequencing (WGS), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) spectrometry, Fourier transform infrared (FTIR) spectroscopy, and microfluidics technology. Following, we provide examples of commercially available diagnostic platforms for AST. Finally, perspectives on the implementation of emerging concepts towards developing paradigm-changing technologies and methodologies for AMR diagnostics are discussed.

Antimicrobial Resistance of Campylobacter Species Isolated from Broilers in Live Bird Markets in Shanghai, China

This study was conducted to determine the prevalence of antimicrobial resistance in Campylobacter spp. isolates from broilers in live bird markets (LBMs). A total of 209 Campylobacter spp. isolates (84 Campylobacter jejuni; 125 Campylobacter coli) were recovered from 364 broiler cecum samples collected from five LBMs in Shanghai, China. Minimum inhibitory concentrations of 13 antimicrobials were determined using agar dilution method. More than 96% of the Campylobacter spp. isolates were resistant to quinolones and tetracyclines. A high prevalence of macrolide resistance (erythromycin, 84.0%; azithromycin, 80.8%) was observed in C. coli, but not in C. jejuni (erythromycin, 6.0%; azithromycin, 2.4%). C. coli also showed significantly higher resistance than C. jejuni to clindamycin, gentamicin, and kanamycin. In contrast, C. coli isolates had lower resistance to florfenicol than the C. jejuni isolates. The majority of the C. jejuni (88.1%) and C. coli (97.6%) isolates exhibited multidrug resistance (MDR) to three or more classes of antimicrobials. All of the 208 ciprofloxacin-resistant Campylobacter spp. isolates were positive for the C257T mutation of the gyrA gene. In addition, the tet(O) gene was identified in all of the 202 doxycycline-resistant Campylobacter spp. isolates. Furthermore, 75.7% and 20.4% of the 103 azithromycin-resistant Campylobacter spp. isolates were positive for the A2075G mutation of the 23S rRNA gene and the presence of the erm(B) gene, respectively. Moreover, the cat gene was found in 14.3% (8/56) and 76.8% (73/95) of the chloramphenicol-resistant C. jejuni and C. coli isolates, respectively. To the best of our knowledge, this is the first report of the prevalence of antimicrobial resistance among Campylobacter spp. isolates originating from LBMs. The high prevalence of MDR Campylobacter spp. isolates in LBMs highlights the need to implement efficient intervention measures to control not only Campylobacter contamination in LBMs but also dissemination of antimicrobial resistance among Campylobacter spp. in poultry production.

Culture-based Methods for Detection of Antibiotic Resistance in Agroecosystems: Advantages, Challenges, and Gaps in Knowledge

Various culture-based methodologies are used in assessment of antibiotic resistance in samples collected in agroecosystems. Culture-based methods commonly involve isolating target bacteria on general or selective media and assessing growth in response to specific concentrations of antibiotics. The advantages of culture-based methods are multifold. In particular, isolation of bacteria is key to understanding phenotypic characteristics of isolates and their resistance patterns, and most national and international antibiotic resistance monitoring projects are isolate based. This review covers current knowledge of bacterial groups and antibiotics commonly targeted in resistance studies using bacterial culture and discusses the range in methods used, data interpretation, and factors supporting and confounding the use of culture-based methods in assessment of antibiotic resistance. Gaps in knowledge related to study design and resistance databases are discussed. Finally, a case is made for the integration of culture-based and molecular methods to better inform our understanding of antibiotic resistance in agroecosystems.

Whole-Genome Sequencing Analysis Accurately Predicts Antimicrobial Resistance Phenotypes in Campylobacter spp

The objectives of this study were to identify antimicrobial resistance genotypes for Campylobacter and to evaluate the correlation between resistance phenotypes and genotypes using in vitro antimicrobial susceptibility testing and whole-genome sequencing (WGS). A total of 114 Campylobacter species isolates (82 C. coli and 32 C. jejuni) obtained from 2000 to 2013 from humans, retail meats, and cecal samples from food production animals in the United States as part of the National Antimicrobial Resistance Monitoring System were selected for study. Resistance phenotypes were determined using broth microdilution of nine antimicrobials. Genomic DNA was sequenced using the Illumina MiSeq platform, and resistance genotypes were identified using assembled WGS sequences through blastx analysis. Eighteen resistance genes, including tet(O), blaOXA-61, catA, lnu(C), aph(2″)-Ib, aph(2″)-Ic, aph(2')-If, aph(2″)-Ig, aph(2″)-Ih, aac(6')-Ie-aph(2″)-Ia, aac(6')-Ie-aph(2″)-If, aac(6')-Im, aadE, sat4, ant(6'), aad9, aph(3')-Ic, and aph(3')-IIIa, and mutations in two housekeeping genes (gyrA and 23S rRNA) were identified. There was a high degree of correlation between phenotypic resistance to a given drug and the presence of one or more corresponding resistance genes. Phenotypic and genotypic correlation was 100% for tetracycline, ciprofloxacin/nalidixic acid, and erythromycin, and correlations ranged from 95.4% to 98.7% for gentamicin, azithromycin, clindamycin, and telithromycin. All isolates were susceptible to florfenicol, and no genes associated with florfenicol resistance were detected. There was a strong correlation (99.2%) between resistance genotypes and phenotypes, suggesting that WGS is a reliable indicator of resistance to the nine antimicrobial agents assayed in this study. WGS has the potential to be a powerful tool for antimicrobial resistance surveillance programs.

Identification of a novel G2073A mutation in 23S rRNA in amphenicol-selected mutants of Campylobacter jejuni

OBJECTIVES

This study was conducted to examine the development and molecular mechanisms of amphenicol resistance in Campylobacter jejuni by using in vitro selection with chloramphenicol and florfenicol. The impact of the resistance development on growth rates was also determined using in vitro culture.

METHODS

Chloramphenicol and florfenicol were used as selection agents to perform in vitro stepwise selection. Mutants resistant to the selective agents were obtained from the selection process. The mutant strains were compared with the parent strain for changes in MICs and growth rates. The 23S rRNA gene and the L4 and L22 ribosomal protein genes in the mutant strains and the parent strain were amplified and sequenced to identify potential resistance-associated mutations.

RESULTS

C. jejuni strains that were highly resistant to chloramphenicol and florfenicol were obtained from in vitro selection. A novel G2073A mutation in all three copies of the 23S rRNA gene was identified in all the resistant mutants examined, which showed resistance to both chloramphenicol and florfenicol. In addition, all the mutants selected by chloramphenicol also exhibited the G74D modification in ribosomal protein L4, which was previously shown to confer a low-level erythromycin resistance in Campylobacter species. The mutants selected by florfenicol did not have the G74D mutation in L4. Notably, the amphenicol-resistant mutants also exhibited reduced susceptibility to erythromycin, suggesting that the selection resulted in cross resistance to macrolides.

CONCLUSIONS

This study identifies a novel point mutation (G2073A) in 23S rRNA in amphenicol-selected mutants of C. jejuni. Development of amphenicol resistance in Campylobacter likely incurs a fitness cost as the mutant strains showed slower growth rates in antibiotic-free media.

Characteristics of Escherichia coli from raw vegetables at a retail market in the Czech Republic

A large epidemic caused by shigatoxigenic Escherichia coli (E. coli) in spring 2011 in Germany resulted in reduction of trust in the health safety of raw vegetables and sprouted seeds. This study focused on the detection and characterization of E. coli in raw vegetables and sprouted seeds sold in the Czech Republic. Out of 91 samples, 24 (26.4%) were positive for the presence of E. coli. Resistance to antimicrobial agents was determined by the disk diffusion method and E-test. Polymerase chain reaction was used for the detection of selected genes encoding virulence--eaeA, hly, stx1, and stx2 and genes encoding resistance to tetracycline--tet(A), tet(B), tet(C), and tet(G) and to β-lactams--blaTEM, blaSHV, and blaCTX. The blaTEM gene was detected in two isolates, the tet(B) gene in three and tet(A) in one isolate. No hly, stx1, or stx2 genes were present, but the eaeA gene was found in three (11.1%) isolates from imported vegetables. These isolates can be considered as potentially enteropathogenic. Results of this study show that raw vegetables and sprouted seeds sold in the retail market can represent a potential risk for consumers.

Antimicrobial resistance in campylobacter: susceptibility testing methods and resistance trends

Most Campylobacter infections are self-limiting but antimicrobial treatment (e.g., macrolides, fluoroquinolones) is necessary in severe or prolonged cases. Susceptibility testing continues to play a critical role in guiding therapy and epidemiological monitoring of resistance. The methods of choice for Campylobacter recommended by the Clinical and Laboratory Standards Institute (CLSI) are agar dilution and broth microdilution, while a disk diffusion method was recently standardized by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Macrolides, quinolones, and tetracyclines are among the common antimicrobials recommended for testing. Molecular determination of Campylobacter resistance via DNA sequencing or PCR-based methods has been performed. High levels of resistance to tetracycline and ciprofloxacin are frequently reported by many national surveillance programs, but resistance to erythromycin and gentamicin in Campylobacter jejuni remains low. Nonetheless, variations in susceptibility observed over time underscore the need for continued public health monitoring of Campylobacter resistance from humans, animals, and food.

Inaccuracy of the disk diffusion method compared with the agar dilution method for susceptibility testing of Campylobacter spp

The agar dilution method has been standardized by the CLSI for the susceptibility testing of Campylobacter species, and according to these standards, the disk diffusion method should be used only in screening for macrolide and ciprofloxacin resistance. Nevertheless, the disk diffusion test is currently widely used, since it is easy to perform in clinical microbiology laboratories. In this study, the disk diffusion method was compared to the agar dilution method by analyzing the in vitro activities of seven antimicrobial agents against 174 Campylobacter strains collected in Finland between 2003 and 2008. Recommendations of the CLSI were followed using Mueller-Hinton agar plates with 5% of sheep blood. For each strain, the disk diffusion tests were performed two to four times. Of the 33 erythromycin-resistant strains (MIC, ≥16 μg/ml), 24 (73%) constantly showed a 6-mm erythromycin inhibition zone (i.e., no inhibition), while for seven strains the inhibition zone varied from 6 to 44 mm in repeated measurements. Among the 141 erythromycin-susceptible strains (MIC, <16 μg/ml), erythromycin inhibition zones varied between 6 and 61 mm. Of the 87 ciprofloxacin-resistant strains, 47 (54%) showed 6-mm inhibition zones, while 40 strains showed inhibition zones between 6 and 60 mm. Significant differences between the repetitions were observed in the disk diffusion for all antimicrobial agents and all strains except for the macrolide-resistant strains regarding the macrolides. For 17 (10%) strains, the variation in repeated measurements was substantial. These results show that the disk diffusion method may not be a reliable tool for the susceptibility testing of Campylobacter spp. Further studies are needed to assess whether the disk diffusion test could be improved or whether all susceptibilities of campylobacters should be tested using an MIC-based method.