23S rRNA gene mutations contributing to macrolide resistance in Campylobacter jejuni and Campylobacter coli

Genomic and clinical characteristics of campylobacteriosis in Australia

Campylobacter spp. are a common cause of bacterial gastroenteritis in Australia, primarily acquired from contaminated meat. We investigated the relationship between genomic virulence characteristics and the severity of campylobacteriosis, hospitalisation, and other host factors.We recruited 571 campylobacteriosis cases from three Australian states and territories (2018-2019). We collected demographic, health status, risk factors, and self-reported disease data. We whole genome sequenced 422 C. jejuni and 84 C. coli case isolates along with 616 retail meat isolates. We classified case illness severity using a modified Vesikari scoring system, performed phylogenomic analysis, and explored risk factors for hospitalisation and illness severity.On average, cases experienced a 7.5 day diarrhoeal illness with additional symptoms including stomach cramps (87.1 %), fever (75.6 %), and nausea (72.0 %). Cases aged ≥75 years had milder symptoms, lower Vesikari scores, and higher odds of hospitalisation compared to younger cases. Chronic gastrointestinal illnesses also increased odds of hospitalisation. We observed significant diversity among isolates, with 65 C. jejuni and 21 C. coli sequence types. Antimicrobial resistance genes were detected in 20.4 % of isolates, but multidrug resistance was rare (0.04 %). Key virulence genes such as cdtABC (C. jejuni) and cadF were prevalent (>90 % presence) but did not correlate with disease severity or hospitalisation. However, certain genes (e.g. fliK, Cj1136, and Cj1138) appeared to distinguish human C. jejuni cases from food source isolates.Campylobacteriosis generally presents similarly across cases, though some are more severe. Genotypic virulence factors identified in the literature to-date do not predict disease severity but may differentiate human C. jejuni cases from food source isolates. Host factors like age and comorbidities have a greater influence on health outcomes than virulence factors.

Combined genomic-proteomic approach in the identification of Campylobacter coli amoxicillin-clavulanic acid resistance mechanism in clinical isolates

Introduction

Aminopenicillins resistance among Campylobacter jejuni and Campylobacter coli strains is associated with a single mutation in the promoting region of a chromosomal beta-lactamase blaOXA61, allowing its expression. Clavulanic acid is used to restore aminopenicillins activity in case of blaOXA61 expression and has also an inherent antimicrobial activity over Campylobacter spp. Resistance to amoxicillin-clavulanic acid is therefore extremely rare among these species: only 0.1% of all Campylobacter spp. analyzed in the French National Reference Center these last years (2017-2022).

Material and methods

Whole genome sequencing with bioinformatic resistance identification combined with mass spectrometry (MS) was used to identify amoxicillin-acid clavulanic resistance mechanism in Campylobacters.

Results

A G57T mutation in blaOXA61 promoting region was identified in all C. jejuni and C. coli ampicillin resistant isolates and no mutation in ampicillin susceptible isolates. Interestingly, three C. coli resistant to both ampicillin and amoxicillin-clavulanic acid displayed a supplemental deletion in the promoting region of blaOXA61 beta-lactamase, at position A69. Using MS, a significant difference in the expression of BlaOXA61 was observed between these three isolates and amoxicillin-clavulanic acid susceptible C. coli.

Conclusion

A combined genomics/proteomics approach allowed here to identify a rare putative resistance mechanism associated with amoxicillin-clavulanic acid resistance for C. coli.

Campylobacter jejuni ST50, a pathogen of global importance: A comparative genomic analysis of isolates from Australia, Europe and North America

Campylobacter jejuni is the leading cause of bacterial gastroenteritis globally, and infections are often transmitted through consumption of raw or undercooked poultry. Campylobacter jejuni ST50 is among the top ten sequence types (STs) reported in the collected isolates listed at PubMLST records from poultry, food and clinical sources for Asia, Europe, North America, Oceania and South America. This study was designed to determine the most commonly reported C. jejuni STs globally using the PubMLST database and assess similarities between genomes of C. jejuni ST50 isolates from geographically distinct locations. To gain a better understanding of C. jejuni diversity, we compared draft genome sequences of 182 ST50 isolates recovered from retail or caecal poultry samples in Oceania, Europe and North America that were collected over a period of 9 years (2010 to 2018). Overall, phylogenetic analysis revealed that isolates from geographically distinct locations tended to cluster based on the continent where the sample was collected. Among ST50 isolates from Europe and North America, we identified resistance determinants associated with phenotypic resistance to beta-lactams (EU: 55%; GB: 43.1%), tetracyclines (CA: 77.3%; EU: 37.5%; GB: 9.8%; US: 43.5%) and fluoroquinolones (EU: 60.0%; GB: 15.7%); no resistance determinants were identified in isolates from Australia. In general, the majority of the virulence genes, with rare exceptions such as wlaN, cj1138, hddA and rfbC, were evenly distributed throughout the genomes of all ST50 isolates in this study. Genomic-based characterization of C. jejuni ST50 isolates from poultry on three continents highlighted that geographically distinct isolates have evolved independently but only represent a glimpse into the diversity of C. jejuni.

Antimicrobial resistance and interspecies gene transfer in Campylobacter coli and Campylobacter jejuni isolated from food animals, poultry processing, and retail meat in North Carolina, 2018-2019

The Center for Disease Control and Prevention identifies antimicrobial resistant (AMR) Campylobacter as a serious threat to U.S. public health due to high community burden, increased transmissibility, and limited treatability. The National Antimicrobial Resistance Monitoring System (NARMS) plays an important role in surveillance of AMR bacterial pathogens in humans, food animals and retail meats. This study investigated C. coli and C. jejuni from live food animals, poultry carcasses at production, and retail meat in North Carolina between January 2018-December 2019. Whole genome sequencing and bioinformatics were used for phenotypic and genotypic characterization to compare AMR profiles, virulence factors associated with Guillain-Barré Syndrome (GBS) (neuABC and cst-II or cst-III), and phylogenic linkage between 541 Campylobacter isolates (C. coli n = 343, C. jejuni n = 198). Overall, 90.4% (489/541) Campylobacter isolates tested positive for AMR genes, while 43% (233/541) carried resistance genes for three or more antibiotic classes and were classified molecularly multidrug resistant. AMR gene frequencies were highest against tetracyclines (64.3%), beta-lactams (63.6%), aminoglycosides (38.6%), macrolides (34.8%), quinolones (24.4%), lincosamides (13.5%), and streptothricins (5%). A total of 57.6% (114/198) C. jejuni carried GBS virulence factors, while three C. coli carried the C. jejuni-like lipooligosaccharide locus, neuABC and cst-II. Further evidence of C. coli and C. jejuni interspecies genomic exchange was observed in identical multilocus sequence typing, shared sequence type (ST) 7818 clonal complex 828, and identical species-indicator genes mapA, ceuE, and hipO. There was a significant increase in novel STs from 2018 to 2019 (2 in 2018 and 21 in 2019, p<0.002), illustrating variable Campylobacter genomes within food animal production. Introgression between C. coli and C. jejuni may aid pathogen adaption, lead to higher AMR and increase Campylobacter persistence in food processing. Future studies should further characterize interspecies gene transfer and evolutionary trends in food animal production to track evolving risks to public health.

Identification of the first erm(B)-positive Campylobacter jejuni and Campylobacter coli associated with novel multidrug resistance genomic islands in Australia

OBJECTIVES

This report describes the first identification of two Campylobacter isolates harbouring erm(B) in Australia.

METHODS

Two erm(B)-positive isolates, Campylobacter coli 18V1065H1 and Campylobacter jejuni 19W1001H1, were isolated from diarrhoeal faecal samples from two travellers who had recently returned from Southeast Asia. Isolates underwent whole-genome sequencing using an Illumina NextSeq system and were analysed with the Nullarbor pipeline. Antimicrobial resistance genes were identified using AMRFinderPlus and sequence types (STs) were determined by multilocus sequence typing and the PubMLST Campylobacter jejuni/coli typing scheme.

RESULTS

Besideserm(B), C. jejuni 19W1001H1 possessed six other resistance genes [aad9, aadE, aph(3')-Illa, bla_OXA-185, catA13 and tet(O)], the gyrA T86I mutation and the RE-CmeABC multidrug efflux pump variant. Campylobacter coli 18V1065H1 also possessed six resistance genes [aad9, aadE, aph(3')-IIIa, bla_OXA-61, sat4 and tet(O)] in addition to erm(B); however, this isolate lacked genetic evidence for resistance to fluoroquinolones (no gyrA mutation). The erm(B) locus differed between isolates and neither was identical to previously identified erm(B) multidrug resistance genomic island (MDRGI) types. Both erm(B)-bearing isolates belonged to novel sequence types: ST9967 (C. jejuni 19W1001H1) and ST10161 (C. coli 18V1065H1).

CONCLUSIONS

This study detected the presence oferm(B) in Campylobacter for the first time in Australia. This novel mechanism of macrolide resistance is a major concern both for human and animal health and warrants close surveillance as macrolides are often the drug of choice for treating campylobacteriosis. The erm(B) gene is associated with several MDRGIs and dissemination of this resistance mechanism will likely limit treatment options for Campylobacter infections.

Prediction of antimicrobial resistance in clinical Campylobacter jejuni isolates from whole-genome sequencing data

Campylobacter jejuni is recognised as the leading cause of bacterial gastroenteritis in industrialised countries. Although the majority of Campylobacter infections are self-limiting, antimicrobial treatment is necessary in severe cases. Therefore, the development of antimicrobial resistance (AMR) in Campylobacter is a growing public health challenge and surveillance of AMR is important for bacterial disease control. The aim of this study was to predict antimicrobial resistance in C. jejuni from whole-genome sequencing data. A total of 516 clinical C. jejuni isolates collected between 2014 and 2017 were subjected to WGS. Resistance phenotypes were determined by standard broth dilution, categorising isolates as either susceptible or resistant based on epidemiological cutoffs for six antimicrobials: ciprofloxacin, nalidixic acid, erythromycin, gentamicin, streptomycin, and tetracycline. Resistance genotypes were identified using an in-house database containing reference genes with known point mutations and the presence of resistance genes was determined using the ResFinder database and four bioinformatical methods (modified KMA, ABRicate, ARIBA, and ResFinder Batch Upload). We identified seven resistance genes including tet(O), tet(O/32/O), ant(6)-Ia, aph(2″)-If, blaOXA, aph(3')-III, and cat as well as mutations in three genes: gyrA, 23S rRNA, and rpsL. There was a high correlation between phenotypic resistance and the presence of known resistance genes and/or point mutations. A correlation above 98% was seen for all antimicrobials except streptomycin with a correlation of 92%. In conclusion, we found that WGS can predict antimicrobial resistance with a high degree of accuracy and have the potential to be a powerful tool for AMR surveillance.

Formation of the Resistance of Campylobacter jejuni to Macrolide Antibiotics

The tendency to the formation of macrolide resistance in campylobacteriosis pathogens is considered as a serious threat to public health due to ubiquity of campylobacter strains resistant to a wide range of antibiotics, primarily fluoroquinolones and tetracyclines. To assess the prevalence of resistant Campylobacter spp., we performed screening for macrolide sensitivity among 40 Campylobacter jejuni strains isolated from raw milk, poultry product, and washings from the equipment of the poultry processing plants. Phenotypic resistance to erythromycin, the most popular antibiotic for the treatment of campylobacteriosis, was revealed in 27.5% C. jejuni strains; 10% strains were resistant to azithromycin. The search and selection for gene markers of Campylobacter resistance to macrolides was performed. It was found that the resistance of C. jejuni to erythromycin is realized mainly via synthesis of proteins that protect ribosomes (the presence of coding sequences was detected in 45% of the studied strains) and the transmembrane pump mechanism (efflux pump CmeABC genes were found in 36% isolates); both mechanisms are transmissible. Chromosomal mutations in the 23S rRNA sequence detected in 18% strains seem to play a less significant role.

Phenotypic and molecular characterization of erythromycin resistance in Campylobacter jejuni and Campylobacter coli strains isolated from swine and broiler chickens

ABSTRACT: Campylobacter spp. is a bacterial agent that causes gastroenteritis in humans and may trigger Guillain-Barré Syndrome (GBS) and is also considered one of the main foodborne diseases in developed countries. Poultry and pigs are considered reservoirs of these microorganisms, as well as raw or undercooked by-products are often incriminated as a source of human infection. Treatment in human cases is with macrolide, such erythromycin, that inhibits the protein synthesis of the microorganism. This study aimed to isolate Campylobacter jejuni and Campylobacter coli from intestinal content samples of broiler chickens (n=20) and swine (n=30) to characterize the erythromycin resistance profile of the strains and to detect molecular mechanisms involved in this resistance. The minimum inhibitory concentration was determined by agar dilution. The Mismatch Amplification Mutation Assay-Polymerase Chain Reaction (MAMA-PCR) was performed to detect mutations at positions 2074 and 2075 of 23S rRNA region, in addition to PCR test to detect the erm(B) gene. From the intestinal content of broiler chickens, 18 strains of C. jejuni and two strains of C. coli were isolated, whereas, from swine samples, no C. jejuni strain and 14 strains of C. coli were isolated. All C. coli strains were resistant, and three C. jejuni strains from broilers chickens were characterized with intermediate resistance to erythromycin. The MIC of the strains ranged from ≤0.5mg/μL to ≥128mg/μL. All resistant strains had the A2075G mutation, and one strain with intermediate resistance had the A2075G mutation. However, the A2074C mutation and the erm(B) gene were not detected. High resistance levels were detected in C. coli strains isolated from swine. The MAMA-PCR is a practical tool for detecting the erythromycin resistance in Campylobacter strains.

Molecular characterization of Campylobacter spp. recovered from beef, chicken, lamb and pork products at retail in Australia

Australian rates of campylobacteriosis are among the highest in developed countries, yet only limited work has been done to characterize Campylobacter spp. in Australian retail products. We performed whole genome sequencing (WGS) on 331 C. coli and 285 C. jejuni from retail chicken meat, as well as beef, chicken, lamb and pork offal (organs). Campylobacter isolates were highly diverse, with 113 sequence types (STs) including 38 novel STs, identified from 616 isolates. Genomic analysis suggests very low levels (2.3-15.3%) of resistance to aminoglycoside, beta-lactam, fluoroquinolone, macrolide and tetracycline antibiotics. A majority (>90%) of isolates (52/56) possessing the fluoroquinolone resistance-associated T86I mutation in the gyrA gene belonged to ST860, ST2083 or ST7323. The 44 pork offal isolates were highly diverse, representing 33 STs (11 novel STs) and harboured genes associated with resistance to aminoglycosides, lincosamides and macrolides not generally found in isolates from other sources. Prevalence of multidrug resistant genotypes was very low (<5%), but ten-fold higher in C. coli than C. jejuni. This study highlights that Campylobacter spp. from retail products in Australia are highly genotypically diverse and important differences in antimicrobial resistance exist between Campylobacter species and animal sources.

Microevolution of Campylobacter jejuni during long-term infection in an immunocompromised host

Campylobacteriosis typically manifests as a short-lived, self-limiting gastrointestinal infection in humans, however prolonged infection can be seen in cases with underlying immunodeficiency. Public Health England received 25 isolates of Campylobacter jejuni from an individual with combined variable immunodeficiency over a period of 15 years. All isolates were typed and archived at the time of receipt. Whole genome sequencing (WGS) and antimicrobial susceptibility testing were performed to examine the relatedness of the isolates and to investigate the changes in the genome that had taken place over the course of the infection. Genomic typing methods were compared to conventional phenotypic methods, and revealed that the infection was caused by a single, persistent strain of C. jejuni belonging to clonal complex ST-45, with evidence of adaptation and selection in the genome over the course of the infection. Genomic analysis of sequence variants associated with antimicrobial resistance identified the genetic background behind rRNA gene mutations causing variable levels of resistance to erythromycin. This application of WGS to examine a persistent case of campylobacteriosis provides insight into the mutations and selective pressures occurring over the course of an infection, some of which have important clinical relevance.

Campylobacter armoricus sp. nov., a novel member of the Campylobacter lari group isolated from surface water and stools from humans with enteric infection

During a study on the prevalence and diversity of members of the genus Campylobacter in a shellfish-harvesting area and its catchment in Brittany, France, six urease-positive isolates of members of the genus Campylobacter were recovered from surface water samples, as well as three isolates from stools of humans displaying enteric infection in the same period. These strains were initially identified as members of the Campylobacter lari group by MALDI-TOF mass spectrometry and placed into a distinct group in the genus Campylobacter, following atpA gene sequence analysis based on whole-genome sequencing data. This taxonomic position was confirmed by phylogenetic analysis of the 16S rRNA, rpoB and hsp60 (groEL) loci, and an analysis of the core genome that provided an improved phylogenetic resolution. The average nucleotide identity between the representative strain CA656^T (CCUG 73571^T=CIP 111675^T) and the type strain of the most closely related species Campylobacter ornithocola WBE38^T was 88.5 %. The strains were found to be microaerobic and anaerobic, motile, non-spore-forming, Gram-stain-negative, spiral-shaped bacteria that exhibit catalase, oxidase and urease activities but not nitrate reduction. This study demonstrates clearly that the nine isolates represent a novel species within the C. lari group, for which the name Campylobacter armoricus is proposed. Here, we present phenotypic and morphological features of the nine strains and the description of their genome sequences. The proposed type strain CA656^T has a 1.589 Mbp chromosome with a DNA G+C content of 28.5 mol% and encodes 1588 predicted coding sequences, 38 tRNAs, and 3 rRNA operons.

Determination of azithromycin heteroresistant Campylobacter jejuni in traveler's diarrhea

Campylobacter is the most common cause of traveler's diarrhea (TD) and human bacterial gastroenteritis. A heteroresistant Campylobacter jejuni (C. jejuni) isolate, identified by microbiological methods and characterized with molecular techniques, was obtained from a traveler in Nepal suffering TD. The presence of atypical colonies within the clear zone of inhibition was the first evidence of an atypical phenotype, leading to additional characterization of this heteroresistant strain. Antimicrobial susceptibility testing (AST) and population analysis profiling (PAP) demonstrated heteroresistance to azithromycin (AZM), a first-line antibiotic treatment for Campylobacter infections. Molecular analysis indicated a point mutation occurred on the 23S rRNA gene at the A2075G transitions, and the number of mutated gene copies was proportional to AZM resistance. Heteroresistant C. jejuni subpopulations from acute TD are likely underestimated, which may lead to treatment failures, as was the case for this patient. The presence of a heteroresistant strain in a high antibiotic environment may select for additional drug resistance and enable distribution into hospital and local communities.

Molecular Basis of Macrolide Resistance in Campylobacter Strains Isolated from Poultry in South Korea

We investigated the molecular mechanisms underlying macrolide resistance in 38 strains of Campylobacter isolated from poultry. Twenty-seven strains were resistant to azithromycin and erythromycin, five showed intermediate azithromycin resistance and erythromycin susceptibility, and six showed azithromycin resistance and erythromycin susceptibility. Four Campylobacter jejuni and six Campylobacter coli strains had azithromycin MICs which were 8-16 and 2-8-fold greater than those of erythromycin, respectively. The A2075G mutation in the 23S rRNA gene was detected in 11 resistant strains with MICs ranging from 64 to ≥ 512 μg/mL. Mutations including V137A, V137S, and a six-amino acid insertion (114-VAKKAP-115) in ribosomal protein L22 were detected in the C. jejuni strains. Erythromycin ribosome methylase B-erm(B) was not detected in any strain. All strains except three showed increased susceptibility to erythromycin with twofold to 256-fold MIC change in the presence of phenylalanine arginine ß-naphthylamide (PAßN); the effects of PAßN on azithromycin MICs were limited in comparison to those on erythromycin MICs, and 13 strains showed no azithromycin MIC change in the presence of PAßN. Differences between azithromycin and erythromycin resistance and macrolide resistance phenotypes and genotypes were observed even in highly resistant strains. Further studies are required to better understand macrolide resistance in Campylobacter.

High Prevalence of Resistance to Fluoroquinolones and Tetracycline Campylobacter Spp. Isolated from Poultry in Poland

Campylobacter spp. is a major cause of foodborne diseases in humans, particularly when transmitted by the handling or consumption of undercooked poultry meat. Most Campylobacter infections are self-limiting, but antimicrobial treatment (e.g., fluoroquinolones and macrolides) is necessary in severe or prolonged cases. The indiscriminate use of these drugs, both in clinical medicine and animal production, has a major impact on public health. The aim of the present study was to identify Campylobacter strains, isolated from turkey and broilers, using both PCR and the matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) methods to reveal the accuracy of identification, as well to evaluate the antimicrobial and genetic resistance of the investigated strains. MALDI-TOF and PCR methods were used to show differences, if any, in the specificity of that test. In this study, MALDI-TOF mass spectrometry gave the same results as multiplex PCR, in all cases. The highest rate of resistance (i.e., 100% of turkey and broiler strains) was detected against ciprofloxacin, whereas 58.1% of turkey and 78.6% of broiler strains were resistant to tetracycline. Multidrug-resistant isolates were not found in the study. All ciprofloxacin-resistant strains had a mutation in the gyrA gene, at the Thr-86 position. The presence of the tetO gene was found in 71% of turkey and in 100% of broiler strains. All resistant to tetracycline strains included tetO gene. Additionally, in five turkey and three broiler strains, susceptible to tetracycline, tetO gene was present. These results indicate the high prevalence of Campylobacter strains, which are phenotypically and genetically resistant to fluoroquinolones and tetracycline.

Use of whole-genome sequencing for Campylobacter surveillance from NARMS retail poultry in the United States in 2015

Whole genome sequencing (WGS) has become a rapid and affordable tool for public health surveillance and outbreak detection. In this study, we used the Illuminia MiSeq^® to sequence 589 Campylobacter isolates obtained in 2015 from retail poultry meats as part of the National Antimicrobial Resistance Monitoring System (NARMS). WGS data were used to identify the Campylobacter species and to compare the concordance between resistance genotypes and phenotypes. WGS accurately identified 386 C. jejuni and 203 C. coli using gyrA sequence information. Ten resistance genes, including tetO, bla_OXA-61, aph(2″)-Ic, aph(2″)-If, aph(2″)-Ig, aph(3')-III, ant(6)-1a, aadE, aph(3")-VIIa, and Inu(C), plus mutations in housekeeping genes (gyrA at position 86, 23S rRNA at position 2074 and 2075), were identified by WGS analysis. Overall, there was a high concordance between phenotypic resistance to a given drug and the presence of known resistance genes. Concordance between both resistance and susceptible phenotypes and genotype was 100% for ciprofloxacin, nalidixic acid, gentamicin, azithromycin, and florfenicol. A few discrepancies were observed for tetracycline, clindamycin, and telithromycin. The concordance between resistance phenotype and genotype ranged from 67.9% to 100%; whereas, the concordance between susceptible phenotype and genotype ranged from 98.0% to 99.6%. Our study demonstrates that WGS can correctly identify Campylobacter species and predict antimicrobial resistance with a high degree of accuracy.

Virulence and Antimicrobial Resistance in Campylobacter spp. from a Peruvian Pediatric Cohort

The presence of virulence factors (VFs) and mechanisms of quinolones and macrolide resistance was analyzed in Campylobacter spp. from a pediatric cohort study in Lima. In 149 isolates (39 Campylobacter jejuni and 24 Campylobacter coli from diarrheic cases; 57 C. jejuni and 29 C. coli from controls), the presence of the cdtABC and cadF genes and iam marker was established. Nalidixic acid, ciprofloxacin, erythromycin, and azithromycin susceptibilities were established in 115 isolates and tetracycline-susceptibility was established in 100 isolates. The presence of mutations in the gyrA, parC, and 23S rRNA genes was determined. The cadF gene and all genes from the cdtABC operon were significantly more frequent among C. jejuni (P < 0.0001); the iam marker was more frequent in C. coli (P < 0.0001). No differences were observed in VFs between cases and controls. Almost all isolates were tetracycline-resistant; nalidixic acid and ciprofloxacin resistance reached levels of 90.4% and 88.7%, respectively. Resistance to macrolides was 13% (C. jejuni 4.3%; C. coli 26.1%). Resistance to ciprofloxacin was related to GyrA Thr86 substitutions, while 13 of 15 macrolide-resistant isolates possessed a 23S rRNA mutation (A2075G). Differences in the presence of VFs and alarming levels of resistance to tested antimicrobial agents were observed among C. jejuni and C. coli.

National Antimicrobial Resistance Monitoring System: Two Decades of Advancing Public Health Through Integrated Surveillance of Antimicrobial Resistance

Drug-resistant bacterial infections pose a serious and growing public health threat globally. In this review, we describe the role of the National Antimicrobial Resistance Monitoring System (NARMS) in providing data that help address the resistance problem and show how such a program can have broad positive impacts on public health. NARMS was formed two decades ago to help assess the consequences to human health arising from the use of antimicrobial drugs in food animal production in the United States. A collaboration among the Centers for Disease Control and Prevention, the U.S. Food and Drug Administration, the United States Department of Agriculture, and state and local health departments, NARMS uses an integrated "One Health" approach to monitor antimicrobial resistance in enteric bacteria from humans, retail meat, and food animals. NARMS has adapted to changing needs and threats by expanding surveillance catchment areas, examining new isolate sources, adding bacteria, adjusting sampling schemes, and modifying antimicrobial agents tested. NARMS data are not only essential for ensuring that antimicrobial drugs approved for food animals are used in ways that are safe for human health but they also help address broader food safety priorities. NARMS surveillance, applied research studies, and outbreak isolate testing provide data on the emergence of drug-resistant enteric bacteria; genetic mechanisms underlying resistance; movement of bacterial populations among humans, food, and food animals; and sources and outcomes of resistant and susceptible infections. These data can be used to guide and evaluate the impact of science-based policies, regulatory actions, antimicrobial stewardship initiatives, and other public health efforts aimed at preserving drug effectiveness, improving patient outcomes, and preventing infections. Many improvements have been made to NARMS over time and the program will continue to adapt to address emerging resistance threats, changes in clinical diagnostic practices, and new technologies, such as whole genome sequencing.

The Current State of Macrolide Resistance in Campylobacter spp.: Trends and Impacts of Resistance Mechanisms

Campylobacter spp., especially Campylobacter jejuni and C. coli, are leading bacterial foodborne pathogens worldwide. In the United States, an estimated 0.8 million cases of campylobacteriosis occur annually, mostly involving C. jejuni Campylobacteriosis is generally self-limiting, but in severe cases, treatment with antibiotics may be mandated. The increasing incidence of fluoroquinolone resistance in Campylobacter has rendered macrolides such as erythromycin and azithromycin the drugs of choice for human campylobacteriosis. The prevalence of macrolide resistance in C. jejuni remains low, but macrolide resistance can be common in C. coli Substitutions in the 23S rRNA gene, specifically A2075G, and less frequently A2074C/G, remain the most common mechanism for high-level resistance to macrolides. In C. jejuni, resistance mediated by such substitutions is accompanied by a reduced ability to colonize chickens and other fitness costs, potentially contributing to the low incidence of macrolide resistance. Interestingly, similar fitness impacts have not been noted in C. coli Also noteworthy is a novel mechanism first reported in 2014 for a C. coli isolate from China and mediated by erm(B) harbored on multidrug resistance genomic islands. The incidence of erm(B) appears to reflect clonal expansion of certain strains, and whole-genome sequencing has been critical to the elucidation of erm(B)-associated macrolide resistance in Campylobacter spp. With the exception of one report from Spain, erm(B)-mediated macrolide resistance has been restricted to Campylobacter spp., mostly C. coli, of animal and human origin from China. If erm(B)-mediated macrolide resistance does not confer fitness costs in C. jejuni, the range of this gene may expand in C. jejuni, threatening to compromise treatment effectiveness for severe campylobacteriosis cases.

Ribosomal Mutations Conferring Macrolide Resistance in Legionella pneumophila

Monitoring the emergence of antibiotic resistance is a recent issue in the treatment of Legionnaires' disease. Macrolides are recommended as first-line therapy, but resistance mechanisms have not been studied in Legionella species. Our aim was to determine the molecular basis of macrolide resistance in L. pneumophila Twelve independent lineages from a common susceptible L. pneumophila ancestral strain were propagated under conditions of erythromycin or azithromycin pressure to produce high-level macrolide resistance. Whole-genome sequencing was performed on 12 selected clones, and we investigated mutations common to all lineages. We reconstructed the dynamics of mutation for each lineage and demonstrated their involvement in decreased susceptibility to macrolides. The resistant mutants were produced in a limited number of passages to obtain a 4,096-fold increase in erythromycin MICs. Mutations affected highly conserved 5-amino-acid regions of L4 and L22 ribosomal proteins and of domain V of 23S rRNA (G2057, A2058, A2059, and C2611 nucleotides). The early mechanisms mainly affected L4 and L22 proteins and induced a 32-fold increase in the MICs of the selector drug. Additional mutations related to 23S rRNA mostly occurred later and were responsible for a major increase of macrolide MICs, depending on the mutated nucleotide, the substitution, and the number of mutated genes among the three rrl copies. The major mechanisms of the decreased susceptibility to macrolides in L. pneumophila and their dynamics were determined. The results showed that macrolide resistance could be easily selected in L. pneumophila and warrant further investigations in both clinical and environmental settings.

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.

Mobile elements and chromosomal changes associated with MLS resistance phenotypes of invasive pneumococci recovered in the United States

Pneumococcal macrolide resistance is usually expressed as one of two phenotypes: the M phenotype conferred by the mef gene or the MLSB phenotype caused by modification of ribosomal targets, most commonly mediated by an erm methylase. Target-site modification leading to antibiotic resistance can also occur due to sequence mutations within the 23S rRNA or the L4 and L22 riboproteins. We screened 4,535 invasive isolates resistant to erythromycin and 18 invasive isolates nonsusceptible to quinupristin-dalfopristin (Q-D) to deduce the potential mechanisms involved. Of 4,535 erythromycin-resistant isolates, 66.2% were polymerase chain reaction (PCR)-positive for mef alone, 17.8% for ermB alone, and 15.1% for both mef and ermB. Thirty-seven isolates (0.9%) were PCR negative for both determinants. Of these, 3 were positive for ermA (subclass ermTR) and 25 had chromosomal mutations. No chromosomal mutations (in 23S rRNA, rplD, or rplV) nor any of the macrolides/lincosamides/streptogramin (MLS) resistance genes screened for (ermT, ermA, cfr, lsaC, and vgaA) were found in the remaining nine isolates. Of 18 Q-D nonsusceptible isolates, 14 had chromosomal mutations and one carried both mef and ermB; no chromosomal mutations or other resistance genes were found in 3 isolates. Overall, we found 28 mutations, 13 of which have not been previously described in Streptococcus pneumoniae. The role of these mutations remains to be confirmed by transformation assays.

Mutational and transcriptomic changes involved in the development of macrolide resistance in Campylobacter jejuni

Macrolide antibiotics are important for clinical treatment of infections caused by Campylobacter jejuni. Development of resistance to this class of antibiotics in Campylobacter is a complex process, and the dynamic molecular changes involved in this process remain poorly defined. Multiple lineages of macrolide-resistant mutants were selected by stepwise exposure of C. jejuni to escalating doses of erythromycin or tylosin. Mutations in target genes were determined by DNA sequencing, and the dynamic changes in the expression of antibiotic efflux transporters and the transcriptome of C. jejuni were examined by real-time reverse transcription-PCR, immunoblotting, and DNA microarray analysis. Multiple types of mutations in ribosomal proteins L4 and L22 occurred early during stepwise selection. On the contrary, the mutations in the 23S rRNA gene, mediating high resistance to macrolides, were observed only in the late-stage mutants. Upregulation of antibiotic efflux genes was observed in the intermediately resistant mutants, and the magnitude of upregulation declined with the occurrence of mutations in the 23S rRNA gene. DNA microarray analysis revealed the differential expression of 265 genes, most of which occurred in the intermediate mutant, including the upregulation of genes encoding ribosomal proteins and the downregulation of genes involved in energy metabolism and motility. These results indicate (i) that mutations in L4 and L22 along with temporal overexpression of antibiotic efflux genes precede and may facilitate the development of high-level macrolide resistance and (ii) that the development of macrolide resistance affects the pathways important for physiology and metabolism in C. jejuni, providing an explanation for the reduced fitness of macrolide-resistant Campylobacter.

Genotypes and antibiotic resistance of Campylobacter coli in fattening pigs

Campylobacter coli is a food-borne zoonotic pathogen causing human gastroenteritis worldwide. The organism is a commensal in the intestine of many food production animals including fattening pigs. The role of the pig as a potential reservoir for C. coli affecting human either directly or via poultry has hardly been investigated and genetic characterization of porcine strains is needed to address this question. For this aim multilocus sequence typing (MLST) and flaB typing was applied to 256 C. coli isolates from faeces of fattening pig collected during 2009 at different slaughterhouses in Switzerland. In addition genotypic resistances towards macrolides and quinolones based on point mutations in the 23S rRNA and gyrA genes, respectively, were determined. Of the 67 sequence types (STs) obtained by MLST, 37 were found for the first time. flaB typing revealed 46 different types with 14 of them being novel and was useful to further differentiate strains with an identical ST. Quinolone resistance was detected in 33.6% and macrolide resistance was found in 10.6% of isolates. Comparison with 99 C. coli pig isolates from 2001 revealed a significant decrease in antibiotic resistance towards both groups of antibiotics and there was high overlap between genotypes of 2001 and 2009. Little overlap of porcine genotypes was found with 97 C. coli isolates from poultry collected 2008, however, macrolide resistance was significantly higher in pig isolates. In conclusion, C. coli from Swiss pig are heterogeneous containing many novel STs, findings that could reflect the partitioned Swiss pig production with almost no international breed exchange. The antibiotic resistance echoes the use of corresponding drugs in the Swiss livestock production and indicates the efficacy of restrictive application of antibiotics in order to reduce resistances.

Ribosomal operon intergenic sequence region (ISR) heterogeneity in Campylobacter coli and Campylobacter jejuni

AIMS

The intergenic sequence regions (ISR) between the 16S and 23S genes of Campylobacter jejuni and Campylobacter coli are markedly different for each species. However, in the genomic sequence for Camp. coli RM2228, two rRNA operons have an ISR that is characteristic of Camp. coli, and the third operon is characteristic of Camp. jejuni. The aim of this study was to determine the prevalence of ISR heterogeneity in these organisms.

METHODS AND RESULTS

PCR primers were designed to yield a 327-base pair (bp) product for Camp. coli and 166-bp product for Camp. jejuni. A strain like Camp. coli RM2228 should yield products of both sizes. DNA from a panel of Camp. coli (n=133) and Camp. jejuni (n=134) isolates were tested. All of the isolates yielded products of the predicted size for the species. To verify the data for Camp. coli RM2228, each ribosomal operon from the isolate was individually amplified by PCR and tested with the ISR primer pair. Products of both sizes were produced as predicted.

CONCLUSIONS

The cross-species heterogeneity of the ISR seen in Camp. coli RM2228 is uncommon.

SIGNIFICANCE AND IMPACT OF THE STUDY

The heterogeneity must have been caused by horizontal gene transfer at a frequency lower than predicted from housekeeping gene data. Thus, it can be expected that species identification based on the ISR can be confused in rare isolates.

Repeated therapeutic dosing selects macrolide-resistant Campylobacter spp. in a turkey facility

AIMS

This study assessed the effects of the therapeutic use of Tylan® in a large-scale turkey production facility on the selection of macrolide-resistant Campylobacter.

METHODS AND RESULTS

A flock of production turkeys (c. 30,000 birds) was followed from brooding to slaughter, and the effects of macrolide application was assessed in one half of the flock from finishing stage to final product and compared against the control barn where no macrolide was used. Overall, Campylobacter prevalence in turkeys was almost 100% by 4 weeks of age. When Campylobacter prevalence was assessed in relation to treatment, high levels of macrolide resistance were evident in this group following treatment, with Campylobacter coli becoming the dominant strain type. Over time, and in the absence of a selection agent, the population of resistant strains decreased suggesting that there was a fitness cost associated with macrolide resistance carriage and persistence. Macrolide resistance was detected in the control barn at a very low level (four isolates recovered during the study), suggesting that the creation or selection of macrolide-resistant Campylobacter was correlated with the treatment regime used. Molecular analysis of a selection of macrolide-resistant Campylobacter recovered was assessed using PCR, RFLP and sequence analysis of the 23S rRNA. The majority of isolates displaying high-level macrolide resistance (>256 μg ml(-1)) possessed an A2075G transition mutation in the 23S rRNA and the CmeABC efflux pump.

CONCLUSIONS

These studies suggest that macrolide resistance can be promoted through the application of treatment during the grow-out phase and once established in a production facility has the potential to persist and be transferred to final product.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study highlights the prudent use of antimicrobials in treatment of disease in poultry. Of significance is the presence of macrolide-resistant Campylobacter in poultry production and finished product as a consequence of macrolide usage.

Campylobacter jejuni bacteremia and Helicobacter pylori in a patient with X-linked agammaglobulinemia

We describe a 15-year-old patient with X-linked agammaglobulinemia who developed malabsorption and bacteremia due to infection of Helicobacter pylori and Campylobacter jejuni. The Campylobacter bacteremia was only recognized after subculturing of blood culture bottles that failed to signal in the automated system. After 2 weeks of treatment with meropenem and erythromycin for 4 weeks, the patient developed a relapse of bacteremia 10 months later with a high level erythromycin resistant C. jejuni. Sequencing revealed an A2058C mutation in the 23 S rRNA gene associated with this resistance. Treatment with doxycycline for 4 weeks finally resulted in complete eradication. This case report illustrates the importance for physicians to use adapted culture methods and adequate prolonged therapy in patients with an immunodeficiency. A summary of published case reports and series of patients with hypogammaglobulinemia or agammaglobulinemia with Campylobacter or Helicobacter bacteremia is given.

Phenotypic and Genotypic Antimicrobial Resistance Profiles of Campylobacter jejuni Isolated from Cattle, Sheep, and Free-Range Poultry Faeces

Minimum inhibitory concentrations (MIC) of 13 antimicrobial agents were determined by broth microdilution for 72 Campylobacter jejuni strains from livestock. Twenty-three (31.9%) isolates were fully susceptible; all isolates were susceptible to erythromycin, chloramphenicol, streptomycin, gentamicin, sulfamethoxazole, and meropenem, and all but one to kanamycin. Resistance to quinolones was highest (52.8%), reaching similar values among poultry, dairy cattle, and sheep, but lower in beef cattle. Resistance to tetracyclines (48.6%) was mainly associated to dairy cattle and β-lactams (26.4%) to poultry. Multidrug resistance was mainly detected in dairy cattle (28.6%) and poultry (21.0%), whereas beef cattle had the highest percentage of fully susceptible isolates. Two real-time PCR assays to detect point mutations associated to quinolone (C257T in the gyrA gene) and macrolide (A2075G in the 23S rRNA genes) resistance were developed and validated on these strains. The analysis of a further set of 88 isolates by real-time PCR confirmed the absence of macrolide resistance and demonstrated the reproducibility and processability of the assay.

23S rRNA mutation A2074C conferring high-level macrolide resistance and fitness cost in Campylobacter jejuni

To examine the development of macrolide resistance in Campylobacter jejuni and assess the fitness of the macrolide-resistant mutants, two macrolide-susceptible C. jejuni strains, American Type Culture Collection (ATCC) 33291 and H1, from different geographic areas were exposed to tylosin in vitro. Multiple mutant strains were obtained from the selection. Most of the high-level macrolide-resistant strains derived from the selection exhibited the A2074C transversion in all three copies of 23S rRNA and displayed strong stability in the absence of antibiotic selection pressure. The competition experiments demonstrated that the strains containing the A2074C transversion imposed a fitness cost in competition mixtures. In addition, the fitness cost of the mutation was not ameliorated after approximately 500 generations of evolution under laboratory conditions. These findings indicate that the A2074C transversion in C. jejuni is not only correlated with stable and high-level macrolide resistance but also associated with a fitness cost.

Genetic analyses of the antibiotic resistance of Bifidobacterium bifidum strain Yakult YIT 4007

Bifidobacterium bifidum strain Yakult YIT 4007 (abbreviated as B. bifidum YIT 4007) is a commercial strain and resistant to erythromycin, neomycin, and streptomycin. Resistances to these antibiotics were endowed by sequential isolation of resistant mutants from its susceptible progenitor strain YIT 4001. Comparison of nucleotide sequences of various candidate genes of both strains led us to find that B. bifidum YIT 4007 had mutations on three copies of 23S ribosomal RNA genes, an 8 bp deletion of the rluD gene for pseudouridine synthase, and a mutation on the rpsL gene for ribosomal protein S12. The responsibility of these mutations to antibiotic resistances was supported by analyses of newly isolated mutants resistant to these antibiotics. The antibiotic resistances of B. bifidum YIT 4007 were evidently acquired by mutations of the structural genes on the chromosome and not associated with mobile genetic elements like insertion sequences, phages, and plasmids.

Inter- and intra-genomic heterogeneity of the intervening sequence in the 23S ribosomal RNA gene of Campylobacter jejuni and Campylobacter coli

An intervening sequence (IVS) can be present or absent in the 23S rRNA of Campylobacter jejuni and Campylobacter coli. As part of a survey, we used a polymerase chain reaction (PCR) assay to detect the presence of the IVS in 43 isolates of C. coli and 82 isolates of C. jejuni. An IVS was present in 40 (93.0%) of the C. coli and only 34 (41.5%) of the C. jejuni isolates. Twelve (27.9%) of the C. coli isolates and seven (8.5%) of the C. jejuni isolates resulted in two polymerase chain reaction products, indicating heterogeneity in the presence of the 23S rRNA IVS. Fourteen of the isolates with two products were evaluated by pulse-field gel electrophoresis; 13 different patterns were observed. The total band size of one isolate was substantially greater than the expected 1.7 Mb, possibly indicating a mixed culture. Southern blot analyses demonstrated the expected three rRNA operons in all tested isolates. Nested PCR reactions with operon-specific primers followed by primers for the IVS confirmed that the strains of interest contained either one or two operons carrying the IVS and the remaining operon(s) did not. Sequence analysis of the IVS and flanking regions of the 23S rRNA genes did not discriminate C. jejuni and C. coli as distinct populations. These results indicate horizontal transfer of 23S rRNA genes or portions of the genes between C. jejuni and C. coli. Also, data showing sequence polymorphisms between the three 23S rRNA loci outside of the IVS region suggest that the isolates with intra-genomic heterogeneity appear to be members of clones that have an ancient defect in gene conversion mechanisms needed for concerted evolution of the ribosomal operons.