Quinolone and macrolide resistance in Campylobacter jejuni and C. coli: resistance mechanisms and trends in human isolates

A Study on Campylobacter jejuni and Campylobacter coli through Commercial Broiler Production Chains in Thailand: Antimicrobial Resistance, the Characterization of DNA Gyrase Subunit A Mutation, and Genetic Diversity by Flagellin A Gene Restriction Fragment Length Polymorphism

Contaminated poultry meat is regarded as the main source of human campylobacteriosis. During September 2014 and February 2015, breeder flocks, hatcheries, and broiler farms from two chicken production chains were investigated chronologically. Five commercial breeder flocks (Breeder Flocks 1-5), two hatcheries (Hatcheries A and B), and five broiler flocks (Broiler Flocks 1-5) were sampled in this study. Campylobacter colonization of both breeder and broiler flocks was determined from cloacal swabs and environmental samples (pan feeders, footwear, darkling beetles, flies, feed, and water). The eggs from the breeder flocks were followed to hatcheries. At the hatcheries, early embryonic deaths, egg trays, eggshells, hatchers, and water were investigated. Cloacal swabs were taken from broilers at Days 1, 14, and 28 (all broiler flocks), and either 35 (Broiler Flocks 1 and 2) or 43 (Broiler Flocks 3-5). Thirty-six Campylobacter jejuni and 94 Campylobacter coli isolates collected through two broiler production chains were tested by twofold agar dilution for their susceptibility to antimicrobial agents. Most Campylobacter isolates were multidrug resistant (MDR), defined as being resistant to three or more antimicrobial classes ( C. jejuni : 100%; C. coli : 98.9%), and exhibited high resistance to enrofloxacin ( C. jejuni : 100%; C. coli : 98.9%). The vast majority of C. coli were resistant to tetracycline (97.9%), trimethoprim-sulfamethoxazole (81.9%), and doxycycline (79.8%), but only 55.6%, 36.1%, and 50% of C. jejuni isolates revealed resistance to these antimicrobial agents, respectively. A selected subset of 24 C. jejuni and 24 C. coli were characterized for their mutations in the quinolone resistance determining region of the DNA gyrase subunit A gene by nucleotide sequence analysis. The Thr-86-Ile substitution (ACA-ATA in C. jejuni or ACT-ATT in C. coli ) was found in all isolates. Moreover, a total of 130 Campylobacter isolates were typed with the use of polymerase chain reaction-restriction fragment length polymorphism of the flagellin A gene (flaA-RFLP) to determine their genetic relationships. Ten distinct clusters were recognized by flaA-RFLP typing. The results showed that horizontal transmission was the major route of Campylobacter transmission in this study. In conclusion, the emergence of MDR and high resistance rates to several antimicrobials are major concerns identified in this study. The prudent use of these agents and active surveillance of resistance at the farm level are essential steps to reduce the public health risks identified in this work.

Structures and transport dynamics of a Campylobacter jejuni multidrug efflux pump

Resistance-nodulation-cell division efflux pumps are integral membrane proteins that catalyze the export of substrates across cell membranes. Within the hydrophobe-amphiphile efflux subfamily, these resistance-nodulation-cell division proteins largely form trimeric efflux pumps. The drug efflux process has been proposed to entail a synchronized motion between subunits of the trimer to advance the transport cycle, leading to the extrusion of drug molecules. Here we use X-ray crystallography and single-molecule fluorescence resonance energy transfer imaging to elucidate the structures and functional dynamics of the Campylobacter jejuni CmeB multidrug efflux pump. We find that the CmeB trimer displays a very unique conformation. A direct observation of transport dynamics in individual CmeB trimers embedded in membrane vesicles indicates that each CmeB subunit undergoes conformational transitions uncoordinated and independent of each other. On the basis of our findings and analyses, we propose a model for transport mechanism where CmeB protomers function independently within the trimer.

Multidrug efflux pumps significantly contribute for bacteria resistance to antibiotics. Here the authors present the structure of Campylobacter jejuni CmeB pump combined with functional FRET assays to propose a transport mechanism where each CmeB protomers is functionally independent from the trimer.

Developing New Antimicrobial Therapies: Are Synergistic Combinations of Plant Extracts/Compounds with Conventional Antibiotics the Solution?

The discovery of penicillin nearly 90 years ago revolutionized the treatment of bacterial disease. Since that time, numerous other antibiotics have been discovered from bacteria and fungi, or developed by chemical synthesis and have become effective chemotherapeutic options. However, the misuse of antibiotics has lessened the efficacy of many commonly used antibiotics. The emergence of resistant strains of bacteria has seriously limited our ability to treat bacterial illness, and new antibiotics are desperately needed. Since the discovery of penicillin, most antibiotic development has focused on the discovery of new antibiotics derived from microbial sources, or on the synthesis of new compounds using existing antibiotic scaffolds to the detriment of other lines of discovery. Both of these methods have been fruitful. However, for a number of reasons discussed in this review, these strategies are unlikely to provide the same wealth of new antibiotics in the future. Indeed, the number of newly developed antibiotics has decreased dramatically in recent years. Instead, a reexamination of traditional medicines has become more common and has already provided several new antibiotics. Traditional medicine plants are likely to provide further new antibiotics in the future. However, the use of plant extracts or pure natural compounds in combination with conventional antibiotics may hold greater promise for rapidly providing affordable treatment options. Indeed, some combinational antibiotic therapies are already clinically available. This study reviews the recent literature on combinational antibiotic therapies to highlight their potential and to guide future research in this field.

Antibiotic susceptibility profiles among Campylobacter isolates obtained from international travelers between 2007 and 2014

Campylobacter infection is a common cause of diarrhea among international travelers. We studied antibiotic resistance patterns among Campylobacter isolates obtained from international travelers according to travel destination. Three collections of isolates obtained from international travelers between 2007 and 2014 (Institute of Tropical Medicine, the “Laboratoire Hospitalier Universitaire de Bruxelles “and the Belgian National Reference Centre for Campylobacter) were used. Isolates were tested for minimal inhibitory concentration (MIC) values (E-test macromethod) for fluoroquinolones, macrolides, tetracyclines, amoxicillin–clavulanic acid, and meropenem. Single isolates from 261 travelers were available; median (IQR) age was 25.4 (4–42) years, 85.8% were symptomatic (information for 224 patients available). Overall resistance to ciprofloxacin was 60.9%, ranging from 50.8% in Africa to 75.0% in Asia. Resistance to erythromycin was 4.6%, with the highest rate observed for Southern Asia (15.2%, seven isolates, six of them recovered from patients returning from India). A total of 126 isolates (48.3%) were resistant to tetracycline. No resistance to amoxicillin–clavulanic acid or meropenem was detected. Ciprofloxacin resistance tended to increase over time (53.9% in 2007 versus 72.2% in 2014), erythromycin resistance remained stable (median annual resistance 4.2%). Most (86.2%) ciprofloxacin-resistant isolates had MIC values ≥32 mg/l, and all erythromycin-resistant isolates had MIC values ≥256 mg/l. Co-resistance to ciprofloxacin and erythromycin was observed in 11 (4.2%) isolates, seven of which came from Southern Asia. Among all regions of travel, more than half of Campylobacter isolates were resistant to ciprofloxacin. Overall resistance to erythromycin was below 5% but reached 15.2% in Southern Asia.

Molecular Characterization of Methicillin-Resistant Staphylococcus aureus Isolated from Australian Animals and Veterinarians

This study aimed to determine the frequency and molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) from Australian animals and whether animal-derived MRSA was similar to that from Australian veterinarians. A total of 1,080 clinical coagulase positive Staphylococcus isolates from Australian animals were collected during 2013. Sixteen (4%) of 360 S. aureus isolates were MRSA. Most MRSA came from companion animals, while none came from livestock. MRSA isolates were characterized using whole genome sequencing. ST22-IV (EMRSA-15) was the most common clone in dogs and cats. Clonal complex (CC) 8 was most common in horses. Most ST22-IV isolates were resistant to ciprofloxacin. Animal-derived MRSA genomes were interrogated for the presence of host-specific genetic markers (staphylokinase gene [scn], chemotaxis-inhibiting proteins gene [chp], staphylococcal complement inhibitor gene [sak], enterotoxin A gene [sea], and Von Willebrand Factor binding protein gene [vwb]). A subset of MRSA genomes previously collected from Australian veterinarians was also interrogated. There was no clear pattern in the distribution of host-specific markers among animal and veterinarian isolates. Animal- and veterinarian-derived MRSA were intermingled in the phylogenetic tree. The absence of MRSA in Australian livestock is in stark contrast with its presence in livestock from other countries. Possible explanations include Australia's geographic isolation, the absence of live animal importation into Australia, and most notably, the restrictions placed on the use of antimicrobials of critical importance in Australian livestock.

Epidemiology of antimicrobial resistant Campylobacter spp. isolated from retail meats in Canada

Campylobacter is an important zoonotic pathogen found in livestock and can cause illness in humans following consumption of raw and undercooked meat products. The objectives of this study were to determine the prevalence of Campylobacter spp. in retail meat (poultry, turkey, pork and beef) purchased in Alberta, Canada and to assess antimicrobial resistance and genetic relatedness of recovered Campylobacter strains with previously isolated strains from clinical and environmental sources. A Comparative Genomic Fingerprinting (CGF) method was used for assessing genetic relatedness of isolates. A total of 606 samples comprising 204, 110, 145 and 147 samples of retail chicken, turkey, ground beef and pork, respectively, were obtained. Campylobacter was isolated from 23.5% (48/204) of chicken samples and 14.2% (8/110) of turkey samples. Pork and beef samples were negative for Campylobacter. Campylobacter jejuni was the most common (94.6%) spp. found followed by C. coli (5.4%). Resistance to tetracycline was found in 48.1% of isolates, followed by resistance to ciprofloxacin (5.5%), nalidixic acid (5.5%), azithromycin (1.78%), and erythromycin (1.78%). All isolates were susceptible to clindamycin, florfenicol, gentamicin and telithromycin. Tetracycline resistance was attributable to the presence of the tetO gene. CGF analysis showed that Campylobacter isolated from poultry meat in this study were genetically related to clinical isolates recovered from human infections and to those isolated from animals and the environment.

Trans-Cinnamaldehyde, Carvacrol, and Eugenol Reduce Campylobacter jejuni Colonization Factors and Expression of Virulence Genes in Vitro

Campylobacter jejuni is a major foodborne pathogen that causes severe gastroenteritis in humans characterized by fever, diarrhea, and abdominal cramps. In the human gut, Campylobacter adheres and invades the intestinal epithelium followed by cytolethal distending toxin mediated cell death, and enteritis. Reducing the attachment and invasion of Campylobacter to intestinal epithelium and expression of its virulence factors such as motility and cytolethal distending toxin (CDT) production could potentially reduce infection in humans. This study investigated the efficacy of sub-inhibitory concentrations (SICs, concentration not inhibiting bacterial growth) of three GRAS (generally recognized as safe) status phytochemicals namely trans-cinnamaldehyde (TC; 0.005, 0.01%), carvacrol (CR; 0.001, 0.002%), and eugenol (EG; 0.005, 0.01%) in reducing the attachment, invasion, and translocation of C. jejuni on human intestinal epithelial cells (Caco-2). Additionally, the effect of these phytochemicals on Campylobacter motility and CDT production was studied using standard bioassays and gene expression analysis. All experiments had duplicate samples and were replicated three times on three strains (wild type S-8, NCTC 11168, 81-176) of C. jejuni. Data were analyzed using ANOVA with GraphPad ver. 6. Differences between the means were considered significantly different at P < 0.05. The majority of phytochemical treatments reduced C. jejuni adhesion, invasion, and translocation of Caco-2 cells (P < 0.05). In addition, the phytochemicals reduced pathogen motility and production of CDT in S-8 and NCTC 11168 (P < 0.05). Real-time quantitative PCR revealed that phytochemicals reduced the transcription of select C. jejuni genes critical for infection in humans (P < 0.05). Results suggest that TC, CR, and EG could potentially be used to control C. jejuni infection in humans.

Fluoroquinolone and macrolide resistance in Campylobacter jejuni isolated from broiler slaughterhouses in southern Brazil

Campylobacter jejuni is recognized as a leading cause of acute bacterial gastroenteritis in humans. The over-use of antimicrobials in the human population and in animal husbandry has led to an increase in antimicrobial-resistant infections, particularly with fluoroquinolones and macrolides. The aim of the present study was to provide information of the current status of antimicrobial resistance patterns in Campylobacter jejuni from poultry sources. Fifty strains were recovered from broiler slaughterhouses in Rio Grande do Sul state, Brazil, 2012. The strains were investigated for antimicrobial susceptibility against three agents (ciprofloxacin, nalidixic acid and erythromycin) by minimal inhibitory concentrations. The strains were analysed by polymerase chain reaction-restriction fragment length polymorphism for detection of the Thr-86 mutation that confers resistance to ciprofloxacin. In addition, all the strains were tested for the presence of efflux systems (cmeB gene) conferring antimicrobial resistance. The minimum inhibitory concentrations results showed that 98% of isolates were sensitive to erythromycin and most isolates were resistant to ciprofloxacin (94%) and nalidixic acid (90%). A complete correlation was observed between the minimum inhibitory concentrations and PCR-RFLP assay. Finally, the cmeB gene that is responsible for multidrug resistance was detected in 16 isolates out the 50 strains (32%).

Rising fluoroquinolone resistance in Campylobacter isolated from feedlot cattle in the United States

Antibiotic resistance, particularly to fluoroquinolones and macrolides, in the major foodborne pathogen Campylobacter is considered a serious threat to public health. Although ruminant animals serve as a significant reservoir for Campylobacter, limited information is available on antibiotic-resistant Campylobacter of bovine origin. Here, we analyzed the antimicrobial susceptibilities of 320 C. jejuni and 115 C. coli isolates obtained from feedlot cattle farms in multiple states in the U.S. The results indicate that fluoroquinolone resistance reached to 35.4% in C. jejuni and 74.4% in C. coli, which are significantly higher than those previously reported in the U.S. While all fluoroquinolone resistant (FQ^R) C. coli isolates examined in this study harbored the single Thr-86-Ile mutation in GyrA, FQ^RC. jejuni isolates had other mutations in GyrA in addition to the Thr-86-Ile change. Notably, most of the analyzed FQ^RC. coli isolates had similar PFGE (pulsed field gel electrophoresis) patterns and the same MLST (multilocus sequence typing) sequence type (ST-1068) regardless of their geographic sources and time of isolation, while the analyzed C. jejuni isolates were genetically diverse, suggesting that clonal expansion is involved in dissemination of FQ^RC. coli but not C. jejuni. These findings reveal the rising prevalence of FQ^RCampylobacter in the U.S. and provide novel information on the epidemiology of antibiotic-resistant Campylobacter in the ruminant reservoir.

The Food Production Environment and the Development of Antimicrobial Resistance in Human Pathogens of Animal Origin

Food-borne pathogens are a serious human health concern worldwide, and the emergence of antibiotic-resistant food pathogens has further confounded this problem. Once-highly-efficacious antibiotics are gradually becoming ineffective against many important pathogens, resulting in severe treatment crises. Among several reasons for the development and spread of antimicrobial resistance, their overuse in animal food production systems for purposes other than treatment of infections is prominent. Many pathogens of animals are zoonotic, and therefore any development of resistance in pathogens associated with food animals can spread to humans through the food chain. Human infections by antibiotic-resistant pathogens such as Campylobacter spp., Salmonella spp., Escherichia coli and Staphylococcus aureus are increasing. Considering the human health risk due to emerging antibiotic resistance in food animal-associated bacteria, many countries have banned the use of antibiotic growth promoters and the application in animals of antibiotics critically important in human medicine. Concerted global efforts are necessary to minimize the use of antimicrobials in food animals in order to control the development of antibiotic resistance in these systems and their spread to humans via food and water.

Pathogens of Food Animals: Sources, Characteristics, Human Risk, and Methods of Detection

Pathogens associated with food production (livestock) animals come in many forms causing a multitude of disease for humans. For the purpose of this review, these infectious agents can be divided into three broad categories: those that are associated with bacterial disease, those that are associated with viruses, and those that are parasitic in nature. The goal of this chapter is to provide the reader with an overview of the most common pathogens that cause disease in humans through exposure via the food chain and the consequence of this exposure as well as risk and detection methods. We have also included a collection of unusual pathogens that although rare have still caused disease, and their recognition is warranted in light of emerging and reemerging diseases. These provide the reader an understanding of where the next big outbreak could occur. The influence of the global economy, the movement of people, and food makes understanding production animal-associated disease paramount to being able to address new diseases as they arise.

Bibliometric analysis of publications on Campylobacter: (2000-2015)

BACKGROUND

Campylobacter species are widespread zoonotic pathogens. Campylobacter jejuni causes a form of gastroenteritis called campylobacteriosis. Campylobacter drug resistance is considered a serious threat. In order to better understand national and international research output on Campylobacter, we conducted this bibliometric overview of publications on Campylobacter. This study can be used to assess extent of interaction and response of researchers, food regulators, and health policy makers to global burden of campylobacateriosis.

METHODS

Scopus database was used to retrieve publications with the following keywords (Campylobacter/campylobacteriosis, C. jejuni, C. coli). The study period was set from 2000 to 2015. All types of journal documents, excluding errata, were considered. Bibliometric indicators such as annual growth of publications, country contribution, international collaboration, and citation analysis were presented. The quality of retrieved data was indirectly assessed by Hirsch index and impact factor of journals.

RESULTS

A total of 5522 documents were retrieved with median (Q1-Q3) citations of 9 (2-23) and h-index of 113. Annual number of publications showed a fluctuating increase. The core leading journals were Applied and Environmental Microbiology journal and Journal of Food Protection with 246 (4.46%) publications for each. The USA (1309; 23.6%) was the most productive country while Danmarks Tekniske Universitet (150; 2.7%) was the most productive institution. Half of the top ten productive countries were European. France had the lowest percentage (33.5%) of articles with international collaboration while Netherlands (57.7%) had the highest percentage of articles with international collaboration. Approximately half (50.1%) of retrieved articles were published in journals under the subject area of "immunology/microbiology". Main themes in highly cited articles were molecular biology/genetics and public health burden of campylobacteriosis. There were 728 (13.1%) articles on campylobacter-related drug resistance, and the top cited articles focused mainly on increasing resistance to quinolones and fluoroquinolones.

CONCLUSIONS

There was a clear increase in number of publications on Campylobacter. Rational use of antimicrobials in humans, poultry, and animals is highly recommended. International collaboration is highly required particularly in implementing new diagnostic screening technologies to minimize global health burden of Campylobacter and ensure food safety.

Complete Genome Sequences of Multidrug-Resistant Campylobacter jejuni Strain 14980A (Turkey Feces) and Campylobacter coli Strain 14983A (Housefly from a Turkey Farm), Harboring a Novel Gentamicin Resistance Mobile Element

Multidrug resistance (MDR) in foodborne pathogens is a major food safety and public health issue. Here we describe whole-genome sequences of two MDR strains of Campylobacter jejuni and Campylobacter coli from turkey feces and a housefly from a turkey farm. Both strains harbor a novel chromosomal gentamicin resistance mobile element.

Risks Involved in the Use of Enrofloxacin for Salmonella Enteritidis or Salmonella Heidelberg in Commercial Poultry

The objectives of the present study were to evaluate the risks involved in the use of Enrofloxacin for Salmonella Enteritidis (SE) or Salmonella Heidelberg (SH) in commercial poultry and determine the effects of a probiotic as an antibiotic alternative. Two experiments were conducted to evaluate the risks involved in the use of Enrofloxacin for SE or SH in commercial poultry. Experiment 1 consisted of two trials. In each trial, chickens were assigned to one of three groups; control + SE challenged; Enrofloxacin 25 mg/kg + SE; and Enrofloxacin 50 mg/kg + SE. Chickens received Enrofloxacin in the drinking water from days 1 to 5 of age. On day 6, all groups received fresh water without any treatment. All chickens were orally gavaged with 10⁷ cfu/chick of SE at 7 days of age and euthanized on 8 days of age. In Experiment 2, turkey poults were assigned to one of the three groups; control + SH; probiotic + SH; and Enrofloxacin 50 mg/kg + SH. Poults received probiotic or Enrofloxacin in the drinking water from days 1 to 5 of age. On day 6, poults received fresh water without any treatment. Poults were orally gavaged with 10⁷ cfu/poult of SH at 7 days of age. Poults were weighed and humanely killed 24 h post-SH challenge to evaluate serum concentration of fluorescein isothiocyanate-dextran to evaluate intestinal permeability, metagenomics, and SH infection. In both trials of Experiment 1, chickens treated with Enrofloxacin were more susceptible to SE organ invasion and intestinal colonization when compared with control non-treated chickens (P < 0.05). In Experiment 2, poults treated with 50 mg/kg of Enrofloxacin showed an increase in body weight, however, this group also showed an increase in SH susceptibility, intestinal permeability, and lower proportion of Firmicutes and Bacteroidetes, but with control group had the highest proportion of Proteobacteria. By contrast, poults that received the probiotic had the highest proportion of Firmicutes and Bacteroidetes, but lowest Proteobacteria. The results of the present study suggest that prophylactic utilization of Enrofloxacin at five times the recommended dose in poultry increases the susceptibility to salmonellae infections, and confirms that probiotics may be an effective tool in salmonellae infections.

Adaptation of Campylobacter jejuni to biocides used in the food industry affects biofilm structure, adhesion strength, and cross-resistance to clinical antimicrobial compounds

The emergence of biocide-adapted Campylobacter jejuni strains that developed into biofilms and their potential to develop clinical resistance to antimicrobial compounds was studied. C. jejuni was grown in sub-lethal concentrations of five biocides used in the food industry. C. jejuni exhibited adaptation to these biocides with increased minimum inhibitory concentrations. The 3-D structures of the biofilms produced by the biocide-adapted cells were investigated by atomic force microscopy (AFM). The results revealed marked variability in biofilm architecture, including ice-crystal-like structures. Adaptation to the biocides enhanced biofilm formation, with significant increases in biovolume, surface coverage, roughness, and the surface adhesion force of the biofilms. Adaptation to commercial biocides induced resistance to kanamycin and streptomycin. This study suggests that the inappropriate use of biocides may lead to cells being exposed to them at sub-lethal concentrations, which can result in adaptation of the pathogens to the biocides and a subsequent risk to public health.

Distribution of Antimicrobial Resistance in Campylobacter Strains Isolated from Poultry at a Slaughterhouse and Supermarkets in Japan

Fifty strains of Campylobacter jejuni/coli were detected in 108 specimens of chicken meat and organs sampled at six supermarkets and one poultry slaughterhouse (large scale) between April and October 2013 (isolation rates: 84.8% from the slaughterhouse, 29.3% from the supermarkets). 46/50 strains were successfully recovered and subjected to the E-test to examine their susceptibility to three fluoroquinolone antibacterial agents authorized for use in poultry in Japan: enrofloxacin (ERFX), ofloxacin (OFLX), and norfloxacin (NLFX). 29 isolates (63%) were resistant to all three agents and 2 isolates (4.3%) were resistant to two agents (ERFX and OFLX). The resistance rates of strains isolated fom the supermarkets and slaughterhouse were 61.9% and 72.0%, respectively. Because the chickens processed at the slaughterhouse were raised without the use of fluoroquinolone, the results did not suggest a positive relationship between the use of these agents and the distribution of antimicrobial-resistant bacteria. Susceptibility to macrolide antibiotics (erythromycin [EM]) was also tested in 42 strains, and one strain (2.4%), C. coli from a retailer sample, showed resistance. Previous studies have detected high rates of fluoroquinolone-resistant strains, suggesting an expanding distribution of resistant bacteria. The detection of EM-resistant bacteria downstream in the food distribution chain (i.e., closer to consumers) is a concern for human health.

Antimicrobial-Resistant Escherichia coli Survived in Dust Samples for More than 20 Years

In a retrospective study, 119 sedimentation dust samples stored between five and 35 years from various barns of intensive livestock farming were evaluated for the occurrence of cultivatable Escherichia coli. Growth of E. coli occurred in 54 samples. Successful cultivation was achieved in samples from as early as 1994. The frequency of detection increased from earlier to later time periods, but the concentrations, which ranged between 3.4 × 10(2) and 1.1 × 10(5) colony-forming units per gram, did not correlate with sample age (Spearman rank correlation; p > 0.05). We hypothesize that E. coli cells survived in dust samples without cell division because of the storage conditions. Dry material (dust) with low water activities (arithmetic mean < 0.6) and storage at 4°C in the dark likely facilitated long-term survival. E. coli were isolated on MacConkey agar with and without ciprofloxacin supplementation. For 110 isolates (79 from non-supplemented media and 31 from supplemented media), we determined the E. coli phylotype and antimicrobial resistance. Six phylogenetic groups were identified. Phylogroups A and B1 predominated. Compared to group A, phylogroup B1 was significantly associated with growth on ciprofloxacin-supplemented media (chi-square test, p = 0.003). Furthermore, the antibiotic resistance profiles determined by a microdilution method revealed that isolates were phenotypically resistant to at least one antimicrobial substance and that more than 50% were resistant to a minimum of five out of 10 antibiotics tested. A linear mixed model was used to identify factors associated with the number of phenotypic resistances of individual isolates. Younger isolates and isolates from fattening poultry barns tended to be resistant to significantly more antibiotics than older isolates and those from laying-hen houses (p = 0.01 and p = 0.02, respectively). Sample origin and storage conditions may have influenced the number of antimicrobial resistances. Overall, we found that under particular conditions, dust from farm animal houses can be reservoirs for antimicrobial-resistant E. coli for at least 20 years. The survival strategies that allow E. coli to survive such long periods in environmental samples are not fully understood and could be an interesting research topic for future studies.

Antimicrobial Susceptibility of Campylobacter Cuniculorum Isolated from Rabbits Reared in Intensive and Rural Farms

The present study aimed to investigate the antimicrobial susceptibility in Campylobacter cuniculorum. To do so, 29 isolates from rabbits reared in 18 intensive and 11 rural farms not epidemiologically correlated were tested. Minimum inhibitory concentration of 8 antimicrobial agents was determined using the agar dilution method recommended by the Clinical and Laboratory Standards Institute (Wayne, PA, USA), modified - for what supplements in the base medium and incubation conditions concern - for C. cuniculorum isolates. The isolates obtained from rural farming resulted susceptible to all the antimicrobial agents tested, with the exception of one isolate resistant to nalidixic acid. All the isolates obtained from intensively farmed rabbits were sensitive to chloramphenicol and ampicillin; 16 isolates were resistant to tetracycline; 15 to nalidixic acid and erythromycin; 13 and 10 isolates to ciprofloxacin and enrofloxacin, respectively; and only 1 to gentamicin. The resistance of several isolates to macrolides and fluoroquinolones, which are the drugs of choice in treatment of human campylobacteriosis, could pose a risk to human health if a pathogenic role of C. cuniculorum was demonstrated.

High-Level Ciprofloxacin-Resistant Campylobacter jejuni Isolates Circulating in Humans and Animals in Incheon, Republic of Korea

Campylobacter jejuni is one of the major causative pathogens of outbreaks or sporadic cases of diarrhoeal diseases worldwide. In this study, we compared the phenotypic and genetic characteristics of C. jejuni isolates of human and food-producing animal origins in Korea and examined the genetic relatedness between these two groups of isolates. Regardless of isolation source, all C. jejuni isolates harboured four virulence genes, cadF, cdtB, ciaB and racR, whereas the wlaN and virB11 genes were more frequently observed in human isolates. Antimicrobial susceptibility testing showed that the majority of C. jejuni isolates displayed high-level resistance to fluoroquinolone (95.2%) or tetracycline (76.2%) antibiotics, and 12.4% of isolates exhibited multidrug resistance (more than three classes of antibiotics tested). Pulsed-field gel electrophoresis (PFGE) of all Campylobacter isolates revealed 51 different SmaI-PFGE patterns and six major clusters containing both human and animal isolates. These results indicate that genetically diverse strains of C. jejuni with antimicrobial drug-resistance and virulence properties have prevailed in Incheon. Nevertheless, some particular populations continue to circulate within the community, providing the evidence for an epidemiological link of C. jejuni infections between humans and food-producing animals. Therefore, the continued monitoring and surveillance of C. jejuni isolates of human and food-producing animal origins are required for public health and food safety.

Countering drug resistance, infectious diseases, and sepsis using metal and metal oxides nanoparticles: Current status

One fourth of the global mortalities is still caused by microbial infections largely due to the development of resistance against conventional antibiotics among pathogens, the resurgence of old infectious diseases and the emergence of hundreds of new infectious diseases. The lack of funds and resources for the discovery of new antibiotics necessitates the search for economic and effective alternative antimicrobial agents. Metal and metal oxide nanoparticles including silver and zinc oxide exhibit remarkable antimicrobial activities against pathogens and hence are one of the most propitious alternative antimicrobial agents. These engineered nanomaterials are approved by regulatory agencies such as USFDA and Korea's FITI, for use as antimicrobial agents, supplementary antimicrobials, food packaging, skin care products, oral hygiene, and for fortifying devices prone to microbial infections. Nevertheless, detailed studies, on molecular and biochemical mechanisms underlying their antimicrobial activity are missing. To take the full advantage of this emerging technology selective antimicrobial activity of these nanoparticles against pathogens should be studied. Optimization of these nanomaterials through functionalization to increase their efficacy and biocompatibility is also required. Urgent in vivo studies on the toxicity of nanomaterials at realistic doses are also needed before their clinical translation.

Molecular subtyping and erythromycin resistance of Campylobacter in China

AIMS

To investigate the erythromycin resistance patterns and mechanism for Campylobacter isolates in China.

METHODS AND RESULTS

The minimum inhibitory concentrations of erythromycin on 858 Chinese Campylobacter isolates were analysed. PCR and DNA sequencing were used to identify mutations in the 23S rRNA and the presence of the ermB gene in the 158 erythromycin resistance isolates (18·4%). About 83% (131/158) had A2075G mutation in their 23S rRNA; no A2074C/G mutants were found. The ermB gene was identified in 30 Campylobacter coli isolates (19%). Four types of multidrug-resistant gene islands (MDRGIs) were found. Fifty-three types were identified by multilocus sequence typing among the resistant isolates. All isolates of STs 6322 and 1145 had the ermB gene.

CONCLUSIONS

The erythromycin resistance rate of Camp. coli (58·56%) was much higher than Campylobacter jejuni (0·67%). The insertion sites between cadF and CCO1582 and between nfsB and cinA on the chromosome might be hot spots for MDRGI transformation.

SIGNIFICANCE AND IMPACT OF THE STUDY

Point mutation in domain V of the 23S rRNA and the ermB gene accounted for 100% of the erythromycin resistance of Campylobacter in China.

Antimicrobial Susceptibility Profiles of Human Campylobacter jejuni Isolates and Association with Phylogenetic Lineages

Campylobacter jejuni is a zoonotic pathogen and the most common bacterial cause of human gastroenteritis worldwide. With the increase of antibiotic resistance to fluoroquinolones and macrolides, the drugs of choice for treatment, C. jejuni was recently classified as a serious antimicrobial resistant threat. Here, we characterized 94 C. jejuni isolates collected from patients at four Michigan hospitals in 2011 and 2012 to determine the frequency of resistance and association with phylogenetic lineages. The prevalence of resistance to fluoroquinolones (19.1%) and macrolides (2.1%) in this subset of C. jejuni isolates from Michigan was similar to national reports. High frequencies of fluoroquinolone-resistant C. jejuni isolates, however, were recovered from patients with a history of foreign travel. A high proportion of these resistant isolates were classified as multilocus sequence type (ST)-464, a fluoroquinolone-resistant lineage that recently emerged in Europe. A significantly higher prevalence of tetracycline-resistant C. jejuni was also found in Michigan and resistant isolates were more likely to represent ST-982, which has been previously recovered from ruminants and the environment in the U.S. Notably, patients with tetracycline-resistant C. jejuni infections were more likely to have contact with cattle. These outcomes prompt the need to monitor the dissemination and diversification of imported fluoroquinolone-resistant C. jejuni strains and to investigate the molecular epidemiology of C. jejuni recovered from cattle and farm environments to guide mitigation strategies.

Agricultural Applications for Antimicrobials. A Danger to Human Health: An Official Position Statement of the Society of Infectious Diseases Pharmacists

The use of antibiotics in agriculture, particularly in food-producing animals, is pervasive and represents the overwhelming majority of antibiotic use worldwide. The link between antibiotic use in animals and antibiotic resistance in humans is unequivocal. Transmission can occur by ingesting undercooked meats harboring resistant bacteria, by direct contact of animals by animal handlers, and by various other means. Antibiotics used in aquaculture and antifungals used in horticulture are also an evolving threat to human health. Regulations aimed at decreasing the amount of antibiotics used in food production to limit the development of antibiotic resistance have recently been implemented. However, further action is needed to minimize antibiotic use in agriculture. This article describes the extent of this current problem and serves as the official position of the Society of Infectious Diseases Pharmacists on this urgent threat to human health.

Mycoplasmas and Their Antibiotic Resistance: The Problems and Prospects in Controlling Infections

The present review discusses the problem of controlling mycoplasmas (class Mollicutes), the smallest of self-replicating prokaryotes, parasites of higher eukaryotes, and main contaminants of cell cultures and vaccines. Possible mechanisms for the rapid development of resistance to antimicrobial drugs in mycoplasmas have been analyzed. Omics technologies provide new opportunities for investigating the molecular basis of bacterial adaptation to stress factors and identifying resistomes, the total of all genes and their products contributing to antibiotic resistance in microbes. The data obtained using an integrated approach with post-genomics methods show that antibiotic resistance may be caused by more complex processes than has been believed heretofore. The development of antibiotic resistance in mycoplasmas is associated with essential changes in the genome, proteome, and secretome profiles, which involve many genes and proteins related to fundamental cellular processes and virulence.

Impact of mutations in DNA gyrase genes on quinolone resistance in Campylobacter jejuni

Amino acid substitutions providing quinolone resistance to Campyloabcter jejuni have been found in the quinolone resistance-determining region of protein DNA gyrase subunit A (GyrA), with the highest frequency at position 86 followed by position 90. In this study, wild-type and mutant recombinant DNA gyrase subunits were expressed in Escherichia coli and purified using Ni-NTA agarose column chromatography. Soluble 97 kDa GyrA and 87 kDa DNA gyrase subunit B were shown to reconstitute ATP-dependent DNA supercoiling activity. A quinolone-inhibited supercoiling assay demonstrated the roles of Thr86Ile, Thr86Ala, Thr86Lys, Asp90Asn, and Asp90Tyr amino acid substitutions in reducing sensitivity to quinolones. The marked effect of Thr86Ile on all examined quinolones suggested the advantage of this substitution in concordance with recurring isolation of quinolone-resistant C. jejuni. An analysis of the structure-activity relationship showed the importance of the substituent at position 8 in quinolones to overcome the effect of Thr86Ile. Sitafloxacin (SIT), which has a fluorinate cyclopropyl ring at R-1 and a chloride substituent at R-8, a characteristic not found in other quinolones, showed the highest inhibitory activity against all mutant C. jejuni gyrases including ciprofloxacin-resistant mutants. The results suggest SIT as a promising drug for the treatment of campylobacteriosis caused by CIP-resistant C. jejuni. Copyright © 2016 John Wiley & Sons, Ltd.

The use of FTA cards for transport and detection of gyrA mutation of Campylobacter jejuni from poultry

The purpose of the present study was to evaluate a technique involving the use of commercially available FTA classic card (Whatman) for transporting and detection of DNA to use in PCR analysis and genetic sequencing of Campylobacter jejuni of poultry origin. Fifty isolates of Campylobacter jejuni were obtained from broiler carcasses in Rio Grande do Sul, Brazil. Antimicrobial susceptibility testing to ciprofloxacin revealed that all 50 isolates were resistant to ciprofloxacin. Each isolate was transferred to Brucella broth tubes and incubated overnight at 41.5°C. Cell cultures were diluted to match a McFarland Turbidity Standard 0.5, and 110 μL of the cell suspension were applied to one circle on Whatman FTA classic cards. The samples were then covered and allowed to dry at room temperature. Cards were identified and stored at room temperature until further use (3 mo after collection). FTA cards were shipped for analysis to the Department of Poultry Science, University of Arkansas. Amplification of the Campylobacter gyrA gene was successful and demonstrated strong bands for a large amplicon for all 50 samples preserved on FTA cards. Mutations present in each gene were confirmed by DNA sequencing. Then, 7 samples were chosen for the sequencing. The detection of a mutation regarding ciprofloxacin-resistant isolates revealed that 7 samples had a mutation in the gyrA gene. In conclusion, the characteristics of the profiles suggest that the DNA has maintained its integrity after 3 mo of storage at room temperature and is a suitable template for PCR and sequencing from Campylobacter samples. The application of this technology has potential in numerous methodologies, especially when working in remote areas and in developing countries where access to laboratory facilities and equipment is limited.

Campylobacter in Poultry: Ecology and Potential Interventions

Avian hosts constitute a natural reservoir for thermophilic Campylobacter species, primarily Campylobacter jejuni and Campylobacter coli, and poultry flocks are frequently colonized in the intestinal tract with high numbers of the organisms. Prevalence rates in poultry, especially in slaughter-age broiler flocks, could reach as high as 100% on some farms. Despite the extensive colonization, Campylobacter is essentially a commensal in birds, although limited evidence has implicated the organism as a poultry pathogen. Although Campylobacter is insignificant for poultry health, it is a leading cause of food-borne gastroenteritis in humans worldwide, and contaminated poultry meat is recognized as the main source for human exposure. Therefore, considerable research efforts have been devoted to the development of interventions to diminish Campylobacter contamination in poultry, with the intention to reduce the burden of food-borne illnesses. During the past decade, significant advance has been made in understanding Campylobacter in poultry. This review summarizes the current knowledge with an emphasis on ecology, antibiotic resistance, and potential pre- and postharvest interventions.

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.

Constitutive and Inducible Expression of the rRNA Methylase Gene erm(B) in Campylobacter

Macrolides are the antimicrobials of choice for treating human campylobacteriosis. The recent emergence of erm(B) in Campylobacter bacteria threatens the utility of this class of antibiotics. Here we report the constitutive and inducible expression of erm(B) in Campylobacter isolates derived from diarrheal patients and food-producing animals. Constitutive expression of erm(B) was associated with insertion and deletion in the regulatory region of the gene, providing the first documentation of the differential expression of erm(B) in Campylobacter bacteria.

A single nucleotide change in mutY increases the emergence of antibiotic-resistant Campylobacter jejuni mutants

OBJECTIVES

Mutator strains play an important role in the emergence of antibiotic-resistant bacteria. Campylobacter jejuni is a leading cause of foodborne illnesses worldwide and is increasingly resistant to clinically important antibiotics. The objective of this study was to identify the genetic basis that contributes to a mutator phenotype in Campylobacter and determine the role of this phenotype in the development of antibiotic resistance.

METHODS

A C. jejuni isolate (named CMT) showing a mutator phenotype was subjected to WGS analysis. Comparative genomics, site-specific reversion and mutation, and gene knockout were conducted to prove the mutator effect was caused by a single nucleotide change in the mutY gene of C. jejuni.

RESULTS

The C. jejuni CMT isolate showed ∼ 100-fold higher mutation frequency to ciprofloxacin than the WT strain. Under selection by ciprofloxacin, fluoroquinolone-resistant mutants emerged readily from the CMT isolate. WGS identified a single nucleotide change (G595 → T) in the mutY gene of the CMT isolate. Further experiments using defined mutant constructs proved its specific role in elevating mutation frequencies. The mutY point mutation also led to an ∼ 700-fold increase in the emergence of ampicillin-resistant mutants, indicating its broader impact on antibiotic resistance. Structural modelling suggested the G595 → T mutation probably affects the catalytic domain of MutY and consequently abolishes the anti-mutator function of this DNA repair protein.

CONCLUSIONS

The G595 → T mutation in mutY abolishes its anti-mutator function and confers a mutator phenotype in Campylobacter, promoting the emergence of antibiotic-resistant Campylobacter.

Prevalence and Antimicrobial Resistance of Campylobacter Isolated from Dressed Beef Carcasses and Raw Milk in Tanzania

Campylobacter species are commonly transmitted to humans through consumption of contaminated foods such as milk and meat. The aim of this study was to investigate the prevalence, antimicrobial resistance, and genetic determinants of resistance of Campylobacter isolated from raw milk and beef carcasses in Tanzania. The antimicrobial resistance genes tested included blaOXA-61 (ampicillin), aph-3-1 (aminoglycoside), tet(O) (tetracycline), and cmeB (multi-drug efflux pump). The prevalence of Campylobacter was 9.5% in beef carcasses and 13.4% in raw milk, respectively. Using multiplex-polymerase chain reaction (PCR), we identified 58.1% of the isolates as Campylobacter jejuni, 30.7% as Campylobacter coli, and 9.7% as other Campylobacter spp. One isolate (1.6%) was positive for both C. jejuni and C. coli specific PCR. Antimicrobial susceptibility testing using the disk diffusion assay and the broth microdilution method showed resistance to: ampicillin (63% and 94.1%), ciprofloxacin (9.3% and 11.8%), erythromycin (53.7% and 70.6%), gentamicin (0% and 15.7%), streptomycin (35.2% and 84.3%), and tetracycline (18.5% and 17.7%), respectively. Resistance to azithromycin (42.6%), nalidixic acid (64.8%), and chloramphenicol (13%) was determined using the disk diffusion assay only, while resistance to tylosin (90.2%) was quantified using the broth microdilution method. The blaOXA-61 (52.6% and 28.1%), cmeB (26.3% and 31.3%), tet(O) (26.3% and 31.3%), and aph-3-1 (5.3% and 3.0%) were detected in C. coli and C. jejuni. These findings highlight the extent of antimicrobial resistance in Campylobacter occurring in important foods in Tanzania. The potential risks to consumers emphasize the need for adequate control approaches, including the prudent use of antimicrobials to minimize the spread of antimicrobial-resistant Campylobacter.

Resistance to β-lactam and tetracycline in Campylobacter spp.isolated from broiler slaughterhouses in southern Brazil

Abstract The study was carried out to screen and analyze the genetic characteristics of antimicrobial resistance in Campylobacter spp. from poultry sources. A total of 141 strains of Campylobacter isolated from samples of broilers of slaughterhouses in southern Brazil was identified by phenotypic and genotypic methods. Campylobacter isolates were evaluated for its antimicrobial susceptibility and the presence of resistance genes. The strains were investigated for antimicrobial susceptibility against two agents (ampicillin and tetracycline) by disk diffusion method. PCR assay was used to confirm the specie and the presence of ampicillin (blaOXA-61), tetracycline tet(O), and the energy-dependent multi-drug efflux pump (cmeB) genes. Campylobacter jejuni was the most ubiquitous; its presence was determined in 140 samples out of 141 (99.3%), whereas Campylobacter coli was found only in one of the contaminated samples (0.70%). The results obtained showed 65% and 35.5% of Campylobacter isolates resistant to β-lactams and tetracyclines, respectively. The cmeB gene responsible for multidrug resistance was detected in 26 isolates out 141 strains (18.5%). Moreover, 36 out of 141 Campylobacter strains (25.6%) were found to be resistant to at least two different antimicrobia resistance markers (β-lactams and tetracyclines).

Novel Drug Targets for Food-Borne Pathogen Campylobacter jejuni: An Integrated Subtractive Genomics and Comparative Metabolic Pathway Study

Campylobacters are a major global health burden and a cause of food-borne diarrheal illness and economic loss worldwide. In developing countries, Campylobacter infections are frequent in children under age two and may be associated with mortality. In developed countries, they are a common cause of bacterial diarrhea in early adulthood. In the United States, antibiotic resistance against Campylobacter is notably increased from 13% in 1997 to nearly 25% in 2011. Novel drug targets are urgently needed but remain a daunting task to accomplish. We suggest that omics-guided drug discovery is timely and worth considering in this context. The present study employed an integrated subtractive genomics and comparative metabolic pathway analysis approach. We identified 16 unique pathways from Campylobacter when compared against H. sapiens with 326 non-redundant proteins; 115 of these were found to be essential in the Database of Essential Genes. Sixty-six proteins among these were non-homologous to the human proteome. Six membrane proteins, of which four are transporters, have been proposed as potential vaccine candidates. Screening of 66 essential non-homologous proteins against DrugBank resulted in identification of 34 proteins with drug-ability potential, many of which play critical roles in bacterial growth and survival. Out of these, eight proteins had approved drug targets available in DrugBank, the majority serving crucial roles in cell wall synthesis and energy metabolism and therefore having the potential to be utilized as drug targets. We conclude by underscoring that screening against these proteins with inhibitors may aid in future discovery of novel therapeutics against campylobacteriosis in ways that will be pathogen specific, and thus have minimal toxic effect on host. Omics-guided drug discovery and bioinformatics analyses offer the broad potential for veritable advances in global health relevant novel therapeutics.

Practical Guidance for Clinical Microbiology Laboratories: Diagnosis of Bacterial Gastroenteritis

Bacterial gastroenteritis is a disease that is pervasive in both the developing and developed worlds. While for the most part bacterial gastroenteritis is self-limiting, identification of an etiological agent by bacterial stool culture is required for the management of patients with severe or prolonged diarrhea, symptoms consistent with invasive disease, or a history that may predict a complicated course of disease. Importantly, characterization of bacterial enteropathogens from stool cultures in clinical laboratories is one of the primary means by which public health officials identify and track outbreaks of bacterial gastroenteritis. This article provides guidance for clinical microbiology laboratories that perform stool cultures. The general characteristics, epidemiology, and clinical manifestations of key bacterial enteropathogens are summarized. Information regarding optimal specimen collection, transport, and processing and current diagnostic tests and testing algorithms is provided. This article is an update of Cumitech 12A (P. H. Gilligan, J. M. Janda, M. A. Karmali, and J. M. Miller, Cumitech 12A, Laboratory diagnosis of bacterial diarrhea, 1992).

Characterization of Campylobacter jejuni DNA gyrase as the target of quinolones

Quinolones have long been used as the first-line treatment for Campylobacter infections. However, an increased resistance to quinolones has raised public health concerns. The development of new quinolone-based antibiotics with high activity is critical for effective, as DNA gyrase, the target of quinolones, is an essential enzyme for bacterial growth in several mechanisms. The evaluation of antibiotic activity against Campylobacter jejuni largely relies on drug susceptibility tests, which require at least 2 days to produce results. Thus, an in vitro method for studying the activity of quinolones against the C. jejuni DNA gyrase is preferred. To identify potent quinolones, we investigated the interaction of C. jejuni DNA gyrase with a number of quinolones using recombinant subunits. The combination of purified subunits exhibited DNA supercoiling activity in an ATP dependent manner. Drug concentrations that inhibit DNA supercoiling by 50% (IC50s) of 10 different quinolones were estimated to range from 0.4 (sitafloxacin) to >100 μg/mL (nalidixic acid). Sitafloxacin showed the highest inhibitory activity, and the analysis of the quinolone structure-activity relationship demonstrated that a fluorine atom at R-6 might play the important role in the inhibitory activity against C. jejuni gyrase. Measured quinolone IC50s correlated well with minimum inhibitory concentrations (R = 0.9943). These suggest that the in vitro supercoiling inhibition assay on purified recombinant C. jejuni DNA gyrase is a useful and predictive technique to monitor the antibacterial potency of quinolones. And furthermore, these data suggested that sitafloxacin might be a good candidate for clinical trials on campylobacteriosis.

Antimicrobial susceptibility testing of bacteria that cause gastroenteritis

Gastroenteritis due to enteric pathogens is generally a self-limiting disease for which antimicrobial treatment is not required. However, treatment should be considered for cases of severe or prolonged diarrhea, extraintestinal isolation of bacteria, or diarrhea in immunocompromised hosts, the elderly, and infants. Various resistance trends and current issues concerning antimicrobial susceptibility testing of enteric pathogens are reviewed in this article, including Campylobacter, Salmonella, Shigella, Vibrio, Aeromonas, Plesiomonas, and Clostridium difficile. Updated interpretive criteria from breakpoint-setting organizations are reviewed, along with explanations for recent changes in antimicrobial breakpoints.

Antimicrobial susceptibility profiles and molecular typing of Campylobacter jejuni and Campylobacter coli isolates from ducks in South Korea

Campylobacter is a food-borne zoonotic pathogen that causes human gastroenteritis worldwide. Campylobacter bacteria are commensal in the intestines of many food production animals, including ducks and chickens. The objective of the study was to determine the prevalence of Campylobacter species in domestic ducks, and the agar dilution method was used to determine resistance of the isolates to eight antibiotics. In addition, multilocus sequence typing (MLST) was performed to determine the sequence types (STs) of selected Campylobacter isolates. Between May and September 2012, 58 duck farms were analyzed, and 56 (96.6%) were positive for Campylobacter. Among the isolates, 82.1% were Campylobacter jejuni, 16.1% were C. coli, and one was unidentified by PCR. Of the 46 C. jejuni isolates, 87.0%, 10.9%, and 21.7% were resistant to ciprofloxacin, erythromycin, and azithromycin, respectively. Among the C. coli isolates, all 9 strains were resistant to ampicillin, and 77.8% and 33.3% were resistant to ciprofloxacin and azithromycin, respectively. The majority of the Campylobacter isolates were classified as multidrug resistant. Twenty-eight STs were identified, including 20 STs for C. jejuni and 8 STs for C. coli. The most common clonal complexes in C. jejuni were the ST-21 complex and the ST-45 complex, while the ST-828 complex predominated in C. coli. The majority of isolates were of STs noted in ducks and humans from earlier studies, along with seven STs previously associated only with human disease. These STs overlapped between duck and human isolates, indicating that Campylobacter isolates from ducks should be considered potential sources of human infection.

Enhanced transmission of antibiotic resistance in Campylobacter jejuni biofilms by natural transformation

Campylobacter jejuni is a leading food-borne pathogen, and its antibiotic resistance is of serious concern to public health worldwide. C. jejuni is naturally competent for DNA transformation and freely takes up foreign DNA harboring genetic information responsible for antibiotic resistance. In this study, we demonstrate that C. jejuni transfers antibiotic resistance genes more frequently in biofilms than in planktonic cells by natural transformation.

Antibiotics in agriculture and the risk to human health: how worried should we be?

The use of antibiotics in agriculture is routinely described as a major contributor to the clinical problem of resistant disease in human medicine. While a link is plausible, there are no data conclusively showing the magnitude of the threat emerging from agriculture. Here, we define the potential mechanisms by which agricultural antibiotic use could lead to human disease and use case studies to critically assess the potential risk from each. The three mechanisms considered are as follows 1: direct infection with resistant bacteria from an animal source, 2: breaches in the species barrier followed by sustained transmission in humans of resistant strains arising in livestock, and 3: transfer of resistance genes from agriculture into human pathogens. Of these, mechanism 1 is the most readily estimated, while significant is small in comparison with the overall burden of resistant disease. Several cases of mechanism 2 are known, and we discuss the likely livestock origins of resistant clones of Staphylococcus aureus and Enterococcus faecium, but while it is easy to show relatedness the direction of transmission is hard to assess in robust fashion. More difficult yet to study is the contribution of mechanism 3, which may be the most important of all.