Nosocomial infection caused by class 1 integron-carrying Staphylococcus aureus in a hospital in South China

Kanamycin promotes biofilm viability of MRSA strains showing extremely high resistance to kanamycin

Staphylococcus aureus is widely distributed in environment and can cause various human infection and food poisoning cases. Also, this pathogen is a typical biofilm former, which further complicates its pathogenicity. Antibiotics have been widely used to eliminate pathogenic bacteria, but their indiscriminate use has also led to the widespread emergence of drug-resistant bacteria, such as Methicillin-Resistant Staphylococcus aureus (MRSA). In this study, the effect of antibiotics on biofilm formation of MRSA strains 875 and 184 was explored. Firstly, MRSA 875 belongs to SCCmec type IV, ST239, carrying the atl, icaA, icaD, icaBC, and aap genes, and MRSA 184 belongs to SCCmec type II, ST5, carrying the atl, icaD, icaBC, aap, and agr genes. Then, a total of 8 antibiotics have been selected, including kanamycin, gentamycin, cipprofloxacin, erythromycin, meropenem, penicillin G, tetracycline, vancomycin. Minimum inhibitory concentrations (MICs) of each antibiotic were determined, and MIC of MRSA 875 and 184 to kanamycin/gentamicin are 2048/64 μg/mL and 2048/4 μg/mL, respectively. A total of 10 concentrations, ranging from 1/128 to 4 MIC with 2-fold, were used to study biofilm formation. Biofilm biomass and viability were determined during different phases, including initial adhesion (8 h), proliferation (16 h), accumulation (24 h) and maturation (48 h). Importantly, kanamycin at specific concentrations showed significant promotion of biofilm biomass and biofilm viability, with none of such observation acquired from other antibiotics. This study provides scientific basis and new research ideas for the quality control technology of microorganisms and safety prevention of MRSA.

Antibiotic resistance pattern of waterborne causative agents of healthcare-associated infections: A call for biofilm control in hospital water systems

BACKGROUND

In recent years, the global spread of antimicrobial resistance has become a concerning issue, often referred to as a "silent pandemic". Healthcare-associated infections (HAIs) caused by antibiotic-resistant bacteria (ARB) are a recurring problem, with some originating from waterborne route. The study aimed to investigate the presence of clinically relevant opportunistic bacteria and antibiotic resistance genes (ARGs) in hospital water distribution systems (WDSs).

METHODS

Water and biofilm samples (n = 192) were collected from nine hospitals in Isfahan and Kashan, located in central Iran, between May 2022 and June 2023. The samples were analyzed to determine the presence and quantities of opportunistic bacteria and ARGs using cultural and molecular methods.

RESULTS

Staphylococcus spp. were highly detected in WDS samples (90 isolates), with 33 % of them harboring mecA gene. However, the occurrences of E. coli (1 isolate), Acinetobacter baumannii (3 isolates), and Pseudomonas aeruginosa (14 isolates) were low. Moreover, several Gram-negative bacteria containing ARGs were identified in the samples, mainly belonging to Stenotrophomonas, Sphingomonas and Brevundimonas genera. Various ARGs, as well as intI1, were found in hospital WDSs (ranging from 14 % to 60 %), with higher occurrences in the biofilm samples.

CONCLUSION

Our results underscore the importance of biofilms in water taps as hotspots for the dissemination of opportunistic bacteria and ARG within hospital environments. The identification of multiple opportunistic bacteria and ARGs raises concerns about the potential exposure and acquisition of HAIs, emphasizing the need for proactive measures, particularly in controlling biofilms, to mitigate infection risks in healthcare settings.

Molecular characterization of non-aureus staphylococci and Mammaliicoccus from Hipposideros bats in Southwest Nigeria

Bats are not only ecologically valuable mammals but also reservoirs of zoonotic pathogens. Their vast population, ability to fly, and inhabit diverse ecological niches could play some role in the spread of antibiotic resistance. This study investigated non-aureus staphylococci and Mammaliicoccus colonization in the Hipposideros bats at Obafemi Awolowo University, Ile-Ife, Nigeria. Pharyngeal samples (n = 23) of the insectivorous bats were analyzed, and the presumptive non-aureus staphylococcal and Mammaliicoccus isolates were confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The isolates were characterized based on antibiotic susceptibility testing and whole-genome sequencing (WGS). Six bacterial genomes were assembled, and three species were identified, including Mammaliicoccus sciuri (n = 4), Staphylococcus gallinarum (n = 1), and Staphylococcus nepalensis (n = 1). All the isolates were resistant to clindamycin, while the M. sciuri and S. gallinarum isolates were also resistant to fusidic acid. WGS analysis revealed that the M. sciuri and S. gallinarum isolates were mecA-positive. In addition, the M. sciuri isolates possessed some virulence (icaA, icaB, icaC, and sspA) genes. Multi-locus sequence typing identified two new M. sciuri sequence types (STs) 233 and ST234. The identification of these new STs in a migratory mammal deserves close monitoring because previously known ST57, ST60, and ST65 sharing ack (8), ftsZ (13), glpK (14), gmk (6), and tpiA (10) alleles with ST233 and ST234 have been linked to mastitis in animals. Moreover, the broad host range of M. sciuri could facilitate the dispersal of antibiotic resistance genes. This study provides evidence of the importance of including migratory animals in monitoring the development and spread of antibiotic resistance.

Enhanced Biofilm Formation by Tetracycline in a Staphylococcus aureus Naturally Lacking ica Operon and atl

Staphylococcus aureus is a major, widespread pathogen, and its biofilm-forming characteristics make it even more difficult to eliminate by biocides. Tetracycline (TCY) is a major broad-spectrum antibiotic, the residues of which can cause deleterious health impacts, and subinhibitory concentrations of TCY have the potential to increase biofilm formation in S. aureus. In this study, we showed how the biofilm formation of S. aureus 123786 is enhanced in the presence of TCY at specific subinhibitory concentrations. S. aureus 123786 used in this study was identified as Staphylococcal Cassette Chromosome mec III, sequence type239 and naturally lacking ica operon and atl gene. Two assays were performed to quantify the formation of S. aureus biofilm. In the crystal violet (CV) assay, the absorbance values of biofilm stained with CV at optical density (OD)540 nm increased after 8 and 16 hr of incubation when the concentration of TCY was 1/2 minimum inhibitory concentration (MIC), whereas at the concentration of 1/16 MIC, the absorbance values increased after 16 and 24 hr of incubation. In tetrazolium salt reduction assay, the absorbance value at OD490 nm of S. aureus 123786 biofilms mixed with 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium solution increased after 8 hr when the concentration of TCY was 1/4 MIC, which may be correlated with the higher proliferation and maturation of biofilm. In conclusion, the biofilm formation of S. aureus 123786 could be enhanced in the presence of TCY at specific subinhibitory concentrations.

A decennial study of the trend of antibiotic studies in China

Antibiotics are one of the greatest inventions in human history and are used worldwide on an enormous scale. Besides its extensive usage in medical and veterinary arenas to treat and prevent the infection, its application is very prominent in other fields, including agriculture, aquaculture, and horticulture. In recent decades, the increased consumption of antibiotics in China saw a vast increase in its production and disposal in various environments. However, in this post-antibiotic era, the abuse and misuse of these valuable compounds could lead to the unreversible consequence of drug resistance. In China, antibiotics are given a broad discussion in various fields to reveal their impact on both human/animals health and the environment. To our knowledge, we are the first paper to look back at the development trend of antibiotic-related studies in China with qualitative and quantitative bibliometric analysis from the past decades. Our study identified and analyzed 5559 papers from its inception (1991) to December 6, 2021, from the Web of Science Core Collection database. However, with few authors and institutions focusing on long-term studies, we found the quality of contributions was uneven. Studies mainly focused on areas such as food science, clinical research, and environmental studies, including molecular biology, genetics and environmental, ecotoxicology, and nutrition, which indicate possible primary future trends. Our study reports on including potentially new keywords, studies' milestones, and their contribution to antibiotic research. We offer potential topics that may be important in upcoming years that could help guide future research.

Antimicrobial Resistance, SCCmec, Virulence and Genotypes of MRSA in Southern China for 7 Years: Filling the Gap of Molecular Epidemiology

As the prevalence of Staphylococcus aureus infections is of worldwide concern, phenotype and genotype in prevalent MRSA strains require longitudinal investigation. In this study, the antibiotic resistance, virulence gene acquisition, and molecular type were determined on a large scale of nosocomial S. aureus strains in Southern China during 2009-2015. Bacterial identification and antimicrobial susceptibility to 10 antibiotics were tested by Vitek-2. Virulence genes encoding staphylococcal enterotoxins (SEA, SEB, SEC, SED, and SEE), exfoliative toxins (ETA and ETB), Panton-Valentine leukocidin (PVL), and toxic shock syndrome toxin (TSST) were detected by PCR, with SCCmec typing also conducted by multiplex PCR strategy. Genotypes were discriminated by MLST and spaA typing. MLST was performed by amplification of the internal region of seven housekeeping genes. PCR amplification targeting the spa gene was performed for spa typing. No resistance to vancomycin, linezolid, or quinupristin and increase in the resistance to trimethoprim/sulfamethoxazole (55.5%) were identified. A total of nine SCCmec types and subtypes, thirteen STs clustered into thirteen spa types were identified, with ST239-SCCmec III-t037 presenting the predominant methicillin-resistant S. aureus (MRSA) clone. Typically, SCCmec type IX and ST546 were emergent types in China. Isolates positive for both pvl and tsst genes and for both eta and etb genes were also identified. Important findings in this study include: firstly, we have provided comprehensive knowledge on the molecular epidemiology of MRSA in Southern China which fills the gap since 2006 or 2010 from previous studies. Secondly, we have presented the correlation between virulence factors (four major groups) and genotypes (SCCmec, ST and spa types). Thirdly, we have shown evidence for earliest emergence of type I SCCmec from 2012, type VI from 2009 and type XI from 2012 in MRSA from Southern China.

Intense pulsed light for inactivating planktonic and biofilm molds in food

It has been reported that about a quarter of the world's agriculture products is unable to be consumed each year because of mold contamination, resulting in incalculable economic losses. Despite modern food technology and the various preservation techniques available, the problem of mold contamination of food is still not adequately controlled. In this study, we simulated the biofilm formed by Aspergillus niger and Penicillium glaucum in liquid and solid food in 96 well cell culture plates and polycarbonate membrane models, respectively, and investigated the fungicidal effect of IPL on planktonic and biofilm molds at three different capacitance parameters at room and refrigerator temperatures. The results show that IPL can achieve fungicidal rates of over 99% for planktonic molds and over 90% for biofilm molds, and that the smaller the capacitance, the more frequent the irradiation required to achieve the same fungicidal rate. In addition, temperature, A. niger or Penicillium glaucum have no effect on the fungicidal effect of IPL. We believe that IPL is a promising non-thermal physical sterilization technique for fungal inhibition on food surfaces.

Prevalence and Potential Risk Factors for the Acquisition of Antibiotic-Resistant Staphylococcus spp. Bacteria Among Pastoralist Farmers in Kajiado Central Subcounty, Kenya

Antimicrobial resistance (AMR) is a growing health problem globally. To address this challenge, there is a need to generate baseline data on the prevalence and AMR profile of the main disease-causing bacteria. Here, we interrogated the prevalence of bacteria in the nasal cavity of healthy pastoralists in Kajiado Central Subcounty, Kenya, and the occurrence of AMR in Staphylococcus isolates among the study subjects. Nasal swabs from 176 pastoralists were cultured, and the bacteria isolates identified using standard phenotypic and biochemical bacteriological methods. Among the obtained 195 isolates, the most prevalent isolates were coagulase-negative Staphylococcus (CoNS) (44.9%), followed by Enterococci spp. (43.2%) while Staphylococcus aureus prevalence was 8%. Antimicrobial sensitivity of the Staphylococcus spp. isolates to 14 antibiotics representing six antibiotic groups was undertaken using the Kirby-Bauer disk diffusion method. Among the CoNS, the highest resistance was reported in amoxicillin (78.7%) and ceftazidime (76%), while the most resistance for S. aureus was reported in ceftazidime (100%), amoxicillin (71.4%), and streptomycin (71.4%). From an administered questionnaire looking at gender, animal contact frequency, history of hospital visitation and antibiotic usage, and habitual intake of raw milk, the study showed that male participants had a higher risk of carrying multiple drug resistant (MDR) bacteria than females (p = 0.02, OR = 1.3). Likewise, habitual intake of raw milk was significantly associated MDR acquisition (p = 0.02, OR = 1.82). This study reveals a high prevalence of AMR Staphylococcus isolates in the study area laying a foundation for further analysis of molecular characterization of the observed resistance as well as the development of interventions that can reduce the occurrence of AMR in the study area.

Biofilm formation of two genetically diverse Staphylococcus aureus isolates under beta-lactam antibiotics

PURPOSE

Our aim was to evaluate the biofilm formation of 2 genetically diverse Staphylococcus aureus isolates, 10379 and 121940, under different concentrations of beta-lactam antibiotics on biomass content and biofilm viability.

METHODS

Biofilm formation and methicillin resistance genes were tested using PCR and multiplex PCR. PCR was combined with bioinformatics analysis to detect multilocal sequence typing (MLST) and SCCmec types, to study the genetical correlation between the tested strains. Then, the crystal violet (CV) test and XTT were used to detect biomass content and biofilm activity. Antibiotic susceptibility was tested using a broth dilution method. According to their specific MIC, different concentrations of beta-lactam antibiotics were used to study its effect on biomass content and biofilm viability.

RESULTS

Strain 10379 carried the icaD, icaBC, and MRSA genes, not the icaA, atl, app, and agr genes, and MLST and SCCmec typing was ST45 and IV, respectively. Strain 121940 carried the icaA, icaD, icaBC, atl, and agr genes, not the aap gene, and MLST and SCCmec typed as ST546 and IV, respectively. This suggested that strains 10379 and 121940 were genotypically very different. Two S. aureus isolates, 10379 and 121940, showed resistance to beta-lactam antibiotics, penicillin, ampicillin, meropenem, streptomycin and kanamycin, some of which promoted the formation of biofilm and biofilm viability at low concentrations.

CONCLUSION

Despite the large differences in the genetic background of S. aureus 10379 and 121940, some sub-inhibitory concentrations of beta-lactam antibiotics are able to promote biomass and biofilm viability of both two isolates.

A comparative study on antibiotic resistance and virulence properties of Staphylococcus aureus isolated from hospitalized patients and hospital environment

BACKGROUND

We compared the characteristics of clinical Staphylococcus aureus and S. aureus isolated from environmental surfaces in 3 hospitals.

METHODS

Clinical S. aureus isolates were collected from hospitalized patients. Environmental surfaces were sampled from the rooms of patients infected with S. aureus. After identifying rooms with the target organism, 3-5 high-touch surfaces in patient care areas were sampled using swabs before room cleaning by environmental services. S. aureus isolates were subjected to genotyping, antimicrobial susceptibility testing, and virulence determinant screening. The isolates were analyzed for integron content and sequences of variable region amplification products.

RESULTS

There were epidemiologically unrelated 79 clinical and 62 environmental S. aureus isolates. Overall, 11.4% of clinical and 59.7% of environmental isolates were methicillin-resistant. The environmental and clinical S. aureus exhibited very different virulence profiles: 79% of the environmental isolates were negative for virulence genes compared to 2.5% of clinical isolates (P < .001). Environmental isolates were more resistant to antibiotics compared to clinical isolates. Class 1 integrons were only detected in 7 of 62 environmental isolates, of which 3 isolates had integrons with cysteine synthase cassette, 1 had aadA1, and 1 had an unknown cassette.

CONCLUSION

These data indicate the different characteristics between environmental and clinical S. aureus, which may reflect different reservoirs from which the 2 groups acquired the strains.

Pseudomonas aeruginosa: A typical biofilm forming pathogen and an emerging but underestimated pathogen in food processing

Pseudomonas aeruginosa (P. aeruginosa) is a notorious gram-negative pathogenic microorganism, because of several virulence factors, biofilm forming capability, as well as antimicrobial resistance. In addition, the appearance of antibiotic-resistant strains resulting from the misuse and overuse of antibiotics increases morbidity and mortality in immunocompromised patients. However, it has been underestimated as a foodborne pathogen in various food groups for instance water, milk, meat, fruits, and vegetables. Chemical preservatives that are commonly used to suppress the growth of food source microorganisms can cause problems with food safety. For these reasons, finding effective, healthy safer, and natural alternative antimicrobial agents used in food processing is extremely important. In this review, our ultimate goal is to cover recent advances in food safety related to P. aeruginosa including antimicrobial resistance, major virulence factors, and prevention measures. It is worth noting that food spoilage caused by P. aeruginosa should arouse wide concerns of consumers and food supervision department.

Quercetin modulates the gut microbiota as well as the metabolome in a rat model of osteoarthritis

Although the mechanism of osteoarthritis (OA) has been widely studied and the use of quercetin for OA therapy is well documented, the relevant characteristics of the microbiome and metabolism remain unclear. This study reports changes in the gut microbiota and metabolism during quercetin therapy for OA in a rat model and provides an integrative analysis of the biomechanism. In this study, the rats were categorized into 3 different groups: the OA model, quercetin treatment, and control groups. The OA rats was conducted using a monoiodoacetate (MIA) injection protocol. The rats in the quercetin group received daily intragastric administration of quercetin from day 1 to day 28. Stool samples were collected, and DNA was extracted. We used an integrated approach that combined the sequencing of whole 16S rRNA, short-chain fatty acid (SCFA) measurements and metabolomics analysis by mass spectrometry (MS) to characterize the functional impact of quercetin on the gut microbiota and metabolism in a rat model of OA. The use of quercetin partially abrogated intestinal flora disorder and reversed fecal metabolite abnormalities. Compared with the control rats, the OA rats showed differences at both the class level (Clostridia, Bacteroidia, and Bacilli) and the genus level (Lactobacillus and unidentified Ruminococcaceae). Acetic acid, propionic acid and 24 metabolites were significantly altered among the three groups. However, the changes were significantly abrogated in quercetin-treated OA rats. Consequently, this study provided important evidence regarding perturbations of the gut microbiome and the function of these changes in a potential new mechanism of quercetin treatment.

Significant downtrend of antimicrobial resistance rate and rare β-lactamase genes and plasmid replicons carriage in clinical Pseudomonas aeruginosa in Southern China

OBJECTIVES

Pseudomonas aeruginosa is a medically important pathogen showing intrinsic low permeability to various antimicrobial agents and its potential to acquire multiple resistance mechanism. A longitudinal surveillance aimed to investigate the antimicrobial resistance and its determinants of Pseudomonas aeruginosa in Southern China. A total of 2163 P. aeruginosa isolates were obtained from patients in Southern China during 2004-2016.

METHODS

The antimicrobial susceptibility of the isolates was performed by disk diffusion and Vitek 2 automated system and interpreted according to the Clinical and Laboratory Standard Institute (CLSI) 2015.

RESULTS

A significant downtrend of resistant rate (>10.0%) was observed for tested antibiotic agents including ciprofloxacin (>30.0%), gentamicin (29.0%), tobramycin (24.2%) and ceftazidime (24.0%) except for aztreonam and amikacin. A total of 269 randomly selected isolates were further studied on the carriage of β-lactam resistance genes by using 7 groups of multiplex PCRs targeting on 20 genes. β-lactam resistance genes were rarely detected with a rate lower than 8%. Among all β-lactam resistance genes, bla_SHV acquired the highest identification rate (18/269, 6.7%), followed by bla_OXA-1-like (6/269, 2.2%) and bla_PER (6/269, 2.2%). In addition, 8 different plasmid replicons were amplified using 8 groups of multiplex PCRs including 18 sets of primers. Only five plasmid replicons were identified in 5 different P. aeruginosa isolates. Insignificant clonal relatedness among the positive strains identified by regular PCR were further verified by randomly amplified polymorphic DNA (RAPD)-PCR.

CONCLUSION

This study has provided comprehensive knowledge on current antimicrobial resistance, β-lactam resistance genes and plasmid replicons carriage in a large scale of clinical P. aeruginosa isolates.

Analysis and Construction of a Competitive Endogenous RNA Regulatory Network of Baicalin-Induced Apoptosis in Human Osteosarcoma Cells

BACKGROUND

Baicalin is an extract from the traditional Chinese herb Scutellaria baicalensis and has the potential to treat osteosarcoma (OS). However, the transcriptome-level mechanism of baicalin-mediated antitumor effects in OS has not yet been investigated. The aim of this study was to analyze the competitive endogenous RNA (ceRNA) regulatory network involved in baicalin-induced apoptosis of OS cells.

METHODS

In this study, CCK-8 and flow cytometry assays were used to detect the antitumor effects of baicalin on human OS MG63 cells. Furthermore, transcriptome sequencing was employed to establish the long noncoding RNA (lncRNA), microRNA (miRNA), and mRNA profiles.

RESULTS

Baicalin inhibited MG63 cell proliferation and induced apoptosis. Totals of 58 lncRNAs, 31 miRNAs, and 2136 mRNAs in the baicalin-treated MG63 cells were identified as differentially expressed RNAs compared to those in control cells. Of these, 2 lncRNAs, 3 miRNAs, and 18 mRNAs were included in the ceRNA regulatory network. The differentially expressed RNAs were confirmed by quantitative real-time PCR (qRT-PCR).

CONCLUSIONS

By identifying the ceRNA network, our results provide new information about the possible molecular basis of baicalin, which has potential applications in OS treatment.

Systematic Understanding of the Mechanism of Baicalin against Gastric Cancer Using Transcriptome Analysis

BACKGROUND

Gastric cancer (GC) is the most common type of cancer. It is highly malignant and is characterized by rapid and uncontrolled growth. The antitumour activity of Baicalin was studied in multiple cancers. However, its mechanism of action has not been fully elucidated. We provided a systematic understanding of the mechanism of action of baicalin against GC using a transcriptome analysis of RNA-seq.

METHODS

Human GC cells (SGC-7901) were exposed to 200 μg/ml baicalin for 24 h. RNA-seq with a transcriptome, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to identify the antitumour effects of baicalin on SGC-7901 cells in vitro. A protein-protein interaction (PPI) network of differentially expressed genes (DEGs) was constructed. A competitive endogenous RNA (ceRNA) network was constructed and further analysed after validation using qRT-PCR.

RESULTS

A total of 68 lncRNAs, 20 miRNAs, and 1648 mRNAs were differentially expressed in baicalin-treated SGC-7901 GC cells. Three lncRNAs, 6 miRNAs, and 7 mRNAs were included in the ceRNA regulatory network. GO analysis revealed that the main DEGs were involved in the biological processes of the cell cycle and cell death. KEGG pathway analysis further suggested that the p53 signalling pathway was involved in the baicalin-induced antitumour effect on SGC-7901 cells. Further confirmation using qPCR indicated that baicalin induced an antitumour effect on SGC-7901 cells, which is consistent with the results of the sequencing data.

CONCLUSIONS

In summary, the mechanism of baicalin against GC involves multiple targets and signalling pathways. These results provide new insight into the antitumour mechanism of baicalin and help the development of new strategies to cure GC.

Bioprocessing and integration of a high flux screening systematic platform based on isothermal amplification for the detection on 8 common pathogens

During a large variety of common pathogens, E. coli, P. aeruginosa, MRSA, MRCNS, V. parahaemolyticus, L. monocytogenes and Salmonella are the leading pathogens responsible for large number of human infections and diseases. In this study, a high flux screening based on nucleic acid isothermal amplification technique has been developed. For the 8 common pathogens, species-specific targets had been selected and analyzed for their unique specificity. After optimization, separate LAMP reaction assays had been bioprocessed and integrated into one systematic detection platform, including 8 strips (PCR tubes) and 96-well plates. Eight standard strains verified for the accuracy. Application of the established high flux screening platform was used for detection for 48 samples in 4 different 96-well plates, with 2 groups of 2 operators using double-blind procedure. The accuracy of 100% was obtained, with the total time consumption as 66-75 min (for 12 samples detection on 8 different pathogens). As concluded, through the bioprocess of the systematic platform based on LAMP technique, it's been demonstrated to be capable of simultaneous detection of 8 pathogens, with high sensitivity, specificity, rapidity and convenience.

"One-step" characterization platform for pathogenic genetics of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is an important human pathogen causing a variety of life-threatening diseases. In recent years, the health problem caused by S. aureus contaminated food has become a global health problem. S. aureus can express various pathogenic factors, mainly used for adhesion, colonization, invasion and infection of the host. Therefore, rapid and accurate detection of virulence genes in S. aureus is necessary to prevent outbreaks caused by this pathogen. PCR is a useful tool for rapid detection of foodborne pathogens. The objective of this study was to detect the presence of major toxin genes in S. aureus, including sea, seb, sec, see, pvl and tsst, by using a PCR plate. Of the 13 strains tested, 12 (92.3%) were found to be positive for one or more toxin genes. This study realized the one-step detection of main toxin factors in S. aureus.

Antimicrobial Resistance and Molecular Characterization of Class 1 Integron in Salmonella Isolates Recovered from Pig Farms in Chongqing, China

Salmonella is considered one of the leading causes for foodborne diseases in humans. Pork and its products contaminated with Salmonella are increasingly recognized as an important source of human salmonellosis. The aim of this study was to investigate the antimicrobial resistance and prevalence of integrons in Salmonella isolates from pig farms. In total, 92 of 724 (12.7%) samples were Salmonella-positive, including 64 (15.0%) from fecal samples, 27 (12.6%) from floor samples, 1 (4.5%) from water samples, and 0 from feed and air samples. These isolates showed the highest resistance to tetracycline (85.9%), followed by trimethoprim (67.4%), ampicillin (60.9%), and chloramphenicol (51.1%). In addition, 51 isolates carried the complete class 1 integron, most of which (42/51) harbored antibiotic resistance cassettes. A total of six gene cassettes including orfF, est-X, dfrA1+aadA1, aadA1, dfrA12+aadA2, and sat were identified, in which the most prevalent one was orfF (29.4%). Furthermore, all 19 class 1 integron-positive isolates harboring dfr genes showed resistance to trimethoprim (SXT), suggesting that the trimethoprim resistance gene (dfr) may contribute to the emergence of SXT resistance phenotype. Therefore, considering the significance of integrons and related resistance genes for public health, special measures should be taken to control Salmonella spp. on the pig farms and to prevent spread of integrons and associated resistance genes.

Pathogenic and Virulence Factor Detection on Viable but Non-culturable Methicillin-Resistant Staphylococcus aureus

Food safety and foodborne infections and diseases have been a leading hotspot in public health, and methicillin-resistant Staphylococcus aureus (MRSA) has been recently documented to be an important foodborne pathogen, in addition to its recognition to be a leading clinical pathogen for some decades. Standard identification for MRSA has been commonly performed in both clinical settings and food routine detection; however, most of such so-called "standards," "guidelines," or "gold standards" are incapable of detecting viable but non-culturable (VBNC) cells. In this study, two major types of staphylococcal food poisoning (SFP), staphylococcal enterotoxins A (sea) and staphylococcal enterotoxins B (seb), as well as the panton-valentine leucocidin (pvl) genes, were selected to develop a cross-priming amplification (CPA) method. Limit of detection (LOD) of CPA for sea, seb, and pvl was 75, 107.5, and 85 ng/μl, indicating that the analytical sensitivity of CPA is significantly higher than that of conventional PCR. In addition, a rapid VBNC cells detection method, designated as PMA-CPA, was developed and further applied. PMA-CPA showed significant advantages when compared with PCR assays, in terms of rapidity, sensitivity, specificity, and accuracy. Compared with conventional VBNC confirmation methods, the PMA-CPA showed 100% accordance, which had demonstrated that the PMA-CPA assays were capable of detecting different toxins in MRSA in VBNC state. In conclusion, three CPA assays were developed on three important toxins for MRSA, and in combination with PMA, the PMA-CPA assay was capable of detecting virulent gene expression in MRSA in the VBNC state. Also, the above assays were further applied to real samples. As concluded, the PMA-CPA assay developed in this study was capable of detecting MRSA toxins in the VBNC state, representing first time the detection of toxins in the VBNC state.

Development of a Direct and Rapid Detection Method for Viable but Non-culturable State of Pediococcus acidilactici

Pediococcus acidilactici may significantly reduce the pH-value, and thus has different influence, including serving as a probiotic in human microbiota but a spoilage in human food as it could change the flavor. Pediococcus acidilactici is also capable of entering into the viable but non-culturable (VBNC) state causing false negative results of standard culture-based detection method. Thus, development of detection method for VBNC state P. acidilactici is of great significance. In this study, propidium monoazide (PMA) combined with cross priming amplification (CPA) was developed to detect the VBNC cells of P. acidilactici and applied on the detection in different systems. With detection limit of 10⁴ cells/ml, high sensitivity, and 100% specificity, PMA-CPA can successfully detect VBNC cells of P. acidilactici and be applied in with high robustness.

Direct Detection of Viable but Non-culturable (VBNC) Salmonella in Real Food System by a Rapid and Accurate PMA-CPA Technique

Salmonella enterica is a typical foodborne pathogen with multiple toxic effects, including invasiveness, endotoxins, and enterotoxins. Viable but nonculturable (VBNC) is a type of dormant form preserving the vitality of microorganisms, but it cannot be cultured by traditional laboratory techniques. The aim of this study is to develop a propidium monoazide-crossing priming amplification (PMA-CPA) method that can successfully detect S. enterica rapidly with high sensitivity and can identify VBNC cells in food samples. Five primers (4s, 5a, 2a/1s, 2a, and 3a) were specially designed for recognizing the specific invA gene. The specificity of the CPA assay was tested by 20 different bacterial strains, including 2 standard S. enterica and 18 non-S. enterica bacteria strains covering Gram-negative and Gram-positive isolates. Except for the two standard S. enterica ATCC14028 and ATCC29629, all strains showed negative results. Moreover, PMA-CPA can detect the VBNC cells both in pure culture and three types of food samples with significant color change. In conclusion, the PMA-CPA assay was successfully applied on detecting S. enterica in VBNC state from food samples.

Study on the Viable but Non-culturable (VBNC) State Formation of Staphylococcus aureus and Its Control in Food System

A Viable but non-culturable (VBNC) state is a bacterial survival strategy under reverse conditions. It poses a significant challenge for public health and food safety. In this study, the effect of external environmental conditions including acid, nutrition, and salt concentrations on the formation of S. aureus VBNC states at low temperatures were investigated. Different acidity and nutritional conditions were then applied to food products to control the VBNC state formation. Four different concentration levels of each factor (acid, nutrition, and salt) were selected in a total of 16 experimental groups. Nutrition showed the highest influence on the VBNC state formation S. aureus, followed by acid and salt. The addition of 1% acetic acid could directly kill S. aureus cells and inhibit the formation of the VBNC state with a nutrition concentration of 25, 50, and 100%. A propidium monoazide-polymerase chain reaction (PMA-PCR) assay was applied and considered as a rapid and sensitive method to detect S. aureus in VBNC state with the detection limit of 104 CFU/mL.

Analysis on the virulomes and resistomes of multi-drug resistance clinical Escherichia coli isolates, as well as the interactome with gut microbiome

Escherichia coli is one of the most diverse microbial species. Pathogenic E. coli is capable of causing various diseases in humans, including several types of diarrhea, urinary tract infections, sepsis, and meningitis. This study focused on the antibiotic susceptibility profile and genomic analysis of a clinical E. coli Guangzhou-Eco330 isolated from a hospitalized 8-year-old female patient suffered from pulmonary infection in 2017. Susceptibility to 15 antibiotics were determined using Vitek2™ Automated Susceptibility System and Etest strips and interpreted based on CLSI guidelines. The genome was sequenced using Illumina Hiseq 2500 platform and assembled de novo using Velvet, followed by bioinformatics analysis. The genome has a length of 5,132,642 bp and contains 4989 predicted genes with an average GC content of 50.51%. The carriage of rfbE gene suggested the strain belonging to O157. In the genome, 70 non-coding RNAs, 50 repeat sequences, 18 transposons, 78 GIs, 9 CRISPRs, and 3 large prophages were identified. 37 PHI related genes and 108 virulence genes were determined to contribute to its pathogenicity. Specifically, the acquisition of multiple antibiotic resistance genes including bla_CTX-M-55, bla_OXA-10, bla_CMY-48, tetB, and qnrS1 contributed to its resistance to penicillins, telracyclines, cephalosporin, and quinolones. The understanding of the genome may aid in further study on the clinical control of multi-drug resistance E. coli.

Prevalence and Characterisation of Class 1 and 2 Integrons in Multi-drug Resistant Staphylococcus Aureus Isolates from Pig Farms in Chongqing, China

Introduction

Integrons are mobile DNA elements that allow for acquisition and dissemination of antibiotic-resistance genes among pig farm-derived bacteria. Limited information is available on integrons of Staphylococcus aureus from pig farms. The aim of this study was to characterise and investigate the prevalence of class 1 and 2 integrons in multi-drug resistant (MDR) S. aureus isolates from pig farms.

Material and Methods

A total of 724 swabs were collected from 12 pig farms in Chongqing, China, and examined by conventional microbial and molecular methods.

Results

In total, 68 isolates were S. aureus, 57 of which were methicillin resistant (MRSA). All 68 isolates were MDR strains and carried integrons, of which 88.2% (60/68) harboured both class 1 and 2. In addition, 85.3% (58/68) of the class 2 integron-positive isolates carried the β-lactam resistance gene (bla_TEM-1 ), and 66.7% (40/60) of the class 1 integron-positive isolates carried the aadA1c, aadA1 or dfrA1 gene for respective streptomycin and spectinomycin or trimethoprim resistance.

Conclusions

Class 1 and 2 integrons are common among the pig farm-derived S. aureus isolates. On account of their significance for public health, the prevalence of the integrons and their associated resistance genes in pig farm-derived S. aureus isolates should be paid special attention.

Study on the virulome and resistome of a vancomycin intermediate-resistance Staphylococcus aureus

Methicillin-resistant S. aureus (MRSA) has been considered a potential "Super Bugs", responsible for various infectious diseases. Vancomycin has been the most effective antibitic to treat MRSA originated infections. In this study, we aimed at investigating the genomic features of a vancomycin intermediate-resistance S. aureus strain Guangzhou-SauVS2 isolated from a female patient suffering from chronic renal function failure, emphasizing on its antimicrobial resistance and virulence determinants. The genome has a total length of 2,605,384 bp and the G+C content of 33.21%, with 2,239 predicted genes annotated with GO terms, COG categories, and KEGG pathways. Besides the carriage of vancomycin b-type resistance protein responsible for the vancomycin intermediate-resistance, S. aureus strain Guangzhou-SauVS2 showed resistance to β-lactams, quinolones, macrolide, and tetracycline, due to the acquisition of corresponding antimicrobial resistance genes. In addition, virulence factors including adherence, antiphagocytosis, iron uptake, and toxin were determined, indicating the pathogenesis of the strain.

Role of integrons in the proliferation of multiple drug resistance in selected bacteria occurring in poultry production

1. The increase in microbial resistance, and in particular multiple drug resistance (MDR), is an increasing threat to public health. The uncontrolled use of antibiotics and antibacterial chemotherapeutics in the poultry industry, especially in concentrations too low to cause inhibition, and the occurrence of residues in feed and in the environment play a significant role in the development of resistance among zoonotic food-borne microorganisms.2. Determining the presence and transmission methods of resistance in bacteria is crucial for tracking and preventing antibiotic resistance. Horizontal transfer of genetic elements responsible for drug resistance is considered to be the main mechanism for the spread of antibiotic resistance.3. Of the many well-known genetic elements responsible for horizontal gene transfer, integrons are among the most important factors contributing to multiple drug resistance. The mechanism of bacterial drug resistance acquisition through integrons is one of the essential elements of MDR prevention in animal production.

Microbiome characterization and re-design by biologic agents for inflammatory bowel disease insights

The therapeutic effect of inflammatory bowel disease has improved in the past decades, but most of patients cannot tolerate, do not respond to drugs, or relapse after treating with conventional therapy. Therefore, new and more effective treatment methods are still needed in treatment of IBD. In this review, we will discuss the relevant mechanisms and the latest research progress of biologics (anti-TNF treatments, interleukin inhibitors, integrin inhibitors, antisense oligonucleotide, and JAK inhibitors) for IBD, focus on the efficacy and safety of drugs for moderate-to-severe IBD, and summarize the clinical status and future development direction of biologics in IBD.

The Occurrence of Type I, II, and III Integrons in Multi-drug Resistance and Methicillin-Resistant Staphylococcus aureus Isolates in Iran

Integrons are mobilizable platforms-DNA elements with impacts on moving antibiotic resistance genes among bacteria and capable of spreading multi-drug resistance (MDR) in pathogens. Methicillin-resistant Staphylococcus aureus (MRSA) strains are the main cause of community-acquired and nosocomial infections with high mortality and morbidity rates worldwide. This work is mainly aimed at calculating the frequency of Type I, II, and III integrons within multi-drug resistance and Methicillin-resistant S. aureus Isolates in Iran. In this cross-sectional study, 230 clinical isolates of S. aureus were gathered from patients of educational hospitals in the provinces of Iran. These isolates were verified utilizing particular biochemical examinations and then assessed for antibiotic susceptibility through disk diffusion technique and standard procedures were done. Genomic and plasmid DNA of all isolates were extracted using Extraction Kit and PCR assay was used for the detection of Type I, II and III integrons genes. Out of the 230 S. aureus isolates, 136 (59.1%) isolates were MRSA and 141 (61.3%) isolates exhibited the MDR pattern. PCR and sequencing showed that 57 (24.8%) of tested isolates carry Type I integron. Among the isolates investigated, MRSA and MDR isolates showed frequencies of 56.1% and 57.9%, respectively. Type II and III integrons were found in none of 230 isolates. The IntI I gene was present in approximately one-quarter of this study isolates. The great prevalence rate of MDR and MRSA isolates and concurrently the existence of Type I integron among those isolates have been considered an important concern in medical society.

High-flux simultaneous screening of common foodborne pathogens and their virulent factors

Rapid and sensitive detection techniques for foodborne pathogens are important to the food industry. However, traditional detection methods rely on bacterial culture in combination with biochemical tests, a process that typically takes 4-7 days to complete. In this study, we described a high-flux polymerase chain reaction (PCR) method for simultaneous detection of nine targeted genes (rfbE, stx1, stx2, invA, oprI, tlh, trh, tdh, and hlyA) with multiplex strains. The designed primers were highly specific for their respective target gene fragments. As the selected primers follow the principles of similar melting and annealing temperature, all the targeted genes could be detected for one strain with the same PCR program. Combining with 96-well PCR plate, by adding a single different gene to each well in each row, both the ATCC strains (E. coli, Salmonella spp., V. parahaemolyticus, L. monocytogenes, P. aeruginosa, S. aureus) and the clinical strains (E. coli, P. aeruginosa, S. aureus) were simultaneously detected to carry their specific and virulence genes. Therefore, using 96-well PCR plate for PCR amplification might be applied to high-flux sequencing of specific and virulence genes.

Characterization on gut microbiome of PCOS rats and its further design by shifts in high-fat diet and dihydrotestosterone induction in PCOS rats

Polycystic ovary syndrome (PCOS) is associated with gut microbiota disturbance. Emerging evidence has shown that gut microbiota plays a major role in the development of PCOS. To better understand how the gut microbiota contributes to the development of PCOS, we investigated the influences of high-fat diet and hyperandrogenism, independently or synergistically, have on the gut microbiota in rats. Furthermore, we explored the associations between gut microbiota and hyperandrogenism or other hallmarks of PCOS. Twenty female SD rats were randomized at aged 3 weeks into 4 groups (n = 5, each); HA: PCOS rats fed with ordinary diet; HF: rats with high-fat diet (HFD); HA-HF: PCOS rats fed with HFD; and C: control rats with ordinary diet. PCOS rat model was induced by 5α-dihydrotestosterone (DHT) injection for 6 weeks. The fasting blood glucose (FBG), plasma insulin, testosterone, free testosterone, TNF-α, MDA, SOD, LPS, TLR4, TG, TC, HDL-C, and LDL-C levels were measured. The molecular ecology of the fecal gut microbiota was analyzed by 16S rDNA high-throughput sequencing. The results showed that rats in the HA and HA-HF group displayed abnormal estrous cycles with increasing androgen level and exhibited multiple large cysts with diminished granulosa layers in ovarian tissues. Compare with the C group, relative abundance of the Bacteroidetes phylum decreased significantly in the other groups (P < 0.05). The Chao1 was the highest in the group C and significantly higher than the HA-HF group (P < 0.05). T, FT, insulin, MDA, LPS, and TNF-α levels had the negative correlation with the richness of community (Chao1 index) in the gut. The rats in the HF and HA-HF groups tended to have lower Shannon and Simpson indices than the C group (P < 0.01, respectively). However, there were no significant differences between C group and the HA group in the Shannon and Simpson values. Beta diversity analysis was then performed based on a weighted UniFrac analysis. The PCoA plots showed a clear separation of the C group from the other groups. ANOSIM analysis of variance confirmed that there were statistically significant separations between the C group and the HA, HA-HF, and HF groups (P < 0.01, respectively). These results showed that DHT with HFD could lower diversity of the gut microbial community. Both HFD and DHT could shift the overall gut microbial composition and change the composition of the microbial community in gut. Furthermore, our analyses demonstrated that the levels of TG, MDA, TNF-α, LPS, TLR4, T, FT, FINS, and HDL-C were correlated with the changes of in the gut microbiome. HFD and DHT were associated with the development and pathology of PCOS by shaping gut microbial communities.

Formation and Control of the Viable but Non-culturable State of Foodborne Pathogen Escherichia coli O157:H7

As a common foodborne pathogen, Escherichia coli O157:H7 produces toxins causing serious diseases. However, traditional methods failed in detecting E. coli O157:H7 cells in the viable but non-culturable (VBNC) state, which poses a threat to food safety. This study aimed at investigating the formation, control, and detection of the VBNC state of E. coli O157:H7. Three factors including medium, salt, and acid concentrations were selected as a single variation. Orthogonal experiments were designed with three factors and four levels, and 16 experimental schemes were used. The formation of the VBNC state was examined by agar plate counting and LIVE/DEAD^® BacLight^TM bacterial viability kit with fluorescence microscopy. According to the effects of environmental conditions on the formation of the VBNC state of E. coli O157:H7, the inhibition on VBNC state formation was investigated. In addition, E. coli in the VBNC state in food samples (crystal cake) was detected by propidium monoazide-polymerase chain reaction (PMA-PCR) assays. Acetic acid concentration showed the most impact on VBNC formation of E. coli O157:H7, followed by medium and salt concentration. The addition of 1.0% acetic acid could directly kill E. coli O157:H7 and eliminate its VBNC formation. In crystal cake, 25, 50, or 100% medium with 1.0% acetic acid could inhibit VBNC state formation and kill E. coli O157:H7 within 3 days. The VBNC cell number was reduced by adding 1.0% acetic acid. PMA-PCR assay could be used to detect E. coli VBNC cells in crystal cake with detection limit at 10⁴ CFU/ml. The understanding on the inducing and inhibitory conditions for the VBNC state of E. coli O157:H7 in a typical food system, as well as the development of an efficient VBNC cell detection method might aid in the control of VBNC E. coli O157:H7 cells in the food industry.

Development and Application of a Simple "Easy To Operate" Propidium Monoazide-Crossing Priming Amplification on Detection of Viable and Viable But Non-culturable Cells of O157 Escherichia coli

O157 Escherichia coli is one of the most important foodborne pathogens causing disease even at low cellular numbers. Thus, the early and accurate detection of this pathogen is important. However, due to the formation of viable but non-culturable (VBNC) status, the golden standard culturing methodology fails to identify O157 E. coli once it enters VBNC status. Crossing priming amplification (CPA) is a novel, simple, easy-to-operate detection technology that amplifies DNA with high speed, efficiency, and specificity under isothermal conditions. The objective of this study was to firstly develop and apply a CPA assay with propidium monoazide (PMA) for the rapid detection of the foodborne E. coli O157:H7 in VBNC state. Five primers (2a/1s, 2a, 3a, 4s, and 5a) were specially designed for recognizing three targets, which were rfbE, stx1, and stx2, and evaluated for its effectiveness in detecting VBNC cell of E. coli O157:H7 with detection limits of pure VBNC culture at 10³, 10⁵, and 10⁵ colony-forming units (CFUs)/ml for rfbE, stx1, and stx2, respectively, whereas those of food samples (frozen pastry and steamed bread) were 10³, 10⁵, and 10⁵ CFUs/ml. The application of the PMA-CPA assay was successfully used on detecting E. coli O157:H7 in VBNC state from food samples. In conclusion, this is the first development of PMA-CPA assay on the detection of VBNC cell, which was found to be useful and a powerful tool for the rapid detection of E. coli O157:H7 in VBNC state. Undoubtedly, the PMA-CPA method can be of high value to the food industry owing to its various advantages such as speed, specificity, sensitivity, and cost-effectiveness.

Effect of Environmental Conditions on the Formation of the Viable but Nonculturable State of Pediococcus acidilactici BM-PA17927 and Its Control and Detection in Food System

Objective: This study aimed to investigate the effect of environmental conditions including nutrient content, acetic acid concentration, salt concentration, and temperature on the formation of viable but nonculturable (VBNC) state of Pediococcus acidilactici, as well as its control and detection in food system. Methods: Representing various environmental conditions in different food systems, 16 induction groups were designed for the formation of VBNC state of P. acidilactici. Traditional plate counting was applied to measure the culturable cell numbers, and Live/Dead Bacterial Viability Kit combined with fluorescent microscopy was used to identify viable cells numbers. The inhibition of bacterial growth and VBNC state formation by adjusting the environmental conditions were investigated, and the clearance effect of VBNC cells in crystal cake system was studied. In addition, a propidium monoazide-polymerase chain reaction (PMA-PCR) assay was applied to detect the VBNC P. acidilactici cells in crystal cake food system. Results: Among the environmental conditions included in this study, acetic acid concentration had the greatest effect on the formation of VBNC state of P. acidilactici, followed by nutritional conditions and salt concentration. Reducing nutrients in the environment and treating with 1.0% acetic acid can inhibit P. acidilactici from entering the VBNC state. In the crystal cake system, the growth of P. acidilactici and the formation of VBNC state can be inhibited by adding 1.0% acetic acid and storing at -20°C. In crystal cake system, the PMA-PCR assay can be used to detect VBNC P. acidilactici cells at a concentration higher than 10⁴ cells/ml. Conclusion: The VBNC state of P. acidilactici can be influenced by the changing of environmental conditions, and PMA-PCR assay can be applied in food system for the detection of VBNC P. acidilactici cells.

Reduction, Prevention, and Control of Salmonella enterica Viable but Non-culturable Cells in Flour Food

The processing and storage conditions of flour food inevitably pose environmental stress, which promote bacteria to enter a viable but non-culturable (VBNC) state. The existence of VBNC cells causes false-negative detection in traditional culture-based detection methods, resulting in food quality and safety issues. This study aimed at investigating the influence factors including nutrition, acid, salt, and temperature for the entry into a VBNC state of Salmonella enterica and an efficient detection method. During induction with multi-stress conditions, nutrition starvation antagonizes with low-level acidity. Besides, high-level acidity was considered as an inhibitor for VBNC induction. Four inducers including nutrition starvation, salt stress, low-level acidity, and low temperature were concluded for a VBNC state. In addition, the keynote conditions for S. enterica entering a VBNC state included (i) nutrient-rich acidic environment, (ii) oligotrophic low-acidity environment, and (iii) oligotrophic refrigerated environment. Based on the keynote conditions, the environmental conditions of high acidity (1.0% v/v acetate) with low temperature (-20°C) could successfully eliminate the formation of S. enterica VBNC cells in flour food. In addition, combining with propidium monoazide pretreatment, PCR technology was applied to detect S. enterica VBNC cells. The sensitivity of the PMA-PCR technology was 10⁵ CFU/ml in an artificially simulated food system. The results derived from this study might aid in the detection and control of VBNC state S. enterica in flour food products.

First Report on the Rapid Detection and Identification of Methicillin-Resistant Staphylococcus aureus (MRSA) in Viable but Non-culturable (VBNC) Under Food Storage Conditions

Formation of viable but non-culturable (VBNC) status in methicillin-resistant Staphylococcus aureus (MRSA) has never been reported, and it poses a significant concern for food safety. Thus, this study aimed to firstly develop a rapid, cost-effective, and efficient testing method to detect and differentiate MRSA strains in the VBNC state and further apply this in real food samples. Two targets were selected for detection of MRSA and toxin, and rapid isothermal amplification detection assays were developed based on cross-priming amplification methodology. VBNC formation was performed for MRSA strain in both pure culture and in artificially contaminated samples, then propidium monoazide (PMA) treatment was further conducted. Development, optimization, and evaluation of PMA-crossing priming amplification (CPA) were further performed on detection of MRSA in the VBNC state. Finally, application of PMA-CPA was further applied for detection on MRSA in the VBNC state in contaminated food samples. As concluded in this study, formation of the VBNC state in MRSA strains has been verified, then two PMA-CPA assays have been developed and applied to detect MRSA in the VBNC state from pure culture and food samples.

Biofilm Formation of Staphylococcus aureus under Food Heat Processing Conditions: First Report on CML Production within Biofilm

This study aimed to evaluate the Staphylococcus aureus biofilm formation and Nε-carboxymethyl-lysine generation ability under food heat processing conditions including pH (5.0-9.0), temperature (25 °C, 31 °C, 37 °C, 42 °C and 65 °C), NaCl concentration (10%, 15% and 20%, w/v) and glucose concentration (0.5%, 1%, 2%, 3%, 5%, 10%, w/v). S. aureus biofilm genetic character was obtained by PCR detecting atl, ica operon, sasG and agr. Biofilm biomass and metabolic activity were quantified with crystal violet and methyl thiazolyl tetrazolium staining methods. S. aureus biofilm was sensitive to food heat processing conditions with 37 °C, pH 7.0, 2% glucose concentration (w/v) and 10% NaCl concentration (w/v) were favorable conditions. Besides, free and bound Nε-carboxymethyl-lysine level in weak, moderate and strong biofilm were detected by optimized high performance liquid chromatography tandem mass spectrometry. Nε-carboxymethyl-lysine level in S. aureus biofilm possessed a significant gap between strong, moderate and weak biofilm strains. This investigation revealed the biological and chemical hazard of Staphylococcus aureus biofilm to food processing environment.

Enterobacteriaceae Antibiotic Resistance in Ready-to-Eat Foods Collected from Hospital and Community Canteens: Analysis of Prevalence

Foodborne diseases and antibiotic resistance are serious widespread health problems in the contemporary world. In this study, we compared the microbiological quality of ready-to-eat (RTE) foods found in community canteens versus hospital canteens in Rome, Italy, focusing on detection and quantification of Enterobacteriaceae and the antibiotic resistance of these bacteria. Our findings show a remarkable difference in Enterobacteriaceae contamination between RTE foods distributed in community canteens (33.5% of samples) and those distributed in hospital canteens (5.3% of samples). This result highlights greater attention to good manufacturing practices and good hygiene practices by the food operators in hospitals compared with food operators in community canteens. As expected, a higher percentage of cold food samples (70.9%) than of hot food samples (10.8%) were positive for these bacteria. Excluding the intrinsic resistance of each bacterial strain, 92.3% of the isolated strains were resistant to at least one antibiotic, and about half of the isolated strains were classified as multidrug resistant. The prevalence of multidrug-resistant strains was 50% in the community samples and 33.3% in hospital canteens. Our results indicate that approximately 38% of RTE foods provided in community canteens is not compliant with microbiological food safety criteria and could be a special risk for consumers through spread of antibiotic-resistant strains. Hygienic processing and handling of foods is necessary for both hospital and community canteens.

Characterization of the resistance class 1 integrons in Staphylococcus aureus isolates from milk of lactating dairy cattle in Northwestern China

Background

Integrons are mobile DNA elements and they have an important role in acquisition and dissemination of antimicrobial resistance genes. However, there are limited data available on integrons of Staphylococcus aureus (S. aureus) from bovine mastitis, especially from Chinese dairy cows. To address this knowledge gap, bovine mastitis-inducing S. aureus isolates were investigated for the presence of integrons as well as characterization of gene cassettes. Integrons were detected using PCR reactions and then further characterized by a restriction fragment-length polymorphism analysis and amplicon sequencing.

Results

All 121 S. aureus isolates carried the class 1 integrase gene intI1, with no intI2 and intI3 genes detected. One hundred and three isolates were positive for the presence of 12 resistance genes, either alone or in combination with other gene cassettes. These resistance genes encoded resistance to trimethoprim (dhfrV, dfrA1, dfrA12), aminoglycosides (aadA1, aadA5, aadA4, aadA24, aacA4, aadA2, aadB), chloramphenicol (cmlA6) and quaternary ammonium compound (qacH) and were organized into 11 different gene cassettes arrangements (A-K). The gene cassette arrays dfrA1-aadA1 (D, 44.6%), aadA2 (K, 31.4%), dfrA12-orfX2-aadA2 (G, 27.3%) and aadA1 (A, 25.6%) were most prevalent. Furthermore, 74 isolates contained combinations of 2 to 4 gene cassette arrays. Finally, all of the integron/cassettes-positive isolates were resistant to aminoglycoside antibiotics.

Conclusions

This is the first study on the integrons and gene cassette arrays in S. aureus isolates from milk of mastitic cows from Northwestern China and provide the evidence for class 1 integron as possible antibiotic resistance determinants on dairy farms.

Complete genomic analysis of multidrug-resistance Pseudomonas aeruginosa Guangzhou-Pae617, the host of megaplasmid pBM413

OBJECTIVES

We previously described the novel qnrVC6 and bla_IMP-45 carrying megaplasmid pBM413. This study aimed to investigate the complete genome of multidrug-resistance P. aeruginosa Guangzhou-Pae617, a clinical isolate from the sputum of a patient who was suffering from respiratory disease in Guangzhou, China.

METHODS

The genome was sequenced using Illumina Hiseq 2500 and PacBio RS II sequencers and assembled de novo using HGAP. The genome was automatically and manually annotated.

RESULTS

The genome of P. aeruginosa Guangzhou-Pae617 is 6,430,493 bp containing 5881 predicted genes with an average G + C content of 66.43%. The genome showed high similarity to two new sequenced P. aeruginosa strains isolated from New York, USA. From the whole genome sequence, we identified a type IV pilin, two large prophages, 15 antibiotic resistant genes, 5 genes involved in the "Infectious diseases" pathways, and 335 virulence factors.

CONCLUSIONS

The antibiotic resistance and virulence factors in the genome of P. aeruginosa strain Guangzhou-Pae617 were identified by complete genomic analysis. It contributes to further study on antibiotic resistance mechanism and clinical control of P. aeruginosa.

Physical relation and mechanism of ultrasonic bactericidal activity on pathogenic E. coli with WPI

OBJECTIVE

This study aimed to investigate the physical relation and mechanism of bactericidal activity on pathogenic E. coli by ultrasonic field with whey protein isolate (WPI).

METHODS

Ultrasound treatment was performed under the conditions of intensity at 65 W/cm², pulse duty ratio at 0.5 for 0-15 min with WPI concentration ranged from 0 to 10%. Viscosity, granularity, surface hydrophobicity, free radical scavenging activity, and thermal denaturation were assessed by rotational viscometer, Malvern Mastersizer 2000 particle size analyzer, fluorescent probe ANS method, DPPH method, and differential scanning calorimetry, respectively.

RESULTS

The thermal denaturation of WPI was not altered by ultrasound field, but the viscosity of WPI was increased upon 10 min treatment. Additionally, its ability to scavenge free radicals and hydrophobicity were increased. The result also showed that the bacteria viability was improved by WPI during ultrasound treatment. However, the WPI protection was decreased by the prolonged treatment.

CONCLUSION

Ultrasound treatment resulted in the increasing of the viscosity, free radicals scavenging activity and hydrophobicity of WPI which led to reduced bactericidal activity on E. coil, while WPI protection was disintegrated by prolonged treatment.

High flux isothermal assays on pathogenic, virulent and toxic genetics from various pathogens

Toxins, encoding by virulence factors, are significant cause of food-borne illnesses and death in the worldwide. Loop-mediated isothermal amplification (LAMP) is one of the widely used methodologies because of the high sensitivity, specificity and rapidity. Nowadays, LAMP has been regarded as an innovative gene amplification technology and emerged as an alternative to PCR-based methodologies in identification of the pathogenic virulent and toxic genetics. The high sensitivity of LAMP enables detection of the pathogens in sample materials even without time consuming and sample preparation. Therefore, we review the typical characteristics of LAMP assay, recent advance in detection of virulence factors and the application of LAMP assay on detection of four commonly virulence factors. As concluded, with the advantages of rapidity, simplicity, sensitivity, specificity and robustness, LAMP is capable of identification the virulence factors. Moreover, the main purpose of this review is to provide theory support for the application of LAMP assay on the virulence factors identification.

Genotyping and high flux sequencing of the bacterial pathogenic elements - integrons

Regarded as a common genetic element responsible for horizontal gene transfer and wide spread of antimicrobial resistance among a large variety of bacteria, integrons are commonly distributed and considered as a determinant in the acquisition and evolution of virulence and antibiotic resistance. To date, the surveillances of integrons have been widely conducted in clinic, community even husbandry. For exact and accurate integron screening, as well as resistant cassettes, reliable monitoring methods is need. Current methods applied on integron screening are mainly conducted by the screening of integrases, followed by the detection of various gene cassettes inserted into integrons. PCR and PCR-related methods (such as RFLP) are mainly employed under such circumstances. Matured LAMP and Sequencing technology have lowered cost and dramatically increased throughput in integron screening and possessed the advantages in similarity analysis of mutated resistant cassettes. This review focused on the classification and characterization of integrons, antimicrobial resistance of integron and genotyping methods for integrons. In methodology, PCR, LAMP and Sequencing technology were mainly introduced for the screening of various classes' integrons and the detection of resistant gene cassettes. Staphylococcus, Pseudomonas and Enterococcus were selected as typical integron-positive clinical and environmental pathogens screened with three methods mentioned above. With the surveillance of the occurrence of integron and resistance gene cassettes conducted in South China, the review also summarized the occurrence, pathogenicity and virulence mediated by integrons.