Evaluation and application of molecular genotyping on nosocomial pathogen-methicillin-resistant Staphylococcus aureus isolates in Guangzhou representative of Southern China

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.

IG1, a Mansonone F Analog, Exhibits Antibacterial Activity against Staphylococcus aureus by Potentially Impairing Cell Wall Synthesis and DNA Replication

Infection caused by Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), is very common in communities and hospitals, which poses a great challenge to human health. Therefore, increasing attention has been paid to finding effective antimicrobial agents. Mansonone F is a natural compound which has an oxaphenalene skeleton and anti-S. aureus activity, but its sources are limited and its synthesis is difficult. Thus, IG1, a C9-substituent mansonone F analog, was assessed for its activity against Staphylococcus aureus and its mechanism of action was investigated. Antimicrobial susceptibility assays showed that IG1 has strong antibacterial activity against S. aureus, including MRSA, with minimum inhibitory concentrations (MICs) ranging from 0.5 to 2 μg/mL, which were very close to those of vancomycin, and these changed little, even with an increase in the amount of the inoculum. To further explore the antibacterial properties of IG1, time-kill experiments were conducted. Compared with vancomycin and moxifloxacin, treatment with different concentrations of IG1 reduced the viability of organisms in a very similar manner and the reduction was not significant, which indicated that IG1 is a potentially strong anti-S. aureus agent. Finally, the antibacterial mechanism was analyzed, with flow cytometric analysis revealing that IG1 treatment resulted in a time-dependent decrease in the DNA content of S. aureus. Transmission electron microscopy (TEM) analysis showed that very few dividing cells could be found and the cell wall was damaged in the field of IG1-treated cells. These results indicate that IG1 is a potential new antibacterial agent against S. aureus, including MRSA.

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.

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.

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.

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.

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.

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.

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.

The fingerprint mapping and genotyping systems application on methicillin-resistant Staphylococcus aureus

As a typical Gram-positive microorganism, S. aureus was recognized as common foodborne pathogenic bacteria in food industry. To study their individuality and pathogenicity mechanism, thirty-three Staphylococci strains were applied to the investigation with the identification of MRSA by PCR targeting on S. aureus specific 16S rRNA and femA genes as well as methicillin-resistant mecA and orfX elements by multiplex-PCR assay. Fingerprinting mapping was then employed using three typing systems (KZ/M13, IS256 and ERIC2) to genotype 33 MRSA strains. As the result indicated, all 33 Staphylococci strains were identified as MRSA. However, diversity occurred among different fingerprinting system results. KZ/M13 system and IS256 system both typed 10 genotypes while ERIC2 system had 8 genotypes. Based on the genotyping results, a discussion was performed in typing ability, discriminatory ability and accordance ratio. Given the above studies, a novel rapid detection method for MRSA was conducted with multiplex-PCR, which possessed rapidity and accuracy. Meanwhile, three fingerprinting systems showed high sensitivity, resolution and classification ratio in MRSA typing. These methods have a broad application prospect in food safety and epidemiology in the future.

Knowledge, Attitude, and Practice with Respect to Antibiotic Use among Chinese Medical Students: A Multicentre Cross-Sectional Study

Objective: Inappropriate antibiotic use leads to antibiotic resistance. This has become a serious global crisis, with more multi-drug resistant infections and fewer effective antibiotics available. This study aims to understand knowledge, attitude, and practice (KAP) with respect to antibiotic use for self-limiting illnesses among medical students in China. Methods: An online cross-sectional survey instrument questionnaire was distributed in six regional universities in China from September to November 2015. Overall, 1819 medical students were enrolled. A pre-tested questionnaire was delivered by the researchers. KAP scores were calculated to determine the appropriation. Chi-squared and multivariable logistic regression and adjusted odd ratios (aORs) with 95% confidence interval (CI) were used to assess the relationship between the demographic characteristics and antibiotic use knowledge and behaviour. Results: In total, 11,192 students completed the questionnaires, with a response rate of 95%. In total, 529 (29%) medical students reported at least one self-limiting illness in the prior month. Of those with a self-limiting illness, 285 (54%) self-medicated, with 77 (27%) using antibiotics; 111 (21%) went to see a doctor, of which 64 (58%) were prescribed antibiotics, and 133 did nothing (25%). In the past year, 279 (15%) of medical students had used antibiotics as prophylaxis, and 273 (15%) of medical students had demanded an antibiotic from a doctor. Meanwhile, 1166 (64%) of them kept a personal stock of antibiotics, and 1034 (57%) of them had bought antibiotics at a pharmacy, of which 97% were purchased without a prescription. Students with high KAP scores with respect to antibiotics were significantly less likely to self-medicate with antibiotics (aOR 0.37, 95% CI 0.15–0.91, p = 0.031), use antibiotics for prophylaxis (aOR 0.35, 95% CI 0.21–0.60, p < 0.0001), or demand an antibiotic (aOR 0.46, 95% CI 0.26–0.81, p = 0.007) from the doctor. Logistical regression showed that students whose fathers had a higher education level, whose mothers had medical background, who were from urban areas were more likely to stock antibiotics and self-medicate with antibiotics. Conclusion: High rates of antibiotic self-medication for self-limiting illness and stocking of antibiotics among medical students were observed. Along with the high rates of medical students receiving unnecessary antibiotics from their doctors were observed. The students’ knowledge and attitude towards to antibiotics, which drive prescribing, highlight the urgent need for effective antibiotic stewardship and training programs in Chinese healthcare institutes and medical schools.

High flux isothermal assays on the pathogenic features of Mycoplasma pneumoniae

As one of the most important pathogens, M. pneumoniae is a causative agent responsible for atypical and other respiratory tract infections, even its extra-pulmonary complications. This study aims to use the high and rapid flux sequencing assays on the M. pneumoniae and further bioinformatic analysis, for the investigation of their clinical features and pathogenic characteristics. The results in this study on the clinical features and pathogenic characteristics of M. pneumoniae may further aid in the control and surveillance and better understanding of this pathogen.

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.

Integron mediated bacterial resistance and virulence on clinical pathogens

Integron was recognized as mobile elements responsible for the emergence and diffusion of antibiotic resistance, virulence and pathogenicity. The existence of resistant integron in pathogens may consequently lead to the increasing number of clinical failures in bacterial mediated diseases, as well as the expenses. In this study, a total of 22 clinical pathogens (including E. faecalis, S. aureus, K. pneumoniae, Enterobacter, P. aeruginosa and Acinetobacter) were subjected to the identification of class 1-class 3 integrons and drug resistant gene cassettes by high flux LAMP method. According to the results, the clinical isolates were screened as carrying class 1 integron with dfrA12-orfF-aadA2 cassette array, class 1 integron with dfrA17-aadA5 cassette array, class 1 integron with aadA2 cassette, class 1 integron with bla_VIM2 cassette, class 1 and class 2 integron with dfrA1-sat1-aadA1 and dfrA12-orfF-aadA2 cassette arrays simultaneously, which was accordantly with the previous data. The optimized high flux LAMP assay was proceeded in water bath at 65 °C for 60 min and determined by naked eye, with the time consumption restricted within 2.5 h. Prior to conventional PCR method, the high flux LAMP assay was demonstrated as a highly-specific and highly-sensitive method. This study offered a valid LAMP method in resistance integrons detection for laboratory use, which was time-saving and easy-determination.

Microbial pathogenicity and virulence mediated by integrons on Gram-positive microorganisms

Gram-positive microorganisms are one of leading pathogenic microorganisms in public health, including several typical "Super Bugs" as methicillin-resistant Staphylococcus aureus, Klebsiella pneumoniae carbapenemase and vancomycin-resistant enterococci, which caused a increasement of infections, clinical failures and expenses. Regarded as a common genetic element responsible for horizontal gene transfer, integrons are widely distributed in various pathogens considered as a determinant in the acquisition and evolution of antibiotic resistance. Current investigations mainly focus on the distribution of integrons in Gram-negative microorganisms, while the role of integron in antibiotic resistance among Gram-positive microorganisms remains unclear and need investigation. To date, the surveillances of integrons in Gram-positive microorganism have been widely conducted in clinic, community even husbandry. China remains one of the worst country in antibiotics abuse worldwide and considered as a potential area for the prevalence of antimicrobial microorganisms and the occurrence of various 'Super Bugs'. Recently, the surveillance of the occurrence of integron and resistance gene cassettes was conducted in South China during the first 10 years of the 21st century. Referred to the surveillance in South China and other investigation in Asian countries, this review aims to summarize the occurrence, pathogenicity and virulence mediated by integrons in typical Gram-positive microorganisms (Staphylococcus, Enterococcus, Corynebacterium and Streptococcus) and the role of integrons in antibiotic resistance.

Effect of aminoglycosides on the pathogenic characteristics of microbiology

Infections caused by pathogen remain to be one of the most important global health issues, and scientists are devoting themselves to seeking effective treatments. Aminoglycoside antibiotics are one kind of widely used antibiotics because of the good efficiency and broad antimicrobial-spectrum. However, it causes some unexpected effects on the pathogenic characteristics of microbiology during the treatment, such as drug resistance and biofilm promotion. Drug resistance is partly due to antibiotics abuse. Simultaneously, aminoglycoside is documented to make divergent effects on biofilm based on their concentrations. Here, we review the mechanism of drug resistance caused by long-term use of aminoglycoside antibiotics, the effects of antibiotic concentration on biofilm formation and the negative effects on intestinal flora to provide theoretical supports for rational use of antibiotics.

Pathogenic features and characteristics of food borne pathogens biofilm: Biomass, viability and matrix

Biofilm is a ubiquitous growth pattern of bacterial species survival but is notorious for its threat on public health and food contamination. Extensive studies of the biofilm structure, formation, quantification, quorum sensing system and underlying control strategies have been reported during the past decades. Insightful elucidation of the pathogenic features and characteristic of bacterial biofilm can facilitate in devising appropriate control strategies for biofilm eradication. Therefore, this review mainly summarized the pathogenic features of biofilms from food borne microorganisms, including the biomass (which could be quantified using crystal violet and fluorogenic dye Syto9 assays), viability (which could be determined by tetrazolium salts, fluorescein diacetate, resazurin staining and alamar blue assays) and matrix (which are commonly detected by dimethyl methylene blue and wheat germ agglutinin assays). In addition, three features were further compared with its particular benefits in specific application.

Direct bacterial loop-mediated isothermal amplification detection on the pathogenic features of the nosocomial pathogen - Methicillin resistant Staphylococcus aureus strains with respiratory origins

Loop-mediated isothermal amplification based detection assays using bacterial culture or colony for direct detection of methicillin resistant Staphylococcus aureus(MRSA) had been developed and evaluated, followed by its extensive application on a large scale of clinical MRSA isolated from respiratory origins, including nasal swabs and sputums. Six primers, including outer primers, inner primers and loop primers, were specifically designed for recognizing eight distinct sequences on four targets: 16SrRNA, femA, mecA and orfX. Twenty-seven reference strains were used to develop, evaluate and optimize this assay. Then, a total of 532 clinical MRSA isolates were employed for each detected targets. And the results were determined through both visual observation of the color change by naked eye and electrophoresis. The specific of each primer had been confirmed, and the optimal amplification was obtained under 65 °C for 40 min. The limit of detections (LOD) of bacteria culture LAMP assays were determined to be 10⁴ CFU/ml for 16S rRNA, femA, as well as orfX and 10⁵ CFU/ml for mecA, respectively. The established novel assays on MRSA detection may provide new strategies for rapid detection of foodborne pathogens.