Longitudinal surveillance on antibiogram of important Gram-positive pathogens in Southern China, 2001 to 2015

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.

Study on spoilage capability and VBNC state formation and recovery of Lactobacillus plantarum

OBJECTIVE

The present study aimed at investigating the capability of L. plantarum strain BM-LP14723 to enter into and recover from the viable but nonculturable (VBNC) state and to cause beer spoilage.

METHODS

VBNC state was induced by incubating in beer with subculturing or low temperature treatment. Culturable, total, and viable cells numbers were assessed by MRS agar plate counting, acridine orange direct counting, and Live/Dead BacLight bacterial viability kit, respectively. Organic acids concentrations were measured by reversed-phase high performance liquid chromatography.

RESULTS

VBNC L. plantarum cells were detected after 189 ± 1.9 days low temperature treatment or 29 ± 0.7 subcultures in beer. The VBNC L. plantarum retained spoilage capability. Addition of catalase is an effective method for the recovery of the VBNC L. plantarum cells.

CONCLUSION

L. plantarum strain BM-LP14723 is capable of entering into and recovery from the VBNC state and maintained spoilage capability. The current study presented that beer-spoilage L. plantarum can hide both in breweries and during transporting and marketing process and thus lead to beer-spoilage incidents.

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.

Complete genome sequence and bioinformatics analyses of Bacillus thuringiensis strain BM-BT15426

OBJECTIVES

This study aimed to investigate the genetic characteristics of Bacillus thuringiensis strain BM-BT15426.

METHODS

B. thuringiensis strain was identified by sequencing the PCR product (amplifying 16S rRNA gene) using ABI Prism 377 DNA Sequencer. The genome was sequenced using PacBio RS II sequencers and assembled de novo using HGAP. Also, further genome annotation was performed.

RESULTS

The genome of B. thuringiensis strain BM-BT15426 has a length of 5,246,329 bp and contains 5409 predicted genes with an average G + C content of 35.40%. Three genes were involved in the "Infectious diseases: Amoebiasis" pathway. A total of 21 virulence factors and 9 antibiotic resistant genes were identified.

CONCLUSIONS

The major pathogenic factors of B. thuringiensis strain BM-BT15426 were identified through complete genome sequencing and bioinformatics analyses which contributes to further study on pathogenic mechanism and phenotype of B. thuringiensis.

Detection on integron carried gene cassettes from pathogens by loop mediated isothermal amplification assays

In this study, a number of frequently detected gene cassettes from bacterial integrons have been detected and characterized by rapid and simple loop-mediated isothermal amplification (LAMP) assays. Six gene cassettes commonly found in class 1 integrons were studied, including dfrA12, dfrA17, aadA2, aadA5, orfF, and bla_VIM2. Primers design, sensitivity, specificity, optimization of each LAMP assay, as well as application of the developed 6 individual LAMP assays on a large scale of bacteria, had been conducted. The optimal amplification was obtained with temperature as 65 °C, reaction time span as 45 min and volume as 25 μl. For application, 272 isolates with various gene cassettes yielded expectable positive amplicons and other 685 integron-negative bacteria showed negative results for the LAMP assays, totaling 100% detection rate and specificity.

First study on the formation and resuscitation of viable but nonculturable state and beer spoilage capability of Lactobacillus lindneri

OBJECTIVES

This study aimed to investigate the spoilage capability of Lactobacillus lindneri during the induction and resuscitation of viable but nonculturable (VBNC) state.

METHODS

L. lindneri strain was identified by sequencing the PCR product (amplifying 16S rRNA gene) using ABI Prism 377 DNA Sequencer. During the VBNC state induction by low temperature storage and beer adaption, total, culturable, and viable cells were assessed by acridine orange direct counting, plate counting, and Live/Dead BacLight bacterial viability kit, respectively. Organic acids and diacetyl concentration were measured by reversed-phase high performance liquid chromatography and head dpace gas chromatography, respectively.

RESULTS

VBNC state of L. lindneri was successfully induced by both beer adaption and low temperature storage, and glycerol frozen stock was the optimal way to maintain the VBNC state. Addition of catalase was found to be an effective method for the resuscitation of VBNC L. lindneri cells. Furthermore, spoilage capability remained similar during the induction and resuscitation of VBNC L. lindneri.

CONCLUSIONS

This is the first report of induction by low temperature storage and resuscitation of VBNC L. lindneri strain, as well as the first identification of spoilage capability of VBNC and resuscitated L. lindneri cells. This study indicated that the potential colonization of L. lindneri strain in brewery environment, formation and resuscitation of VBNC state, as well as maintenance in beer spoilage capability, may be an important risk factor for brewery environment.

Loop-mediated isothermal amplification (LAMP): A novel rapid detection platform for pathogens

Foodborne bacterial infections and diseases have been considered to be a major threat for public health in the worldwide. Increased incidence of human diseases caused by foodborne pathogens have been correlated with growing world population and mobility. Loop-mediated isothermal amplification (LAMP) has been regarded as an innovative gene amplification technology and emerged as an alternative to PCR-based methodologies in both clinical laboratory and food safety testing. Nowadays, LAMP has been applied to detection and identification on pathogens from microbial diseases, as it showed significant advantage in high sensitivity, specificity and rapidity. The high sensitivity of LAMP enables detection of the pathogens in sample materials even without time consuming sample preparation. An overview of LAMP mainly containing the development history, reaction principle and its application to four kind of foodborne pathogens detection are presented in this paper. As concluded, with the advantages of rapidity, simplicity, sensitivity, specificity and robustness, LAMP is capable of applications for clinical diagnosis as well as surveillance of infection diseases. Moreover, the main purpose of this paper is to provide theoretical basis for the clinical application of LAMP technology.

Current methodologies on genotyping for nosocomial pathogen methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen in hospitals and the community. As the rapid spread and wide distribution of antimicrobial resistance (such as MRSA), treatment for infectious diseases caused by microorganisms has become a vital threat. Thus, early identification and genotyping are essential for further therapeutic treatment and the control of rapid expansion of MRSA. In combination with applications and data feedbacks, this review focused on the currently available molecular-based assays on their utility and performance for rapid typing of MRSA, especially on effective molecular-based methods. Besides, a common mobile element SCCmec and prevalence of HA-MRSA, LA-MRSA and CA-MRSA were introduced in this review in order to provide a more complete profile of MRSA.

PMA-LAMP for rapid detection of Escherichia coli and shiga toxins from viable but non-culturable state

In exposure to outer pressure, microorganisms are capable of entry into the Viable But Non-Culturable (VBNC) state, and thus survive under various elimination processing. The survival microorganisms may yield negative results on culturing, and cause false negative for this golden standard methodology. In this study, a novel PMA-LAMP assay on the detection of Enterohemorrhage E. coli and shiga toxins has been developed and evaluated, with further application on a number of food borne E. coli strains. LAMP primers were designed on the target of rfbe for Enterohemorrhage E. coli and stx1with stx2 for shiga toxins. Via specific penetration through the damaged cell membrane of dead cells and intercalating into DNA, PMA could prevent DNA amplification of dead bacteria from LAMP, which enabled the differentiation of bacteria between VBNC state and dead state. The established PMA-LAMP showed significant advantage in rapidity, sensitivity and specificity, compared with regular PCR assay. The applicability had also been verified, demonstrating the PMA-LAMP was capable of detection on Enterohemorrhage E. coli and shiga toxins.