Short chain N-acylhomoserine lactone production by clinical multidrug resistant Klebsiella pneumoniae strain CSG20

Evaluation of the Zybio EXS3000 mass spectrometry in routine identification of Clinical isolates

The matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been widely applied in routine clinical microbiology laboratories as an efficient and reliable technique for diagnostic purpose. In this work, we evaluated the performance of the newly developed Zybio EXS3000 (Zybio Inc., China) in microbial identification and compared it with VITEK MS (bioMérieux, France). For this study, a total of 1340 isolates from various clinical specimens were collected. These isolates were analyzed simultaneously on both EXS3000 and VITEK MS. The inconsistent or unidentifiable data were further identified using the help of either 16S rRNA gene or ITS region sequencing. During the study, we observed that EXS3000 and VITEK MS provided positive confirmatory diagnostics for 95.0% and 96.5% of the isolates, respectively, which were consistent with the sequencing results. However, it is worth noting that the EXS3000 system needs to improve the identification performance of Candida albicans in the follow-up. There are no significant differences between the two devices in terms of microbial identification performance. The advantage of EXS3000 over VITEK MS is in its ability to perform in significantly lesser time period. In conclusion, the results of this investigation showed that EXS3000 can be used to identify microorganisms in clinical microbiology laboratories.

Detection of Quorum Sensing N-Acyl-Homoserine Lactone Molecules Produced by Different Resistant Klebsiella pneumoniae Isolates Recovered from Poultry and Different Environmental Niches

This study aimed to detect and identify the N-acyl-homoserine lactones molecules (AHLs) produced by different resistant Klebsiella pneumoniae isolates recovered from poultry and environmental samples using a modified validated high-performance liquid chromatography method. A total of 56 K. pneumoniae isolates were recovered, investigated for their antibiotic susceptibility, and screened for AHLs production using the Agrobacterium tumefaciens NTL4 biosensor system and a validated high-performance liquid chromatography method. The results revealed the detection of different short- and long-chain AHLs molecules among 39 K. pneumoniae isolates recovered from poultry and environmental samples. All environmental isolates produced nine peaks with retention times for C4-HSL, C6-HSL, C12-HSL, C8-HSL, C14-HSL, C8-oxo-HSL, C10-HSL, C6-oxo-HSL, and C7-HSL. The most quantifiable AHL signal molecules in poultry isolates were C4-HSL, C6-HSL, and C12-HSL. No statistical correlation between the AHL-producing ability of K. pneumoniae isolates and antibiotic resistance was reported. To the best of our knowledge, this study provides the first detailed report on the detection and identification of AHLs in K. pneumoniae isolates recovered from poultry and environmental samples. Furthermore, it provides a new insight available tool other than LC-MS/MS for detection and identification of AHL molecules.

Tea polyphenols inhibits biofilm formation, attenuates the quorum sensing-controlled virulence and enhances resistance to Klebsiella pneumoniae infection in Caenorhabditis elegans model

Bacteria cells can communicate with each other via quorum sensing (QS) system. Various physiological characteristics including virulence factors and biofilm formation are controlled by QS. So interrupting the bacterial communication is an alternative strategy instead of antibiotics for control bacterial infection. The aim of this study was to investigate the effects of tea polyphenols (TPs) on quorum sensing and virulence factors of Klebsiella pneumoniae. In vitro study showed that the anti-QS activity of tea polyphenols against Chromobacterium violaceum in violacein production. At sub-MICs, TPs inhibited the motility, reduced protease and exopolysaccharide (EPS) production and also biofilm formation in K. pneumoniae. In addition, in vivo study showed that tea polyphenols at 200 μg/mL and 400 μg/mL increased the survival rate of Caenorhabditis elegans to 73.3% and 82.2% against K. pneumonia infection. Our findings suggest that tea polyphenols can act as an effective QS inhibitor and can serve as a novel anti-virulence agent for the management of bacterial pathogens.

The Search for Natural Inhibitors of Biofilm Formation and the Activity of the Autoinductor C6-AHL in Klebsiella pneumoniae ATCC 13884

Human nosocomial infections are common around the world. One of the main causes is the bacteria Klebsiella pneumoniae, which shows high rates of resistance to antibiotics. Thus, drugs with novel mechanisms of action are needed. In this work, we report the effects of various natural substances on the formation of biofilm in Klebsiella pneumoniae, as well as its stability. The effect of the molecules on the growth of K. pneumoniae was initially determined by measuring the optical density. The modification of the biofilm, the changes relating to its resistance, the effects on the bacterial adhesion to the urethral catheter and its antagonist role the hexanoyl-homoserinelactone were assessed by crystal violet, as well as by microscopy. The best effects were obtained with 3-methyl-2(5H)-furanone and 2´-hydroxycinnamic acid, which inhibited the formation of biofilm by 67.38% and 65.06%, respectively. Additionally, the remaining biofilm formed was more susceptible to gentamicin. Through microscopy examination, there were evident changes in the biofilm and adherence on the polyvinyl chloride (PVC) urethral catheter. Besides, 3-methyl-2(5H)-furanone inhibited the biofilm-forming effect of the autoinducer hexanoyl-homoserinelactone. Thus, these molecules could be developed as supplemental of antibiotics.

Production of N-acyl homoserine lactones by Chromobacterium haemolyticum KM2 isolated from the river water in Malaysia

Quorum sensing (QS) is a term used to describe cell-to-cell communication that enables bacteria to orchestrate group behaviours according to density of bacterial cells. In Gram-negative bacteria, this signalling system is widely known to regulate a variety of different phenotypes such as antibiotic production and biofilm formation. In this study, we report the production of N-acyl homoserine lactones produced by Chromobacterium haemolyticum strain KM2, a bacterium isolated from a river water of a reserved tropical national park. Preliminary screening of QS activity using biosensor reporter assays indicated that C. haemolyticum strain KM2 produces both short- and long-chain AHLs. Analysis with high-resolution liquid chromatography-mass spectrometry (LC-MS/MS) analysis revealed the production of three AHLs by strain KM2: N-octanoyl-L-homoserine lactone (C8-HSL), N-dodecanoyl-L-homoserine lactone (C12-HSL), and N-3-oxo-dodecanoyl-L-homoserine lactone (OC12-HSL). This bacterial isolate also exhibited strong β-haemolytic activity. To the best of our knowledge, this is the first documentation of QS activity and multiple AHLs production by C. haemolyticum strain KM2.

Dielectrophoresis for Biomedical Sciences Applications: A Review

Dielectrophoresis (DEP) is a label-free, accurate, fast, low-cost diagnostic technique that uses the principles of polarization and the motion of bioparticles in applied electric fields. This technique has been proven to be beneficial in various fields, including environmental research, polymer research, biosensors, microfluidics, medicine and diagnostics. Biomedical science research is one of the major research areas that could potentially benefit from DEP technology for diverse applications. Nevertheless, many medical science research investigations have yet to benefit from the possibilities offered by DEP. This paper critically reviews the fundamentals, recent progress, current challenges, future directions and potential applications of research investigations in the medical sciences utilizing DEP technique. This review will also act as a guide and reference for medical researchers and scientists to explore and utilize the DEP technique in their research fields.

Quorum sensing activity of Citrobacter amalonaticus L8A, a bacterium isolated from dental plaque

Cell-cell communication is also known as quorum sensing (QS) that happens in the bacterial cells with the aim to regulate their genes expression in response to increased cell density. In this study, a bacterium (L8A) isolated from dental plaque biofilm was identified as Citrobacter amalonaticus by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). Its N-acylhomoserine-lactone (AHL) production was screened by using two types of AHL biosensors namely Chromobacterium violaceum CV026 and Escherichia coli [pSB401]. Citrobacter amalonaticus strain L8A was identified and confirmed producing numerous types of AHL namely N-butyryl-L-homoserine lactone (C4-HSL), N-hexanoyl-L-homoserine lactone (C6-HSL), N-octanoyl-L-homoserine lactone (C8-HSL) and N-hexadecanoyl-L-homoserine lactone (C16-HSL). We performed the whole genome sequence analysis of this oral isolate where its genome sequence reveals the presence of QS signal synthase gene and our work will pave the ways to study the function of the related QS genes in this bacterium.

Detection of quorum sensing activity in the multidrug-resistant clinical isolate Pseudomonas aeruginosa strain GB11

A multidrug-resistant clinical bacteria strain GB11 was isolated from a wound swab on the leg of a patient. Identity of stain GB11 as Pseudomonas aeruginosa was validated by using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Detection of the production of signaling molecules, N-acylhomoserine lactones (AHLs), was conducted using three different bacterial biosensors. A total of four different AHLs were found to be produced by strain GB11, namely N-butyryl homoserine lactone (C4-HSL), N-hexanoylhomoserine lactone (C6-HSL), N-octanoyl homoserine lactone (C8-HSL) and N-3-oxo-dodecanoylhomoserine lactone (3-oxo-C12-HSL) using high resolution liquid chromatography tandem mass spectrometry (LC-MS/MS). Of these detected AHLs, 3-oxo-C12-HSL was found to be the most abundant AHL produced by P. aeruginosa GB11.

Labrenzia sp. BM1: a quorum quenching bacterium that degrades N-acyl homoserine lactones via lactonase activity

We report the degradation of quorum sensing N-acylhomoserine lactone molecules by a bacterium isolated from a Malaysian marine water sample. MALDI-TOF and phylogenetic analysis indicated this isolate BM1 clustered closely to Labrenzia sp. The quorum quenching activity of this isolate was confirmed by using a series of bioassays and rapid resolution liquid chromatography analysis. Labrenzia sp. degraded a wide range of N-acylhomoserine lactones namely N-(3-hexanoyl)-l-homoserine lactone (C6-HSL), N-(3-oxohexanoyl)-l-homoserine lactone (3-oxo-C6-HSL) and N-(3-hydroxyhexanoyl)-l-homoserine lactone (3-hydroxy-C6-HSL). Re-lactonisation bioassays confirmed Labrenzia sp. BM1 degraded these signalling molecules efficiently via lactonase activity. To the best of our knowledge, this is the first documentation of a Labrenzia sp. capable of degrading N-acylhomoserine lactones and confirmation of its lactonase-based mechanism of action.

Quorum sensing activity in Pandoraea pnomenusa RB38

Strain RB38 was recovered from a former dumping area in Malaysia. MALDI-TOF mass spectrometry and genomic analysis identified strain RB-38 as Pandoraea pnomenusa. Various biosensors confirmed its quorum sensing properties. High resolution triple quadrupole liquid chromatography–mass spectrometry analysis was subsequently used to characterize the N-acyl homoserine lactone production profile of P. pnomenusa strain RB38, which validated that this isolate produced N-octanoyl homoserine lactone as a quorum sensing molecule. This is the first report of the production of N-octanoyl homoserine lactone by P. pnomenusa strain RB38.

Quorum sensing activity of Aeromonas caviae strain YL12, a bacterium isolated from compost

Quorum sensing is a well-studied cell-to-cell communication method that involves a cell-density dependent regulation of genes expression mediated by signalling molecules. In this study, a bacterium isolated from a plant material compost pile was found to possess quorum sensing activity based on bioassay screening. Isolate YL12 was identified using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and molecular typing using rpoD gene which identified the isolate as Aeromonas caviae. High resolution tandem mass spectrometry was subsequently employed to identify the N-acyl homoserine lactone profile of Aeromonas caviae YL12 and confirmed that this isolate produced two short chain N-acyl homoserine lactones, namely C4-HSL and C6, and the production was observed to be cell density-dependent. Using the thin layer chromatography (TLC) bioassay, both AHLs were found to activate C. violaceum CV026, whereas only C6-HSL was revealed to induce bioluminescence expression of E. coli [pSB401]. The data presented in this study will be the leading steps in understanding the role of quorum sensing in Aeromonas caviae strain YL12.

Quorum sensing activity of Serratia fonticola strain RB-25 isolated from an ex-landfill site

Quorum sensing is a unique bacterial communication system which permits bacteria to synchronize their behaviour in accordance with the population density. The operation of this communication network involves the use of diffusible autoinducer molecules, termed N-acylhomoserine lactones (AHLs). Serratia spp. are well known for their use of quorum sensing to regulate the expression of various genes. In this study, we aimed to characterized the AHL production of a bacterium designated as strain RB-25 isolated from a former domestic waste landfill site. It was identified as Serratia fonticola using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry analysis and this was confirmed by 16S ribosomal DNA sequencing. High resolution triple quadrupole liquid chromatography-mass spectrometry analysis of S. fonticola strain RB-25 spent culture supernatant indicated the existence of three AHLs namely: N-butyryl-L-homoserine lactone (C4-HSL), N-hexanoyl-L-homoserine lactone (C6-HSL) and N-(3-oxohexanoyl) homoserine-lactone (3-oxo-C6 HSL). This is the first report of the production of these AHLs in S. fonticola.