Laccase production from Bacillus aestuarii KSK using Borassus flabellifer empty fruit bunch waste as a substrate and assessing their malachite green dye degradation

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Abstract

Aims

The lignocellulosic waste, Borassus flabellifer empty fruit bunch waste (BFEFBW), was employed to produce laccase using Bacillus aestuarii KSK under solid-state fermentation (SSF) conditions and to assess the efficiency of malachite green (MG) dye decolourization.

Methods and Results

Abiotic factors such as pH (5.0–9.0), temperature (25–45°C) and incubation time (24–96 h) were optimized using Response surface methodology-Box-Behenan Design (RSM-BBD) to exploit the laccase production. The anticipated model revealed that the highest laccase activity of 437 U/ml shows after 60 h of incubation at 35°C at pH 7.0. The bacterial laccase was used to remove 89% of the MG dye in less time.

Conclusion

The laccase from B. aestuarii KSK decolorizes the MG and thereby making it a suitable choice for wastewater treatment from industrial effluents.

Significance and Impact of the Study

This study is the first report on the production of laccase from B. flabellifer empty fruit bunch waste as a substrate. Bacillus aestuarii KSK was isolated from the soil sample and used to produce laccase under SSF conditions. The bacterial laccase has the potential for industrial application in textile waste dye treatment.

Dose–response analysis of Bacillus thuringiensis HD‐1 cry‐ spore reduction on surfaces using formaldehyde with pre‐germination

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Abstract

Aim

To establish a basis for rapid remediation of large areas contaminated with Bacillus anthracis spores.

Methods and Results

Representative surfaces of wood, steel and cement were coated by nebulization with B. thuringiensis HD-1 cry- (a simulant for B. anthracis) at 5.9 ± 0.2, 6.3 ± 0.2 and 5.8 ± 0.2 log10 CFU per cm2, respectively. These were sprayed with formaldehyde, either with or without pre-germination. Low volume (equivalent to ≤2500 L ha−1) applications of formaldehyde at 30 g l−1 to steel or cement surfaces resulted in ≥4 or ≤2 log10 CFU per cm2 reductions respectively, after 2 h exposure. Pre-germinating spores (500 mmol l−1 l-alanine and 25 mmol l−1 inosine, pH 7) followed by formaldehyde application showed higher levels of spore inactivation than formaldehyde alone with gains of up to 3.4 log10 CFU per cm2 for a given dose. No loss in B. thuringiensis cry- viability was measured after the 2 h germination period, however, a pre-heat shock log10 reduction was seen for B. anthracis strains: LSU149 (1.7 log10), Vollum and LSU465 (both 0.9 log10), LSU442 (0.2 log10), Sterne (0.8 log10) and Ames (0.6 log10).

Conclusions

A methodology was developed to produce representative spore contamination of surfaces along with a laboratory-based technique to measure the efficacy of decontamination. Dose–response analysis was used to optimize decontamination. Pre-germinating spores was found to increase effectiveness of decontamination but requires careful consideration of total volume used (germinant and decontaminant) by surface type.

Significance and Impact of the Study

To be practically achievable, decontamination of a wide area contaminated with B. anthracis spores must be effective, timely and minimize the amount of materials required. This study uses systematic dose–response methodology to demonstrate that such an approach is feasible.

Antimicrobial effects of automobile screen washes against Legionella pneumophila

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Abstract

Aims

Legionella pneumophila (Lp), a human pathogen, has been detected in windscreen wiper fluid reservoirs (WWFRs) where commercial screen washes (CSWs) are commonly added. Limited information is available on CSWs against planktonic Lp; however, responses of sessile Lp and planktonic Lp pre-acclimated in nutrient-limited water to CSWs remain unknown. This study thus investigates the antibacterial effects of CSWs on sessile and starved planktonic Lp, in comparison with unstarved Lp.

Methods and Results

Lp biofilms were produced on glass and WWFR materials of high-density polyethylene (HDPE) and polypropylene (PP). Planktonic Lp with and without acclimation in tap water were prepared. Log reductions in cell counts averaged 0.4–5.0 for 10 brands of CSWs against sessile Lp and 1.0–3.9 and 0.9–4.9, respectively, against starved and unstarved planktonic Lp for five CSWs. Both biofilm formation and acclimation in tap water enhanced Lp resistance to CSWs. Significantly different log-reduction values among CSW brands were observed for sessile Lp on HDPE and planktonic Lp regardless of acclimation (p < 0.05).

Conclusions

Biofilm formation, starvation acclimation and CSW brand are crucial factors influencing Lp response to CSWs.

Significance and Impact of Study

This study advances the knowledge of Lp reaction in anthropogenic water systems with CSWs.

Prevalence, genetic diversity, antibiotic resistance and biofilm formation of Acinetobacter baumannii isolated from urban environments

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Abstract

Aim

Acinetobacter baumannii is a well-known nosocomial pathogen that has been isolated from different clinical sources. This pathogen also causes community-acquired infections, with mortality rates as high as 64%. The exact natural habitat of this bacterium is still unknown. In this study, we investigated the prevalence of A. baumannii in diverse soil and high-touch surface samples collected from a university campus, malls, parks, hypermarkets and produce markets, roundabout playground slides and bank ATMs.

Methods and Results

All obtained isolates were characterized for their antibiotic susceptibility, biofilm formation capacities, and were typed by multi-locus sequence analysis. A total of 63 A. baumannii isolates were recovered, along with 46 Acinetobacter pittii and 8 Acinetobacter nosocomialis isolates. Sequence typing revealed that 25 A. baumannii isolates are novel strains. Toilets and sink washing basins were the most contaminated surfaces, accounting for almost 50% of the isolates. A number of A. baumannii (n = 10), A. pittii (n = 19) and A. nosocomialis (n = 5) isolates were recovered from handles of shopping carts and baskets. The majority of isolates were strong biofilm formers and 4 isolates exhibited a multi-drug resistant phenotype.

Conclusions

Our study is the first to highlight community restrooms and shopping carts as potential reservoirs for pathogenic Acinetobacter species. Further studies are required to identify the reasons associated with the occurrence of A. baumannii inside restrooms. Proper disinfection of community environmental surfaces and spreading awareness about the importance of hand hygiene may prevent the dissemination of pathogenic bacteria within the community.

Significance and Impact of the study

Serious gaps remain in our knowledge of how A. baumannii spreads to cause disease. This study will advance our understanding of how this pathogen spreads between healthcare and community environments. In addition, our findings will help healthcare decision-makers implement better measures to control and limit further transmission of A. baumannii.

Antibacterial and antibiofilm activities of thiazolidine‐2,4‐dione and 4‐thioxo‐thiazolidin‐2‐one derivatives against multidrug‐resistant Staphylococcus aureus clinical isolates

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Abstract

Aims

Antimicrobial resistance is one of the highest priorities in global public health with Staphylococcus aureus among the most important microorganisms due to its rapidly evolving antimicrobial resistance. Despite all the efforts of antimicrobial stewardship, research and development of new antimicrobials are still imperative. The thiazolidine ring is considered a privileged structure for the development of new antimicrobials. This study aimed to compare the antibacterial effects of two analogue series of thiazolidine-2,4-dione and 4-thioxo-thiazolidin-2-one against multidrug-resistant Staph. aureus clinical isolates.

Methods and Results

The derivatives 1a, 2a and 2b exhibited MIC between 1–32 μg ml−1, with time-to-kill curves showing a bactericidal effect up to 24 h. In the antibiofilm assay, the most active derivatives were able to inhibit about 90% of biofilm formation. The 4-thioxo-thiazolidine-2-one derivatives were more active against planktonic cells, while the thiazolidine-2,4-dione derivatives were able to disrupt about 50% of the preformed biofilm. In the in vivo infection model using Caenorhabditis elegans as a host, the derivatives 1a, 2a and 2b increased nematode survival with a concentration-dependent effect. Exposure of Staph. aureus to the derivatives 2a and 2b induced surface changes and decrease cell size. None of the derivatives was cytotoxic for human peripheral blood mononuclear cells (PBMC) but showed moderate cytotoxicity for L929 fibroblasts.

Conclusion

The 5-(3,4-dichlorobenzylidene)-4-thioxothiazolidin-2-one (2b) was the most active derivative against Staph. aureus and showed higher selective indices.

Significance and Impact of the Study

4-thioxo-thiazolidin-2-one is a promising scaffold for the research and development of new antimicrobial drugs against multidrug-resistant Staph. aureus.

Altered molecular attributes and antimicrobial resistance patterns of Vibrio cholerae O1 El Tor strains isolated from the cholera endemic regions of India

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Abstract

Aims

The present study aimed to document the comparative analysis of differential hypervirulent features of Vibrio cholerae O1 strains isolated during 2018 from cholera endemic regions in Gujarat and Maharashtra (Western India) and West Bengal (Eastern India).

Methods and Results

A total of 87 V. cholerae O1 clinical strains from Western India and 48 from Eastern India were analysed for a number of biotypic and genotypic features followed by antimicrobial resistance (AMR) profile. A novel polymerase chain reaction was designed to detect a large fragment deletion in the Vibrio seventh pandemic island II (VSP-II) genomic region, which is a significant genetic feature of the V. cholerae strains that have caused Yemen cholera outbreak. All the strains from Western India belong to the Ogawa serotype, polymyxin B-sensitive, hemolytic, had a deletion in VSP-II (VSP-IIC) region and carried Haitian genetic alleles of ctxB, tcpA and rtxA. Conversely, 14.6% (7/48) of the strains from Eastern India belonged to the Inaba serotype, polymyxin B-resistant, nonhemolytic, harboured VSP-II other than VSP-IIC type, classical ctxB, Haitian tcpA and El Tor rtxA alleles. Resistance to tetracycline and chloramphenicol has been observed in strains from both regions.

Conclusions

This study showed hypervirulent, polymyxin B-sensitive epidemic causing strains in India along with the strains with polymyxin B-resistant and nonhemolytic traits that may spread and cause serious disease outcomes in future.

Significance and impact of the study

The outcomes of this study can help to improve the understanding of the hyperpathogenic property of recently circulating pandemic Vibrio cholerae strains in India. Special attention is also needed for the monitoring of AMR surveillance because V. cholerae strains are losing susceptibility to many antibiotics used as a second line of defence in the treatment of cholera.

Rapid and visual detection of Staphylococcus aureus in milk using a recombinase polymerase amplification‐lateral flow assay combined with immunomagnetic separation

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Abstract

Aims

The aim of this study was to develop a novel approach using lateral flow recombinase polymerase amplification (RPA-LF) combined with immunomagnetic separation (IMS) for the rapid detection of Staphylococcus aureus in milk.

Methods and results

Under optimum conditions, the average capture efficiency values for S. aureus strains (104 colony-forming units [CFU] per ml) was above 95.0% in PBST and ~80% in milk within 45 min with 0.7 mg immunomagnetic beads. The RPA-LF assay, which comprised DNA amplification via RPA at 39°C for 10 min and visualization of the amplicons through LF strips for 5 min, detected S. aureus within 15 min. The method only detected S. aureus and did not show cross-reaction with other bacteria, exhibiting a high level of specificity. Sensitivity experiments confirmed a detection limit of RPA-LF assay as low as 600 fg per reaction for the S. aureus genome (corresponding to approximately 36 CFU of S. aureus), which was about 16.7-fold more sensitive than that of the conventional polymerase chain reaction method. When RPA-LF was used in combination with IMS to detect S. aureus inoculated into artificially contaminated milk, it exhibited a detection limit of approximately 40 CFU per reaction.

Conclusions

The newly developed IMS-RPA-LF method enabled detection of S. aureus at levels as low as 40 CFU per reaction in milk samples without culture enrichment for an overall testing time of only 70 min.

Significance and Impact of the Study

The newly developed IMS-lateral flow RPA-LF assay effectively combines sample preparation, amplification and detection into a single platform. Because of its high sensitivity, specificity and speed, the IMS-RPA-LF assay will have important implications for the rapid detection of S. aureus in contaminated food.

Effects of Bacillus subtilis natto JLCC513 on gut microbiota and intestinal barrier function in obese rats

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Abstract

Aims

This study aimed to investigate the effects of Bacillus subtilis natto JLCC513 (JLCC513) on gut microbiota, inflammation and intestinal barrier function in high-fat-diet (HFD) rats.

Methods and Results

Sprague–Dawley (SD) rats were fed HFD for 16 weeks, and treated with JLCC513 in 9th week. The oral administration of JLCC513 decreased body weight and reduced the inflammation level in HFD rats. Pathologically, JLCC513 prevented the detachment of ileal villus and increased the villus height in rats. Mechanistically, western blot analysis showed that the protein levels of tight junction (TJ) proteins involved in intestinal barrier function, including zonula occludens-1 (ZO-1), occludin and claudin-1, were increased after JLCC513 treatment. Meanwhile, JLCC513 treatment also decreased the protein levels of toll-like receptor 4 (TLR4), nuclear factor kappa-B (NF-κB) and NOD-like receptor protein 3 (NLRP3), indicating inhibition of the TLR4/NF-κB/NLRP3 pathway. Furthermore, faecal analysis showed that JLCC513 increased the abundance of Lactobacillus and Oscillospira and the ratio of Firmicutes/Bacteroidetes (F/B), and decreased the levels of Blautia and C_Clostridium.

Conclusions

JLCC513 alleviated intestinal barrier dysfunction by inhibiting TLR4/NF-κB/NLRP3 pathway and regulating gut microbiota disorders.

Significance and Impact of Study

Our study might provide new treatment strategies for obesity and metabolic diseases.

Ultrasound‐assisted facile synthesis of Boron‐Heck‐coupled sclareol analogues as potential antibacterial agents against Staphylococcus aureus

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Abstract

Aim

To evaluate the antimicrobial capability of sclareol and its derivatives against Staphylococcus aureus and its Methicillin-resistant strain (MRSA).

Methods and Results.

A new series of Boron-Heck-coupled sclareol analogues were prepared by structural modifications at the C-15 terminal double bond of sclareol using ultrasonication. The structural modifications were designed to keep the stereochemistry of all the five chiral centres of sclareol intact. A two-step reaction scheme consisting of Boron-Heck coupling of sclareol followed by Wittig reaction was carried out to produce novel sclareol congeners for antimicrobial evaluation. Three compounds SAJ-1, SAJ-2 and SB-11 exhibited strong antibacterial activity against S. aureus and Methicillin-resistant strain (MRSA) with MIC values between 3 and 11 μM. Among all the screened compounds, SAJ-1 and SAJ-2 showed the best antibiofilm profiles against both strains. Moreover, SAJ-1 and SAJ-2 acted synergistically with streptomycin against S. aureus while creating varying outcomes in combination with ciprofloxacin, penicillin and ampicillin. SAJ-1 also acted synergistically with ampicillin against S. aureus, while SB-11 showed synergism with ciprofloxacin against both pathogens. Moreover, SAJ-1 and SAJ-2 also inhibited staphyloxanthin production in S. aureus and MRSA and induced postantibiotic effects against both pathogens.

Conclusions

It can be inferred that SAJ-1, SAJ-2 and SB-11 may act as potential chemical entities for the development of antibacterial substances. The study revealed that SAJ-1 and SAJ-2 are the most suitable sclareol analogues for further studies towards the development of antibacterial substances.

Significance and Impact of the Study

SAJ-1, SAJ-2 and SB-11 show promising antibacterial properties against Staphylococcus aureus. Efforts should be made and more research should be done utilizing in vivo models to determine their efficacy as antibiotics.