Journal of Microbiology

Journal Articles

Hydroxychloroquine an Antimalarial Drug, Exhibits Potent Antifungal Efficacy Against Candida albicans Through Multitargeting.: Sargun Tushar Basrani, Tanjila Chandsaheb Gavandi, Shivani Balasaheb Patil, Nandkumar Subhash Kadam, Dhairyasheel Vasantrao Yadav, Sayali Ashok Chougule, Sankunny Mohan Karuppayil, Ashwini Khanderao Jadhav; J. Microbiol. 2024;62(5):381-391. Published online April 8, 2024; DOI: https://doi.org/10.1007/s12275-024-00111-6

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Abstract: Candida albicans is the primary etiological agent associated with candidiasis in humans. Unrestricted growth of C. albicans can progress to systemic infections in the worst situation. This study investigates the antifungal activity of Hydroxychloroquine (HCQ) and mode of action against C. albicans. HCQ inhibited the planktonic growth and yeast to hyphal form morphogenesis of C. albicans significantly at 0.5 mg/ml concentration. The minimum inhibitory concentrations (MIC(50)) of HCQ for C. albicans adhesion and biofilm formation on the polystyrene surface was at 2 mg/ml and 4 mg/ml respectively. Various methods, such as scanning electron microscopy, exploration of the ergosterol biosynthesis pathway, cell cycle analysis, and assessment of S oxygen species (ROS) generation, were employed to investigate HCQ exerting its antifungal effects. HCQ was observed to reduce ergosterol levels in the cell membranes of C. albicans in a dose-dependent manner. Furthermore, HCQ treatment caused a substantial arrest of the C. albicans cell cycle at the G0/G1 phase, which impeded normal cell growth. Gene expression analysis revealed upregulation of SOD2, SOD1, and CAT1 genes after HCQ treatment, while genes like HWP1, RAS1, TEC1, and CDC 35 were downregulated. The study also assessed the in vivo efficacy of HCQ in a mice model, revealing a reduction in the pathogenicity of C. albicans after HCQ treatment. These results indicate that HCQ holds for the development of novel antifungal therapies.

Two novel synthetic peptides inhibit quorum sensing-dependent biofilm formation and some virulence factors in Pseudomonas aeruginosa PAO1: Mostafa N. Taha , Amal E. Saafan , A. Ahmedy , Eman El Gebaly , Ahmed S. Khairalla; J. Microbiol. 2019;57(7):618-625. Published online June 27, 2019; DOI: https://doi.org/10.1007/s12275-019-8548-2

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21 Citations

Abstract: Quorum sensing (QS) regulates virulence factor expression in Pseudomonas aeruginosa. Inhibiting the QS-controlled virulence factors without inhibiting the growth of P. aeruginosa is a promising approach for overcoming the widespread resistance of P. aeruginosa. This study was proposed to investigate the effects of two novel synthetic peptides on the biofilm development and virulence factor production of P. aeruginosa. The tested strain was P. aeruginosa PAO1. The results indicated that both of the synthetic peptides (LIVRHK and LIVRRK) inhibited (P < 0.05) the formation of biofilms and the production of virulence factors, including pyocyanin, protease, and rhamnolipids, without inhibiting the growth of PAO1. Additionally, we detected transcriptional changes related to QS and found a significant reduction in the levels of gene expression of lasI, lasR, rhlI, and rhlR. This study demonstrates that LIVRRK and LIVRHK are novel synthetic peptides that can act as potent inhibitors of QS-regulated virulence factors in P. aeruginosa. Moreover, these synthetic peptides have potential applications in the treatment of biofilmrelated diseases. Both peptides may be able to control chronic infections and biofilm-associated problems of P. aeruginosa.

Role of putative virulence traits of Campylobacter jejuni in regulating differential host immune responses: Ankita Singh , Amirul Islam Mallick; J. Microbiol. 2019;57(4):298-309. Published online February 22, 2019; DOI: https://doi.org/10.1007/s12275-019-8165-0

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16 Citations

Abstract: Among the major enteric pathogens, Campylobacter jejuni is considered an important source of diarrheal illness in humans. In contrast to the acute gastroenteritis in humans, C. jejuni exhibits prolonged cecal colonization at a high level with little or no pathology in chickens. Although several known virulence determinants of C. jejuni have been found to be associated with a higher degree of pathogenesis in humans, to date, little is known about their functions in the persistent colonization of chickens. The present study was undertaken to assess the role of C. jejuni in imparting differential host immune responses in human and chicken cells. Based on the abundance of major genes encoding virulence factors (GEVFs), we used a particular isolate that harbors the cadF, flaA, peb1, racR, ciaB, cdtB, and hcp genes. This study showed that hypervirulent C. jejuni isolate that encodes a functional type VI secretion system (T6SS) has a greater ability to invade and create characteristic “attaching and effacing” lesions in human INT407 compared to primary chicken embryo intestinal cells (CEICs). Furthermore, we demonstrated that the higher bacterial invasion in human INT407 triggered higher levels of expression of major proinflammatory cytokines, such as IL- 1β and IL-6, and significant downregulation of IL-17A gene expression (P ≤ 0.05). The findings of the present study suggest that the enhanced ability of C. jejuni to invade human cells is tightly regulated by proinflammatory cytokines in the gut and possibly holds the keys to the observed differences in pathogenesis between human and chicken cells.

Potential for colonization of O111:H25 atypical enteropathogenic E. coli: Marta O. Domingos , Keyde C.M. Melo , Irys Viana Neves , Cristiane M. Mota , Rita C. Ruiz , Bruna S. Melo , Raphael C. Lima , Denise S.P.Q. Horton , Monamaris M. Borges , Marcia R. Franzolin; J. Microbiol. 2016;54(11):745-752. Published online October 29, 2016; DOI: https://doi.org/10.1007/s12275-016-6015-x

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8 Citations

Abstract: Using clonal phylogenetic methods, it has been demonstrated that O111:H25 atypical enteropathogenic E. coli (aEPEC) strains belong to distinct clones, suggesting the possibility that their ability to interact with different hosts and abiotic surfaces can vary from one clone to another. Accordingly, the ability of O111:H25 aEPEC strains derived from human, cat and dogs to adhere to epithelial cells has been investigated, along with their ability to interact with macrophages and to form biofilms on polystyrene, a polymer used to make biomedical devices. The results demonstrated that all the strains analyzed were able to adhere to, and to form pedestals on, epithelial cells, mechanisms used by E. coli to become strongly attached to the host. The strains also show a Localized-Adherence- Like (LAL) pattern of adhesion on HEp-2 cells, a behavior associated with acute infantile diarrhea. In addition, the O111:H25 aEPEC strains derived either from human or domestic animals were able to form long filaments, a phenomenon used by some bacteria to avoid phagocytosis. O111:H25 aEPEC strains were also encountered inside vacuoles, a characteristic described for several bacterial strains as a way of protecting themselves against the environment. They were also able to induce TNF-α release via two routes, one dependent on TLR-4 and the other dependent on binding of Type I fimbriae. These O111:H25 strains were also able to form biofilms on polystyrene. In summary the results suggest that, regardless of their source (i.e. linked to human origin or otherwise), O111:H25 aEPEC strains carry the potential to cause human disease.

Research Support, Non-U.S. Gov'ts

Virulence Determinants in Vancomycin-Resistant Enterococcus faecium vanA Isolated from Different Sources at University Hospital of Londrina, Paraná, Brazil: Flávia Imanishi Ruzon , Suelen Balero de Paula , Renata Lumi Kanoshiki , Jussevania Pereira-Santos , Gilselena Kerbauy , Renata Katsuko Takayama Kobayashi , Lucy Megumi Yamauchi , Márcia Regina Eches Perugini , Sueli Fumie Yamada-Ogatta; J. Microbiol. 2010;48(6):814-821. Published online January 9, 2011; DOI: https://doi.org/10.1007/s12275-010-0099-5

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16 Citations

Abstract: Enterococcus faecium, especially those showing multidrug resistance, has emerged as a significant cause of healthcare-associated infections worldwide. However, relatively little is known about the virulence and pathogenesis of this species. The aim of this study was to determine the occurrence of four putative virulence determinants of E. faecium and to correlate them with phenotypic traits. Using forty E. faecium vanA-type isolates from hospitalized patients and their environmental vicinity, we determined the following: the antimicrobial susceptibility profile, occurrence of the genes cylA, efaA, esp, and gelE, hemolytic and gelatinase activities, capacity to form biofilm and in vitro adhesion to epithelial cells. All isolates were shown to be resistant to vancomycin and teicoplanin, as well as to two or more other antimicrobials. All isolates harbored at least one putative virulence marker, and the prevalence was as follows: esp, 87.5%; efaA, 82.5%; gelE, 70%; and cylA, 65%. The presence of 4 genes was observed in 32.5% isolates. The presence of the efaA was associated with the presence of esp, regardless of the source of the isolates. A positive association with the presence of cylA and hemolytic activity in the sheep blood agar assay was observed. No association was found for gelE and gelatinase production in the agar plate assay, for efaA and LLC-MK2 cell adhesion, and for esp and biofilm formation on polystyrene surface. These results show the presence of putative virulence genes in multiple antimicrobial resistant E. faecium isolates from different sources in a hospital setting.

Modulation of Secreted Virulence Factor Genes by Subinhibitory Concentrations of Antibiotics in Pseudomonas aeruginosa: Lixin Shen , Ying Shi , Dan Zhang , Jinhua Wei , Michael G. Surette , Kangmin Duan; J. Microbiol. 2008;46(4):441-447. Published online August 31, 2008; DOI: https://doi.org/10.1007/s12275-008-0054-x

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46 Citations

Abstract: Recent studies have shown that subinhibitory antibiotics play important roles in regulating bacterial genes including virulence factor genes. In this study, the expression of 13 secreted virulence related gene clusters of Pseudomonas aeruginosa, an important opportunistic pathogen, was examined in the presence of subinhibitory concentrations of 4 antibiotics: vancomycin, tetracycline, ampicilin and azithromycin. Activation of gene expression was observed with phzA1, rhlAB, phzA2, lasB, exoY, and exoS. Subinhibitory concentrations of vancomycin resulted in more than 10-fold increase of rhlAB and phzA2 transcription. Both rhamnolipid production and pyocyanin production were significantly elevated, correlating phenotypes with the increased transcription. P. aeruginosa swarming and swimming motility also increased. Similar results were observed with subinhibitory tetracycline, azithromycin and ampicillin. These results indicate that the antibiotics at low concentrations can up-regulate virulence factors and therefore influence bacterial pathogenesis.

Characterization of Aeromonas hydrophila Isolated from Rainbow Trouts in Korea: Soondeuk Lee , Sookyung Kim , Yoojung Oh , Yeonhee Lee; J. Microbiol. 2000;38(1):1-7.

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Abstract: Eight strains of Aeromonas hydrophila isolated from diseased trout in Korea were characterized and compared with an American type strain by various methods including biochemical and physiological tests, PCR, randomly amplified polymorphic DNA (RAPD), plasmid profiling, and gel electrophoresis of total, membrane, and extracellular proteins. Virulence factors such as surface array proteins, cytotoxin, hemolysin, haemagglutinin, and protease were also investigated. The Korean strains showed het-erogeneity in lysine decarboxylase production, utilization of various carbon sources, and production of acetoin. Five strains had the same profiles of total and membrane proteins. Six strains haemag-glutinated with trout red blood cells (RBCs) which was inhibited by fucose, galactose, and mannose, except for No. 1 where haemagglutination was inhibited by only galactose and mannose, but not by fucose. Four isolates haemagglutinated with human RBCs which was inhibited by fucose and mannose yet not by galactose. The type strain haemagglutinated only with trout RBCs which was inhibited by fucose, galactose, and mannose. Every isolate secreted protease, hemolysin, cytotoxin, and siderophore, but no enterotoxin. Results showed that the Korean isolates, except for No. 7, had very different biochemical and molecular characteristics from those of the American type strain.

Research Support, Non-U.S. Gov't

DD1.5k, the Gene Preferentially Expressed in Bloodstream Isolates of Vancomycin-Resistant Enterococcus faecium: Seung-Han Kim , Dong-Gun Lee , Jin-Hong Yoo , Su-Mi Choi , Jung-Hyun Choi , Wan-Shik Shin , Kyungwon Lee , Dongeun Yong , Wee Gyo Lee , Byung-S. Youn , Moon-Won Kang; J. Microbiol. 2004;42(2):143-146.

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Abstract: Vancomycin-resistant Enterococcus faecium (VREFM) is becoming a threatening pathogen. We identified a gene called DD1.5K by differential display-PCR, which was preferentially expressed in the bloodstream isolates of VREFM. Due to its amino acid similarity to transfer complex protein, trsE, and tissue-specific expression, this gene may be involved in virulence of VREFM.

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