Journal of Microbiology

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Repeated Exposure of Vancomycin to Vancomycin-Susceptible Staphylococcus aureus (VSSA) Parent Emerged VISA and VRSA Strains with Enhanced Virulence Potentials: An Nguyen, J Jean Sophy Roy, Ji-Hoon Kim, Kyung-Hee Yun, Wonsik Lee, Kyeong Kyu Kim, Truc Kim, Akhilesh Kumar Chaurasia; J. Microbiol. 2024;62(7):535-553. Published online May 30, 2024; DOI: https://doi.org/10.1007/s12275-024-00139-8

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The emergence of resistance against the last-resort antibiotic vancomycin in staphylococcal infections is a serious concern for human health. Although various drug-resistant pathogens of diverse genetic backgrounds show higher virulence potential, the underlying mechanism behind this is not yet clear due to variability in their genetic dispositions. In this study, we investigated the correlation between resistance and virulence in adaptively evolved isogenic strains. The vancomycin-susceptible Staphylococcus aureus USA300 was exposed to various concentrations of vancomycin repeatedly as a mimic of the clinical regimen to obtain mutation(s)-accrued-clonally-selected (MACS) strains. The phenotypic analyses followed by expression of the representative genes responsible for virulence and resistance of MACS strains were investigated. MACS strains obtained under 2 and 8 µg/ml vancomycin, named Van2 and Van8, respectively; showed enhanced vancomycin minimal inhibitory concentrations (MIC) to 4 and 16 µg/ml, respectively. The cell adhesion and invasion of MACS strains increased in proportion to their MICs. The correlation between resistance and virulence potential was partially explained by the differential expression of genes known to be involved in both virulence and resistance in MACS strains compared to parent S. aureus USA300. Repeated treatment of vancomycin against vancomycin-susceptible S. aureus (VSSA) leads to the emergence of vancomycin-resistant strains with variable levels of enhanced virulence potentials.

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Targeting the G-quadruplex as a novel strategy for developing antibiotics against hypervirulent drug-resistant Staphylococcus aureus
Maria Sultan, Maria Razzaq, Joohyun Lee, Shreyasi Das, Shrute Kannappan, Vinod Kumar Subramani, Wanki Yoo, Truc Kim, Hye-Ra Lee, Akhilesh K. Chaurasia, Kyeong Kyu Kim
Journal of Biomedical Science.2025;[Epub] CrossRef

Cytophaga hutchinsonii chu_2177, encoding the O-antigen ligase, is essential for cellulose degradation: Yahong Tan , Wenxia Song , Lijuan Gao , Weican Zhang , Xuemei Lu; J. Microbiol. 2022;60(4):364-374. Published online January 7, 2022; DOI: https://doi.org/10.1007/s12275-022-1531-3

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Abstract

Cytophaga hutchinsonii can efficiently degrade crystalline cellulose, in which the cell surface cellulases secreted by the type IX secretion system (T9SS) play important roles, but the degradation mechanism remains unclear, and the anchor mechanism of cellulases on the outer membrane in C. hutchinsonii has not been studied. Here, chu_2177 was identified by transposon mutagenesis and was proved to be indispensable for cellulose utilization in C. hutchinsonii. Disruption of chu_2177 resulted in O-antigen deficiency and chu_ 177 could confer O-antigen ligase activity upon an Escherichia coli waal mutant, indicating that chu_2177 encoded the Ontigen ligase. Moreover, deletion of chu_2177 caused defects in cellulose utilization, cell motility, biofilm formation, and stress resistance. Further study showed that the endoglucanase activity was markedly decreased in the outer membrane but was increased in the culture fluid without chu_2177. Western blot proved that endoglucanase CHU_1336 was not located on the outer membrane but was released in the culture fluid of the Δ2177 mutant. Further proteomics analysis showed that many cargo proteins of T9SS were missing in the outer membrane of the Δ2177 mutant. Our study revealed that the deletion of chu_2177 affected the localization of many T9SS cargo proteins including cellulases on the outer membrane of C. hutchinsonii.

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Screening and genome-wide analysis of lignocellulose-degrading bacteria from humic soil
Tianjiao Zhang, Shuli Wei, Yajie Liu, Chao Cheng, Jie Ma, Linfang Yue, Yanrong Gao, Yuchen Cheng, Yongfeng Ren, Shaofeng Su, Xiaoqing Zhao, Zhanyuan Lu
Frontiers in Microbiology.2023;[Epub] CrossRef
The type IX secretion system: Insights into its function and connection to glycosylation in Cytophaga hutchinsonii
Wenxia Song, Xueke Zhuang, Yahong Tan, Qingsheng Qi, Xuemei Lu
Engineering Microbiology.2022; 2(3): 100038. CrossRef

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

Prevalence of Amino Acid Changes in the yvqF, vraSR, graSR, and tcaRAB Genes from Vancomycin Intermediate Resistant Staphylococcus aureus: Jae Il Yoo , Jung Wook Kim , Gi Su Kang , Hwa Su Kim , Jung Sik Yoo , Yeong Seon Lee; J. Microbiol. 2013;51(2):160-165. Published online April 27, 2013; DOI: https://doi.org/10.1007/s12275-013-3088-7

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Abstract: Vancomycin intermediate Staphylococcus aureus (VISA) strains are increasingly prevalent in the hospital setting, and are of major concern in the treatment of methicillin-resistant S. aureus infections. Multiple mutations in vancomycinsusceptible S. aureus (VSSA) strains likely led to the emergence of VISA, and point mutations in the agr, orf1, yvqF, vraSR, graSR, and tcaRAB genes of VISA strains have been shown to contribute to glycopeptide resistance. Therefore, we investigated point mutations in these genes from 87 VISA and 27 VSSA clinical strains isolated from Korean hospitals. All strains were assigned an agr type (I, II, or III) on the basis of multiplex PCR, with the majority of VISA strains belonging to agr groups I and II. Sequencing revealed amino acid changes in vraS from VISA strains which were not present in the VSSA strains. The E59D substitution in the vraR gene occurred in 36.3% of VSSA/agrI and 92.7% of VISA/agrI strains, suggesting that this mutation associated with emergence of VISA/agrI strains. VISA strains were classified into 31 mutation patterns according to mutations in the yvqF, vraSR, graSR, and tcaRAB genes. In addition, the mutation patterns were correlated with agr and sequence type (ST). The most prevalent pattern included agr type I (ST 72) strains with E59D (vraR), L26F and T224I (graS), D148Q (graR), and L218P, R283H and G312D (tcaA) amino acid substitutions. The minimum inhibitory concentration (MIC) range of mutation pattern 5 toward oxacillin and imipenem was much lower than that of patterns 6 and 24. These results improve our understanding of emergence of VISA strains.

Phenotypic and Genotypic Differences of the Vancomycin-Resistant Enterococcus faecium Isolates from Humans and Poultry in Korea: Jae Young Oh , Seunghun An , Jong Sook Jin , You Chul Lee , Dong Teak Cho , Je Chul Lee; J. Microbiol. 2007;45(5):466-472.; DOI: https://doi.org/2588 [pii]

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Abstract: A total of 98 vancomycin-resistant Enterococcus faecium (VREF) isolates (58 isolates from patients and 40 isolates from poultry) were compared based on their antimicrobial susceptibility, Tn1546 element organization, and pulsed-field gel electrophoresis (PFGE) patterns. This comparison aided in determining the relationships between the groups of isolates. All the VREF isolates harbored the vanA gene; however, 29 (29.6%) of the isolates exhibited the VanB phenotype-vanA genotype. Furthermore, the VREF isolates from humans and poultry exhibited distinct antimicrobial resistance patterns. The PCR mapping of the Tn1546 elements exhibited 12 different transposon types (A to L). The VREF isolates of poultry were classified into types A to D, whereas the human isolates were classified into types E to L. A PFGE analysis demonstrated a high degree of clonal heterogeneity in both groups of isolates; however, the distinct VREF clones appeared in each group of isolates. The deletion of the vanX-vanY genes or insertion of IS1216V in the intergenic region from the vanX-vanY genes is directly associated with the incongruence of the VanB phenotype-vanA genotype in human VREF isolates. These data suggest that the VREF isolates exhibit distinct phenotypic and genotypic traits according to their origins, which suggests that no evidence exists to substantiate the clonal spread or transfer of vancomycin resistance determinants between humans and poultry.

VanB-vanA Incongruent VRE Isolated from Animals and Humans in 1999: Enjoo Shin , Hyunjin Hong , Yasuyoshi Ike , Kyungwon Lee , Yong Ho Park , Dong Taek Cho , Yeonhee Lee; J. Microbiol. 2006;44(4):453-456.; DOI: https://doi.org/2406 [pii]

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Abstract: 16 chicken isolates and four clinical isolates of VanB-vanA incongruent vancomycinresistant Enterococcus faecium strains without vanS were isolated in 1999. Pulsed-field gel electrophoresis revealed only a peripheral relationship between the chicken isolates and clinical isolates, but suggested clonal spread in the chicken isolates.

Prevalence and Antibiotic Susceptibility of Vancomycin-Resistant Enterococci in Chicken Intestines and Fecal Samples from Healthy Young Children and Intensive Care Unit Patients: Shin Moo Kim , Eun Sook Shim , Chi Nam Seong; J. Microbiol. 2001;39(2):116-120.

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Abstract: The prevalence, resistance genotype and antibiotic susceptibility of vancomycin-resistant enterococci (VRE) were determined. Prevalence of VRE in chickens, healthy children and intensive care unit (ICU) patients was 43.0%, 12.7% and 24.1%, respectively. Forty out of 56 isolates from chicken intestines were identified as Enterococcus faecium, and 12 were E. faecalis. All the isolates contained the vanA gene. Nine out of 13 VRE isolates from patients and two out of 21 from healthy young children were identified as E. faecium. The resistance types of E. faecium, E. gallinarium and E. casseliflavus were VanA, VanC1, and VanC2, respectively. The mimimum inhibitory concentrations (MICs) of E. faecium, E. gallinarium, and E. casseliflavus to vancomycin were 512, 8 and 4 g/ml, respectively. Specifically, E. faecium isolates were resistant to most of antibiotics except ampicillin and gentamicin. This is the first report of high VanA type VRE prevalence in nonhospitalized young children in Korea.

Isolation, Identification and Characterization of Vancomycin-Resistant Enterococci from Raw Milk: Sung-Sook Choi , Bong-Su Kim , Nam-Joo Ha; J. Microbiol. 2002;40(2):170-172.

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Abstract: To determine the occurrence of vancomycin-resistant Enterococci in a raw milk sample, raw milk samples were examined for a period of 6 months. Enterococci were isolated directly from Enterococcal selective agar plates supplemented with 2 mg of vancomycin per liter. Nineteen strains were selected and identified by applying the Vitek system. To determine resistance patterns, 19 isolates were tested with vancomycin and teicoplanin. Vancomycin-resistant Enterococci were genotyped by using a PCR analysis and 5 out of 19 isolates were of the VanC type.

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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