Journal of Microbiology

Journal Articles

Availability of polyamines affects virulence and survival of Neisseria meningitidis: Poonam Kanojiya , Riya Joshi , Sunil D. Saroj; J. Microbiol. 2022;60(6):640-648. Published online April 18, 2022; DOI: https://doi.org/10.1007/s12275-022-1589-y

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Abstract: Neisseria meningitidis is a Gram-negative human-restricted pathogen that asymptomatically resides in the human respiratory tract. Meningococcal meningitis and sepsis both are caused by N. meningitidis. The bacterium must adhere to host epithelial cells in order to colonize effectively. The factors that determine the initial attachment to the host and dispersal, are not well understood. Metabolites released by the host may aid in meningococcal colonization and dissemination. Polyamines are aliphatic polycations that assist in cell survival and proliferation. The virulence properties of N. meningitidis after exposure to polyamines were investigated. Adhesion to nasopharyngeal epithelial cells increased in the presence of spermine. Also, the relative expression of adhesin, pilE increased in the presence of spermine. Further, relative expression of ctrA, ctrB and lipB was upregulated in the presence of spermidine, indicating increased capsule formation. Upregulated capsule synthesis of N. meningitidis in the presence of spermidine allows it to survive in murine macrophages. The study suggests the importance of the extracellular pool of polyamines in promoting virulence in N. meningitidis.

Proteomic Analysis of Outer Membrane Proteins from Acinetobacter baumannii DU202 in Tetracycline Stress Condition: Sung-Ho Yun , Chi-Won Choi , Soon-Ho Park , Je Chul Lee , Sun-Hee Leem , Jong-Soon Choi , Soohyun Kim , Seung Il Kim; J. Microbiol. 2008;46(6):720-727. Published online December 24, 2008; DOI: https://doi.org/10.1007/s12275-008-0202-3

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Abstract: Acinetobacter baumannii readily developed antimicrobial resistance to clinically available antibiotics. A. baumannii DU202 is a multi-drug resistant strain, and is highly resistant to tetracycline (MIC>1,024μg/ml). The surface proteome of A. baumannii DU202 in response to the sub-minimal inhibitory concentration (subMIC) of tetracycline was analyzed by 2-DE/MS-MS and 1-DE/LC/MS-MS to understand the pathways that form barriers for tetracycline. Membrane expression of major outer membrane proteins (Omps) was significantly decreased in response to the subMIC of tetracycline. These Omps with sizes of 38, 32, 28, and 21 kDa were identified as OmpA38, OmpA32, CarO, and OmpW, respectively. However, transcription level of these Omps was not significantly changed. 1-DE/LC/MS-MS analysis of secreted proteins showed that OmpA38, CarO, OmpW, and other Omps were increasingly secreted at tetracycline condition. This result suggests that A. baumannii actively regulates the membrane expression and the secretion of Omps to overcome antibiotic stress condition.

Synergistic Antibacterial Effect between Silybin and N,N’-Dicyclohexylcarbodiimide in Clinical Pseudomonas aeruginosa Isolates: Hyun Jun Jung , Dong Gun Lee; J. Microbiol. 2008;46(4):462-467. Published online August 31, 2008; DOI: https://doi.org/10.1007/s12275-008-0138-7

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Abstract: Silybin is a composition of the silymarin group as a hepatoprotective agent, and it exhibits various biological activities, including an antibacterial activity. In this study, the effects of a combination of silybin with N,N′-dicyclohexylcarbodiimide (DCCD) against clinical isolates of Pseudomonas aeruginosa were investigated. In the results of susceptibility assay, silybin showed more potent antibacterial activity in methicilin-resistant Staphylococcus aureus (MRSA) than in P. aeruginosa, but DCCD significantly increased the antibacterial activity of silybin in P. aeruginosa. The antibacterial activity of silybin was affected by the strong action of multidrug-resistant pumps rather than by a permeable disruption of lipopolysaccharide and silybin showed a remarkable synergistic activity in combination with some antibiotic agents against drug-resistant bacteria. Therefore, silybin has a potential as a combination therapeutic agent for treatment of infectious diseases by multidrug-resistant bacteria.

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

Characterization of β-Ketoadipate Pathway from Multi-Drug Resistance Bacterium, Acinetobacter baumannii DU202 by Proteomic Approach: Sonn-Ho Park , Jae-Woo Kim , Sung-Ho Yun , Sun Hee Leem , Hyung-Yeel Kahng , Seung Il Kim; J. Microbiol. 2006;44(6):632-640.; DOI: https://doi.org/2464 [pii]

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Abstract: In this study, the biodegradative activities of monocyclic aromatic compounds were determined from the multi-drug resistant (MDR) Acinetobacter baumannii, which were studied in the form of clinical isolates from a hospital in Korea. These bacteria were capable of biodegrading monocyclic aromatic compounds, such as benzoate and p-hydroxybenzoate. In order to determine which pathways are available for biodegradation in these stains, we conducted proteome analyses of benzoate and p-hydroxybenzoate-cultured A. baumannii DU202, using 2-DE/MS analysis. As genome DB of A. baumannii was not yet available, MS/MS analysis or de novo sequencing methods were employed in the identification of induced proteins. Benzoate branch enzymes [catechol 1,2-dioxygenase (CatA) and benzoate dioxygenase α subunit (BenA)] of the β-ketoadipate pathway were identified under benzoate culture condition and p-hydroxybenzoate branch enzymes [protocatechuate 3,4-dioxygenase α subunit (PcaG) and 3-carboxy-cis,cis-muconate cycloisomerase (PcaB)] of the β-ketoadipate pathway were identified under p-hydroxybenzoate culture condition, respectively, thereby suggesting that strain DU202 utilized the β-ketoadipate pathway for the biodegradation of monocyclic aromatic compounds. The sequence analysis of two purified dioxygenases (CatA and PcaGH) indicated that CatA is closely associated with the CatA of Acinetobacter radiresistance, but PcaGH is only moderately associated with the PcaGH of Acinetobacter sp. ADP1. Interestingly, the fused form of PcaD and PcaC, carboxymuconolactone decarboxylase (PcaCD), was detected on benzoate-cultured A. baumannii DU202. These results indicate that A. baumannii DU202 exploits a different β-ketoadipate pathway from other Acinetobacter species.

Isolation of Norfloxacin Resistant Escherichia coli from the Han River and Characterization of Resistance Mechanism: Yoosun Jung , Hyunjin Hong , Hyeran Nam , Yeonhee Lee; J. Microbiol. 2002;40(1):63-69.

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Abstract: A total of twenty-five norfloxacin resistant Escherichia coli were isolated from Joongrang-chun stream, a branch of the Han River in Seoul, Korea from May to July in 2000 and their norfloxacin resistance mechanism was characterized for target site mutation, permeability, and efflux pump. Fourteen isolates contained the same three mutations, Ser83->Leu and Asp87->Asn in GyrA and Ser90->Ile in ParC. Six isolates had Ser83->Leu and Asp87->Tyr in GyrA and Ser80->Ile in ParC while one isolate had Ser83->Leu and Val103->Ala in GyrA and Ser80->Ile in ParC. Two isolates had mutation(s) in GyrA without any mutation in ParC. Two isolates had Ser80->Arg in ParC instead of the commonly found Ser80->Ile. Every norfloxacin resistant isolate had an efflux system but the correlation between the efflux activity and MIC was not observed. The amount of OmpF for norfloxacin permeability decreased in resistant isolates compared to the susceptible strains. When amplified polymorphic DNA (RAPD) and pulse field gel electrophoresis (PFGE) were performed, these isolates showed no similarity to each other or clinical isolates.

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