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ABSTRACT: Salmonella enterica serovar Enteritidis is one of the leading causes of food-borne diseases in Japan. Typically, Salmonella spp. test positive for lysine-decarboxylase. However, the number of isolates of serovar Enteritidis without lysine-decarboxylase activity increased in Japan in 2003. Among 109 strains from distinct outbreaks, 10 lacked lysine-decarboxylase activity. Nine of the ten lysine-decarboxylase-negative strains showed quite similar pulsed-field gel electrophoresis profiles. Their lysine-decarboxylase phenotype was recovered by introduction of the cadBA locus from an lysine-decarboxylase-positive strain. Although the cad loci of the lysine-decarboxylase-negative strains seemed to be intact without any insertion sequences, cadC, a positive regulator of cadBA, had a single-base deletion at the same position, the 973rd base (cytosine), in all the nine lysine-decarboxylase-negative strains, whereas the wild-type cadC gene has a 1542 bp coding region (514 amino acids). This deletion was expected to produce a truncated (338 amino acids) form of CadC due to a frameshift. Because CadC senses environmental cues such as external pH and lysine through its putative C-terminal periplasmic domain, it is likely that the truncated CadC is not sensitive enough to external signaling to activate the cadBA operon, resulting in loss of the lysine-decarboxylase activity. Our results suggest that dissemination of these genetically closely related strains of serovar Enteritidis accounts for the unusual increase in the isolation of lysine-decarboxylase-negative strains.
FEMS Immunology & Medical Microbiology 05/2006; 46(3):381-5. · 2.44 Impact Factor
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Masatomo Morita,
Kenitiro Ito, Kenji Hirose,
Hideyuki Takahashi,
Ken Shimuta,
Jun Terajima,
Makoto Ohnishi,
Makoto Harada,
Mitsuhiro Matsuzaki,
Haruo Watanabe,
Hidemasa Izumiya
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ABSTRACT: A real-time PCR assay with the cycling probe method was used to detect mutations at codons 83 and 87 in the DNA gyrase A subunit encoded by gyrA in Salmonella enterica serovar Typhi and Paratyphi A clinical isolates. The susceptibility estimated from the results of the gyrA mutation assay was consistent with that identified by the culture method using an E-test. This assay allows rapid screening of S. enterica serovar Typhi and Paratyphi A with reduced susceptibility to ciprofloxacin.
Microbiology and Immunology 02/2006; 50(9):707-11. · 1.30 Impact Factor
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ABSTRACT: We generated nonfimbriated mutants from both Vi-positive and -negative Salmonella typhi to analyze the role of type 1 fimbriae and Vi-antigen in bacterial invasion. A Vi-defective mutant of S. typhi GIFU 10007-3 was more invasive than the wild-type strain GIFU 10007. The wild-type strain expressing Vi-antigen did not agglutinate both Saccharomyces cerevisiae and human erythrocytes but Vi-defective mutants were able to agglutinate S. cerevisiae and human erythrocytes. Nonfimbriated mutants from Vi-negative GIFU 10007-3 lost the ability to adhere to S. cerevisiae but still could agglutinate human erythrocytes. The Vi-negative mutant increased secreted proteins and became 5-fold more invasive than the wild-type strain. Nonfimbriated Vi mutants became 50–120-fold more invasive than the wild-type GIFU 10007. To determine why nonfimbriated Vi mutants still agglutinate human red blood cells, we searched bacterial proteins that could bind human blood-type antigens. We finally identified a candidate 37 kDa outer membrane protein that recognized fucosyl-galactose, a structure common to blood type A, B and H antigens.
FEMS Microbiology Letters 01/2006; 161(1):75 - 82. · 2.04 Impact Factor
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ABSTRACT: Z66 antigen-positive strains of Salmonella enterica serovar Typhi change flagellin expression in only one direction from the z66 antigen to the d or j antigen, which is different from the phase variation of S. enterica serovar Typhimurium. In the present study, we identified a new flagellin gene in z66 antigen-positive strains of S. enterica serovar Typhi. The genomic structure of the region containing this new flagellin gene was similar to that of fljBA operon of biphasic S. enterica serovars. A fljA-like gene was present downstream of the new flagellin gene. A rho-independent terminator was located between the new flagellin gene and the fljA-like gene. Hin-like gene was not present upstream of the new flagellin gene. We generated a mutant strain of S. enterica serovar Typhi, which carries a deletion of the new flagellin gene. Western blotting revealed that the 51-kDa z66 antigen protein was absent from the population of proteins secreted by the mutant strain. Southern hybridization demonstrated that the z66 antigen-positive strains of S. enterica serovar Typhi carried the new flagellin gene and fliC on two different genomic EcoRI fragments. When z66 antigen-positive strains were incubated with anti-z66 antiserum, the flagellin expression by S. enterica serovar Typhi changed from z66 antigen to j antigen. The new flagellin gene and the fljA-like gene were absent in the strain with altered flagellin expression. These results suggested that the new flagellin gene is a fljB-like gene, which encodes the z66 antigen of S. enterica serovar Typhi, and that deletion of fljBA-like operon may explain why S. enterica serovar Typhi alters the flagellin expression in only one direction from the z66 antigen to the d or j antigen.
FEMS Microbiology Letters 01/2006; 234(2):239 - 246. · 2.04 Impact Factor
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Nippon rinsho. Japanese journal of clinical medicine 08/2005; 63 Suppl 7:187-90.
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ABSTRACT: We analyzed the resistance to cefotaxime of a Salmonella enterica serovar Enteritidis isolate from a stool culture of a 4-year-old boy. It produced a beta-lactamase CTX-M-14, encoded by two related R plasmids. The region surrounding the blaCTX-M-14 gene had an original mosaic structure containing insertion sequences (IS26 and IS903D).
Antimicrobial Agents and Chemotherapy 07/2005; 49(6):2568-70. · 4.84 Impact Factor
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ABSTRACT: We performed susceptibility testing with Shigella sonnei isolates from imported and domestic cases of infection in Japan during 2001 and 2002. Some S. sonnei isolates were resistant to nalidixic acid, tetracycline, and trimethoprim-sulfamethoxazole. Most of the nalidixic acid-resistant strains showed reduced susceptibility to fluoroquinolones but did not show fluoroquinolone resistance.
Antimicrobial Agents and Chemotherapy 04/2005; 49(3):1203-5. · 4.84 Impact Factor
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Emerging infectious diseases 02/2005; 11(1):172-4. · 6.17 Impact Factor
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ABSTRACT: Z66 antigen-positive strains of Salmonella enterica serovar Typhi change flagellin expression in only one direction from the z66 antigen to the d or j antigen, which is different from the phase variation of S. enterica serovar Typhimurium. In the present study, we identified a new flagellin gene in z66 antigen-positive strains of S. enterica serovar Typhi. The genomic structure of the region containing this new flagellin gene was similar to that of fljBA operon of biphasic S. enterica serovars. A fljA-like gene was present downstream of the new flagellin gene. A rho-independent terminator was located between the new flagellin gene and the fljA-like gene. Hin-like gene was not present upstream of the new flagellin gene. We generated a mutant strain of S. enterica serovar Typhi, which carries a deletion of the new flagellin gene. Western blotting revealed that the 51-kDa z66 antigen protein was absent from the population of proteins secreted by the mutant strain. Southern hybridization demonstrated that the z66 antigen-positive strains of S. enterica serovar Typhi carried the new flagellin gene and fliC on two different genomic EcoRI fragments. When z66 antigen-positive strains were incubated with anti-z66 antiserum, the flagellin expression by S. enterica serovar Typhi changed from z66 antigen to j antigen. The new flagellin gene and the fljA-like gene were absent in the strain with altered flagellin expression. These results suggested that the new flagellin gene is a fljB-like gene, which encodes the z66 antigen of S. enterica serovar Typhi, and that deletion of fljBA-like operon may explain why S. enterica serovar Typhi alters the flagellin expression in only one direction from the z66 antigen to the d or j antigen.
FEMS Microbiology Letters 06/2004; 234(2):239-46. · 2.04 Impact Factor
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ABSTRACT: Among roughly one thousand incidents of shigellosis annually in Japan, approximately 70% of the cases are estimated to be associated with overseas travel. However, at the end of 2001, reports of domestically acquired Shigella sonnei infections suddenly increased. We report here the first multi-prefectural outbreak of Shigella sonnei infections linked to the consumption of imported oysters in Japan at the end of 2001. Isolates of S. sonnei from patients epidemiologically linked to eating contaminated oysters and from the imported oysters themselves showed an indistinguishable pulsed-field gel electrophoresis pattern and drug resistance pattern.
Microbiology and Immunology 02/2004; 48(1):49-52. · 1.30 Impact Factor
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ABSTRACT: The growth of a gamma-glutamyl aminopeptidase (GGT)-deficient Neisseria meningitidis strain was much slower than that of the parent strain in rat cerebrospinal fluid (CSF) and in a synthetic CSF-mimicking medium, and the growth failure was suppressed by the addition of cysteine. These results suggested that, in the environment of cysteine shortage, meningococcal GGT provided an advantage for meningococcal multiplication by supplying cysteine from environmental gamma-glutamyl-cysteinyl peptides.
Journal of Bacteriology 02/2004; 186(1):244-7. · 3.83 Impact Factor
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ABSTRACT: A multiplex polymerase chain reaction (PCR) assay was developed for the identification of Salmonella enterica serovar Typhimurium. Three sets of primers were designed for detecting O4, H:i, and H:1,2 antigen genes from the antigen-specific genes rfbJ, fliC, and fljB, respectively. These were evaluated in a multiplex PCR assay by using DNAs from S. enterica serovar Typhimurium, 15 other Salmonella serovars, and 8 non-Salmonella enteric pathogens. Multiplex PCR proved to be capable of identifying S. enterica serovar Typhimurium specifically and differentiating it from other Salmonella serovars in addition to non-Salmonella enteric pathogens. Thus, this multiplex PCR assay can be practically applied to the identification of S. enterica serovar Typhimurium.
Japanese journal of infectious diseases 09/2003; 56(4):151-5. · 1.49 Impact Factor
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Nippon rinsho. Japanese journal of clinical medicine 03/2003; 61 Suppl 2:390-4.
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ABSTRACT: Salmonella enterica serovar Typhi and serovar Paratyphi A with reduced susceptibility to fluoroquinolones (MICs of ciprofloxacin, 0.25 to 2 microg/ml) have a mutation at codon either Ser-83 or Asp-87 of gyrA gene. A screening method by PCR-restriction fragment length polymorphism (PCR-RFLP) was designed to screen the mutations at codon Ser-83 and Asp-87 of the gyrA gene of S. enterica serovar Typhi and serovar Paratyphi A clinical isolates. This method successfully screened the gyrA mutations of S. enterica serovar Typhi and serovar Paratyphi A with reduced susceptibility to fluoroquinolones.
Microbiology and Immunology 02/2003; 47(2):161-5. · 1.30 Impact Factor
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ABSTRACT: The mutations that are responsible for fluoroquinolone resistance in the gyrA, gyrB, parC, and parE genes of Salmonella enterica serovar Typhi and serovar Paratyphi A were investigated. The sequences of the quinolone resistance-determining region of the gyrA gene in clinical isolates which showed decreased susceptibilities to fluoroquinolones had a single mutation at either the Ser-83 or the Asp-87 codon, and no mutations were found in the gyrB, parC, and parE genes.
Antimicrobial Agents and Chemotherapy 11/2002; 46(10):3249-52. · 4.84 Impact Factor
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ABSTRACT: The PCR primers for O, H, and Vi antigen genes, tyv (rfbE), prt (rfbS), fliC-d, fliC-a, and viaB, were designed and used for the rapid identification of Salmonella enterica serovars Typhi and Paratyphi A with multiplex PCR. The results showed that all the clinical isolates examined of Salmonella serovars Typhi and Paratyphi A were accurately identified by this assay.
Journal of Clinical Microbiology 03/2002; 40(2):633-6. · 4.15 Impact Factor
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ABSTRACT: Transcription of the stationary-phase sigma factor RpoS of Salmonella typhi increased in the macrophage. A single rpoS mutant of S. typhi was constructed to analyze the role of RpoS in intracellular multiplication of the bacterium and host cell killing. This mutant was sensitive to starvation, low pH and hydrogen peroxide; however, it could still multiply inside resting macrophages and was less cytotoxic than the wild-type strain. Therefore, S. typhi might produce RpoS-dependent factors which could contribute to host cell death.
FEMS Microbiology Letters 03/1998; 161(1):201 - 208. · 2.04 Impact Factor
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ABSTRACT: We examined the intracellular survival of Vi-capsulated (lipopolysaccharide; (LPS)-masked) and Vi-deleted (LPS-exposed) Salmonella typhi strains inside macrophage cell lines. Growth of LPS-exposed S. typhi was inhibited in both mouse and human macrophage cell lines. However, the LPS-exposed strain survived in a CD14-deficient mouse macrophage cell lines. Wild-type S. typhi strain, which expressed the Vi antigen and masked LPS, survived in the resting human macrophage cell line. When the Vi-capsulated S. typhi entered the cells, the production of tumor necrosis factor-α (TNF-α) was suppressed. In contrast, S. typhimurium and LPS-exposed S. typhi stimulated the macrophages to produce a high level of TNF-α.
FEMS Microbiology Letters 01/1997; 147(2):259 - 265. · 2.04 Impact Factor
