bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Two-Component Regulatory System Involved in Adhesion, Autolysis, and Extracellular Proteolytic Activity of
Staphylococcus aureus
Authors: Fournier Bénédicte , Hooper David C. 
Published: July 2002

ABSTRACT

A transposition mutant of
Staphylococcus aureus
was selected from the parent strain MT23142, a derivative of strain 8325. The site of transposition was near the 5′ terminus of the gene
arlS
. ArlS exhibits strong similarities with histidine protein kinases. Sequence analysis suggested that
arlS
forms an operon with upstream gene
arlR
. The predicted product of
arlR
is a member of the OmpR-PhoB family of response regulators. The
arlS
mutant formed a biofilm on a polystyrene surface unlike the parent strain and the complemented mutant. Biofilm formation was associated with increased primary adherence to polystyrene, whereas cellular adhesion was only slightly decreased. In addition, the
arlS
mutant exhibited increased autolysis and altered peptidoglycan hydrolase activity compared to the parental strain and to the complemented mutant. As it has been shown for coagulase-negative staphylococci that some autolysins are able to bind polymer surfaces, these data suggest that the two-component regulatory system ArlS-ArlR may control attachment to polymer surfaces by affecting secreted peptidoglycan hydrolase activity. Finally, the
arlS
mutant showed a dramatic decrease of extracellular proteolytic activity, including serine protease activity, in comparison to the wild-type strain and the complemented mutant, and cells grown in the presence of phenylmethylsulfonyl fluoride (a serine protease inhibitor) showed an increased autolysin activity. Since the locus
arlR-arlS
strikingly modifies extracellular proteolytic activity, this locus might also be involved in the virulence of
S. aureus
.
The Trimethylamine Methyltransferase Gene and Multiple Dimethylamine Methyltransferase Genes of
Methanosarcina barkeri
Contain In-Frame and Read-Through Amber Codons
Authors: Paul Ligi , Ferguson Donald J. , Krzycki Joseph A. 
Published: July 2002

ABSTRACT

Three different methyltransferases initiate methanogenesis from trimethylamine (TMA), dimethylamine (DMA) or monomethylamine (MMA) by methylating different cognate corrinoid proteins that are subsequently used to methylate coenzyme M (CoM). Here, genes encoding the DMA and TMA methyltransferases are characterized for the first time. A single copy of
mttB
, the TMA methyltransferase gene, was cotranscribed with a copy of the DMA methyltransferase gene,
mtbB1
. However, two other nearly identical copies of
mtbB1
, designated
mtbB2
and
mtbB3
, were also found in the genome. A 6.8-kb transcript was detected with probes to
mttB
and
mtbB1
, as well as to
mtbC
and
mttC
, encoding the cognate corrinoid proteins for DMA:CoM and TMA:CoM methyl transfer, respectively, and with probes to
mttP
, encoding a putative membrane protein which might function as a methylamine permease. These results indicate that these genes, found on the chromosome in the order
mtbC
,
mttB
,
mttC
,
mttP
, and
mtbB1
, form a single transcriptional unit. A transcriptional start site was detected 303 or 304 bp upstream of the translational start of
mtbC
. The MMA, DMA, and TMA methyltransferases are not homologs; however, like the MMA methyltransferase gene, the genes encoding the DMA and TMA methyltransferases each contain a single in-frame amber codon. Each of the three DMA methyltransferase gene copies from
Methanosarcina barkeri
contained an amber codon at the same position, followed by a downstream UAA or UGA codon. The C-terminal residues of DMA methyltransferase purified from TMA-grown cells matched the residues predicted for the gene products of
mtbB1
,
mtbB2
, or
mtbB3
if termination occurred at the UAA or UGA codon rather than the in-frame amber codon. The
mttB
gene from
Methanosarcina thermophila
contained a UAG codon at the same position as the
M. barkeri mttB
gene. The UAG codon is also present in
mttB
transcripts. Thus, the genes encoding the three types of methyltransferases that initiate methanogenesis from methylamine contain in-frame amber codons that are suppressed during expression of the characterized methyltransferases.
Bacterial Diversity in Human Subgingival Plaque
Authors: Paster Bruce J. , Boches Susan K. , Galvin Jamie L. , Ericson Rebecca E. , Lau Carol N. , Levanos Valerie A. , Sahasrabudhe Ashish , Dewhirst Floyd E. 
Published: July 2002

ABSTRACT

The purpose of this study was to determine the bacterial diversity in the human subgingival plaque by using culture-independent molecular methods as part of an ongoing effort to obtain full 16S rRNA sequences for all cultivable and not-yet-cultivated species of human oral bacteria. Subgingival plaque was analyzed from healthy subjects and subjects with refractory periodontitis, adult periodontitis, human immunodeficiency virus periodontitis, and acute necrotizing ulcerative gingivitis. 16S ribosomal DNA (rDNA) bacterial genes from DNA isolated from subgingival plaque samples were PCR amplified with all-bacterial or selective primers and cloned into
Escherichia coli
. The sequences of cloned 16S rDNA inserts were used to determine species identity or closest relatives by comparison with sequences of known species. A total of 2,522 clones were analyzed. Nearly complete sequences of approximately 1,500 bases were obtained for putative new species. About 60% of the clones fell into 132 known species, 70 of which were identified from multiple subjects. About 40% of the clones were novel phylotypes. Of the 215 novel phylotypes, 75 were identified from multiple subjects. Known putative periodontal pathogens such as
Porphyromonas gingivalis
,
Bacteroides forsythus
, and
Treponema denticola
were identified from multiple subjects, but typically as a minor component of the plaque as seen in cultivable studies. Several phylotypes fell into two recently described phyla previously associated with extreme natural environments, for which there are no cultivable species. A number of species or phylotypes were found only in subjects with disease, and a few were found only in healthy subjects. The organisms identified only from diseased sites deserve further study as potential pathogens. Based on the sequence data in this study, the predominant subgingival microbial community consisted of 347 species or phylotypes that fall into 9 bacterial phyla. Based on the 347 species seen in our sample of 2,522 clones, we estimate that there are 68 additional unseen species, for a total estimate of 415 species in the subgingival plaque. When organisms found on other oral surfaces such as the cheek, tongue, and teeth are added to this number, the best estimate of the total species diversity in the oral cavity is approximately 500 species, as previously proposed.
PhaC and PhaR Are Required for Polyhydroxyalkanoic Acid Synthase Activity in
Bacillus megaterium
Authors: McCool Gabriel J. , Cannon Maura C. 
Published: July 2002

ABSTRACT

Polyhydroxyalkanoic acids (PHAs) are a class of polyesters stored in inclusion bodies and found in many bacteria and in some archaea. The terminal step in the synthesis of PHA is catalyzed by PHA synthase. Genes encoding this enzyme have been cloned, and the primary sequence of the protein, PhaC, is deduced from the nucleotide sequences of more than 30 organisms. PHA synthases are grouped into three classes based on substrate range, molecular mass, and whether or not there is a requirement for
phaE
in addition to the
phaC
gene product. Here we report the results of an analysis of a PHA synthase that does not fit any of the described classes. This novel PHA synthase from
Bacillus megaterium
required PhaC (PhaC
Bm
) and PhaR (PhaR
Bm
) for activity in vivo and in vitro. PhaC
Bm
showed greatest similarity to the PhaCs of class III in both size and sequence. Unlike those in class III, the 40-kDa PhaE was not required, and furthermore, the 22-kDa PhaR
Bm
had no obvious homology to PhaE. Previously we showed that PhaC
Bm
, and here we show that PhaR
Bm
, is localized to inclusion bodies in living cells. We show that two forms of PHA synthase exist, an active form in PHA-accumulating cells and an inactive form in nonaccumulating cells. PhaC was constitutively produced in both cell types but was more susceptible to protease degradation in the latter type. Our data show that the role of PhaR is posttranscriptional and that it functions directly or indirectly with PhaC
Bm
to produce an active PHA synthase.
Mutations in the 16S rRNA Genes ofHelicobacter pyloriMediate Resistance to Tetracycline
Authors: Trieber Catharine A. , Taylor Diane E. 
Published: July 2002

ABSTRACTLow-cost and rescue treatments forHelicobacter pyloriinfections involve combinations of several drugs including tetracycline. Resistance to tetracycline has recently emerged inH.pylori. The 16S rRNA gene sequences of two tetracycline-resistant clinical isolates (MIC = 64 μg/ml) were determined and compared to the consensusH.pylori16S rRNA sequence. One isolate had four nucleotide substitutions, and the other had four substitutions and two deletions. Natural transformation with the 16S rRNA genes from the resistant organisms conferred tetracycline resistance on susceptible strains. 16S rRNA genes containing the individual mutations were constructed and tested for the ability to confer resistance. Only the 16S rRNA gene containing the triple mutation, AGA965-967TTC, was able to confer tetracycline resistance onH.pylori26695. The MICs of tetracycline for the transformed strains were equivalent to those for the original clinical isolates. The two original isolates were also metronidazole resistant, but this trait was not linked to the tetracycline resistance phenotype. Serial passage of severalH.pyloristrains on increasing concentrations of tetracycline yielded mutants with only a very modest increase in tetracycline resistance to a MIC of 4 to 8 μg/ml. These mutants all had a deletion of G942 in the 16S rRNA genes. The mutations in the 16S rRNA are clearly responsible for tetracycline resistance inH.pylori.
Respiratory Viral Infections among Pediatric Inpatients and Outpatients in Taiwan from 1997 to 1999
Authors: Tsai Huey-Pin , Kuo Pin-Hwa , Liu Ching-Chuan , Wang Jen-Ren 
Published: July 2002

ABSTRACT

The present study examined the association of specific virus infections with acute respiratory tract conditions among hospitalized and outpatient children in a subtropical country. A total of 2,295 virus infections were detected in 6,986 patients between 1997 and 1999, including infections caused by respiratory syncytial virus (RSV) (1.7%), parainfluenza virus (2.0%), influenza B virus (2.6%), adenovirus (4.0%), herpes simplex virus type 1 (4.4%), influenza A virus (5.5%), and enterovirus (12.7%). There were 61 mixed infections, and no consistent seasonal variation was found. One or more viruses were detected among 24.8% of hospitalized patients and 35.0% of outpatients. The frequencies and profiles of detection of various viruses among in- and outpatients were different. The occurrence of enterovirus infections exceeded that of other viral infections detected in 1998 and 1999 due to outbreaks of enterovirus 71 and coxsackievirus A10. RSV was the most prevalent virus detected among hospitalized children, whereas influenza virus was the most frequently isolated virus in the outpatient group. Most respiratory viral infections (39.3%) occurred in children between 1 and 3 years old. RSV (
P
< 0.025) and influenza A virus (
P
< 0.05) infections were dominant in the male inpatient group. In addition, most pneumonia and bronchiolitis (48.4%) was caused by RSV among hospitalized children less than 6 months old. Adenovirus was the most common agent associated with pharyngitis and tonsilitis (45.5%). These data expand our understanding of the etiology of acute respiratory tract viral infections among in- and outpatients in a subtropical country and may contribute to the prevention and control of viral respiratory tract infections.
Epidemiological Validation of Pulsed-Field Gel Electrophoresis Patterns for Methicillin-Resistant
Staphylococcus aureus
Authors: Blanc D. S. , Struelens M. J. , Deplano A. , De Ryck R. , Hauser P. M. , Petignat C. , Francioli P. 
Published: July 2002

ABSTRACT

To determine the stability of pulsed-field gel electrophoresis (PFGE) patterns of methicillin-resistant
Staphylococcus aureus
in the nosocomial setting, we analyzed isolates from long-term carriers (>1 month) and from patients involved in well-defined nosocomial epidemics. The number of fragment differences between the first isolate and subsequent isolates in long-term carriers showed a bimodal distribution, with one group having 0 to 6 fragment differences and the other group having 14 to 24 fragment differences. The PFGE patterns of isolates involved in epidemics also presented a similar bimodal distribution of the number of fragment differences. Typing these isolates with another molecular method (inter-IS
256
PCR) showed that isolates of the first group (i.e., with 1 to 6 fragment differences) were clonally related, whereas the second group (with 14 to 24 fragment differences) could be considered genetically different. Among long-term carriers with clonally related isolates, 74 of 84 (88%) of consecutive isolates showed indistinguishable patterns, whereas 10 of 84 (12%) showed related patterns differing by one to six fragments. Moreover, the frequency of apparition of related patterns is higher when the time between the first and the subsequent isolate is longer. During seven nosocomial epidemics lasting from 1 to 15 months, only 2 of 120 isolates (1.7%) showed a pattern which was different, although related, from the predominant one involved in each of these outbreaks.
Evaluation of Efficiency of Screening Extended-Spectrum β-Lactamase-Producing
Escherichia coli
and
Klebsiella pneumoniae
in Hospitals Where the Bacteria Are Increasingly Prevalent
Authors: Lee K. , Lim J. K. , Yong D. , Yum J. , Chong Y. , Okamoto R. , Inoue M. 
Published: July 2002

ABSTRACT
The disk screening methods for extended-spectrum β-lactamase-producing strains were evaluated. The confirmatory work is reduced significantly in settings such as those in this study, by changing the cefpodoxime breakpoint to ≤20 mm and by not testing cefoxitin-resistant isolates. Cefotaxime and ceftazidime disk screening is reliable, and the laboratory-prepared cefotaxime- and ceftazidime-clavulanic acid disks are stable at −20°C for 12 weeks.
Evaluation of BacT/ALERT System for Detection of
Mycoplasma hominis
in Simulated Blood Cultures
Authors: Waites Ken B. , Canupp Kay C. 
Published: July 2002

ABSTRACT

We used simulated blood cultures inoculated with clinical isolates of
Mycoplasma hominis
to determine whether liquid media of the BacT/ALERT (Organon Teknika, Durham, N.C.) will support growth of this fastidious organism and whether its presence can generate a positive signal with the instrument. Viability of clinical isolates of
M. hominis
was maintained for 7 days in BacT/ALERT media, and organisms were able to multiply when 1% gelatin was added to neutralize the mycoplasmastatic effects of the sodium polyanetholsulfonate anticoagulant. Without the addition of gelatin to BacT/ALERT bottles, the mycoplasmas declined in numbers or became completely nonviable. Mycoplasmal growth was further enhanced in BacT/ALERT PF both supplemented with gelatin, arginine, and DNA in comparison to broth with only gelatin added. No BacT/ALERT bottles containing
M. hominis
in simulated blood cultures were flagged positive by the instrument, despite growth of microorganisms of up to 10
7
CFU/ml after incubation for up to 7 days, suggesting that inadequate CO
2
production or some other mechanism prevents the instrument from recognizing the presence of the organism and its metabolic products. The fastidious cultivation requirements and relatively slow growth of
M. hominis
warrant that dependence on automated systems and techniques designed to detect conventional bacteria will not be reliable for recovery of
M. hominis
and that specialized media and incubation conditions designed for optimum cultivation of mycoplasmas should be employed when this organism is suspected on clinical grounds.
Molecular Typing of
Penicillium marneffei
Isolates from Thailand by
Not
I Macrorestriction and Pulsed-Field Gel Electrophoresis
Authors: Trewatcharegon Sompong , Sirisinha Stitaya , Romsai Amparat , Eampokalap Boonchaoy , Teanpaisan Rawee , Chaiyaroj Sansanee C. 
Published: July 2002

ABSTRACT

Penicillium marneffei
is recognized as one of the most frequently detected opportunistic pathogens of AIDS patients in northern Thailand. We undertook a genomic epidemiology study of 64
P. marneffei
isolates collected from immunosuppressed patients by pulsed-field gel electrophoresis (PFGE) with restriction enzyme
Not
I. Among the 69 isolates fingerprinted by PFGE, 17 were compared by
Hae
III restriction endonuclease typing. The PFGE method demonstrated a higher degree of discriminatory power than restriction endonuclease typing with
Hae
II. Moreover, an impressive diversity of
P. marneffei
isolates was observed, as there were 54 distinct macrorestriction profiles among the 69 isolates of
P. marneffei
. These profiles were grouped into two large clusters by computer-assisted similarity analysis: macrorestriction pattern I (MPI) and MPII, with nine subprofiles (MPIa to MPIf and MPIIa to MPIIc). We observed no significant correlation between the macrorestriction patterns of the
P. marneffei
isolates and geographical region or specimen source. It is interesting that all isolates obtained before 1995 were MPI, and we found an increase in the incidence of infections with MPII isolates after 1995. We conclude that PFGE is a highly discriminatory typing method and is well suited for computer-assisted analysis. Together, PFGE and
Not
I macrorestriction allow reliable identification and epidemiological characterization of isolates as well as generate a manageable database that is convenient for expansion with information on additional
P. marneffei
isolates.
Evaluation of a Fluorescence In Situ Hybridization Assay for Differentiation between Tuberculous and Nontuberculous
Mycobacterium
Species in Smears of Lowenstein-Jensen and Mycobacteria Growth Indicator Tube Cultures Using Peptide Nucleic Acid Probes
Authors: Hongmanee Poonpilas , Stender Henrik , Rasmussen Ole F. 
Published: July 2002

ABSTRACT

A new fluorescence in situ hybridization assay based on peptide nucleic acid probes (MTB and NTM probes targeting tuberculous and nontuberculous species, respectively) for the identification of
Mycobacterium tuberculosis
complex and differentiation between tuberculous and nontuberculous mycobacteria (NTM) was evaluated using Lowenstein-Jensen (LJ) solid cultures from 100 consecutive sputum samples and 50 acid-fast bacillus (AFB)-positive sputum samples as well as Mycobacteria Growth Indicator Tube (MGIT) liquid cultures from 80 AFB-positive sputum samples.
Mycobacterium
species could be identified from a total of 53 LJ cultures and 77 MGIT cultures. The diagnostic specificities of the MTB and NTM probes were 100% for both cultures. The diagnostic sensitivities of the MTB probe for the LJ and MGIT cultures were 98 and 99%, respectively, whereas the sensitivities of the NTM probe were 57 and 100%, respectively. The relatively low sensitivity of the NTM probe was due to a high proportion of
M. fortuitum
, which is not identified by the probe.
Yield of Vancomycin-Resistant Enterococci and Multidrug-Resistant
Enterobacteriaceae
from Stools Submitted for
Clostridium difficile
Testing Compared to Results from a Focused Surveillance Program
Authors: Hacek Donna M. , Bednarz Patrice , Noskin Gary A. , Zembower Teresa , Peterson Lance R. 
Published: July 2002

ABSTRACT

It has been suggested that a method of performing surveillance for vancomycin-resistant enterococci (VRE) is to screen specimens submitted for
Clostridium difficile
testing. We compared this approach to our focused surveillance program of high-risk units during October 1997 to compare the yield of VRE and multidrug-resistant
Enterobacteriaceae
(MDRE) with both methods. Of the stools submitted for
C. difficile
testing, 14% were positive for VRE or MDRE, whereas rectal swabs from routine surveillance yielded 11% VRE- or MDRE-positive results. Although stools submitted for
C. difficile
testing resulted in a higher percentage of positive cultures, 14 VRE- and 2 MDRE-positive patients from our high-risk population were missed because many patients had no stool submitted for
C. difficile
testing. Therefore, while screening stools submitted for
C. difficile
testing cannot replace our focused surveillance program, it appears advantageous to assess these stools at various intervals to detect new patient reservoirs of drug-resistant organisms that may benefit from routine surveillance cultures.
Possible Horizontal Transfer of the
vanB2
Gene among Genetically Diverse Strains of Vancomycin-Resistant
Enterococcus faecium
in a Korean Hospital
Authors: Lee Wee Gyo , Jernigan John A. , Rasheed James K. , Anderson Gregory J. , Tenover Fred C. 
Published: July 2002

ABSTRACT

A total of 25 isolates of
vanB
-containing
Enterococcus faecium
were recovered from patients in a single Korean hospital over a 20-month period. There were two distinct
vanB2
patterns among the 11 pulsed-field gel electrophoresis types; 17 contained the prototype
vanB2
and 8 contained a novel
vanB2
with a 177-bp deletion in

vanY
B

. Both
vanB2
genes were transmissible in vitro at a mean frequency of 1.1 × 10
−8
transconjugants/donor. These results suggest the horizontal spread of
vanB2
is occurring among genetically diverse strains of
E. faecium
in Korean hospitals.
Recurrent Self-Limited Fungemia Caused by
Yarrowia lipolytica
in a Patient with Acute Myelogenous Leukemia
Authors: Chang Chulhun Ludgerus , Park Tae Hee , Lee Eun Yup , Lim Young Tak , Son Han Chul 
Published: July 2002

ABSTRACT

Yarrowia lipolytica
is a weakly pathogenic yeast that is rarely isolated from the blood. We observed transient recurrent catheter-related fungemia attributable to this organism in a leukemic patient. The fungemia and accompanying fever subsided spontaneously. The data suggest that it might be possible to withhold specific treatment for
Y. lipolytica
fungemia even in an immunocompromised patient.