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Janet R Gilsdorf

Publications and source records attributed to Janet R Gilsdorf.

17 recordsLinked to original sources
PubMed2006

Identification of new genetic regions more prevalent in nontypeable Haemophilus influenzae otitis media strains than in throat strains.

Nontypeable (NT) Haemophilus influenzae strains cause significant respiratory illness and are isolated from up to half of middle ear aspirates from children with acute otitis media. Previous studies have identified two genes, lic2B and hmwA, that are associated with NT H. influenzae strains isolated from the middle ears of children with otitis media but that are not associated with NT H. influenzae strains isolated from the throats of healthy children, suggesting that they may play a role in virulence in otitis media. In this study, genomic subtraction was used to identify additional genetic regions unique to middle ear strains. The genome of NT H. influenzae middle ear strain G622 was subtracted from that of NT H. influenzae throat strain 23221, and the resultant gene regions unique to the middle ear strain were identified. Subsequently, the relative prevalence of the middle ear-specific gene regions among a large panel of otitis media and throat strains was determined by dot blot hybridization. By this approach, nine genetic regions were found to be significantly more prevalent in otitis media strains. Classification tree analysis of lic2B, hmwA, and the nine new potential otitis media virulence genes revealed two H. influenzae pathotypes associated with otitis media.

Bacterial Proteins↗
PubMed2006

Multicentre surveillance of the prevalence and molecular epidemiology of macrolide resistance among pharyngeal isolates of group A streptococci in the USA.

OBJECTIVES: Rates of macrolide resistance in group A streptococci (GAS) were reported to be low in the US in the 1990s. However, we documented an unexpectedly high rate of macrolide resistance among GAS in Pittsburgh, PA, in 2001 and 2002. In an effort to define the current prevalence of macrolide-resistant GAS in the US, a multicentre surveillance project was initiated. METHODS: Between October 2002 and May 2003, 50 pharyngeal GAS isolates per month were requested from each of the nine participating sites representing a wide geographical distribution. Standard susceptibility testing was performed and the macrolide resistance phenotype was assessed using double-disc diffusion testing. Monthly and annual rates of macrolide resistance were calculated for each site. An adjusted overall rate of macrolide resistance was determined to account for differences in the numbers of GAS isolates sent from each centre. RESULTS: Overall, 171 of the 2797 collected isolates of GAS (6.1%) were resistant to erythromycin. The adjusted overall resistance rate was 5.2%. Rates of macrolide resistance varied by site (range 3.0-8.7%) and also by month (<2% to >10%). The M phenotype of macrolide resistance accounted for >60% of all macrolide-resistant isolates recovered in this study. CONCLUSIONS: These data suggest an increasing prevalence and broad geographical distribution of macrolide-resistant GAS in the US, indicating the need for ongoing local and national longitudinal surveillance to define the extent of this problem.

Anti-Bacterial Agents↗
PubMed2006

Heterogeneity in tandem octanucleotides within Haemophilus influenzae lipopolysaccharide biosynthetic gene losA affects serum resistance.

Haemophilus influenzae is subject to phase variation mediated by changes in the length of simple sequence repeat regions within several genes, most of which encode either surface proteins or enzymes involved in the synthesis of lipopolysaccharides (LPS). The translational repeat regions that have been described thus far all consist of tandemly repeated tetranucleotides. We describe an octanucleotide repeat region within a putative LPS biosynthetic gene, losA. Approximately 20 percent of nontypeable H. influenzae strains contain copies of losA and losB in a genetic locus flanked by infA and ksgA. Of 30 strains containing losA at this site, 24 contained 2 tandem copies of the octanucleotide CGAGCATA, allowing full-length translation of losA (on), and 6 strains contained 3, 4, 6, or 10 tandem copies (losA off). For a serum-sensitive strain, R3063, with losA off (10 repeat units), selection for serum-resistant variants yielded a heterogeneous population in which colonies with increased serum resistance had losA on (2, 8, or 11 repeat units), and colonies with unchanged sensitivity to serum had 10 repeats. Inactivation of losA in strains R3063 and R2846 (strain 12) by insertion of the cat gene decreased the serum resistance of these strains compared to losA-on variants and altered the electrophoretic mobility of LPS. We conclude that expression of losA, a gene that contributes to LPS structure and affects serum resistance, is determined by octanucleotide repeat variation.

Blood Bactericidal Activity↗
PubMed2005

New considerations in infectious disease outbreaks: the threat of genetically modified microbes.

Genetically altered microbes are used widely in the conduct of scientific study and have facilitated the development of new medical therapies, preventive strategies, and diagnostic tools. Unfortunately, such organisms may also cause infectious disease outbreaks as a result of accidental or intentional transmission to humans. The unique microbial properties of genetically altered pathogens and the clinical symptoms exhibited by persons infected with them may impede the usual diagnostic and clinical evaluations or preventive strategies. Practicing physicians and clinicians at microbiology laboratories, who would be the first to observe such infections, must consider the broad clinical possibilities of illnesses caused by deliberately altered microorganisms and the potential difficulty in confirming a diagnosis.

Bacterial Infections↗
PubMed2005

In vitro activity of telithromycin against macrolide-susceptible and macrolide-resistant pharyngeal isolates of group A streptococci in the United States.

In vitro susceptibility testing of 2,797 group A streptococcus (GAS) isolates demonstrated that telithromycin was fully active against all macrolide-susceptible strains and among 80 of 115 macrolide-resistant GAS expressing the M phenotype. Telithromycin resistance was identified in 2 of 45 strains expressing the inducible macrolide-lincosamide-streptogramin B phenotype and four of nine isolates expressing the constitutive macrolide-lincosamide-streptogramin B resistance phenotype.

Anti-Bacterial Agents↗
PubMed2005

Identification of new hmwA alleles from nontypeable Haemophilus influenzae.

High-molecular-weight proteins of Haemophilus influenzae mediate attachment to epithelial cells. Previous reports describe several allelic versions of hmwA genes that have different adherence properties. Here we report three new alleles of hmwA (hmwA from strain AAr96, hmwA from strain AAr105, and hmwA from strain G822), demonstrating the high degree of DNA variation of these genes among different strains.

Amino Acid Sequence↗
PubMed2004

Library on a slide for bacterial comparative genomics.

BACKGROUND: We describe a novel application of microarray technology for comparative genomics of bacteria in which libraries of entire genomes rather than the sequence of a single genome or sets of genes are arrayed on the slide and then probed for the presence or absence of specific genes and/or gene alleles. RESULTS: We first adopted a 96-well high throughput working protocol to efficiently isolate high quality genomic DNA. We then optimized conditions to print genomic DNA onto a glass slide with high density (up to 15000 spots) and to sensitively detect gene targets in each genome spot using fluorescently labeled DNA probe. Finally, we created an E. coli reference collection array and probed it for the presence or absence of the hemolysin (hly) gene using a dual channel non-competing hybridization strategy. Results from the array hybridization matched perfectly with previous tests. CONCLUSIONS: This new form of microarray technology, Library on a Slide, is an efficient way for sharing and utilizing large strain collections in comparative genomic analyses.

Bacterial Typing Techniques↗
PubMed2004

Diversity and sharing of Haemophilus influenzae strains colonizing healthy children attending day-care centers.

BACKGROUND: Children attending day-care centers (DCCs) are at risk for Haemophilus influenzae nasopharyngeal colonization and acute otitis media. The degree to which a given strain circulates within a day-care center and the heterogeneity of strains among DCCs in a geographic area are not well-characterized. This study describes the prevalence rates of H. influenzae colonization in a large number of children attending day-care centers and examines the genetic diversity of colonizing strains and the degree of sharing among children. METHODS: Throat cultures were collected from 198 healthy children <3 years old attending 16 day-care centers in Michigan. All H. influenzae isolates were genetically typed by enterobacterial repetitive intergenic consensus PCR as the initial screening technique to identify unique strains within each child. Pulsed field gel electrophoresis was used subsequently to examine the genetic diversity of strains between children. RESULTS: There were 127 (64%) children colonized with H. influenzae. Wide variation in rates of colonization was identified among day-care centers (0 to 95%). A total of 179 genetically unique H. influenzae strains were isolated, and 47 children (37%) were colonized with 2 or more genetically distinct H. influenzae organisms. Evidence of sharing of the same strain in different children was found in 13 of 15 colonized DCCs and 23% of genotypically unique strains were shared. CONCLUSION: The degree of sharing of H. influenzae among children in this study suggests transmission of these potentially pathogenic microorganisms in day-care centers.

Carrier State↗
PubMed2004

Prevalence of the hifBC, hmw1A, hmw2A, hmwC, and hia Genes in Haemophilus influenzae Isolates.

Adherence of Haemophilus influenzae to respiratory epithelial cells is the first step in the pathogenesis of H. influenzae infection and is facilitated by the action of several adhesins located on the surface of the bacteria. In this study, prevalences of hifBC, which represent the pilus gene cluster; hmw1A, hmw2A, and hmwC, which represent high-molecular-weight (HMW) adhesin genes; and hia, which represents H. influenzae adhesin (Hia) genes were determined among clinical isolates of encapsulated type b (Hib) and nonencapsulated (NTHi) H. influenzae. hifBC genes were detected in 109 of 170 (64%) Hib strains and in 46 of 162 (28%) NTHi isolates (P = 0.0001) and were more prevalent among the invasive type b strains than invasive NTHi strains (P = 0.00003). Furthermore, hifBC genes were significantly more prevalent (P = 0.0398) among NTHi throat isolates than NTHi middle ear isolates. hmw1A, hmw2A, hmwC, and hia genes were not detected in Hib strains. Among NTHi isolates, the prevalence of hmw1A was 51%, the prevalence of hmw2A was 23%, the prevalence of hmwC was 48%, and the prevalence of hia was 33%. The hmw genes were significantly more prevalent among middle ear than throat isolates, while hia did not segregate with a respiratory tract site. These results show the variability of the presence of adhesin genes among clinical H. influenzae isolates and suggest that hemagglutinating pili may play a larger role in H. influenzae nasopharyngeal colonization than in acute otitis media whereas the HMW adhesins may be virulence factors for acute otitis media.

Adhesins, Bacterial↗
PubMed2002

Mucin in middle ear effusions inhibits attachment of Haemophilus influenzae to mucosal epithelial cells.

Although otitis media with effusion is often preceded by an infection of the tympanic cavity, when cultured, many effusions show no culturable bacteria. Based on the hypothesis that the effusion might play a protective role in the course of infection, the influence of this fluid on adhesion of H. influenzae (Hi) type-b strain 770235 and nontypeable H. influenzae (NTHi) strains to buccal epithelial cells was investigated. Effusions were classified as mucoid, seromucoid and serous. Mucoid secretions inhibited adhesion to a significantly greater extent (62%) than did seromucous (52%) and serous effusions (47%) ( P<0.001). The glycoprotein and high-molecular-weight fractions showed similar levels of inhibition. Sialic acid concentration, and, to a lesser extent, protein concentration, correlated with the level of inhibition. Desialylated effusions lost their ability to block bacterial attachment. Thus, middle ear effusion fluid exhibits an inhibitory effect that is due to mucins, which determine viscosity and represent the sialylated high-molecular-weight glycoprotein fraction of the effusion.

Bacterial Adhesion↗
PubMed2002

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Anti-Bacterial Agents↗