Elucidation of Essential and Nonessential Genes in the
            <i>Haemophilus influenzae</i>
            Rd Cell Wall Biosynthetic Pathway by Targeted Gene Disruption

Trepod, Catherine M.; Mott, John E.

doi:10.1128/aac.49.2.824-826.2005

Cited by 10 publications

(3 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Mutations in genes within the sialometabolism region of DNA in strains Rd, 375 and 486, with the exception of nagA and nagB , were made. nagB encodes the last of the five steps of the Neu5Ac catabolic pathway (converting glucosamine-6-phosphate to fructose-6-phosphate), suggesting that the gene product may be essential because of its close association with central metabolism, as had been previously described for nagA [ 27 ].…”

Section: Resultsmentioning

confidence: 91%

Sialic acid mediated transcriptional modulation of a highly conserved sialometabolism gene cluster in Haemophilus influenzae and its effect on virulence

et al. 2010

View full text Add to dashboard Cite

BackgroundSialic acid has been shown to be a major virulence determinant in the pathogenesis of otitis media caused by the bacterium Haemophilus influenzae. This study aimed to characterise the expression of genes required for the metabolism of sialic acid and to investigate the role of these genes in virulence.ResultsUsing qRT-PCR, we observed decreased transcriptional activity of genes within a cluster that are required for uptake and catabolism of 5-acetyl neuraminic acid (Neu5Ac), when bacteria were cultured in the presence of the sugar. We show that these uptake and catabolic genes, including a sialic acid regulatory gene (siaR), are highly conserved in the H. influenzae natural population. Mutant strains were constructed for seven of the nine genes and their influence upon LPS sialylation and resistance of the bacteria to the killing effect of normal human serum were assessed. Mutations in the Neu5Ac uptake (TRAP transporter) genes decreased virulence in the chinchilla model of otitis media, but the attenuation was strain dependent. In contrast, mutations in catabolism genes and genes regulating sialic acid metabolism (siaR and crp) did not attenuate virulence.ConclusionThe commensal and pathogenic behaviour of H. influenzae involves LPS sialylation that can be influenced by a complex regulatory interplay of sialometabolism genes.

show abstract

Section: Resultsmentioning

confidence: 91%

Sialic acid mediated transcriptional modulation of a highly conserved sialometabolism gene cluster in Haemophilus influenzae and its effect on virulence

et al. 2010

View full text Add to dashboard Cite

show abstract

“…The essentiality of this enzyme in H. influenzae was demonstrated by targeted gene disruption (18). A remarkable increase of ␤-lactamase-nonproducing ampicillin-resistant (BLNAR) H. influenzae strains has been reported in Japan (14).…”

mentioning

confidence: 99%

Horizontal Gene Transfer of ftsI , Encoding Penicillin-Binding Protein 3, in Haemophilus influenzae

Takahata

Ida

Senju

et al. 2007

Antimicrob Agents Chemother

View full text Add to dashboard Cite

Horizontal gene transfer has been identified in only a small number of genes in Haemophilus influenzae, an organism which is naturally competent for transformation. This report provides evidence for the genetic transfer of the ftsI gene, which encodes penicillin-binding protein 3, in H. influenzae. Mosaic structures of the ftsI gene were found in several clinical isolates of H. influenzae. To identify the origin of the mosaic sequence, complete sequences of the corresponding gene from seven type strains of Haemophilus species were determined. Comparison of these sequences with mosaic regions identified a homologous recombination of the ftsI gene between H. influenzae and Haemophilus haemolyticus. Subsequently, ampicillin-resistant H. influenzae strains harboring identical ftsI sequences were genotyped by pulsed-field gel electrophoresis (PFGE). Divergent PFGE patterns among ␤-lactamase-nonproducing ampicillin-resistant (BLNAR) strains from different hospitals indicated the potential for the genetic transfer of the mutated ftsI gene between these isolates. Moreover, transfer of the ftsI gene from BLNAR strains to ␤-lactamase-nonproducing ampicillin-susceptible (BLNAS) H. influenzae strains was evaluated in vitro. Coincubation of a BLNAS strain (a rifampin-resistant mutant of strain Rd) and BLNAR strains resulted in the emergence of rifampin-and cefdinir-resistant clones at frequencies of 5.1 ؋ 10 ؊7 to 1.5 ؋ 10 ؊6 . Characterization of these doubly resistant mutants by DNA sequencing of the ftsI gene, susceptibility testing, and genotyping by PFGE revealed that the ftsI genes of BLNAR strains had transferred to BLNAS strains during coincubation. In conclusion, horizontal transfer of the ftsI gene in H. influenzae can occur in an intraspecies and an interspecies manner.

show abstract

“…Extended spectrum β-lactamases have not been documented for H. in uenzae. A major concern relates to amino acid substitutions in the transpeptidase region of penicillin-binding protein (PBP) 3, which is the sole indispensable PBP of the species [10]. β-lactamase-negative ampicillin-resistant (BLNAR) strains with mutational resistance are usually grouped according to decisive substitutions and antimicrobial spectrum, where group I and II confer resistance to aminopenicillins only, while the target range of group III includes cephalosporins [11,12].…”

Section: Introductionmentioning

confidence: 99%

Haemophilus influenzae one day in Denmark: prevalence, circulating clones, and dismal resistance to aminopenicillins

Nørskov‐Lauritsen

Pedersen

Lam

et al. 2021

Eur J Clin Microbiol Infect Dis

View full text Add to dashboard Cite

PurposeHaemophilus in uenzae is a common cause of mucosal infections that warrants accurate surveillance.We aimed to assess the prevalence of the species in clinical specimens, and characterise population structure and resistance to aminopenicillins by whole genome sequencing. MethodsWe assessed the point prevalence by entering the database records of one day in Denmark, and examined the genome sequences of nationwide, collected isolates from the same day. ResultsThe prevalence of H. in uenzae in clinical samples on the 10 th of January 2018 was 1.78 per 100,000 person-days (all samples), and 2.47 per 1,000 hospital bed-days (hospital samples). Of 2,009 bacteria deemed clinically relevant and collected in a concerted action by the Danish departments of clinical microbiology, 62 (3.1%) were H. in uenzae. All 62 isolates belonged to phylogenetic group I and were unencapsulated. Three strains from separate Danish regions had identical core genome sequences, but a small number of intergenic mutations testi ed to circulating clones, rather than individual cases of patient-to-patient transmission. The TEM-1 β-lactamase gene was present in 24 strains, while 13 strains were genetically categorised as ampicillin-resistant due to substitutions in penicillin-binding protein 3; shared patterns of amino acid substitutions in unrelated strains indicated putative lateral transfer of chromosomal resistance. ConclusionsCirculating clones of H. in uenzae are frequent, and host factors, rather than direct transmission of epidemic strains, may be the primary cause of infection. The bleak presence of ampicillin resistance revealed by sequencing of point prevalence strains underscores the necessity for close examination of testing methods.

show abstract

Elucidation of Essential and Nonessential Genes in the Haemophilus influenzae Rd Cell Wall Biosynthetic Pathway by Targeted Gene Disruption

Cited by 10 publications

References 5 publications

Sialic acid mediated transcriptional modulation of a highly conserved sialometabolism gene cluster in Haemophilus influenzae and its effect on virulence

Sialic acid mediated transcriptional modulation of a highly conserved sialometabolism gene cluster in Haemophilus influenzae and its effect on virulence

Horizontal Gene Transfer of ftsI , Encoding Penicillin-Binding Protein 3, in Haemophilus influenzae

Haemophilus influenzae one day in Denmark: prevalence, circulating clones, and dismal resistance to aminopenicillins

Contact Info

Product

Resources

About