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Appl. Environ. Microbiol., 06 1997, 2258-2265, Vol 63, No. 6
P Kuhnert, B Heyberger-Meyer, AP Burnens, J Nicolet and J Frey
The family of RTX (RTX representing repeats in the structural toxin) toxins
is composed of several protein toxins with a characteristic nonapeptide
glycine-rich repeat motif. Most of its members were shown to have cytolytic
activity. By comparing the genetic relationships of the RTX toxin genes we
established a set of 10 gene probes to be used for screening as-yet-unknown
RTX toxin genes in bacterial species. The probes include parts of apxIA,
apxIIA, and apxIIIA from Actinobacillus pleuropneumoniae, cyaA from
Bordetella pertusis, frpA from Neisseria meningitidis, prtC from Erwinia
chrysanthemi, hlyA and elyA from Escherichia coli, aaltA from
Actinobacillus actinomycetemcomitans and lktA from Pasteurella haemolytica.
A panel of pathogenic and nonpathogenic gram-negative bacteria were
investigated for the presence of RTX toxin genes. The probes detected all
known genes for RTX toxins. Moreover, we found potential RTX toxin genes in
several pathogenic bacterial species for which no such toxins are known
yet. This indicates that RTX or RTX-like toxins are widely distributed
among pathogenic gram-negative bacteria. The probes generated by PCR and
the hybridization method were optimized to allow broad-range screening for
RTX toxin genes in one step. This included the binding of unlabelled probes
to a nylon filter and subsequent hybridization of the filter with labelled
genomic DNA of the strain to be tested. The method constitutes a powerful
tool for the assessment of the potential pathogenicity of poorly
characterized strains intended to be used in biotechnological applications.
Moreover, it is useful for the detection of already-known or new RTX toxin
genes in bacteria of medical importance.
Copyright © 1997, American Society for Microbiology
Detection of RTX toxin genes in gram-negative bacteria with a set of specific probes
Institute of Veterinary Bucteriology, University of Berm, Switzerland. KUHNERT@VBI.UNIBE.CH
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