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into antibiotic susceptible strains of
Pseudomonas aeruginosa
by phages released
from multiple antibiotic resistant lysogenic strains of
P. aeruginosa
or by general-
ized transducing phages that already carry multiple antibiotic resistance markers
(Blahova et al.
1999
,
2000
; Brabban et al.
2005
). Resistance to imipenem,
ceftazidime, and cefotaxime was transduced into antibiotic susceptible
P. aeruginosa
by a phage released from a lysogenic strain (Blahova et al. 1999;
Brabban et al.
2005
).
3.5 Transfer of Genomic Islands
Recently, a novel T4SS has been identified in
N. gonorrhoeae
that secretes chro-
mosomal DNA in the surrounding environment in a non-contact-dependent manner
(Hamilton et al.
2005
; Juhas et al.
2009
). This T4SS is localized in the large,
horizontally acquired gonococcal genetic island present in the chromosome of
N. gonorrhoeae
, thus, by facilitating chromosomal DNA secretion this GEI also
encodes the mechanism of its own dissemination by transformation (Juhas
et al.
2009
).
A new conjugation type GEI-encoded T4SS has been also described. It is
evolutionarily distant from all previously described T4SSs and plays a key role in
the horizontal transfer of a wide variety of GEIs originating from a broad spectrum
of bacteria, including
Haemophilus
spp.,
Pseudomonas
spp.,
Erwinia carotovora
(
Pectobacterium carotovorum
),
Salmonella enterica
serovar Typhi,
Legionella
pneumophila
, and others (Juhas et al.
2007
,
2008
,
2009
) by conjugation.
The 153-kb
E. faecalis
pathogenicity island (PAI) was first described by Shankar
et al. (
2002
). It encodes several pathogenicity factors, among them the enterococcal
surface protein (esp) conferring increased biofilm formation and colonization, a
cytolysin with hemolytic, cytolytic, and antibacterial activity, the aggregation
substance, surface proteins, and general stress proteins (Shankar et al.
2002
). The
E. faecalis
PAI is widely distributed among isolates of different origins, clonal
types, and complexes, and it probably evolved by modular gain and loss of internal
gene clusters (McBride et al.
2009
). Laverde Gomez et al. (
2011
) demonstrated for
the first time precise excision, circularization, and horizontal transfer of the entire
PAI from the chromosome of
E. faecalis
strain UW3114. This PAI (ca. 200 kb)
contained some deletions and insertions as compared to the PAI of the reference
strain MMH594, transferred precisely and integrated site specifically into the
chromosome of
E. faecalis
and
E. faecium
. The internal PAI structure was
maintained after transfer. Biofilm formation and cytolytic activity were enhanced
in
E. faecalis
transconjugants after acquisition of the PAI. A 66-kb conjugative
pheromone-responsive erythromycin resistance plasmid (pLG2) that was trans-
ferred in parallel with the PAI was sequenced. It contains complete replication
and conjugation modules of enterococcal origin in a mosaic-like composition; it is
likely that it promotes horizontal transfer of the PAI (Laverde Gomez et al.
2011
).
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