Staphylococcus epidermidis - virulence factors and innate ... - Munin

(391). Finally, arginine deiminase, the main enzyme coded for by the operon, is important in the
inhibition of human peripheral blood mononuclear cell proliferation in Streptococcus pyogenes
(392). The opp3- operon encodes an ABC transporter system. Similar opp-operons in other
bacterial species have a wide array of functions, such as pheromone transport, chemotaxis and
expression of virulence determinants (391, 393). ACME –opp3 belong to the same family as
opp1 and opp2, two natural chromosomal operons encoding ABC transporters involved in
nutrient up-take from the bacterial environment (394).
ACME integrates into orfX in both the USA300 clone and ATCC12228 strain, and is flanked by
SCCmec- specific repeat sequences (391). The SCCmec elements nearby and their cassette
chromosome recombinases (ccrA/ccrB) is believed to be important when moving this island from
one strain to another (391, 395-397)
ACME was first described in the community associated methicillin-resistant S. aureus (Ca-
MRSA) USA300 strain and the biofilm-negative S. epidermidis strain ATCC12228 (391). In S.
aureus ACME was initially considered as a new and putative important virulence factor. This
was due to its presence in the pathogenic and widespread S. aureus strain, USA300 (398-401),
and its correlation to methicillin resistance through it co-localization in to the SCCmec element
(391, 396), and because an isogenic ACME-negative mutant showed significantly reduced fitness
in a rabbit infection model (402). However, and in contrast to Diep`s study from 2008, a recent
study did not show that the presence of ACME was associated with increased virulence in a rat
model of necrotizing pneumonia (403) Thus, currently ACMEs role as a virulence factor in S.
aureus is unclear.
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