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GLOSSARY
Caenorhabditis elegans: This nematode lives in soil and eats environmental bacteria. It is a
simple and easy to handle model that ca be used to evaluate the virulence of bacterial pathogens.
It is increasingly being used to study host-pathogen interactions and has helped identify basic
evolutionarily conserved pathways associated with microbial pathogenesis. In particular, this has
revealed important factors of the host response with remarkable parallels in higher organisms.
This organism’s short (2–3-weeks) life span facilitates host-bacteria interaction analysis, offering
an ideal compromise between complexity and tractability.
Staphylococcal cassette chromosome mec (SCCmec) elements: MRSA strains belonging to
multidrug resistant bacteria, produce penicillin binding protein 2a (PBP2a), which is poorly
acylated by ß-lactam antibiotics. The mecA gene, encoding PBP2a, is carried on a peculiar type
of mobile genetic element inserted into the SCCmec. SCCmec elements typically share four
characteristics: first, they carry the mec gene complex (mec) consisting of the methicillin
resistance determinant mecA and its regulatory genes and insertion sequences; second, they carry
the ccr gene complex (ccr) consisting of ccr genes that are responsible for the mobility of the
element and its surrounding sequences; third, they have characteristic directly repeated nucleotide
sequences and inverted complementary sequences at both ends; and last, they integrate into the 3'
end of an open reading frame (ORF), orfX.
The junkyard (J) region: The SCCmec element type has been defined by the combination of ccr
type and mec class. In MRSA strains, six types of SCCmec elements, that is, six combinations of
ccr and mec, have been reported. These six SCCmec elements have been further classified by
differences in regions other than ccr and mec, which are designated junkyard regions. The J
regions comprise three parts: J1 (the region between ccr and the right-flanking chromosomal
region), J2 (the region between mec and ccr), and J3 (the region between orfX and mec).
spa sequence typing: The spa gene of Staphylococcus aureus encodes protein A and is used for
typing of MRSA. The sequence typing of the spa gene repeat region allows studying the
epidemiology of these strains. The repeat region of the spa gene is subject to spontaneous
mutations, as well as loss and gain of repeats. Repeats are assigned an alpha-numerical code, and
the spa type is deduced from the order of specific repeats. Repeats and spa types were
determined by Ridom StaphType, a software tool allowing rapid repeat determination, data
management and retrieval, and Internet-based assignment of new spa types following automatic
quality control of DNA sequence chromatograms.sis, offering an ideal compromise between
complexity and tractability