The most prevalent virulence traits associated with APEC are adhesins (type 1 and P fimbriae, Temperature-sensitive hemagglutinin Tsh, and curli), capsules, iron acquisition systems and serum resistance [2], [3].
Simultaneous carriage of more than one strain of Streptococcus pneumoniae promotes horizontal gene transfer events and may lead to capsule switch and acquisition of antibiotic resistance.
Characteristic ExPEC VFs include various adhesins (P and type I fimbriae), structural components of the bacterial outer membrane (capsule, lipopolysaccharide), iron acquisition and utilization systems (aerobactin and salmochelin siderophores), toxins (hemolysin, cytotoxic necrosis factor) and secretion systems [ 4, 5].
Apart from transovarial transmission, other possible mechanisms of symbiont diffusion include proctophagy, the deposition of capsule containing microbes, and environmental acquisition [9], [53], [54], [55].
Capsular switching – acquisition of novel capsule specific genes through recombination has also facilitates the emergence and persistence of virulent meningococcal lineages (Swartley et al., 1997, Harrison et al., 2010).
Furthermore, as the acquisition of a capsule differing extensively from 6B seems unlikely within clade IC1, it seems destined for elimination following the introduction of polysaccharide conjugate vaccines (which induces immunity against both serotype 6A and 6B) in 2011 [ 8].
The emergence of a novel epidemic V. cholerae O139 serogroup in 1992 was shown to have resulted from the horizontal transfer of the O139 gene cluster into an O1 serogroup strain as well as the acquisition of a capsule polysaccharide and an integrative conjugative element [ 33- 37].
Second, serotype switching can occur through recombination in naturally transformable clones and result in the acquisition of a nonvaccine capsule (5, 7 ).
When the method is used in a clinical situation the capsules should be used to achieve the correct angle of view, but it is very important that the capsules are removed prior to image acquisition.
It sets the stage for pneumococcal evolution through horizontal exchange of genes, which may result in the acquisition of antibiotic resistance or capsule switch [9].
