The successful in vivo horizontal transfer of mobile genetic elements carrying resistance and virulence determinants have contributed immensely to a global dissemination of virulent and multi-drug resistant pathogens. In addition, the pathogenesis of MRSA infection is enhanced via initial colonization of the skin through the component of the microbial surface antigen recognizing adhesive matrix molecules and by their ability to evade host immune response. Furthermore, it was also observed that the genetic diversity of pathogenic MRSA is due to its’ ability to rapidly acquire resistance and virulence determinants. A characteristic feature that made it one of the most important nosocomial pathogen worldwide. Similarly, the expression of virulence gene in MRSA has been observed to be regulated by the accessory gene regulator system (agr). These system is made up of a series of genes whose product build up quorum-sensing regulatory mechanisms that is growth dependent. In addition, at a certain growth stage, the agr systems triggers a pronounced changes in the expression of genes called the quorum sensing. The findings of this review affirms the importance of horizontal gene transfer in the dissemination of resistance and virulence determinants and as well as the genetic diversity of MRSA.
Burkholderia pseudomallei are Gram negative highly pathogenic bacteria of humans and
animals causing a multisystemic disease called melioidosis. They have recently gained a lot of interest
from the research community and public health organisations because of their great potential to be
used as an agent of bioterrorism. This has made the search for simple, rapid, accurate and the most
definitive means of their detection, identification and discrimination very critical and necessary. This
article aimed to review the molecular techniques used for detection, identification and differentiation
of B. pseudomallei. Although, culture and isolation techniques maintained their usefulness in
confirming cases of melioidosis, their time limitation (can take up to a week for confirming diagnosis)
leads to the search for rapid and simple techniques. Consequently, serology-based tests have been
developed which are both faster and less sophisticated. However, the presence of high background
titre levels and cross-reaction with other organisms make it less reliable. Thus, efforts have been
directed to explore rapid and accurate molecular techniques and resulting in the development and
validation of various PCR-based identification techniques targeting either single or multiple genes.
Although requiring some level of instrumentation and expertise, PCR-based techniques have been
reported to be very useful in diagnosis of melioidosis. We recommend the 16S rRNA PCR (especially
augmented with other molecular methods such as gene sequencing and analysis) and MLST
techniques for timely detection, identification and differentiation of B. pseudomallei for routine
diagnosis and epidemiological studies respectively.
Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading nosocomial
pathogen that is also emerging as a zoonotic pathogen. In this review, it was observed that rapid
emergence of new MRSA clones at a higher frequency has ushered in a new knowledge on the clonality
and epidemic potentials of MRSA. Secondly, the success of treatment and management of MRSA
infection is threatened by the diversity in the clonal types. This is because different clones harbours
different antibiotics resistance characteristics and as such respond differently to treatment. Furthermore,
clonal replacement of hospital-acquired MRSA with community -acquired MRSA has also been
observed. Thirdly, the transmission of MRSA even though previously thought to be exclusively within
the hospital setting through hand contact and nasal colonization has now spread to the community and in
addition human to animal and animal to human transmission has also been observed. Similarly, pet
owners, veterinarians and farmers have been described as high-risked group with potentials of becoming
reservoirs of MRSA. Furthermore, the adoption of hand hygiene in healthcare setting have to a great
extent reduced the incidence of MRSA in the hospital. And lastly, the advent of molecular typing such as
Pulsed Field Gel Electrophoresis (PFGE), Multi Locus Sequence Typing (MLST), Staphylococcal protein
A typing (Spa typing) and Double Locus Sequence Typing (DLST) have proven to be a useful tool in
providing valuable information on the evolution and clonal diversity of MRSA. These in turn help
researchers to answer some pertinent questions on the epidemiology of MRSA.