Since resistance traits are genetically encoded, we can sometimes test for the specific genes that confer antibiotic resistance. However, although nucleic acid-based detections systems are generally rapid and sensitive, it is important to remember that the presence of a resistance gene does not necessarily equate to treatment failure, because resistance is also dependent on the mode and level of expression of these genes11.
Some of the most common molecular techniques utilized for antimicrobial resistance detection are as follows
Polymerase chain reaction (PCR) is one of the most commonly used molecular techniques for detecting certain DNA sequences of interest. This involves several cycles of denaturation of sample DNA, annealing of specific primers to the target sequence (if present), and the extension of this sequence as facilitated by a thermostable polymerase leading to replication of a duplicate DNA sequence, in an exponential manner, to a point which will be visibly detectable by gel electrophoresis with the aid of a DNA-intercalating chemical which fluoresces under UV light.
DNA hybridization. This is based on the fact that the DNA pyrimidines (cytosine and thymidine) specifically pair up with purines (guanine and adenine; or uracil for RNA). Therefore, a labeled probe with a known specific sequence can pair up with opened or denatured DNA from the test sample, as long as their sequences complement each other. If this “hybridization” occurs, the probe labels this with a detectable radioactive isotope, antigenic substrate, enzyme or chemiluminescent compound. Whereas if no target sequence is present or the isolate does not have the specific gene of interest, no attachment of probes will occur, and therefore no signals will be detected.
Modifications of PCR and DNA hybridization. With these basic principles, several modifications have been introduced which further improve the sensitivity and specificity of these standard procedures. Examples of such development were the use of 5’-fluorescence-labeled oligonucleotides, the development of molecular beacons, development of DNA arrays and DNA chips, among many others.
This option integrates academic study with relevant supervised work experience. The work placements are arranged by mutual agreement between the students and the employing organizations. Enrolment is limited. Admission is by application to the Science Co-op Office in February prior to third year (late applicants may be considered if they contact the Life Sciences Co-op Coordinator). Selection will be based on previous academic performance and general suitability to the work environment as assessed by resumé and interview. Admissibility to a third-year Microbiology and Immunology Bachelor of Science specialization is prerequisite for admission to the Co-op Option but applicants can apply to Co-op before admission to the third-year microbiology specializations. Graduation from the Co-op program requires completion of four work terms, the normal courses required for the specialization. Detailed information is available from Microbiology and Immunology or the Co-operative Education Office .