Seminario Biología Molecular Semestre 3 Universidad Pontificia Bolivariana

1. Presented by Aura Cristina Peña Santos
Third semester
Universidad Pontificia Bolivariana

2. Staphylococcus aureus
Introduction
It´s a gram-positive, sphere-shaped bacteria, that
cause a wide variety of clinical diseases. It's found
on the skin and mucous membranes, and humans
are the major reservoir for these organisms.
“Grapes-like”

3. MRSA in cancer patients
This type of infection is caused by a staph bacteria
which has become resistant to a large majority of
the antibiotics used for treatments.
Methicillin-resistant Staphylococcus aureus
Introduction
MRSA infections are emerging as serious pathogens
in both the hospital and the community settings.
High-level resistance to methicillin is
caused by the mecA gene
IEC
genes

4. Objectives
This study explores the association between MRSA and bacteriophage-encoded
immune evasion cluster (IEC) genes in cancer and non cancer patients.

5. Materials and methods
Antibiotic susceptibility testing (AST)
2.2 Genomic DNA extraction and gel
electrophoresis
2.3
In this study, the method was used to
determine the antimicrobial resistance
(AMR) profiles, and the susceptibility of
isolates of S. Aureus to different antibiotics.
Disk diffusion method is based on placing
disks impregnated with antibiotics on agar
plates inoculated with the microorganism being
tested and observing its growth and resistance.
In this study, GenJet DNA extraction
kit was used for Genomic DNA
extraction, in order to release
chromosomal DNA from the cellular
matrix to analyse its content by gel
electrophoresis (to identify mixtures of
DNA, RNA, or proteins).
What is the basis of
gel electrophoresis?

6. Materials and methods
Polymerase chain reaction
2.4 Phage typing
2.5
The PCR technique is a method used for
quickly and easily amplifying DNA sequences,
which are based on the principle of enzymatic
replication of the nucleic acids. In this
investigation, the method was employed to
detect the presence of specific genes in
cancer and non cancer patients isolates.
Phage typing was employed to classify the
IEC genes, resulting in the assignment of
types A to H, following the PCR outcomes.

7. Results
Clinical features of S.
aureus isolates
3.1
- No associations were found between
the incidence of MRSA and either the
sex or age of the patients.
- An association between MRSA isolates
and pus samples in non cancer patients,
and MRSA isolates and skin swabs in
cancer patients was observed.
AMR of S. aureus isolates
3.2
Genotypic
characterization
3.3

8. Results
Occurrence of IEC gene
3.4
Phage typing
3.5
- All strains exhibited positive results for the escien gene.
- The distribution patterns of pvl, chp, sak, and agr genes were similar
among MRSA isolates obtained from cancer and non cancer
patients.
- Sea gene was quite significative associated with cancer patients.
- Samples present mecA gene.
The study found out 8 distinct forms of IEC genetic variants.
And type A and B have a predominant presence.

9. Author, year
Discussion
Campo, 2011
Despite pvl-positive MRSA infections
being common in SSTIs, pvl was not
always linked to worse clinical
outcomes for cancer patients with
additional risk factors.
He said: Agree or disagree
Chai, 2022
Li, 2021
Agree
The MRSA isolates demonstrated
resistance to multiple classes of
antibiotics commonly used for
treating MRSA infections.
It has been extensively documented
that MRSA infections among cancer
patients have severe clinical
consequences and a high mortality
rate.
Agree
Agree

10. Conclusions
1 The molecular biology allows the genetic
analyzing of microorganisms isolates as well
as Staphylococcus aureus ones, that enables
understanding of the roll that genes play in
the resistance development.
Analyzing the association between cancer
and immune evasion cluster genes in MRSA
allows for the consideration new therapies
and control methods of resistance in the
illness from molecular biology.
2