Related Experiment Video
Updated: Nov 8, 2025
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Phenotype-Genotype Characterization and Antibiotic-Resistance Correlations Among Colonizing and Infectious
Hanzada T Nour El-Din1, Aymen S Yassin1, Yasser M Ragab1
1Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Cairo, 11562, Egypt.
Introduction:
Methicillin-resistant Staphylococcus aureus (MRSA) presents a profound hazard to public health. MRSA colonizing skin, mucous membranes, and the anterior nares without clinical symptoms is termed "colonizing MRSA". Upon manifestation of clinical symptoms, it is termed "infectious MRSA". Here, we characterize and differentiate colonizing and infectious MRSA, and analyze the phenotypic-genotypic and antibiotic susceptibility correlations.
Methodology:
Clinical MRSA isolates were recovered from intensive care units (ICUs) of two major Egyptian hospitals and their biofilm formation ability was tested. Antibiograms against 16 antibiotics were determined, in addition to the minimum inhibitory concentrations (MICs) of vancomycin and linezolid. The entire collection was typed by enterobacterial repetitive intergenic consensus (ERIC)-PCR, as well as multi-locus sequence typing (MLST). Representative resistance and virulence genes were detected by PCR amplification.
Results:
Forty-nine isolates were confirmed as MRSA, of which 30 isolates were infectious and 19 were colonizing. Versatile resistance patterns were observed in both groups of isolates. We report a higher tendency for biofilm-formation and borderline minimum inhibitory concentrations among infectious isolates. A Positive antibiotic correlation was observed between susceptibility to protein synthesis inhibitors and cell wall inhibitors. Positive correlations were observed between isolation site and rifampicin resistance: nasal samples were enriched in rifampicin-resistant isolates, while urine and blood samples were enriched in susceptible ones. Furthermore, biofilm formation ability was slightly associated with amikacin resistance, and an association between teicoplanin resistance and the presence of the Panton-Valentine leukocidin gene was the only significant phenotype-genotype correlation observed. Finally, ERIC typing and MLST had congruent results.
Conclusion:
Linezolid and vancomycin are still the most convenient choice for MRSA treatment. ERIC PCR and MLST show promising typing combination that could be easily used periodically for tracking the genotypic changes of MRSA, especially within the healthcare facilities. Several correlations were established between groups of antibiotics and the genotypes/phenotypes of the selected isolates.
Insights
This study differentiates colonizing and infectious Methicillin-resistant Staphylococcus aureus (MRSA) by analyzing their antibiotic resistance, biofilm formation, and genetic profiles. Linezolid and vancomycin remain key treatments, with typing methods aiding MRSA surveillance.
Area of Science:
- Microbiology
- Infectious Diseases
- Medical Science
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat.
- Distinguishing between colonizing (asymptomatic) and infectious (symptomatic) MRSA is crucial for effective management.
- Understanding the phenotypic and genotypic characteristics of MRSA is essential for public health strategies.
Purpose of the Study:
- To characterize and differentiate colonizing and infectious MRSA isolates.
- To analyze correlations between phenotypic traits (biofilm formation, antibiotic susceptibility) and genotypic profiles.
- To evaluate the utility of ERIC PCR and MLST for MRSA surveillance.
Main Methods:
- MRSA isolates from Egyptian ICUs were analyzed for biofilm formation and antibiotic susceptibility (16 antibiotics, vancomycin, linezolid MICs).
- Genotyping was performed using enterobacterial repetitive intergenic consensus (ERIC)-PCR and multi-locus sequence typing (MLST).
- PCR was used to detect specific resistance and virulence genes.
Main Results:
- Forty-nine MRSA isolates (30 infectious, 19 colonizing) exhibited diverse resistance patterns.
- Infectious isolates showed a higher tendency for biofilm formation and borderline vancomycin/linezolid MICs.
- Significant correlations included isolation site and rifampicin resistance, and teicoplanin resistance with the Panton-Valentine leukocidin gene; ERIC typing and MLST yielded congruent results.
Conclusions:
- Linezolid and vancomycin are recommended for MRSA treatment.
- ERIC PCR and MLST provide a valuable combination for tracking MRSA genotypic changes in healthcare settings.
- Established correlations highlight the complex interplay between MRSA phenotypes, genotypes, and antibiotic resistance patterns.
Related Concept Videos
01:30Development of Antibiotic Resistance
00:57Antibiotic Selection
01:28Gene Regulation in Microbial Communities: Quorum Sensing