Molecular typing of Neisseria gonorrhoeae causing repeated infections: evolution of porin during passage within a...

Area of Science:

• Microbiology
• Genetics
• Epidemiology

Background:

• Neisseria gonorrhoeae causes gonorrhea, a prevalent sexually transmitted infection.
• Understanding gonococcal strain diversity and transmission is crucial for effective control.
• Serotyping is a traditional method for classifying gonococcal strains, but its discriminatory power can be limited.

Purpose of the Study:

• To compare the discriminatory power of three molecular typing techniques (por gene sequencing, opa-typing, arbitrarily primed-polymerase chain reaction) against serotyping for Neisseria gonorrhoeae.
• To investigate the genetic relatedness of gonococcal isolates from individuals with multiple infections by the same serovar.
• To explore evidence of genetic variation within Neisseria gonorrhoeae during community transmission.

Main Methods:

• Comparison of three molecular typing techniques: por gene sequencing, opa-typing, and arbitrarily primed-polymerase chain reaction.
• Analysis of 33 Neisseria gonorrhoeae isolates from 15 individuals with multiple infections by the same serovar.
• Sequence analysis of por genes to identify mutations and horizontal genetic exchange.

Main Results:

• All three molecular techniques demonstrated higher discriminatory power than serotyping.
• Differences were identified between isolates within the same serovar using molecular methods.
• Despite some sequence variations, 10 out of 15 subjects were reinfected with gonococci expressing identical Por proteins.
• Sequence analysis revealed evidence of horizontal genetic exchange and point mutations in potential surface-exposed regions of the por gene.

Conclusions:

• Molecular typing methods, particularly por gene sequencing, provide enhanced resolution for Neisseria gonorrhoeae strain characterization compared to serotyping.
• Reinfection with gonococci expressing identical Por proteins suggests that Por protein sequence may not always be the primary determinant of reinfection or that rapid genetic changes occur.
• The findings indicate the occurrence of horizontal genetic exchange and point mutations in por genes during Neisseria gonorrhoeae transmission in the community, contributing to strain evolution.