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Gonococcal strains from homosexual men have outer membranes with reduced permeability to hydrophobic molecules
Abstract:
Loci designated penA, penB, and mtr contribute additively to penicillin G resistance in Neisseria gonorrhoeae; the mtr locus also confers resistance to hydrophobic dyes, detergents, and antibiotics, env mutations suppress the phenotypic expression of mtr and penB and are responsible for increased sensitivity to various hydrophobic molecules. We postulated that the host environment is important in the selection of gonococcal strains with these particular outer membrane phenotypes. Thus, mtr strains should predominate in environments that are high in hydrophobic molecules. To test this hypothesis we determined the outer membrane phenotype of 152 strains of N. gonorrhoeae. Rectal and urethral isolates from 58 homosexual men, urethral isolates from 55 heterosexual men, and cervical and rectal isolates from 39 heterosexual women were used in this study. Strains from 43 of the homosexual men were matched with those from heterosexual men with respect to auxotype and year and season of isolation. Cell envelope phenotype was determined for each strain on the basis of its resistance to various hydrophobic compounds. The identity of mtr strains was confirmed by genetic transformation. Among the matched pairs, mtr strains were significantly more prevalent among isolates from homosexual men than among those from heterosexual men (P = 0.03). Serogrouping by coagglutination demonstrated that 17 of 19 mtr strains versus 76 of 131 non-mtr strains belonged to coagglutination group WII (P = 0.01). Coagglutination group WII strains were also associated with homosexuality (P = 0.02). Gonococci were also tested for resistance to fecal lipids, mtr strains were more resistant to growth inhibition by fecal lipids than were non-mtr strains.
Insights
Neisseria gonorrhoeae strains with the mtr (multiple transferable resistance) locus are more prevalent in homosexual men and resistant to hydrophobic molecules like fecal lipids. This suggests the host environment influences gonococcal outer membrane phenotypes.
Area of Science:
- Microbiology
- Genetics
- Epidemiology
Background:
- The mtr locus in Neisseria gonorrhoeae confers resistance to various hydrophobic compounds, including antibiotics and detergents.
- env mutations can alter the expression of resistance loci, impacting sensitivity to hydrophobic molecules.
- The host environment is hypothesized to play a role in selecting for specific gonococcal outer membrane phenotypes.
Purpose of the Study:
- To investigate the prevalence of the mtr locus in Neisseria gonorrhoeae isolates from different host populations.
- To determine if the host environment, specifically factors associated with homosexuality, influences the selection of mtr strains.
- To correlate outer membrane phenotype with specific gonococcal serogroups and resistance to hydrophobic molecules.
Main Methods:
- Determined the outer membrane phenotype of 152 Neisseria gonorrhoeae strains based on resistance to hydrophobic compounds.
- Collected isolates from homosexual men, heterosexual men, and heterosexual women.
- Confirmed mtr strain identity using genetic transformation and serogrouping by coagglutination.
- Assessed resistance to fecal lipids.
Main Results:
- mtr strains were significantly more prevalent in isolates from homosexual men compared to heterosexual men (P = 0.03).
- mtr strains showed increased resistance to growth inhibition by fecal lipids.
- Coagglutination group WII strains were more frequently associated with mtr strains (P = 0.01) and homosexuality (P = 0.02).
Conclusions:
- The host environment, particularly factors associated with homosexuality, appears to select for Neisseria gonorrhoeae strains possessing the mtr locus.
- The mtr locus confers resistance to hydrophobic molecules, including fecal lipids, contributing to strain prevalence in specific environments.
- Outer membrane phenotype, serogroup, and host association are interconnected in Neisseria gonorrhoeae.