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Clinical sciences oral session 3—diagnostic testing: chlamydia & gonorrhoeae
O3-S3.03 Differing Neisseria gonorrhoeae bacterial loads in the pharynx and rectum: implications for gonococcal detection, transmission and control
  1. M Bissessor1,
  2. S Tabrizi2,
  3. C Fairley1,
  4. J Danielewski2,
  5. B Whitton1,
  6. S Bird1,
  7. S Garland2,
  8. M Chen1
  1. 1Melbourne Sexual Health Centre Carlton, Australia
  2. 2Royal Womens hospital, Australia

Abstract

Background To help improve our understanding of the potential transmissibility of gonococcal infections from the pharynx and rectum we measured gonococcal bacterial loads at these sites and examined clinical and laboratory determinants of these loads.

Methods Men who had sex with men were tested for pharyngeal and rectal gonorrhoea by culture using modified Thayer Martin medium and by two real-time quantitative qPCRs targetting opa gene, and porA pseudogene.

Results 1011 rectal and 1076 pharyngeal specimens were obtained from 1076 MSM. Forty three (3.9%) pharyngeal specimens were PCR positive of which 17 were culture positive (sensitivity 39%, 95% CI: 25% to 54%). Forty seven (4.6%) rectal specimens were PCR positive of which 25 were also culture positive (sensitivity 58%, 95% CI 44% to 71%). The median bacterial load among PCR positive rectal infections (18 960 copies per swab) was significantly higher than that for PCR positive pharyngeal infections (2,100 copies per swab) (p=0.001). The median bacterial load among men with symptomatic rectal infection was higher (278 800 copies per swab) than with asymptomatic men, PCR positive rectal infections (13,980 copies per swab, p<0.001). The median bacterial load of gonorrhoea was significantly higher in culture positive than culture negative specimens. This applied for both rectal (p<0.001) as well as pharyngeal infections (p=0.03).

Conclusion Higher bacterial loads of gonorrhoea were observed in rectal infections, particularly with symptomatic rectal infections. This has implications for gonococcal transmission and control.

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