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Determination of the antimicrobial susceptibility of Neisseria gonorrhoeae

Determination of the antimicrobial susceptibility of Neisseria gonorrhoeae. Trevor Winstanley Rebecca Clarke Department of Microbiology Royal Hallamshire Hospital Sheffield UK. 29 July 2003 Freeman Hospital. Gonorrhoea.

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Determination of the antimicrobial susceptibility of Neisseria gonorrhoeae

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  1. Determination of the antimicrobial susceptibility of Neisseria gonorrhoeae Trevor Winstanley Rebecca Clarke Department of Microbiology Royal Hallamshire Hospital Sheffield UK 29 July 2003 Freeman Hospital

  2. Gonorrhoea 2nd most common bacterial STD > 22,500 episodes diagnosed in GUM clinics in England & Wales (2001) Highest incidence Males 20-24 256/100,000 Females 16-19 198/100,000

  3. Epidemiology • Concentrated within demographic and behavioural risk groups • High-levels of • re-infection • concurrent STDs • asymptomatic infection

  4. Public health concern • Increasing incidence • Poor reproductive and sexual health outcomes • High prevalence of resistance • onward transmission • adverse clinical sequelae

  5. Antimicrobial resistance • 10 -12% of gonococcal isolates are resistant to some degree • inner cities • those acquiring infections abroad • gay and bisexual men

  6. Plasmid-mediated

  7. Chromosomal

  8. Chromosomal

  9. U.K. guidelines • Easily treatable • 95% cure from 1st line therapy • Penicillins • Fluoroquinolones • ciprofloxacin, ofloxacin • Cephalosporins • ceftriaxone, cefixime • (Doxycycline / tetracycline)

  10. GRASP • Gonococcal Resistance to Antimicrobials Surveillance Programme • DoH sentinel surveillance • PHLS Communicable Disease Surveillance Centre (CDSC) • PHLS Genitourinary Infections Reference Laboratory (GUIRL) • Department of Infectious Diseases & Microbiology at Imperial College

  11. GRASP 2001 (n = 2666)

  12. Cure rates Uncomplicated genital gonorrhoea Recommended dosage Susceptible > 95% Intermediate 90-95% Resistant < 90% WHO; SRGA; NCCLS

  13. Media NCCLS SRGA BSAC ARMRL GRASP

  14. Objectives • To validate the BSAC disc diffusion method for N.gonorrhoeae • to translate reference into routine • To confirm or refute tentative breakpoints • To extend the range of interpretive criteria

  15. Methodology • 222 distinct isolates from 5 geographical regions • 5 WHO control strains • Disc diffusion tests, MICs • BSAC methodology • ß-lactamase • Nitrocefin

  16. Penicillin

  17. Amoxycillin

  18. Co-amoxyclav

  19. Ciprofloxacin

  20. Nalidixic acid

  21. Tetracycline

  22. Metzler & DeHaan analysis

  23. The MIC breakpoint has been lowered to ensure that isolates with reduced susceptibility to ciprofloxacin are detected.

  24. Quinolone resistance is most reliably detected with nalidixic acid. Strains with reduced susceptibility to fluoroquinolones have no zone of inhibition with nalidixic acid.

  25. Test for -lactamase.

  26. Resistance to ceftriaxone has not been described. Isolates with chromosomally encoded penicillin resistance (low level) have slightly reduced zones of inhibition with ceftriaxone but remain susceptible. Confirm by MIC.

  27. Use tetracycline result to infer susceptibility to doxycycline. Isolates with plasmid-mediated resistance have no zones of inhibition and those with low-level chromosomal resistance have zones 14-26 mm

  28. Next? Cefixime

  29. Clap!

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