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 n 2 nd most common bacterial STD n n > 22, 500 episodes diagnosed in GUM clinics in England & Wales (2001) Highest incidence Males 20 -24 n Females 16 -19 n 256/100, 000 198/100, 000
Epidemiology Concentrated within demographic and behavioural risk groups n High-levels of n re-infection n concurrent STDs n asymptomatic infection n
Public health concern Increasing incidence n Poor reproductive and sexual health outcomes n High prevalence of resistance n onward transmission n adverse clinical sequelae n
Antimicrobial resistance n 10 -12% of gonococcal isolates are resistant to some degree inner cities n those acquiring infections abroad n gay and bisexual men n
Plasmid-mediated ß-lactamase Tetracycline PPNG Positive < 16 mg/L TRNG Negative 16 mg/L PP/TRNG Positive 16 mg/L
Chromosomal ß-lactamase Penicillin Tetracycline Pen. R Negative 1 mg/L < 2 mg/L Tet. R Negative < 1 mg/L 2 - 8 mg/L CMRNG Negative 1 mg/L 2 - 8 mg/L
Chromosomal Ciprofloxacin Intermediate 0. 125 < 1 mg/L Resistant 1 mg/L Spectinomycin Resistant 128 mg/L Ceftriaxone Decreased 0. 5 mg/L Azithromycin Resistant 1 mg/L
U. K. guidelines n Easily treatable n n n Penicillins Fluoroquinolones n n ciprofloxacin, ofloxacin Cephalosporins n n 95% cure from 1 st line therapy ceftriaxone, cefixime (Doxycycline / tetracycline)
GRASP n n Gonococcal Resistance to Antimicrobials Surveillance Programme Do. H sentinel surveillance n PHLS Communicable Disease Surveillance Centre (CDSC) n PHLS Genitourinary Infections Reference Laboratory (GUIRL) n Department of Infectious Diseases & Microbiology at Imperial College
GRASP 2001 (n = 2666) Penicillin Tetracycline Ciprofloxacin Azithromycin Spectinomycin Ceftriaxone Plasmid 3. 0% Chromosome 5. 1% Plasmid 4. 6% Chromosome 27. 9% Intermediate 2. 6% Resistant 3. 1% Resistant 0. 3% Resistant ND
Cure rates Uncomplicated genital gonorrhoea Recommended dosage Susceptible > 95% n Intermediate 90 -95% n Resistant < 90% n WHO; SRGA; NCCLS
Media n n n NCCLS SRGA BSAC ARMRL GRASP
Objectives n To validate the BSAC disc diffusion method for N. gonorrhoeae n to translate reference into routine To confirm or refute tentative breakpoints n To extend the range of interpretive criteria n
Methodology 222 distinct isolates from 5 geographical regions n 5 WHO control strains n Disc diffusion tests, MICs n n n BSAC methodology ß-lactamase n Nitrocefin
Penicillin
Amoxycillin
Co-amoxyclav
Ciprofloxacin
Nalidixic acid
Tetracycline
Metzler & De. Haan analysis
Antibiotic Spectinomycin MIC breakpoint (mg/L) R S 128 64 Zone diameter (mm) Disc content 25 R S 13 14
Antibiotic Spectinomycin Ciprofloxacin MIC breakpoint (mg/L) R Low 128 - 64 25 13 - 14 2 0. 12 -1 0. 06 1 14 15 -28 29 R S Zone diameter (mm) Disc content R Low R S The MIC breakpoint has been lowered to ensure that isolates with reduced susceptibility to ciprofloxacin are detected.
Antibiotic Spectinomycin MIC breakpoint (mg/L) R S 128 64 Ciprofloxacin 2 Nalidixic acid - 0. 12 -1 Zone diameter (mm) Disc content R S 25 13 14 0. 06 1 14 - 30 - 15 -28 Quinolone resistance is most reliably detected with nalidixic acid. Strains with reduced susceptibility to fluoroquinolones have no zone of inhibition with nalidixic acid. 29 -
Antibiotic MIC breakpoint (mg/L) R Low 128 - 64 25 13 - 14 Ciprofloxacin 2 0. 12 -1 0. 06 1 14 15 -28 29 Nalidixic acid - - - 30 - - - Penicillin 2 0. 12 -1 0. 06 1 unit 17 18 -25 26 Spectinomycin Test for -lactamase. R S Zone diameter (mm) Disc content R Low R S
Antibiotic MIC breakpoint (mg/L) R Low 128 - 64 25 13 - 14 Ciprofloxacin 2 0. 12 -1 0. 06 1 14 15 -28 29 Nalidixic acid - - - 30 - - - Penicillin 2 0. 12 -1 0. 06 1 unit 17 18 -25 26 Cefuroxime 2 - 1 5 19 - 20 Ceftriaxone 0. 5 - 0. 25 5 34 - 35 Spectinomycin R S Zone diameter (mm) Disc content R Low R S 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.
Antibiotic MIC breakpoint (mg/L) R Low 128 - 64 25 13 - 14 Ciprofloxacin 2 0. 12 -1 0. 06 1 14 15 -28 29 Nalidixic acid - - - 30 - - - Penicillin 2 0. 12 -1 0. 06 1 unit 17 18 -25 26 Cefuroxime 2 - 1 5 19 - 20 Ceftriaxone 0. 5 - 0. 25 5 34 - 35 Tetracycline 2 - 1 10 13 14 -26 27 Spectinomycin R S Zone diameter (mm) Disc content R Low R S 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
Antibiotic MIC breakpoint (mg/L) R Low 128 - 64 25 13 - 14 Ciprofloxacin 2 0. 12 -1 0. 06 1 14 15 -28 29 Nalidixic acid - - - 30 - - - Penicillin 2 0. 12 -1 0. 06 1 unit 17 18 -25 26 Cefuroxime 2 - 1 5 19 - 20 Ceftriaxone 0. 5 - 0. 25 5 34 - 35 Tetracycline 2 - 1 10 13 14 -26 27 Erythromycin 1 - 0. 5 5 11 - 12 Azithromycin 2 - 1 15 27 - 28 Rifampicin 2 - 1 2 20 - 21 Spectinomycin R S Zone diameter (mm) Disc content R Low R S
Antibiotic MIC breakpoint (mg/L) R Low 128 - 64 25 13 - 14 Ciprofloxacin 2 0. 12 -1 0. 06 1 14 15 -28 29 Nalidixic acid - - - 30 - - - Penicillin 2 0. 12 -1 0. 06 1 unit 17 18 -25 26 Cefuroxime 2 - 1 5 19 - 20 Ceftriaxone 0. 5 - 0. 25 5 34 - 35 Tetracycline 2 - 1 10 13 14 -26 27 Erythromycin 1 - 0. 5 5 11 - 12 Azithromycin 2 - 1 15 27 - 28 Rifampicin 2 - 1 2 20 - 21 Spectinomycin R S Zone diameter (mm) Disc content R Low R S
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