Knowledge Application Systems
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Transcript Knowledge Application Systems
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
2nd most common bacterial STD
> 22,500 episodes diagnosed in GUM
clinics in England & Wales (2001)
Highest incidence
Males
20-24
Females
16-19
256/100,000
198/100,000
Epidemiology
Concentrated within demographic
and behavioural risk groups
High-levels of
re-infection
concurrent STDs
asymptomatic infection
Public health concern
Increasing incidence
Poor reproductive and sexual
health outcomes
High prevalence of resistance
onward transmission
adverse clinical sequelae
Antimicrobial resistance
10 -12% of gonococcal isolates are
resistant to some degree
inner cities
those acquiring infections abroad
gay and bisexual men
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
PenR
Negative
1 mg/L
< 2 mg/L
TetR
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
Easily treatable
Penicillins
Fluoroquinolones
ciprofloxacin, ofloxacin
Cephalosporins
95% cure from 1st line therapy
ceftriaxone, cefixime
(Doxycycline / tetracycline)
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
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%
Intermediate 90-95%
Resistant
< 90%
WHO; SRGA; NCCLS
Media
NCCLS
SRGA
BSAC
ARMRL
GRASP
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
Methodology
222 distinct isolates from 5
geographical regions
5 WHO control strains
Disc diffusion tests, MICs
BSAC methodology
ß-lactamase
Nitrocefin
Penicillin
30
MIC
(mg/L)
Number of isolates
25
32
16
20
8
4
2
15
1
0.5
10
0.25
0.125
5
0.064
0.032
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
Zone diameter (mm)
32
34
36
38
40
42
44
46
48
0.016
0.008
0.004
Amoxycillin
30
MIC
(mg/L)
Number of isolates
25
32
16
8
20
4
2
1
0.5
0.25
15
10
0.125
0.064
0.032
0.016
5
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Zone diameter (mm)
30
32
34
36
38
40
42
44
46
0.008
0.004
Co-amoxyclav
30
MIC
(mg/L)
25
Number of isolates
32
16
20
8
4
2
15
1
0.5
0.25
10
0.125
5
0.064
0.032
0.016
0
6
8
10
12
14
16
18
20
22
24
26
28
30
32
Zone diameter (mm)
34
36
38
40
42
44
46
48
50
0.008
0.004
Ciprofloxacin
35
MIC
(mg/L)
Number of isolates
30
32
16
25
8
4
20
2
1
15
0.5
0.25
10
0.125
0.064
5
0.032
0.016
0
2
4
6
8
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58
Zone diameter (mm)
0.008
0.004
Nalidixic acid
50
MIC
(mg/L)
45
32
Num ber of isolates
40
16
8
35
4
30
2
1
25
0.5
20
0.25
0.125
15
0.064
10
0.032
0.016
5
0.008
0
0.004
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Zone diameter (mm)
30
32
34
36
38
40
42
44
46
48
Tetracycline
30
MIC
(mg/L)
25
Number of isolates
16
8
20
4
2
1
15
0.5
0.25
10
5
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
Zone diameter (mm)
32
34
36
38
40
42
44
46
48
50
Metzler & DeHaan analysis
MIC breakpoint (mg/L)
Antibiotic
Spectinomycin
R
S
128
64
Zone diameter (mm)
Disc
content
25
R
S
13
14
MIC breakpoint (mg/L)
Antibiotic
Spectinomycin
Ciprofloxacin
Zone diameter (mm)
Disc
content
R Low R S
R
Low R
S
128
-
64
25
13
-
14
2
0.12-1
0.06
1
14
15-28
29
The MIC breakpoint has been lowered to ensure that
isolates with reduced susceptibility to ciprofloxacin are
detected.
MIC breakpoint (mg/L)
Antibiotic
Spectinomycin
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
-
MIC breakpoint (mg/L)
Antibiotic
Zone diameter (mm)
Disc
content
R Low R S
R
Low R
S
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.
MIC breakpoint (mg/L)
Antibiotic
Zone diameter (mm)
Disc
content
R Low R S
R
Low R
S
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
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.
MIC breakpoint (mg/L)
Antibiotic
Zone diameter (mm)
Disc
content
R Low R S
R
Low R
S
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
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
MIC breakpoint (mg/L)
Antibiotic
Zone diameter (mm)
Disc
content
R Low R S
R
Low R
S
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
MIC breakpoint (mg/L)
Antibiotic
Zone diameter (mm)
Disc
content
R Low R S
R
Low R
S
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
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Cefixime
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