BSAC recommendations for
interpreting the susceptibility of
urinary tract isolates
Jenny Andrews
BSAC User Group Meeting 2007
UTIs
Frequency of micturition
Dysuria
Urgency
Suprapubic pain
Pyrexia
Pyelonephritis
BSAC User Group Meeting 2007
Bacterial causes of UTIs
Organism
Community
Acquired (%)
Hospital
Acquired (%)
E. coli
75
40
P. mirabilis
3
10
Other coliforms
5
25
P. aeruginosa
1
5
E. faecalis
5
8
S. saprophyticus
5
1
S. epidermidis
2
3
BSAC User Group Meeting 2007
Non-bacterial causes of UTIs
G ro u p
O rg a n is m
In fe c tio n
V iru s e s
A d e n o viru s e s
H a e m o rrh a g ic c ys titis
H u m a n P o lyo m a V iru s
In fe c tio n s in k id n e y a n d
u re te r
U re th ritis
P a ra s ite s
T ric h o m o n a s va g in a lis
Fungi
S c h is to s o m a
h a e m a to b iu m
C a n d id a a lb ic a n s
B la d d e r in fla m m a tio n
U T I in im m u n o
c o m p ro m is e d p a tie n ts
BSAC User Group Meeting 2007
Simple UTIs
Women of child-bearing age
E. coli
P. mirabilis
Klebsiellae
Enterococci
S. saprophyticus
Group B Streptococci
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Prevalence of organisms isolated from
samples taken in the community (female)
City Hospital data
E. coli
Klebsiellae
P. mirabilis
Group B streps
S.saprophyticus
Enterococci
Citrobacter
Enterobacter
Pseudomonas
S. aureus
CNS
0
10
20
30
40
Percentage
BSAC User Group Meeting 2007
50
60
70
80
Complicated UTIs
Male patients
Abnormal anatomy
Catheterisation
Children
Immunocompromised patients
Elderly
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Microbial causes
Enterobacteriaceae
Non-fermenters
Staphylococci
Enterococci
Antibiotic-resistant strains frequently
isolated
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UTI in men
Age group
(years)
Incidence
(%)
Comment
20-60
<1
Very uncommon. Occur in
young men who participate in
anal sex, who are not
circumcised or whose sexual
partner is colonised with
uropathogens
60-70
3
>80
10
Wallach, 2001; McMurdo and Gillespie, 2000
BSAC User Group Meeting 2007
Conditions associated with or
predisposing to lower UTI in men
Prostatitis/Prostate enlargement
(common in older men)
Abnormal urinary tract, anatomical
changes,calculi and tumours
Impaired host defences
Impaired renal function
Bailey 1996
BSAC User Group Meeting 2007
UTI in men – organisms
associated with infection
E.coli the most common pathogen in
acute and chronic prostatitis
Klebsiella spp. and P. mirabilis
isolated less frequently
Hospital acute cases may involve
staphylococci and occasionally
enterococci or Pseudomonas spp
BSAC User Group Meeting 2007
Prevalence of organisms isolated from
samples taken in the community (male)
City Hospital data
E . c o li
Kle bs ie lla e
E nt e ro c o c c i
P ro t e us
CNS
P s e udo m o na s
S e rra t ia
S . a ure us
G ro up B s t re p
E nt e ro ba c t e r
M o rga ne lla
C it ro ba c t e r
A c ine t o ba c t e r
0
10
20
30
40
Percentage
BSAC User Group Meeting 2007
50
60
70
Laboratory diagnosis
Mid Stream Urine
Low epithelial cell count
Pyuria/haematuria
Semi-quantitative culture
105 cfu/ml bacteria considered
significant
Identification (some laboratories do not
ID urine isolates) and susceptibility
testing
BSAC User Group Meeting 2007
BSAC: Systemic recommendations
Non-species specific
Table 6: MIC and zone breakpoints for Enterobacteriaceae (including Salmonella and Shigella spp.).
Interpretation of zone
diameters (mm)
MIC breakpoint (mg/L)
Antibiotic
R>
I
S
Disc content
(µg)
R
I
S
Amikacin1
16
16
8
30
15
16-18
19
Amoxicillin2
16
16
8
10
11
12-14
15
Ampicillin2
16
16
8
10
11
12-14
15
Aztreonam3
8
2-8
1
30
22
23-27
28
Cefaclor
1
-
1
30
34
-
35
Cefamandole4,5
8
-
8
30
19
-
20
Cefepime
8
2-8
1
30
26
27-31
32
Cefixime
1
-
1
5
19
-
20
BSAC User Group Meeting 2007
BSAC: Species specific breakpoints for simple UTIs
Interpretation of zone diameters (mm)
MIC breakpoint (mg/L)
Coliforms
Escherichia coli
Proteus mirabilis
Antibiotic
R>
I
S
Disc content (µg)
R
I
S
R

I
S
R

I
S
Amoxicillin5
32
-
32
25
11
-
12
11
-
12
11
-
12
Ampicillin5
32
-
32
25
11
-
12
11
-
12
11
-
12
Cefalexin6
32
-
32
30
-
-
-
15
-
16
11
-
12
Ciprofloxacin
4
-
4
1
19
-
20
19
-
20
19
-
20
Co-amoxiclav
32
-
32
20/10
11
-
12
11
-
12
11
-
12
Fosfomycin7,8
128
-
128
200/50
-
-
-
19
-
20
33
-
34
Mecillinam9
8
-
8
10
-
-
-
13
-
14
13
-
14
Nalidixic acid
16
-
16
30
17
-
18
17
-
18
17
-
18
Nitrofurantoin
32
-
32
200
-
-
-
19
-
20
-
-
-
Norfloxacin
4
-
4
2
15
-
16
15
-
16
15
-
16
Temocillin
32
-
32
30
11
-
12
11
-
12
11
-
12
Trimethoprim
2
-
2
2.5
16
-
17
16
-
17
16
-
17
NB. These recommendations are for organisms associated with uncomplicated urinary tract infections.
For complicated infections systemic recommendations should be used.
BSAC User Group Meeting 2007
BSAC: Species specific breakpoints for simple UTIs
Interpretation of zone diameters (mm)
MIC breakpoint
(mg/L)
Enterococci
Staphylococcus
saprophyticus
Group B streptococci
Antibiotic
R>
I
S
Disc
content (µg)
R
I
S
R
I
S
R
I
S
Ampicillin
32
-
32
25
19
-
20
25
-
26
25
-
26
Cefalexin3
32
-
32
30
-
-
-
-
-
-
23
-
24
Ciprofloxacin
4
-
4
1
11
-
12
17
-
18
12
-
13
Ciprofloxacin
4
-
4
5
15
-
16
-
-
-
18
-
19
Co-amoxiclav
32
-
32
20/10
20
-
21
27
-
28
27
-
28
Fosfomycin4
128
-
128
200/50
19
-
20
19
-
20
-
-
-
Mecillinam
64
-
64
50
-
-
-
9
-
10
-
-
-
Nalidixic acid
16
-
16
30
17
-
18
-
-
-
-
-
-
Nitrofurantoin
32
-
32
200
14
-
15
19
-
20
19
-
20
Norfloxacin
4
-
4
2
15
-
16
-
-
-
-
-
-
Trimethoprim5
2
-
2
2.5
21
-
22
14
-
15
15
-
16
NB. These recommendations are for organisms associated with uncomplicated urinary tract infections.
For complicated infections and infections caused by Staphylococcus aureus and Staphylococcus epidermidis,
which are associated with more serious infections, systemic recommendations should be used.
BSAC User Group Meeting 2007
Organism Identification
Essential for
interpretation of
susceptibility
Chromogenic media
BSAC User Group Meeting 2007
Chromogenic agar (6570 UTI)
"Coliforms"
Klebsiella-Enterobacter-Serratia
28.6%
TDA +
Proteus-Morganella-Providencia
6.9%
E.coli
72.5%
Data presented by Trevor Winstanley at User Group meetings in 2005
(Power Point presentation available on the BSAC web site (www.bsac.org.uk)
BSAC User Group Meeting 2007
Footnotes to the UTI tables
BSAC User Group Meeting 2007
BSAC recommendations
The recommendations are for organisms
associated with uncomplicated urinary
tract infections
For complicated infections systemic
recommendations should be used
For infections caused by S. aureus and
S. epidermidis, which are associated with
more serious infections, systemic
recommendations should be used
BSAC User Group Meeting 2007
BSAC recommendations
If an organism is isolated from multiple
sites, for example from blood and urine,
interpretation of susceptibility should be
made with regard to the systemic site.
Direct susceptibility tests on urine may be
performed as long as the inoculum gives
semi-confluent growth.
BSAC User Group Meeting 2007
BSAC recommendations
In the absence of definitive organism
identification, use the recommendations
most appropriate for the presumptive
identification, accepting that on some
occasions the interpretation may be
incorrect. A more cautious approach is to
use systemic recommendations
BSAC User Group Meeting 2007
BSAC recommendations
The identification of Enterobacteriaceae to
species level is essential before applying
expert rule for the interpretation of
susceptibility e.g. recommendations for
ampicillin/amoxicillin are for E. coli and P.
mirabilis not for species that have
chromosomal penicillinase (Klebsiella
spp.) or those that typically have inducible
AmpC enzymes (e.g. Enterobacter spp.,
Citrobacter spp. and Serratia spp.)
BSAC User Group Meeting 2007
Under review by EUCAST/BSAC
Use of trimethoprim for the treatment
of enterococci
The clinical efficacy of mecillinam in
the treatment of ESBL infections
BSAC User Group Meeting 2007
Gaps in the “Coliform”
recommendations
“Coliform” means like an E. coli, the
recommendations should not be used for
Enterobacter spp. etc.
ID to species level is essential for the
correct interpretation
BSAC User Group Meeting 2007
Should nalidixic acid be used to
detect FQ resistance?
Using nalidixic acid alone 25-40% of
isolates with LLR will be reported resistant
to ciprofloxacin
Organisms with LLR are probably
susceptible in uncomplicated infections
because of the high concentration of drug
in urine
BSAC User Group Meeting 2007
Summary
BSAC urinary breakpoints are for simple UTIs
For complicated infections systemic
recommendations should be used
ID is necessary for the interpretation of
susceptibility and the application of expert rules
(see the Power Point presentation on the BSAC
web site for the User Group Meeting in 2005
Trevor Winstanley “Expert rules and inexpensive
identification methods”)
EUCAST are preparing a document on expert
rules that should be available at the end of the
year
BSAC User Group Meeting 2007