BSAC recommendations for interpreting the susceptibility of urinary tract isolates

BSAC User Group Meeting 2007BSAC User Group Meeting 2007

BSAC recommendations for BSAC recommendations for interpreting the susceptibility of interpreting the susceptibility of

urinary tract isolatesurinary tract isolates

Jenny AndrewsJenny Andrews


UTIsUTIs

Frequency of micturitionFrequency of micturition

DysuriaDysuria

UrgencyUrgency

Suprapubic painSuprapubic pain

PyrexiaPyrexia

PyelonephritisPyelonephritis


Bacterial causes of UTIsBacterial causes of UTIsOrganismOrganism Community Community

Acquired (%)Acquired (%)Hospital Hospital

Acquired (%)Acquired (%)

E. coliE. coli 7575 4040

P. mirabilisP. mirabilis 33 1010

Other coliformsOther coliforms 55 2525

P. aeruginosaP. aeruginosa 11 55

E. faecalisE. faecalis 55 88

S. saprophyticusS. saprophyticus 55 11

S. epidermidisS. epidermidis 22 33


Non-bacterial causes of UTIsNon-bacterial causes of UTIs

Group Organism Infection

Viruses Adenoviruses Haemorrhagic cystitis

Human Polyoma Virus Infections in kidney and ureter

Parasites Trichomonas vaginalis Urethritis

Schistosoma haematobium

Bladder inflammation

Fungi Candida albicans UTI in immuno compromised patients


Simple UTIsSimple UTIs

Women of child-bearing ageWomen of child-bearing ageE. coliE. coliP. mirabilisP. mirabilisKlebsiellaeKlebsiellaeEnterococciEnterococciS. saprophyticusS. saprophyticusGroup B StreptococciGroup B Streptococci


Prevalence of organisms isolated from Prevalence of organisms isolated from samples taken in the community (female)samples taken in the community (female)

0 10 20 30 40 50 60 70 80

CNS

S. aureus

Pseudomonas

Enterobacter

Citrobacter

Enterococci

S.saprophyticus

Group B streps

P. mirabilis

Klebsiellae

E. coli

Percentage

City Hospital data


Complicated UTIsComplicated UTIs

Male patientsMale patients

Abnormal anatomyAbnormal anatomy

CatheterisationCatheterisation

ChildrenChildren

Immunocompromised patientsImmunocompromised patients

ElderlyElderly


Microbial causesMicrobial causes

Enterobacteriaceae Enterobacteriaceae

Non-fermentersNon-fermenters

StaphylococciStaphylococci

EnterococciEnterococci

Antibiotic-resistant strains frequently Antibiotic-resistant strains frequently isolatedisolated


UTI in menUTI in menAge groupAge group

(years)(years)

IncidenceIncidence

(%)(%)

CommentComment

20-6020-60 <1<1 Very uncommon. Occur in Very uncommon. Occur in young men who participate in young men who participate in anal sex, who are not anal sex, who are not circumcised or whose sexual circumcised or whose sexual partner is colonised with partner is colonised with uropathogensuropathogens

60-7060-70 33

>80>80 1010

Wallach, 2001; McMurdo and Gillespie, 2000


Conditions associated with or Conditions associated with or predisposing to lower UTI in menpredisposing to lower UTI in men

Prostatitis/Prostate enlargement Prostatitis/Prostate enlargement (common in older men)(common in older men)

Abnormal urinary tract, anatomical Abnormal urinary tract, anatomical changes,calculi and tumourschanges,calculi and tumours

Impaired host defencesImpaired host defences

Impaired renal functionImpaired renal function

Bailey 1996


E.coliE.coli the most common pathogen in the most common pathogen in acute and chronic prostatitisacute and chronic prostatitis

KlebsiellaKlebsiella spp. and spp. and P. mirabilisP. mirabilis isolated less frequentlyisolated less frequently

Hospital acute cases may involve Hospital acute cases may involve staphylococci and occasionally staphylococci and occasionally enterococci or enterococci or PseudomonasPseudomonas spp spp

UTI in men – organisms UTI in men – organisms associated with infectionassociated with infection


Prevalence of organisms isolated from Prevalence of organisms isolated from samples taken in the community (male)samples taken in the community (male)

0 10 20 30 40 50 60 70

Acinetobacter

C itrobacter

Morganella

Enterobacter

Group B strep

S. aureus

Serratia

Pseudomonas

CNS

Proteus

Enterococci

Klebsiellae

E. coli

Percentage

City Hospital data


Laboratory diagnosisLaboratory diagnosisMid Stream UrineMid Stream Urine

Low epithelial cell count Low epithelial cell count

Pyuria/haematuriaPyuria/haematuria

Semi-quantitative cultureSemi-quantitative culture

101055 cfu/ml bacteria considered significant cfu/ml bacteria considered significant

Identification (some laboratories do not ID Identification (some laboratories do not ID urine isolates) and susceptibility testingurine isolates) and susceptibility testing


BSAC: Systemic recommendationsBSAC: Systemic recommendationsNon-species specificNon-species specific

Table 6: MIC and zone breakpoints for Enterobacteriaceae (including Salmonella and Shigella spp.).

MIC breakpoint (mg/L)Interpretation of zone

diameters (mm)

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: Species specific breakpoints for simple UTIsBSAC: 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.


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: Species specific breakpoints for simple UTIsBSAC: Species specific breakpoints for simple UTIs


Organism IdentificationOrganism Identification

Essential for Essential for interpretation of interpretation of susceptibility susceptibility

Chromogenic mediaChromogenic media


Chromogenic agar Chromogenic agar (6570 UTI)(6570 UTI)

"Coliforms"

TDA +

E.coli

Klebsiella-Enterobacter-Serratia

28.6%

Proteus-Morganella-Providencia

6.9%

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)


Footnotes to the UTI tables


BSAC recommendationsBSAC recommendations

The recommendations are for organisms The recommendations are for organisms associated with uncomplicated urinary associated with uncomplicated urinary tract infectionstract infectionsFor complicated infections systemic For complicated infections systemic recommendations should be usedrecommendations should be usedFor infections caused by For infections caused by S. aureusS. aureus and and S. epidermidisS. epidermidis, which are associated with , which are associated with more serious infections, systemic more serious infections, systemic recommendations should be usedrecommendations should be used



If an organism is isolated from multiple If an organism is isolated from multiple sites, for example from blood and urine, sites, for example from blood and urine, interpretation of susceptibility should be interpretation of susceptibility should be made with regard to the systemic site.made with regard to the systemic site.

Direct susceptibility tests on urine may be Direct susceptibility tests on urine may be performed as long as the inoculum gives performed as long as the inoculum gives semi-confluent growth.semi-confluent growth.



In the absence of definitive organism In the absence of definitive organism identification, use the recommendations identification, use the recommendations most appropriate for the presumptive most appropriate for the presumptive identification, accepting that on some identification, accepting that on some occasions the interpretation may be occasions the interpretation may be incorrect. A more cautious approach is to incorrect. A more cautious approach is to use systemic recommendationsuse systemic recommendations



The identification of Enterobacteriaceae to The identification of Enterobacteriaceae to species level is essential before applying species level is essential before applying expert rule for the interpretation of expert rule for the interpretation of susceptibility e.g. recommendations for susceptibility e.g. recommendations for ampicillin/amoxicillin are for ampicillin/amoxicillin are for E. coliE. coli and and P. P. mirabilismirabilis not for species that have not for species that have chromosomal penicillinase (chromosomal penicillinase (KlebsiellaKlebsiella spp.) or those that typically have inducible spp.) or those that typically have inducible AmpC enzymes (e.g. AmpC enzymes (e.g. EnterobacterEnterobacter spp., spp., CitrobacterCitrobacter spp. and spp. and SerratiaSerratia spp.) spp.)


Under review by EUCAST/BSACUnder review by EUCAST/BSAC

Use of trimethoprim for the treatment Use of trimethoprim for the treatment of enterococciof enterococci

The clinical efficacy of mecillinam in The clinical efficacy of mecillinam in the treatment of ESBL infectionsthe treatment of ESBL infections


Gaps in the “Coliform” Gaps in the “Coliform” recommendationsrecommendations

““Coliform” means like an Coliform” means like an E. coliE. coli, the , the recommendations should not be used for recommendations should not be used for EnterobacterEnterobacter spp. etc. spp. etc.

ID to species level is essential for the ID to species level is essential for the correct interpretationcorrect interpretation


Should nalidixic acid be used to Should nalidixic acid be used to detect FQ resistance?detect FQ resistance?

Using nalidixic acid alone 25-40% of Using nalidixic acid alone 25-40% of isolates with LLR will be reported resistant isolates with LLR will be reported resistant to ciprofloxacinto ciprofloxacin

Organisms with LLR are probably Organisms with LLR are probably susceptible in uncomplicated infections susceptible in uncomplicated infections because of the high concentration of drug because of the high concentration of drug in urinein urine


SummarySummary

BSAC urinary breakpoints are for simple UTIsBSAC urinary breakpoints are for simple UTIsFor complicated infections systemic For complicated infections systemic recommendations should be usedrecommendations should be usedID is necessary for the interpretation of ID is necessary for the interpretation of susceptibility and the application of expert rules susceptibility and the application of expert rules (see the Power Point presentation on the BSAC (see the Power Point presentation on the BSAC web site for the User Group Meeting in 2005 web site for the User Group Meeting in 2005 Trevor Winstanley “Expert rules and inexpensive Trevor Winstanley “Expert rules and inexpensive identification methods”)identification methods”) EUCAST are preparing a document on expert EUCAST are preparing a document on expert rules that should be available at the end of the rules that should be available at the end of the yearyear

Documents

BSAC recommendations for interpreting the susceptibility of urinary tract isolates