ast and the clinician

7/29/2019 AST and the Clinician

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AST and the Clinician

Piotr Chlebicki

Senior Consultant

Department of Infectious Diseases

SGH


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The assignment

Use of antibiotics in clinical practice:

- common infections- approach to diagnosis & treatment


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I modified it a bit

1. How do clinicians prescribe antibiotics ?

2. How does microbiology lab influenceprescribing?

3. A few clinical cases


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How do clinicians prescribe antibiotics?

A. Based on culture results

B. Empirically = 7 steps 1. Define the problem/disease/syndrome

2. Severe?

3. At risk of MDRO?

4. Immunocompromized?

5. List possible bugs and consider local

resistance patterns 6. Pick the best antibiotic

7. Decide duration


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How does microbiology lab

influence prescribing?

Organism identification and pathogen

susceptibility patterns Selective reporting

MIC reporting

Local epidemiology Choice of available tests

Rapid diagnostic tests

Automatic alerts for targeted pathogens


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Antibiograms

How many isolates? Duplicates? Outpatient?

When last updated? Impact on prescribing:

developing clinical pathways for empiric

antimicrobial treatment

monitoring resistance trends

updating the drug formulary

developing antimicrobial restriction policies


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Antibiogram


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Antibiogram single unit


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Selective antimicrobial

susceptibility reporting Susceptibilities are reported for only the most

appropriate and least expensive drugs towhich the organism is susceptible.

The use of a cascading microbiology report

encourages clinicians to select more narrow-spectrum and cost-effective antimicrobialagents.

Very effective!!


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Susceptibility pattern of urinaryE. coliAntibiotic Susceptibility

Ampicillin R

Co-amoxiclav S

Cephalexin S

Cefuroxime S

Cefotaxime S

Ceftazidime S

Cefepime S

Cefoxitin S

Pip-tazobactam S

Meropenem S

Ciprofloxacin S

Nitrofurantoin S

Co-trimoxazole S

Amikacin S

Gentamicin S


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Antimicrobial stewardship

there is an association between antibiotic susceptibility

reporting from microbiology laboratories and antibioticprescribing for the treatment of urinary tract infections.

Ciprofloxacin and risk of resistant organisms e.g.C. diffi


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Prospective interrupted time series

A. Before - susceptibility to amoxicillin,nitrof urantoin, trimethoprim and co-amoxiclav routinely

reported

B. After (9 months) - susceptibility to cefalexin wasreported in place of susceptibility to co-amoxiclav.


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Result


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Antimicrobial stewardship

Prioritization of tested antimicrobials and selective reportingof susceptibility profiles (e.g., not routinely reporting

susceptibility ofS. aureus to rifampin to prevent inadvertentmonotherapy with rifampin) can aid in the prudent use ofantimicrobials and direct appropriate therapy based on localguidelines


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MIC reporting





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MRSA MIC

2012 in SGH

Of the 112 tested isolates, 58 had MIC of 1.5or greater (51.8%)


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Case 1

52 year old man, PMH of DM, smoker

complains of fever and cough for 3 days. 120/70 HR 100, RR 25, 38.6C

Creps over rt lung


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2. Severe?

3. At risk of MDRO? 4. Immunocompromized?


resistance patterns 6. Pick the best antibiotic

7. Decide duration


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Diagnostic testing

Mild CAP = testing optional

More severe CAP = more testing


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MIC reporting





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Gram stain


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Quality of specimen Please reject


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Rapid diagnostic testing Urinary streptococcal antigen

Legionella urinary antigen Respiratory virus multiplex PCR

H d i bi l l b


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influence prescribing? Organism identification and pathogen


MIC reporting





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Antibiotics Likely pathogens

Antimicrobial resistance

Can he be treated with azithromycin alone?

How about IV penicilln and Klacid?


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Spectrum IPD - Singapore experience

Journal of Medical Microbiology (2009), 58, 101104


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Methods All invasive pneumococcal isolates cultured

from sterile sites from adult patientshospitalized at SGH between 1 January 2000

and 31 December 2007


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Results Pneumococcal isolates from 192 patients

Blood cultures (92.7 %) Pleural fluid (2.1 %)

Intraophthalmic (1.6 %)

CSF (1.0 %) Synovium (1.0 %),


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Resistance in SGH The median penicillin MIC was 0.016 mg/ml

(range 0.0162 mg/ml)

Median ceftriaxone MIC 0.016 mg/ml (range

0.0041 mg/ml)


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Resistance in SGH All 186 non-meningitis isolates would be

classified as penicillin-susceptiblefollowing the new CLSI breakpoints

One isolate from a patient with meningitis had

an MIC to penicillin of 2 mg/ml, but the otherfive isolates were susceptible.

Ceftriaxone MIC >0.5 = 6/192 cases (3.13%)


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NARSS 2010


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Guideline


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Case 2 33 yo woman presents to Bedok polyclinic

with dysuria, urgency and frequency x 2 days. She has no fever or flank pain.

She had 2 similar episodes in the past 2

years


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2. Severe?

3. At risk of MDRO? 4. Immunocompromized?


resistance patterns

6. Pick the best antibiotic

7. Decide duration


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What is the bug?


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Which antibiotic? Depends on the prevalence of resistance in a

community IDSA suggests thresholds above which a

drug is not recommended

20% for trimethoprimsulfamethoxazole 10% for fluoroquinolones



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MIC reporting





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Old, good times (2002)


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New, not that good times (2009)


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Methods and patients Bedok Polyclinic

January 1 to December 31, 2009 1,352 patients coded as UTI

666 (49.3%) patients had urine cultures

333 (50%) culture-positive

34 , 299

1365 years = 214

> 65 years = 117


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Limitations No correlation with symptoms

No correlation with pyuria No attempt to differentiate true community

acquired vs healthcare associated


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Case 3 Hematology department in SGH introduced

febrile neutropenia protocol several yearsago. Cefepime was the drug of choice for

empiric therapy

Recent studies and resistance trends suggestthat it may not be the best choice

Is there any other antibiotic that is better?


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Cefepime versus other All-cause mortality was significantly higher

with cefepime as compared with otherantibiotics, RR 1.39 [1.04, 1.86], without

heterogeneity 21 trials, 3471 participants


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Piperacillin-tazobactam versus other

All-cause mortality was lower with

piperacillin-tazobactam versus all otherantibiotics , RR 0.56 [0.34, 0.92], 8 trials,

1314 participants

The difference was statistically significantalso in the comparison restricted to

carbapenems, RR 0.46 [0.22, 0.95].



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MIC reporting

Local epidemiology

Choice of available tests




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SGH data for hematology 2012


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CGH data, ESBL E coli, 2012

C 3


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Case 3

Febrile neutropenia protocol was changed

Pip tazo or cefepime plus amikacin will beused for the empiric therapy of febrileneutropenia


i fl ibi ?


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MIC reporting




S


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Summary

The impact of microbiology lab on prescribersis profound

It not only influence the choice of antibioticsfor individual patients but also hospital

policies and guidelines

ast and the clinician

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