ast and the clinician (4)

7/29/2019 AST and the Clinician (4)

1/15

AST and the Clinician

Piotr Chlebicki

Senior Consultant

Department of Infectious DiseasesSGH

The assignment

Use of antibiotics in clinical practice:

- common infections- approach to diagnosis & treatment

I modified it a bit

1. How do clinicians prescribe antibiotics ?

2. How does microbiology lab influence

prescribing?

3. A few clinical cases


2/15

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

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

Antibiograms

How many isolates? Duplicates? Outpatient?When last updated?

Impact on prescribing:

developing clinical pathways for empiricantimicrobial treatment

monitoring resistance trends

updating the drug formulary

developing antimicrobial restriction policies

Antibiogram


3/15

Antibiogram single unit

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

Very effective!!

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

Antimicrobial stewardship

there is an association between antibiotic susceptibilityreporting from microbiology laboratories and antibiotic

prescribing for the treatment of urinary tract infections.

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


4/15

Prospective in terrupted 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.

Result

Antimicrobial stewardship

Prioritization of tested antimicrobials and selective reportingof susceptibility profiles (e.g., not routinely reportingsusceptibility ofS. aureus to rifampin to prevent inadvertentmonotherapy with rifampin) can aid in the prudent use ofantimicrobials and direct appropriate therapy based on localguidelines



Organism identification and pathogensusceptibility patterns

Selective reporting

MIC reporting

Local epidemiology





5/15

MRSA MIC

2012 in SGH

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

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



B. Empirically = 7 steps

1. Define the problem/disease/syndrome

2. Severe?

3. At risk of MDRO?



resistance patterns

6. Pick the best antibiotic 7. Decide duration


6/15

Diagnostic testing

Mild CAP = testing optional

More severe CAP = more testing





MIC reporting

Local epidemiology




Gram stain Quality of specimen

Please re ject


7/15

Rapid diagnostic testing

Urinary streptococcal antigen

Legionella urinary antigen

Respiratory virus multiplex PCR





MIC reporting

Local epidemiology




Antibiotics

Likely pathogens

Antimicrobial resistance

Can he be treated with azithromycin alone?

How about IV penicilln and Klacid?


8/15

Spectrum IPD - Singapore experience

Journal of Medical Microbiology (2009), 58, 101104

Methods

All invasive pneumococcal isolates culturedfrom sterile sites from adult patients

hospitalized at SGH between 1 January 2000and 31 December 2007

Results

Pneumococcal isolates from 192 patients

Blood cultures (92.7 %)

Pleural fluid (2.1 %)

Intraophthalmic (1.6 %)

CSF (1.0 %)

Synovium (1.0 %),


9/15

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)

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 other

five isolates were susceptible.

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

NARSS 2010 Guideline


10/15

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



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

2. Severe?

3. At risk of MDRO?



resistance patterns

6. Pick the best antibiotic

7. Decide duration

What is the bug? Which antibiotic?

Depends on the prevalence of resistance in acommunity

IDSA suggests thresholds above which adrug is not recommended

20% for trimethoprimsulfamethoxazole

10% for fluoroquinolones


11/15





MIC reporting

Local epidemiology




Old, good times (2002)

New, not that good times (2009) 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


12/15

Limitations

No correlation with symptoms

No correlation with pyuria

No attempt to differentiate true community

acquired vs healthcare associated

Case 3

Hematology department in SGH introducedfebrile neutropenia protocol several years

ago. Cefepime was the drug of choice forempiric therapy

Recent studies and resistance trends suggest

that it may not be the best choice

Is there any other antibiotic that is better?


13/15

Cefepime versus other

All-cause mortality was significantly higherwith cefepime as compared with other

antibiotics, RR 1.39 [1.04, 1.86], withoutheterogeneity 21 trials, 3471 participants

Piperacillin-tazobactam versus other

All-cause mortality was lower withpiperacillin-tazobactam versus all other

antibiotics , RR 0.56 [0.34, 0.92], 8 trials,1314 participants

The difference was statistically significant

also in the comparison restricted to

carbapenems, RR 0.46 [0.22, 0.95].


14/15





MIC reporting

Local epidemiology




SGH data for hematology 2012


15/15

CGH data, ESBL E coli, 2012 Case 3

Febrile neutropenia protocol was changed

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



Organism identification and pathogensusceptibility patterns

Selective reporting

MIC reporting

Local epidemiology




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 (4)

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