"Don't forget to take a handful of our complimentary antibiotics on your way out“

Choose the Appropriate Antibiotic Think before prescribing, Are we using Right drug for the Right bug ?

Deciding on whether to use an antibiotic:  Day 1: guess the disease, guess the bug  Day 2: guess the sensitivity pattern BUT TOO LATE?  Day 3: know the full picture: BUT TOO LATE?  Day 1 Clinical assessment  Day 2 Positive microbiology  Day 3 Antibiotic sensitivity tests

 A primary tenet of antimicrobial therapy is to use the least toxic, most cost-effective, and most clinically effective agents and to refrain from costly, broader-spectrum agents.

 سابقه واكنش جانبي به ماده ضد ميكروبي آلرژي ( مثل پني سيلين )  سن  نابهنجاري هاي متابوليك و ژنتيكي  بارداري  عملكرد كبد و كليه  محل عفونت انتشار آنتي بيوتيک در بافت و سلول هاي ميزبان  پروتئين هاي سرمي متصل شونده به دارو  وضعيت سيستم ايمني بيمار  عفونت زايي و بيماري زايي باکتري  شدت بيماري انتخاب آنتی بیوتیک : فاكتور هاي ميزبان ( بيمار )

انتخاب آنتی بیوتیک  گروه A: داروهای انتخابی  گروه B: داروهای جایگزین  گروه C: داروهایی که در موارد مقاومت به گروه های بالا استفاده خواهد شد.  گروه U: فقط برای عفونت های ادراری –بنابراین اگر ایزوله غیر ادراری است این دسته گزارش نمی شوند

Suggested Groupings of Antimicrobial Agents with FDA Clinical Indications That Should Be Considered for Routine Testing and Reporting by Clinical Microbiology laboratories for Enterobacteriaceae

AST Methods  Serial dilution  Disk (disc) diffusion  Gradient diffusion (E-Test)

Select colonies Prepare inoculum suspension Disk Diffusion Procedure

Mix well Standardize inoculum suspension Disk Diffusion Procedure cont..

Swab plate Remove sample Disk Diffusion Procedure cont..

– Within 15 minutes of adjusting the turbidity dip a sterile cotton swab into the sample streak a lawn of bacteria on Mueller-Hinton agar Leave the lid agar for 3-5 minutes (no more than 15 minutes) to allow plate to dry Disk Diffusion Procedure cont..

Incubate18-24 hr, 35°C Incubate hr, 35°C Result Disk Diffusion Procedure cont..

Results – Antibiotics diffuse out onto the agar – Concentration of antibiotics decrease as they diffuse further away from the disks – After incubation, observe for a clearing on the bacterial lawn (zone of inhibition) Bacterial growth Zone of inhibition incubation 21

Bacterial lawnZone of inhibition SXT=10 mm

K Hari Krishnan Tirunelveli Medical College

تفسير نتايج حاصل از روش انتشار از ديسك

بيمار دختري 2 ساله تفسير نتايج حاصل از روش انتشار از ديسك

Disk-Diffusion Interpretation  E. coli – Source: CSF Cefazolin: S Cefalotin: S Ceftazidim: S

Serial Dilution 32 µg/ml 4 µg/ml 8 µg/ml 2 µg/ml 16 µg/ml 0.25 µg/ml 0.5 µg/ml 1 µg/ml µg/ml control

MIC Interpretive Criteria (  g/ml) DrugSuscIntRes cefazolin  8 8 8 816  32 gentamicin  4 4 4 48  16

Serial Dilution Output  MIC (Minimum Inhibitory Concentration)  Example: –E. coli source: Blood source: Blood – MIC ampicillin = 4 µg/ml – MIC Gentamicin = 2 µg/ml –E. coli Source: UrineSource: Urine MIC ampicillin = 20 µg/mlMIC ampicillin = 20 µg/ml

Synergism

Antibiotic Sensitivity Testing