AST and the Clinician

Piotr Chlebicki

Senior ConsultantDepartment of Infectious Diseases

SGH

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

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

� 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 empiric

antimicrobial treatment

� monitoring resistance trends � updating the drug formulary

� developing antimicrobial restriction policies

Antibiogram

Antibiogram – single unitSelective antimicrobial susceptibility reporting

� Susceptibilities are reported for only the most appropriate and least expensive drugs to which the organism is susceptible.

� The use of a cascading microbiology report encourages clinicians to select more narrow-spectrum and cost-effective antimicrobial agents.

� Very effective!!

Selective reporting

� One slide with image

� One slide with study

Case 1

� 52 year old man, PMH of DM, smoker complains of fever and cough for 3 days.

� 120/70 HR 100, RR 25, 38.6°C� Creps over rt lung

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

Diagnostic testing

� Mild CAP = testing optional

� More severe CAP = more testing

Gram stain

Quality of specimen

� Please reject

Rapid diagnostic testing

� Urinary streptococcal antigen

� RT PCR

� Routine blood cultures yielded negative results in 94% of patients

� Clinical scoring system

Antibiotics

� Likely pathogens

� Antimicrobial resistance

� Can he be treated with azithromycin alone?

� How about IV penicilln and Klacid?

Spectrum IPD - Singapore experience

Journal of Medical Microbiology (2009), 58, 101–104

Methods

� All invasive pneumococcal isolates cultured from sterile sites from adult patients hospitalized at SGH between 1 January 2000 and 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 %),

Resistance in SGH

� The median penicillin MIC was 0.016 mg/ml (range 0.016–2 mg/ml)

� Median ceftriaxone MIC 0.016 mg/ml (range 0.004–1 mg/ml)

Resistance in SGH

� All 186 non-meningitis isolates would be classified as penicillin-susceptible following 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%)

� Respirology . 2007 Mar;12(2):254-61.� Epidemiology, clinical characteristics and antimicrobial resistance patterns of community-acquired pneumonia in 1702 hospitalized

children in Singapore.� Chiang WC, Teoh OH, Chong CY, Goh A, Tang JP, Chay OM.� Source� Department of Respiratory Medicine, Kandang Kerbau Children's Hospital, Singapore. chiang.wen.chin@kkh.com.sg

� Abstract� OBJECTIVE AND BACKGROUND: � Childhood community -acquired pneumonia (CAP) remains a leading cause of morbidity and mortality worldwide. The f eatures of childhood

CAP v ary between countries. The aim of this study was to delineate the clinical characteristics, complications, spectrum of pathogens and patterns of antimicrobial resistance associated with hospitalized cases of childhood CAP in Singapore.

� METHODS: � A retrospective study was conducted of patients discharged from Singapore's only children's hospital over a 3-y ear period with a principal

diagnosis of CAP.� RESULTS: � A total of 1702 children, with a median age of 4.2 years (range: 1 month-16.3 years) were enrolled. A pathogen was identifiable in 38.4% of

cases, including My coplasma pneumoniae in 20.3%, typical respiratory bacteria in 10.3% (64.6%Streptococcus pneumoniae; 21.7% non-ty peable Haemophilus influenzae), viruses in 5.5% and mixed bacterial/viral infections in 2%. The majority of M. pneumoniae inf ections were in school-aged children (>5 y ears). Sev erity of infection was greater in CAP caused by typical bacteria, as reflected by length of hospital stay, CRP lev el, white cell and absolute neutrophil counts. Mortality from typical bacterial infections (8.9%) exceeded that from M. pneumoniae (0.3%) and v iral pneumonias (0%) (P < 0.001). Aminopenicillins were of ten prescribed empirically for suspected S. pneumoniae and H. inf luenzae inf ections; however, resistance to these agents was frequently documented among S. pneumoniae (58.5%) and H. influenzae isolates (51%).

� CONCLUSION: � In Singaporean children hospitalized with CAP, M. pneumoniae is the most commonly identified causative organism, followed by common

respiratory v iruses, S. pneumoniae and H. influenzae. Streptococcus pneumoniae and H. influenzae are associated with greater severity of inf ection than other organisms, and hav e high levels of resistance to commonly prescribed antibiotics.

� PMID: 17298459 [PubMed - indexed f or MEDLINE]

NARSS 2010 Guideline

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

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

What is the bug? Which antibiotic?

� Depends on the prevalence of resistance in a community

� IDSA suggests thresholds above which a drug is not recommended � 20% for trimethoprim–sulfamethoxazole� 10% for fluoroquinolones

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 ♀� 13–65 years = 214 � > 65 years = 117

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 introduced febrile neutropenia protocol several years ago. Cefepime was the drug of choice for empiric therapy

� Recent studies and resistance trends suggest that it may not be the best choice

� Is there any other antibiotic that is better?

Cefepime versus other

� All-cause mortality was significantly higher with cefepime as compared with other antibiotics, RR 1.39 [1.04, 1.86], without heterogeneity 21 trials, 3471 participants

Piperacillin-tazobactam versus other

� All-cause mortality was lower with piperacillin-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].

SGH data for hematology 2012

CGH data, ESBL E coli, 2012 Case 3

� Febrile neutropenia protocol was changed

� Pip tazo or cefepime plus amikacin will be used for the empiric therapy of febrile neutropenia

Summary

� The impact of microbiology lab on prescribers is profound

� It not only influence the choice of antibiotics for individual patients but also hospital policies and guidelines