antibiotics - a rational approach
TRANSCRIPT
Dr. Soulat Hafeez
House Officer
Medical Unit 4
Definition Of Antibiotic
A chemical substance produced by micro organisms, which has the capacity to inhibit the growth of or to kill other micro organisms
Antibiotic TherapyIdeally is determined by isolation and antibiotic susceptibility
of the offending.Usually not available in ER.Abx treatment initiated on clinical diagnosis and likely
organism involved.Early empirical treatment may be lifesaving.
THERAPY BASED ON
1. Site of infection
2. Safety of the agent
3. State of the patient (age, renal, hepatic funtions etc)
4. Cost of the therapy
Appropriate Use of AbxEmploy empirically when there is a
reasonable clinical suspicion of infectionChoose antibiotics active against the most
likely organism(s)Choose antibiotics known to penetrate
involved tissueUse correct doses of antibiotics – don’t
underdose
Appropriate Use of Abx…cont’d
Know when bacterostatic antibiotics are adequate or bacterocidal drugs are required
In serious, potentially life-threatening infections, start broad, then de-escalate after cultures back
Stop antibiotics when infection resolved or when evidence accumulates against existence of infection
Inappropriate Use of AbxWong antibioticWrong dose of right drugUsing a 2nd or 3rd line drug when a first line drug
could still be usedUsing antibiotics in situations when antibiotics are not
indicatedContinuing antibiotics when infection is resolved or
not likelyKeeping coverage broad when cultures reveal a single
organismReacting to culture results by starting antibiotics
without considering the significance of the culture
Common Mistakes in Diagnosing InfectionBase diagnosis on a single positive data point
when other data points are negative React to a positive culture when there is no
clinical evidence of infectionUse serial cultures to determine when
infection has resolved Obtain cultures randomly when clinical
suspicion of infection is low
First Step: Determine WhetherCulture Represents Real PathogenColonizer: Any organism actually present in
or on patient, but does not invade tissue or cause clinical disease
Contaminant: Any organism growing in culture that is not actually present in or on the patient, but came from the environment into the culture medium
Three Examples1. A +ve sputum culture taken from a patient without
fever, leukocytosis, new infiltrate or pulmonary symptoms should be taken as a colonizer
2. A +ve urine culture taken from a patient without dysuria, frequency, and with a small to moderate amount of WBC in the U/A has asymptomatic bacteriuria
3. A +ve wound culture taken from a clean appearing, granulating wound that is not painful, has no purulence in a patient with no fever and a normal WBC, represents a colonizer (rather than a true pathogen) and should not be treated
Sputum CulturePathogen if:Sputum is grossly
purulentPatient is febrileInfiltrates on CXR> 5-10 WBC per hpf< 5-10 epithelial
cells per hpf
Colonizer if:Sputum is scant,
clear or whitePatient is afebrileNo infiltrates on
CXR< 5-10 WBC per hpf> 5-10 epithelial
cells per hpf
Urine CulturePathogen if:> 100,000 cfuIf urinalysis reveals:
> 10 WBCPos. Leuk. EsterasePos. nitriteFew or no epi’s
If patient symptomatic
Contaminant if:10,000 cfu or lessIf urinalysis reveals:
< 10 WBCNeg. Leuk. EsteraseNeg. nitriteMany epi’s
If patient asymptomatic
Drugs Absolutely C/I in Pregnancy ----- “Category X Drugs”Mnemonic “SAFE Mom Takes Really Good
Care”
SULFONAMYIDES, AMINOGLYCOSIDES, FLUOROQUINOLONES, ERYTHROMYCIN.
METRONIDAZOLETETRACYCLINERIBAVIRINGRISEOFULVINCHLORAMPHENICOL
ABX TO AVOID IN CHILDREN UNDER 18
Abx TO AVOID IN LACTATING MOTHERS
ABX TO AVOID IN RENAL FAILURENote, here add drugs that are
contraindicated and drugs that can be administered but with reduced dose.
ABX TO AVOID IN HEPATIC FAILURE.SAME AS FOR RENAL FAILURE.
Meningitis
1. Initiate Empirical Antibiotic Therapy2. All patients with head trauma,
immunocmpromised states, known malignancies, or focal nerological findings (including stupor/coma) should undergo neuroimaging study prior to Lumbar Puncture
3. Obtain CSF D/R sample, if not C/I4. If Bacterial Meningitis is suspected, initiate
empirical antibiotic therapy even prior to Imaging and LP
Principles of Management
Clinical FeaturesFever, Headache, Neck stiffness, and Change
in Mental Status75% of patients have atleast 2 out of these 4
features
Antibiotics for Empirical Treatment of Bacterial Meningitis
Infants < 3 months Ampicillin + Cefotaxime
Adults < 55 years Ceftriaxone + Vancomycin
Adults with Alcoholism or debilitating illness
Ceftriaxone + Vancomycin+ Ampicillin
Hospital acquired, post neuro- surgery, neutropenic patients
Ceftazidime + Vancomycin+ Ampicillin
Pneumonia
Principles of ManagementClassify the pneumonia :
1. Community Acquired, or2. Health-Care Associated
Hospital Acquired Ventilator Associated
Determine severity: CURB 65 Pneumonia Severity Index
Definition of Health-Care Associated Pneumonia Health-Care Associated Pneumonia has any
one of the following features:Hospitalization for > 48 hoursHospitalization for > 2 days in prior 3 monthsAntibiotic therapy in prior 3 monthsChronic dialysisHome wound careContact with a family member who has MDR
infection
Severity of PneumoniaCURB 65
ConfusionUrea > 7 mmolR/R > 30BP : Systolic < 90 ; Diastolic < 60 mmHgAge > 65 years
Score: 0 - 1 --------- Out- patient treatment
2 --------- In patient: Non ICU >2 --------- ICU care
Empirical Antibiotic Treatment of Community Acquired Pneumonia
Outpatients 1. Macrolide ( Clarithro or Azithro)2. Doxycycline3. Respiratory FQ ( Moxi or Gemi or Levo)4. B-Lactam plus Macrolide
In Patients: Non ICU 1. Respiratory FQ ( Moxi or Gemi or Levo)2. B-Lactam plus Macrolide
In Patients : ICU 1. B-Lactam plus Macrolide2. B-Lactam plus FQ
If Pseudomonas is suspected
1. B-Lactam plus FQ2. B-Lactam plus Aminoglycoside3. B-Lactam plus FQ plus Aminoglycoside
If MRSA is suspected Add Linezolid or Vancomycin
Empirical Antibiotic Treatment of Health Care Associated Pneumonia
No risk for MDR Pathogens
1. B – Lactam ( Ceftriaxone 2 gm IV OD) alone
2. FQ alone3. Ertapenem alone
Risk Factors for MDR pathogens
1. B – Lactam ( 3rd / 4th Gen Cephalosporin or Tazocin) plus FQ / Aminoglycoside plus Linezolid/ Vancomycin
Urinary Tract Infections
Principles of ManagementAlways obtain Urine C/S ( except in
uncomplicated cystitis in women)Identify and Correct (if possible)
predisposing factorsRelief of symptoms does not indicate
bacteriologic cureEach course of treatment should be classified
as a Cure or Failure
Treatment Regimens for Bacterial UTI