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Infections in general Practice. Philip G. Murphy Consultant in Medical Microbiology The Adelaide and Meath Hospitals incorporating the National Children’s Hospital, Tallaght. System approach. URT LRT 70% of antibiotics SST GUT- STD CNS meningitis emergency GIT diarrhoea
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Infections in general Practice Philip G. Murphy Consultant in Medical Microbiology The Adelaide and Meath Hospitals incorporating the National Children’s Hospital, Tallaght.
System approach • URT • LRT 70% of antibiotics • SST • GUT- STD • CNS meningitis emergency • GIT diarrhoea • Common viral: HS, VZ • Others: tropical parasites, Toxoplasmosis etc • Post-op hospital & minor ops. in GP
Factors influencing prescribing Choice Organism susceptibility Concurrent therapy Drug rep pressure Patient pressure Policies Prophylaxis Drug familiarity: Dosage / cost Toxicity / kinetics Bioavailability Best guess susceptibility Patient immune state Nature of infection Patient physiology Allergy history Breast feeding Pregnancy Age Compliance
Antimicrobial therapy • Usually - empirical • Why? - to avoid delay in initiating therapy for serious infection - eg. community acquired pneumonia • - difficulty in establishing the identity of the pathogen eg. acute/chronic otitis, sinusitis, bronchitis • - unavoidable delay in laboratory • processing of clinical samples.
Choice of empirical therapy • Empirical therapeutic choice requires • knowledge of : • - likely causative pathogen • - local, national and world-wide antimicrobial susceptibility patterns
Microbial aetiology • Haemophilus influenzae • Streptococcus pneumoniae • Moraxella catarrhalis • Mycoplasma pneumoniae • Chlamydia pneumoniae • Chlamydia psittaci • Legionella pneumoniae • Coxiella burnetti Conventional Atypical
Susceptibility of Haemophilusinfluenzae isolates to doxycycline • Combined 1992/93 data • (% susceptibility) • EU isolates 99.5 • Belfast isolates 100 • USA isolates 100 • Breakpoint MIC <2 mg/L
Streptococcus pneumoniae Resistance mechanisms • PBP alteration in numbers and size • Genetic mosaicism and transformation • Acquired resistance from oral viridans Streptococci. • No beta lactamase • No plasmid mediation
Penicillin Breakpoints sensitive < 0.01 mg/l commonly 0.03 - 0.1 mg/l formerly 0.006 - 0.008 mg/l low level resistance 0.1 - 1.0 mg/l (intermediate) high level resistance >1.0 mg/l
NI PHL (PRP) 1988 - 1995 YearResistanceSensitive 1988 4 (0.8) 484 1989 0 410 1990 4 (1) 400 1991 0 395 1992 0 377 1993 3 (0.9) 345 1994 12 (3.1) 372 1995 46 (10.6) 388 Goldsmith et al BMJ 1996
InvasiveStreptococcus pneumoniaeErythromycin resistance Irl & Eu 2004 Ireland
InvasiveStreptococcus pneumoniaepenicillin resistance IRL & EU 2004 Ireland
Antibiotic strategyLRTI • Chronic chest • Mild: tetracycline • Moderate: amoxicillin +/- quinolone • Severe: ceph, or aug +/- quinolone • Pneumonia • mild: amoxicillin • moderate: cephalosporin + macrolide • Severe: macrolide + quinolone
Enteric infection • H. pylori • Campylobacter jejuni/coli • Salmonellae • Shigellae • Hepatitis • Parasitic • Rotavirus
Campylobacter therapy • Fluid and electrolyte replacement • Avoid anti-motility agents • Antimicrobials if indicated : early treatment if Dx known • - ie. if fever present, bloody diarrhoea, > 8 stools / day, • worsening S&S, ? s&s > 1 week • Erythromycin 250 mg po qid 5-7 days • (carriage eliminated in 72 h) • If septicaemic add an aminoglycoside • Others : Fluoroquinolones, tetracyclines, FFP &Ig’s • not Beta lactams (except Co-amoxiclav)
Viral infection • Herpes simplex: cold sores, genital • Varicella zoster: chickenpox, shingles • Parvovirus • EBV: Infectious mononucleosis • CMV • Hepatitis • HIV
CellulitisSkin & soft tissue infection 90 % Streptococcal (BHStrep) 10 % Staphylococcal (S. aureus) Rx penicillin +/- flucloxacillin Titrate dose Vs symptoms