Introduction To Infectious Disease

Question 1

List Factors contributing to failure of antimicrobial therapy


Answer 1

Failure d/t host factors

Immunosuppression e.g. HIV infection, chemotherapy

Presence of fluid preventing penetration by medicines

Bacteremia

Failure to drain the fluid or pus or to remove foreign body or to remove necrotic tissue

Failure d/t microorganism itself

Primary and secondary resistance (intrinsic vs acquired resistance)

d/t overuse of antimicrobial agents

Increased prevalence of immunosuppressed patients receiving long-term antimicrobials to prevent infections

Question 2

State Reasons for failure of antimicrobial therapy


Answer 2

Less frequency

Interactions

Malabsorption

Wrong route of administration

Nonadherence

Increased metabolism/excretion

Pregnancy

High protein binding

Poor penetration of site of infection

Inappropriate selection of therapy

Question 3

Factors leading to failure of antimicrobial therapy


Answer 3

• Subtherapeutic levels
• Under-dose
• Less frequency
• Interactions
• Malabsorption
• Wrong route of administration
• Nonadherence
• Increased metabolism/excretion
• Pregnancy
• High protein binding
• Poor penetration of site of infection
• Inappropriate selection of therapy

Question 4

Factors leading to failure of antimicrobial therapy


Answer 4

Non-infectious condition
• Non-bacterial/no pathogen detected
• Polymicrobial infection
• Wrong selection of antimicrobial agent
• Host factors
• Laboratory errors in identification and/or susceptibility testing

Question 5

State the Disadvantages of combination antimicrobial therapy

Answer 5

Disadvantages of combination antimicrobial therapy


Increased cost
• Increased risk of adverse drug reactions and toxicities
• Risk of superinfection
• Antagonistic effects

Question 6

Why is the Combination antimicrobial therapy used

Answer 6

• Used to broaden spectrum of coverage
• Achieve synergistic activity
• Prevent emergence of resistance
• Increase coverage in mixed infections

Question 7

Factors that infections depend on


Answer 7

Patient’s history

Physical examination

Knowledge of the most likely microorganisms

Antibiogram – susceptibility results

Question 8

What occurs mainly in superficial or in bone and joint infections

Answer 8

• Swelling
• erythema
• tenderness
• purulent discharge

Question 9

Identification of pathogens


Answer 9

1. Collection of specimen (sample of infected materials e.g. blood, sputum, urine, stool, wound, spinal fluid, joint fluid, pus aspirations etc)
2. Specimen collected prior to initiating antimicrobial agents
3. Gram stain performed
4. Bacterial infection or Acid-fast stain (mainly mycobacteria or actinomycetes)
5. Serological tests using antigens and antibodies
6. Culture and sensitivity to assess the susceptibility of pathogens to antibiotics

Question 10

Selection of presumptive therapy


Answer 10

1. Rational selection of antimicrobial therapy depends on: Most likely pathogen, Severity of infection, Acuity of the disease, Host factors, Medicine-related factors, Need for combination therapy, Influenced by local, national or international antimicrobial treatment guidelines
2. Other considerations in selection of regimen depend on: Prior knowledge of colonization or infection, Previous antimicrobial use and response, Site of infection, Most likely microorganism, Knowing site of infection, possible microorganisms, resistance pattern of such microorganisms, Local antibiogram and resistance pattern

Question 11

Selection of presumptive therapy


Answer 11

1. Host factors: Age of the patient, Pregnancy and breastfeeding, History of allergies, History of adverse drug reactions/toxicities, Metabolic and genetic variations, Hepatic and renal function, Severity of disease process, Potential interaction with other medicines (or food), Concomitant medicine therapy, Concomitant conditions
2. Host factors: Concomitant medicine therapy, Dose adjustments/interactions, Knowledge of common interactions and possible outcome of interactions is vital e.g. metronidazole & alcohol => disulfiram reaction, Aminoglycosides and some medicines => nephrotoxicity or ototoxicity, Quinolones and some medicines => cationic binding => ↓ absorption of quinolones, Macrolides – inhibitors of metabolism => ↓ metabolism of other medicines
3. Medicine factors: Integration of PK and PD properties of medicines vital to ensure effectiveness and prevent development of resistance, Prevention of occurrence of adverse drug reactions/toxicities, Consider whether exhibit concentration-dependent bactericidal effects e.g. aminoglycosides, FQ, Maximu

Question 12

Integration of PK and PD properties of medicines is vital to ensure effectiveness and prevent development of what?

Answer 12

Resistance

Question 13

Considerations for effectiveness of medicines


Answer 13

1. Exhibit concentration-dependent bactericidal effects (e.g. aminoglycosides, FQ)
2. Maximum plasma concentration (AUC for time-concentration curve) determines the outcome
3. Time-dependent bactericidal effects (e.g. penicillins, cephalosporins)
4. Duration of exposure influences the response to medicines

Question 14

Factors influencing response to medicines


Answer 14

• Minimum inhibitory concentration (MIC)
• Area under the concentration-time curve (AUC)
• Maximal plasma concentration
• Time that the medicine concentration is above MIC

Question 15

Selection of presumptive therapy


Answer 15

• Medicines factors
• Tissue penetration capacity
• Site of infection (e.g., CNS)