L-18 Anti-infective therapy
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Questions and Answers

Which of the following is NOT a primary factor to consider when selecting an antimicrobial agent?

  • The patient's age and whether they are pregnant.
  • Patient preference for a specific brand of medication. (correct)
  • The cost of the therapy, considering parenteral versus oral options.
  • The specific antibiogram of the institution and unit involved.

    • A patient showing a significant increase in eosinophils could potentially indicate which of the following conditions?

  • A bacterial infection causing neutrophilia
  • Tuberculosis infection
  • Drug allergy or metazoan infection (correct)
  • Lymphoma

    • Which of the following is the MOST likely cause of a purulent inflammation in a bone or joint?

  • Bacterial infection (correct)
  • Viral infection
  • Autoimmune disorders
  • Fungal infection

    • What is often the best practice for collecting blood samples for culture from a patient with acute fever?

    <p>Collecting a sample at the time of sharp elevation in temperature (D)</p> Signup and view all the answers

    A patient with a fever, flank pain, and dysuria is MOST likely experiencing an infection caused by which of the following?

    <p>Enteric <em>E. coli</em> (C)</p> Signup and view all the answers

    Which type of infection is NOT specifically mentioned as one where resistance to chemotherapy can be a problem?

    <p>Bacterial infections (D)</p> Signup and view all the answers

    The identification of pathogens is carried out using differential stains and which other method?

    <p>Molecular biological techniques (D)</p> Signup and view all the answers

    Exposure to which of the following animals can be a risk factor for contracting histoplasmosis?

    <p>Chickens (D)</p> Signup and view all the answers

    Which organism is most likely to cause hospital-acquired pneumonia?

    <p>Enterobacter (B)</p> Signup and view all the answers

    A patient develops bacteremia from a urinary tract infection. Which type of bacteria is most likely responsible?

    <p>Gram-negative bacilli (B)</p> Signup and view all the answers

    What is the most common bacterial cause of bacteremia associated with IV catheters?

    <p>Staphylococcus (A)</p> Signup and view all the answers

    A lymphoma patient presents with meningitis. Which organism is most likely the cause?

    <p>Listeria monocytogenes (D)</p> Signup and view all the answers

    For a drug primarily eliminated through the kidneys, what parameter should be assessed to determine the appropriate dose?

    <p>Creatinine clearance (D)</p> Signup and view all the answers

    Which of the following is a characteristic of a time-dependent antibiotic?

    <p>It requires frequent small doses to maintain therapeutic levels (D)</p> Signup and view all the answers

    Inflammation in the brain typically has what effect on antibiotic penetration into the cerebrospinal fluid (CSF)?

    <p>Facilitates penetration of many antibiotics (C)</p> Signup and view all the answers

    What property of trimethoprim allows it to achieve good concentrations in prostatic fluids?

    <p>Its non-ionized state at plasma pH (B)</p> Signup and view all the answers

    The reduced penetration of penicillin G into the prostate is primarily due to what property of the molecule?

    <p>Its ionized state at plasma pH (B)</p> Signup and view all the answers

    Which of the following classes of drugs can potentially cause CNS toxicity if not dosed correctly in patients with renal dysfunction?

    <p>Beta-lactams (B)</p> Signup and view all the answers

    Which route of administration is most suitable for an antibiotic when high serum levels are immediately required to combat a serious infection, and when the drug is degraded by the digestive system?

    <p>Parenteral (B)</p> Signup and view all the answers

    A patient with a severe meningeal infection is being treated with an antibiotic that does not cross the blood-brain barrier. Which administration route would be most effective to deliver the drug to the infection site?

    <p>Intrathecal (B)</p> Signup and view all the answers

    Why might a doctor choose to use a combination of antibiotics, despite the potential drawbacks?

    <p>To broaden the spectrum of coverage and increase synergistic effects (A)</p> Signup and view all the answers

    What is a major disadvantage of using a bacteriostatic antibiotic in combination with a bactericidal antibiotic?

    <p>The bacteriostatic antibiotic could inhibit the action of bactericidal agent (C)</p> Signup and view all the answers

    What is the primary mechanism by which bacteria develop drug resistance described in this text?

    <p>Mutation of DNA which modifies target sites of drugs and drug inactivation (C)</p> Signup and view all the answers

    Which of the following hematological toxicities is correctly paired with its associated antibiotic?

    <p>Nafcillin - neutropenia (B)</p> Signup and view all the answers

    A patient presents with a headache, rigid neck, and sensitivity to light. Which condition does this symptom combination most strongly suggest?

    <p>Meningitis (C)</p> Signup and view all the answers

    When is 'empiric therapy' typically initiated in a critically ill patient?

    <p>Immediately after specimens for lab analysis are obtained (B)</p> Signup and view all the answers

    What is the primary distinction between bacteriostatic and bactericidal drugs?

    <p>Bactericidal drugs kill bacteria while bacteriostatic drugs limit the spread of infection by inhibiting growth allowing the immune system to clear the pathogens (D)</p> Signup and view all the answers

    Which of the following is NOT a factor in determining the selection of drugs for empiric therapy?

    <p>Patient's preference of medication (A)</p> Signup and view all the answers

    A patient is prescribed a medication known to cause photosensitivity. Which of the following medication combinations could be responsible?

    <p>Azithromycin and Quinolones (C)</p> Signup and view all the answers

    A critically ill patient has an infection that requires immediate therapy, before the identification of the organism. What kind of therapy is most appropriate?

    <p>Empiric therapy (A)</p> Signup and view all the answers

    Why might chloramphenicol be categorized as bactericidal against Pneumococci but bacteriostatic against gram-negative rods?

    <p>Because of differences in the drug concentration achieved in different bacteria. (C)</p> Signup and view all the answers

    Which of the following scenarios would most likely warrant the use of a bactericidal antibiotic over a bacteriostatic one?

    <p>A patient with a compromised immune system. (C)</p> Signup and view all the answers

    A patient is receiving an antibiotic known to cause ototoxicity. Which of the following antibiotics could be responsible?

    <p>Aminoglycosides (C)</p> Signup and view all the answers

    Why is it important to collect samples for culture before aspirating an abscess?

    <p>Aspiration may reduce the microbial load, affecting culture results. (A)</p> Signup and view all the answers

    A patient presents with a skin infection. The culture reveals S. epidermidis. What is the most important consideration in this case?

    <p>It is important to distinguish colonization from infection. (C)</p> Signup and view all the answers

    Which of the following is the primary reason for performing a urinalysis alongside a urine culture?

    <p>To detect signs of inflammation (WBC) and potential infection (nitrite and esterase). (C)</p> Signup and view all the answers

    A patient has a delayed skin rash after penicillin administration. Which of these statements is MOST accurate for prescribing cephalosporins?

    <p>Cephalosporins can be administered because the reaction to penicillin was delayed. (C)</p> Signup and view all the answers

    Why is it important to be aware that sulfonamides can cause kernicterus in neonates?

    <p>Sulfonamides compete with bilirubin for binding sites, increasing the risk of kernicterus. (B)</p> Signup and view all the answers

    An elderly patient on isoniazid shows signs of hepatic toxicity. What is MOST important to consider regarding this observation?

    <p>Elderly patients are more prone to hepatic issues with isoniazid, dose adjustment might be necessary. (A)</p> Signup and view all the answers

    Why is it important to be aware of the pharmacokinetic changes during pregnancy when prescribing drugs?

    <p>The changes in intravascular volume, GFR and metabolism may lead to a need to adjust drug dosages. (D)</p> Signup and view all the answers

    A patient with a known G6PDH deficiency needs treatment for an infection. Why should prescribing sulfonamides, nitrofurantoin, antimalarials, dapsone or chloramphenicol be avoided or carefully considered?

    <p>These drugs can cause hemolytic anemia in a person with G6PDH deficiency. (D)</p> Signup and view all the answers

    A patient with a liver disease needs antibiotics. Which group of drugs requires careful adjustment due to potential accumulation?

    <p>Chloramphenicol, Clindamycin, Erythromycin, Metronidazole and Rifampin (D)</p> Signup and view all the answers

    What is the most likely causative organism for a community-acquired pneumonia based on the information provided?

    <p>S. pneumoniae (D)</p> Signup and view all the answers

    Flashcards

    Bacterial Infections

    Infections caused by bacteria that may be treated with antibiotics.

    Fungal Infections

    Infections caused by fungi. Often resistant to chemotherapy.

    Helminthiasis

    Infections caused by parasitic worms, like tapeworms or roundworms.

    Protozoal Infections

    Infections caused by protozoa, single-celled organisms. An example is amebiasis.

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    Viral Infections

    Infections caused by viruses. Some examples are COVID-19, Herpes, HIV, and Influenza.

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    Identification of Pathogens

    Tests performed to determine the specific type of bacteria causing an infection.

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    Sensitivity Testing

    Testing methods used to determine the sensitivity of bacteria to specific antibiotics.

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    Infected Body Materials

    Samples of body fluids collected before starting antibiotics to prevent contamination.

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    Creatinine Clearance

    A measure of how well a drug is eliminated by the kidneys.

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    Half-Life

    The time it takes for a drug's concentration to decrease by half in the body.

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    Pharmacodynamics

    The effect of a drug on the body's cells and tissues.

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    Pharmacokinetics

    The study of how a drug moves through the body - absorption, distribution, metabolism, and elimination.

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    Tissue Penetration

    The ability of a drug to reach the site of infection at effective concentrations.

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    Blood-Brain Barrier

    A barrier that protects the brain from harmful substances.

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    CSF Penetration

    The ability of a drug to pass from the bloodstream into the cerebrospinal fluid.

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    Inflammation Facilitates Penetration

    Inflammation allowing antibiotics to cross the blood-brain barrier more easily.

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    Time-Dependent Killing

    A type of antibiotic that requires frequent small doses to maintain a constant level in the body.

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    Concentration-Dependent Killing

    A type of antibiotic that can be given in large doses for longer periods to achieve its therapeutic effect.

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    Antibiotic Resistance

    The ability of bacteria to survive and multiply even when exposed to the maximum dose of an antibiotic that is safe for the human host.

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    Broad Spectrum Antibiotics

    Antibiotics that are effective against a wide range of bacteria, including both gram-positive and gram-negative types.

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    Combination Therapy

    Using multiple antibiotics simultaneously to treat an infection, often for bacterial infections like tuberculosis.

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    Superinfection

    When the use of antibiotics disrupts the natural balance of bacteria in the body, allowing harmful bacteria like Candida to thrive and cause infections.

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    Narrow Spectrum Antibiotics

    Antibiotics effective against a limited group of bacteria, usually either gram-positive or gram-negative.

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    Aspirating Abscesses Before Culture

    Before taking a sample for culture, aspirate abscesses first to reduce the number of microbes and ensure a more accurate result.

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    Colonization vs. Infection

    It's important to differentiate between bacterial colonization (normal presence without infection) and actual infection, especially in sensitive areas like the skin or throat. Colonization by harmless bacteria can lead to false positive results.

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    Coagulase-Negative Staphylococcus (e.g., S.epidermidis) Contamination

    Coagulase-negative Staphylococcus (e.g., S.epidermidis) commonly found on skin can contaminate cultures, leading to false positive results. This bacteria is generally harmless but can cause problems in certain situations.

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    Urine Culture and Urinalysis

    When analyzing urine, it's crucial to perform a urine culture along with a urinalysis test. This includes checking for white blood cells (WBC), nitrite, and esterase, all indicators of possible infection.

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    Allergic Reactions vs. Adverse Effects

    It's important to distinguish between allergic reactions (immune system response) and adverse effects (side effects) to medications. For example, penicillin can cause both allergic reactions and gastrointestinal (GI) issues.

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    Cephalosporins and Penicillin Sensitivity

    Cephalosporins, a type of antibiotic, can be prescribed to patients with penicillin allergies ONLY if they experienced delayed reactions (e.g., skin rash). Immediate reactions like anaphylaxis (severe allergic reaction) or laryngospasm (throat swelling) rule out cephalosporins.

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    Drug Toxicity in Neonates

    Sulfonamides can cause a condition called kernicterus in newborns, leading to brain damage. Chloramphenicol can cause a serious condition called gray baby syndrome.

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    Isoniazid Toxicity in Elderly

    Isoniazid, an antibiotic used to treat tuberculosis, can cause liver toxicity in older adults. It's important to weigh the benefits of therapy against potential risks.

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    Teratogenic Effects in Pregnancy

    Pregnancy is a sensitive time for medication use. Teratogenic effects (birth defects) are a serious concern and should be carefully considered when prescribing medications.

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    Pharmacokinetics in Pregnancy

    Pregnant women often experience changes in their body systems. This can affect how drugs are absorbed, distributed, metabolized, and excreted. Therefore, dosages of some drugs may need to be adjusted.

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    Hematological Toxicity

    Drugs like nafcillin, piperacillin, cefotetan, chloramphenicol, and trimethoprim can cause various blood-related problems, like low white blood cell counts, platelet dysfunction, or difficulty in forming blood clots.

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    Nephrotoxicity

    Aminoglycosides and vancomycin can damage the kidneys, potentially causing issues with filtering waste and regulating fluids.

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    Ototoxicity

    Aminoglycosides, erythromycin, and some other drugs can harm the hearing and balance organs in the inner ear.

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    Photosensitivity

    Drugs like azithromycin, quinolones, tetracyclines, pyrazinamide, sulfamethoxazole, and trimethoprim can cause increased sensitivity to sunlight, leading to sunburn.

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    Empiric Therapy

    Giving a broad-spectrum antibiotic immediately to critically ill patients before knowing the specific infection is called empiric therapy.

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    Selection Criteria for 'Empiric Therapy'

    A doctor might prescribe a combination of drugs, targeting gram-positive and gram-negative bacteria, based on factors like the infection site, patient history, and travel history.

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    Bactericidal vs Bacteriostatic

    A doctor might decide to use a bactericidal drug, which kills the bacteria, based on the patient's immune status. This is more aggressive than bacteriostatic drugs.

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    Cost of Therapy

    The cost of the treatment is a crucial factor in choosing antibiotics. For example, a doctor might choose amoxicillin over levofloxacin if the patient's budget is limited.

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    Prophylaxis

    Prophylactic therapy aims to prevent infections. It's used for people at high risk of contracting a specific infection.

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    Oral Administration

    Oral administration is the preferred route for outpatient therapy and mild to moderate infections due to its convenience and cost effectiveness.

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    Study Notes

    Anti-Infective Agents: Principles

    • Anti-infective agents are used to treat infections caused by various microorganisms.

    Types of Infections

    • Bacterial Infections: Bacterial infections are a broad category, but specific types like tuberculosis and atypical infections are also classified separately. Leprosy (Hansen's disease) is another type of bacterial infection.
    • Mycobacterial Infections: While categorized with bacterial infections, mycobacterial infections like tuberculosis are distinct. Atypical bacterial infections are also a separate category.
    • Fungal Infections: Fungal infections exhibit resistance to chemotherapy, a significant factor in their treatment.
    • Helminthiasis: This encompasses all worm infections.
    • Protozoal Infections: Protozoal infections, like amebiasis, exemplify this category.
    • Viral Infections: Viral infections, including COVID-19, herpes, HIV, influenza, HCV, and HBV, are significant.

    Selection of Antimicrobial Agents

    • Choosing the right antibiotic depends on several factors including:
      • Sensitivity of the infecting organism to the antibiotic.
      • Severity and location of the infection.
      • Safety – the antibiotic's impact on renal and hepatic function.
      • Patient characteristics like age and pregnancy status.
      • Cost of treatment (parenteral vs. oral).
      • Antibiogram of the institution (and specific unit-specific antibiograms). For instance, VRSA (Vancomycin-resistant Staphylococcus aureus) should be considered.
      • Potential sources of infection like hospitals (nosocomial infections), nursing homes, or homes.

    Important Questions to Ask Patients

    • Patient history is vital to understand the source of infection. Questions to ask patients include:
      • Presence of other sick individuals at home.
      • Presence of pets, like chickens or pigeons, as these may be related to particular infections (histoplasmosis, cryptococcosis, or ornithosis).
      • Whether the patient is currently employed or where they have recently traveled.
      • Whether the patient has consumed contaminated food or been exposed to an environment with potential infection sources (like an ICU).

    Points to Ponder

    • Infection symptoms should be evaluated for possible causes.
      • Tuberculosis and lymphoma can elevate monocyte counts.
      • Drug allergies and metazoan infections can increase eosinophils.
      • Purulent bone and joint inflammation indicate potential infection.
      • Presence of neutrophils in body fluids (spinal fluid, sputum, urine) could indicate bacterial infection.
      • Flank pain and dysuria may point to enteric E.coli infections.
      • Cough with sputum may suggest pulmonary infections by bacteria, mycobacteria, viruses, or mycoplasmas.

    Identification of Pathogens

    • Identification methods include differential stains and molecular biology techniques.
    • Disc diffusion methods using biochemical assays and mechanized tests help identify the pathogen.
    • Infected tissue sample collection is necessary before antibiotic therapy.
    • Blood cultures taken from febrile patients are used to diagnose blood-borne bacterial infections.
    • Samples for cultures should be collected before any abscess aspiration.
    • Extra caution is required when taking samples from skin, perineum, oral cavity, nose, eyes, and ears as colonization must be differentiated from actual infection (e.g. Staphylococci).

    Host Factors

    • Carefully differentiate between allergic reactions and adverse effects (e.g., penicillin).

    • Consider the factors when prescribing cephalosporins to penicillin-sensitive patients. Delayed reactions (skin rash) vs immediate reactions (anaphylaxis, laryngospasm) must be evaluated.

    • In infants (neonates), Kernicterus is a concern with sulfonamides, while gray baby syndrome may result from chloramphenicol.

    • In elderly patients, administering isoniazid may cause hepatic toxicity, requiring careful monitoring of benefits compared to harm.

    • Pregnancy necessitates careful attention to potential teratogenic effects of the antibiotic.

    • Penicillins, cephalosporins, and aminoglycosides are rapidly cleared in pregnancy, so dosages may require adjustment.

    • Genetic factors can influence how the body processes drugs, affecting treatment. For example, G6PDH deficiency may lead to hemolytic anemia caused by certain drugs.

    • Liver disease, renal dysfunction or slow acetylator status require that dosage of some antibiotics be adjusted due to their pharmacokinetics.

    Highest Probabilities of Infection-Causing Organisms

    • Common organisms causing urinary tract infections (UTIs), joint infections, and community-acquired pneumonia are presented.
    • Potential organisms associated with hospital-acquired pneumonia, bacteremia from urinary tract, bacteremia from intravenous catheters or diseases with immunosuppression are given.
    • Common causes of meningitis in healthy adults and patients with lymphoma are given for consideration.

    Other Drug Factors

    • Consider drug elimination by the kidneys (Cockcroft-Gault equation).
    • Post-antibiotic effect and concentration-dependent killing of bacteria are considered when selecting the appropriate drug.
    • Time-dependent killing (e.g., beta-lactam antibiotics) requires frequent small doses.
    • Tissue penetration of the drug is an essential factor when dealing with infections in different tissues (brain, prostate, bone, etc.)

    CSF Penetration and Prostate Infections

    • Penetrating the blood-brain barrier in infections of the central nervous system depends on the ability of the drug to cross this barrier to reach the cerebrospinal fluid (CSF).
    • Inflammation can help penetration through certain tissues and organs (abscesses).
    • Infections of the prostate are difficult to treat due to the inability of some antibiotics to cross into the prostatic epithelium, and sometimes the low pH of prostatic tissue.

    Toxicity

    • Renal dysfunction requires appropriate antibiotic dosage adjustment for cephalosporins, quinolones, and imipenem.
    • Hematological toxicities (neutropenia, platelet dysfunction or bone marrow suppression) and nephrotoxicity (related to the kidneys) or ototoxicity (related to the ears) are presented as possible adverse effects of some drugs.
    • Drug-induced photosensitivity is another potential adverse effect to be aware of.

    Empiric Therapy

    • The selection of appropriate antibiotics requires consideration of the potential pathogens in the given clinical situation.
    • Empiric therapy involves the use of broad-spectrum antibiotics before the specific pathogen is identified.
    • Conditions like neutropenia, headaches, stiff neck, sensitivity to light may point to bacterial infections or meningitis.
    • Factors like site of infection, patient history, travel history, and age can guide the selection of drugs.

    Bacteriostatic vs. Bactericidal Drugs

    • Bacteriostatic drugs halt bacterial growth and replication at achievable serum levels, and rely on the host's immune system to eliminate the pathogen completely.
    • Bactericidal agents kill bacteria, decreasing the total number of viable organisms. In some cases, drugs are both bacteriostatic and bactericidal against some pathogens, but not others.

    Other Key Factors

    • Consideration of cost of therapy (comparing, for instance, amoxicillin to levofloxacin).
    • Consideration of prophylactic treatment to prevent potential health hazards.

    Routes of Administration

    • Oral administration is common in outpatient and mild infection cases, but food can impact absorption.
    • Intravenous (parenteral) administration is essential for severe infections where high serum levels are needed or for drugs that are inactivated by the digestive system.
    • Intra-thecal administration is necessary in meningeal infections where the drug can't reach the brain.
    • Topical, sublingual, subcutaneous, and inhalational routes are other options.

    Antibiotic Spectra

    • Narrow-spectrum antibiotics target a single organism or a group of organisms.
    • Extended-spectrum antibiotics affect a wider range of organisms, including both gram-positive and gram-negative bacteria.
    • Broad-spectrum antibiotics can affect diverse types of bacteria, possibly altering normal bacterial flora and potentially contributing to infections like candidiasis (yeast infections).

    Combination Therapy

    • Therapies using a single drug per pathogen are preferred. Combination therapy may be necessary when the pathogens are more severe.
    • Combination therapy can exhibit synergy in some cases to increase the effectiveness of the drug.
    • Combination therapy can increase the risk of adverse effects, like additive toxicity (like nephrotoxicity from some antibiotics and vancomycin). Also note that drugs can induce beta-lactamases, potentially deactivating other antibiotics.

    Drug Resistance

    • Bacterial resistance occurs if the maximal tolerated level of antibiotic by the host isn't sufficient to stop the pathogen from progressing.
    • Some pathogens have inherent antibiotic resistance.
    • Resistance can occur from spontaneous DNA mutations or genetic transfer events. Altered target sites, reduced drug accumulation, or inactivation of the drug can lead to resistance.

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    Anti Infective Agents: Principles PDF

    Description

    This quiz tests your knowledge on essential aspects of microbiology, particularly in selecting antimicrobial agents and identifying infections. It covers topics such as pathogen identification, risk factors for specific infections, and understanding laboratory practices for culture samples. Prepare to challenge your understanding of infectious diseases and their management.

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