chemotherapy

What is an antimicrobial drug?

A drug that injures or kills microorganisms without harming host cells; in this course, antimicrobials primarily refer to antibacterial drugs (antibiotics).

What infections were emphasized as being treated with antibacterial drugs?

Tuberculosis (TB), C. difficile, MRSA, bacterial pneumonia, urinary tract infections (UTIs).

Antimicrobials vs antibiotics

For this course they are used almost interchangeably because most antimicrobials discussed are antibacterial drugs.

Can antibiotics treat viral infections?

No. Antibiotics target bacteria, not viruses.

What are the 3 major mechanisms of antibacterial drugs?

1. Inhibit bacterial cell wall synthesis/function 2. Inhibit bacterial protein synthesis 3. Inhibit bacterial DNA/RNA synthesis/function.

Why don’t cell wall inhibitors work on viruses?

Viruses have no bacterial cell wall, so there is no target for the drug.

What are the two most common general adverse effects of antibiotics?

Allergic reactions and GI upset (nausea, vomiting, diarrhea).

Which antibiotic allergy is most commonly encountered clinically?

Penicillin allergy.

What does bactericidal mean?

Kills bacteria.

What does bacteriostatic mean?

Stops bacterial growth and reproduction.

Broad-spectrum antibiotic

Active against many different bacterial species.

Narrow-spectrum antibiotic

Targets fewer, more specific bacterial species.

Before prescribing an antibiotic, what should ideally happen first?

Identify the organism (culture when possible), then choose an antibiotic the organism is susceptible to.

What bacterial characteristics help determine antibiotic selection?

Gram stain (positive vs negative), bacterial shape (cocci vs rods), susceptibility testing.

Why does infection location matter when selecting an antibiotic?

The drug must be able to reach the infected tissue (ex: must cross the blood-brain barrier for meningitis).

Besides the organism, what patient factors influence antibiotic selection?

Pregnancy, immune status, allergies, safety, cost, dosing schedule, route, and ability to adhere.

Application: A patient has bacterial meningitis. Why might one antibiotic work while another fails even if both kill bacteria?

The medication must be able to cross the blood-brain barrier to reach the infection.

Application: Why might a physician prescribe a once-daily antibiotic instead of one taken every 6 hours?

Better patient adherence increases the likelihood the medication is taken correctly.

Application: A child refuses pills and injections. What medication factor becomes especially important?

Route of administration (liquid formulation may improve adherence).

What major antibiotic class is considered a mainstay of bacterial treatment?

Penicillins.

Penicillins

Broad-spectrum antibiotics commonly used for many bacterial infections.

What major limitation of penicillins should PTs recognize?

Penicillin allergy is common.

Cephalosporins

Antibiotics frequently used when penicillin cannot be used and commonly prescribed for UTIs.

Bacitracin

OTC topical antibiotic commonly used on minor skin wounds.

Why might a wound care PT encounter bacitracin?

It is frequently used topically to prevent skin wound infection.

Aminoglycosides

Broad-spectrum antibiotics commonly used for wound and tissue infections.

Macrolides (Erythromycin)

Broad-spectrum antibiotics commonly prescribed for respiratory infections.

Fluoroquinolone example emphasized in lecture

Ciprofloxacin (Cipro).

Primary clinical uses of Cipro

UTIs and numerous bacterial infections.

Why is Cipro heavily emphasized in PT pharmacology?

It has a major association with tendinopathy and tendon rupture.

Application: A patient finished Cipro 4 days ago and now reports sudden Achilles pain during therapy. What should the PT suspect?

Fluoroquinolone-induced tendinopathy or tendon rupture until proven otherwise.

Application: How should a PT modify treatment if fluoroquinolone-associated tendon pain is suspected?

Avoid aggressive tendon loading, stop stressing the tendon, communicate with the medical team.

Sulfonamides

Less commonly used systemically because of resistance.

Silver sulfadiazine

Topical sulfonamide commonly used for burn wound care.

Why should PTs know silver sulfadiazine?

It is commonly encountered during burn rehabilitation and wound care.

What is antibiotic resistance?

Natural or acquired bacterial ability to defend against antibiotics.

Major cause of antibiotic resistance

Inappropriate or excessive antibiotic use.

How does prescribing antibiotics for viral infections contribute to resistance?

It unnecessarily exposes bacteria to antibiotics without treating the viral illness.

How does agricultural antibiotic use contribute to resistance?

Antibiotics used in livestock increase bacterial exposure and selection for resistant organisms.

Why has antibiotic prescribing become more selective over time?

To reduce unnecessary antibiotic exposure and slow resistance development.

Application: A patient with viral cold symptoms requests antibiotics. Why would prescribing them be inappropriate?

Antibiotics do not treat viruses and contribute to bacterial resistance.

PT role in reducing antibiotic resistance

Prevent infection spread through hand hygiene, PPE, wound care, equipment cleaning, and infection-control practices.

Which resistant organism was specifically emphasized as requiring additional precautions?

MRSA.

Application: You’re treating a patient with MRSA. What PT responsibilities become especially important?

Follow isolation precautions, use PPE appropriately, maintain excellent hand hygiene, disinfect equipment, prevent spread to others.

Application: Two patients have pneumonia but receive different antibiotics. Why?

Different organisms, susceptibility patterns, allergies, infection severity, patient factors, or antibiotic penetration may require different medications.

Application: Why is identifying the organism before prescribing an antibiotic considered best practice?

It allows selection of the narrowest effective antibiotic, improving treatment and reducing resistance.

Application: An older adult suddenly develops confusion and functional decline. Besides dementia, what infection should the PT consider?

Urinary tract infection (UTI), which commonly presents atypically in older adults.

Application: An older adult’s confusion rapidly improves after antibiotic treatment. What likely caused the symptoms?

Infection (such as UTI) rather than progressive dementia.

Exam pearl: What antibiotic name did the instructor specifically recommend knowing?

Ciprofloxacin (Cipro) because of its major PT implication of tendon injury.

Exam pearl: Which is more important for the final—memorizing every antibiotic mechanism or recognizing drug classes and PT implications?

Recognizing major drug classes, mechanisms in general, and PT implications was emphasized over memorizing every individual mechanism.

What is a virus?

A microorganism containing a nucleic acid core and protein shell that cannot reproduce without using a host cell’s machinery.

What viruses were emphasized in lecture?

Influenza, HIV, hepatitis A/B/C, and COVID (mentioned in discussion).

Why can’t viruses reproduce independently?

They require a host cell to replicate their genetic material and produce new viruses.

What are the two major categories of antiviral agents?

Vaccines and antiviral drugs.

What is prophylaxis?

Prevention of disease before infection occurs.

Vaccines are primarily used for…

Prevention (prophylaxis) of viral infections.

Antiviral drugs may be used for…

Prevention (prophylaxis) and treatment of viral infections.

Application: A patient asks why they still need a vaccine if antiviral medications exist. How would you respond?

Vaccines prevent infection before it occurs, whereas antiviral medications are generally used after exposure or infection and often cannot completely eliminate the virus.

What is a vaccine?

A preparation that stimulates the immune system to recognize a virus before future exposure without causing the full disease.

What types of viruses may be used in vaccines?

Killed viruses or weakened (attenuated) viruses with intact antigenic sites.

Why must the antigen remain intact in a vaccine?

So the immune system can recognize it and develop future immunity.

Why are some vaccines contraindicated in patients with severe egg allergies?

Some vaccines are produced using egg media.

What did the instructor emphasize regarding vaccine safety?

Vaccines are safe and extensive research has found no causal relationship between MMR vaccination and autism.

Which organizations were referenced as supporting vaccine safety?

American Academy of Pediatrics (AAP) and Institute of Medicine (IOM).

Application: A parent asks whether the MMR vaccine causes autism. Based on lecture, how should the PT respond?

Current scientific evidence demonstrates no causal relationship between the MMR vaccine and autism.

Why are vaccines important from a PT perspective?

They prevent diseases that can produce lifelong disability requiring rehabilitation.

Which vaccine-preventable disease has had one of the greatest historical impacts on PT?

Polio.

How did polio influence the PT profession?

PTs played a major role in treating paralysis and weakness in polio clinics, and many neurorehabilitation principles developed from caring for these patients.

What condition may older adults still develop years after surviving polio?

Post-polio syndrome.

Application: An older adult with a history of childhood polio reports new weakness decades later. What condition should the PT suspect?

Post-polio syndrome.

General mechanism of antiviral drugs

Inhibit viral replication while minimizing damage to host cells.

Why is treating viral infections more difficult than treating bacterial infections?

Viruses replicate inside human cells, making it difficult to damage the virus without harming host cells.

What growing challenge was emphasized with antiviral drugs?

Viral resistance.

Interferons are…

Naturally occurring proteins with antiviral activity that increase resistance of nearby healthy cells.

How do interferons work?

They stimulate nearby healthy cells to produce antiviral proteins and resist viral infection.

Originally, interferons were primarily used to treat…

Viral infections.

What diseases are interferons commonly used to treat today?

Multiple sclerosis, hepatitis B, hepatitis C, leukemias, lymphomas, and some cancers.

Which interferon use is most relevant for PT practice?

Multiple sclerosis.

Application: A patient with MS begins interferon therapy. What general medication category are they receiving?

An antiviral-derived immune-modulating protein (interferon).

What is HIV?

Human immunodeficiency virus that progressively attacks the immune system.

What is AIDS?

Advanced stage of HIV disease characterized by severe immune suppression.

Without treatment, HIV leads to…

Progressive immune suppression and increased susceptibility to opportunistic infections.

What are opportunistic infections?

Infections that occur because the immune system is weakened.

Besides infections, HIV increases risk for what other conditions?

Certain cancers and tuberculosis.

What is ART?

Antiretroviral therapy consisting of multiple medications that inhibit HIV replication.

What was ART formerly called?

HAART (Highly Active Antiretroviral Therapy).

How many medications are commonly included in ART?

Three or more medications.

Why are multiple HIV medications used together?

Different drugs inhibit different stages of viral replication, improving effectiveness and reducing resistance.

Did the instructor expect memorization of every HIV drug class?

No. The individual drug classes were presented as FYI only.

What is the primary goal of ART?

Prevent HIV progression and convert HIV into a manageable chronic disease.

What major challenge affects ART success?

Medication adherence because of complex regimens and side effects.

How has HIV prognosis changed over time?

With ART and early diagnosis, HIV has become a chronic manageable illness rather than an immediately fatal disease.

Untreated pediatric HIV commonly results in…

Developmental delays.

What is PrEP?

Pre-exposure prophylaxis using medication to reduce the risk of acquiring HIV before exposure.

Why is injectable PrEP considered an important advancement?

Long-acting injections improve adherence compared with daily medication.

Application: A patient asks why they should take HIV medication if they are not infected but are high-risk. Which therapy are they describing?

Pre-exposure prophylaxis (PrEP).

Application: A patient with HIV reports taking three different antiviral medications. Why is combination therapy preferred?

HIV replicates rapidly and mutates; combination therapy targets multiple stages of replication and reduces resistance.

Application: A patient with HIV is newly diagnosed today. What prognosis should the PT generally expect compared with decades ago?

With early ART and adherence, HIV is often managed as a chronic disease.

Application: Why are patients with HIV more susceptible to opportunistic infections?

HIV progressively suppresses immune function, decreasing the body’s ability to fight infection.