Infectious Diseases

Infectious Diseases: Overview of Microorganisms and Transmission

  • Categories of Infectious Microorganisms

    • Bacteria:

    • Characteristics: Single-celled organisms lacking a nucleus.

    • Mycoplasmas:

    • Characteristics: Type of bacterium with no cell wall.

    • Viruses:

    • Characteristics: Multiply only within living cells of a host.

    • Protozoans:

    • Characteristics: Single-celled organisms with a nucleus.

    • Prions:

    • Characteristics: Transmitted from animals to humans; contain proteins without nucleic acids.

Chain of Transmission

  • The chain of transmission consists of six components:

    • Reservoir (Environment/Habitat):

    • Description: Where pathogens live and multiply.

    • Portal of Exit:

    • Description: Method through which pathogens exit the reservoir.

    • Examples: Skin-to-skin, blood, mucous membranes, oral cavity, feces, saliva, semen.

    • Mode of Transport:

    • Description: How pathogens move from reservoir to susceptible host.

    • Types:

      • Direct transmission

      • Airborne droplet contact

      • Vector-borne transmission (bites)

      • Indirect transmission (contaminated equipment, water, food).

    • Portal of Entry:

    • Description: Openings where pathogens enter the host.

    • Examples: Mouth, eyes, urinary tract, respiratory tract, wounds.

    • Susceptible Host:

    • Description: Individual most at risk for infection (patients or healthcare workers).

Clinical Manifestations of Infectious Diseases

  • Clinical manifestations vary by microorganism and affected system:

    • Cardiovascular System:

    • Symptoms: Capillary hemorrhaging, changes in heart rate, and blood pressure.

    • Respiratory System:

    • Symptoms: Sore throat, cough, shortness of breath, changes in respiratory rate, decreased exercise tolerance.

    • Central Nervous System:

    • Examples: Meningitis, encephalitis.

    • Symptoms: Headaches, photophobia, stiff neck, altered consciousness, seizures.

    • Gastrointestinal System (GI):

    • Symptoms: Nausea, vomiting, diarrhea (food poisoning).

    • Genitourinary System:

    • Symptoms: Flank pain, pain with urination, increased frequency, urgency.

    • Integumentary System:

    • Symptoms: Cardinal signs of inflammation (redness, swelling, warmth, pain).

Infection Control Measures

  • Importance of controlling transmission as a healthcare provider:

    • Practices:

    • Handwashing

    • Wearing appropriate PPE

    • Covering coughs

    • Wearing masks when indicated

    • Keeping immunizations up to date.

Specific Infections and Their Characteristics

Clostridium difficile (C. diff)

  • Characteristics:

    • Causes diarrhea and colitis.

    • Produces exotoxins damaging to epithelial cells of the GI tract.

    • Symptoms: Persistent diarrhea, abdominal cramping, fever (watery stools three times a day or more).

    • Treatment: Requires discontinuing antibiotics, beginning treatment with Flagyl.

    • Transmission: Both direct and indirect contact.

    • Hand hygiene: Requires soap and water, not alcohol-based solution.

Staphylococcus aureus

  • Transmission:

    • Through direct contact; infected area touched by uninfected person.

  • Examples of localized infections: Skin abscesses, boils, oozing blisters.

  • Common infection sites:

    • Skin (axilla, groin, perineum), nasal passages.

  • Deep tissue infections:

    • Cellulitis, osteomyelitis, bacterial arthritis, endocarditis.

Streptococcal Infections

  • Common types:

    • Streptococcal Pharyngitis:

    • Known as strep throat; infection of tonsils.

    • Scarlet Fever:

    • Complication of untreated strep, can stem from untreated wounds.

    • Impetigo:

    • Common in children; causes crusty skin lesions.

    • Necrotizing Fasciitis:

    • Rare, spreads rapidly, is life-threatening.

    • Streptococcal Pneumonia:

    • Community-acquired pneumonia, often in the elderly, may follow influenza.

Epstein-Barr Virus (Mono)

  • Characteristics:

    • Causes mononucleosis.

    • Largely asymptomatic in children, symptomatic in young adults.

    • Symptoms: Enlarged lymph nodes, neck pain, fatigue, evening spikes in fever, abdominal pain, hepatomegaly, splenic enlargement (risk of rupture).

    • Dormancy: Virus remains dormant in B lymphocytes, can reactivate when immune system is compromised (anxiety, stress, disease).

    • Complications: Chronic fatigue syndrome, increased risk of multiple sclerosis (MS), predisposition to certain cancers.

Varicella Zoster Virus (Shingles)

  • Reactivation disease stemming from chicken pox in infancy/childhood.

  • Chicken pox:

    • Self-limiting respiratory illness; complications rare during childhood.

    • Symptoms: Rose petal rash, headaches, light sensitivity, itching.

    • Resolution: Typically occurs within a week or two.

  • Shingles (reactivation):

    • Manifests as unilateral, painful blisters along dermatomes; resolution takes weeks.

    • Postherpetic neuralgia: Residual pain after healing of blisters.

    • Transmissible to unvaccinated individuals who have not had chicken pox.

Osteomyelitis and Myositis

Osteomyelitis

  • Characteristics: Bone infection, commonly caused by Staphylococcus infection.

  • Chief complaints: Back pain or bone pain in adults, acute severe pain in children.

  • Symptoms may include systemic complications (low-grade fever) and localized manifestations (edema, redness, tenderness).

  • Diagnosis: Can be complicated by the rapid spread of infectious agents and the initial lack of pain in certain infection stages.

Myositis

  • Definition: Inflammation of the muscles; multiple causes including autoimmune conditions, infections.

  • Infections causing myositis: Commonly caused by Staphylococcus and parasites (e.g., trichinella, tapeworm larvae).

  • Symptoms: Nonspecific including malaise, muscle swelling, pain, tenderness, lethargy.

  • Diagnosis: Based on history, muscle biopsy, and possibly electromyography and CBC.

Prosthetic Joint Infections

  • Categories of Infections*:

    • Timing of Occurrence:

    • Early (< 3 months post-surgery): Acute symptoms (fever, joint pain, warmth, redness).

    • Delayed (3-24 months post-surgery): Symptoms may vary; less acute.

    • Late (> 24 months post-surgery): Symptoms may arise due to chronic infection.

  • Routes of Infection:

    • Homogenous (30%): From dental, skin, urinary tract infections or procedures.

    • Locally introduced (70%): Occurring due to localized wound infection or operative contamination.

  • Clinical Manifestations: Symptoms may include pain at the site of the prosthesis, fever, purulent drainage, constant joint pain, risk of implant failure.

Pharmacological Management of Infectious Conditions

Immune Disorders Management

  • Hypersensitivity Reactions:

    • Medications:

    • Epinephrine for anaphylaxis.

    • Antihistamines for histamine response management.

    • Corticosteroids for immune suppression.

    • Albuterol for bronchoconstriction (asthma).

  • Weakened Immune System:

    • Vaccines for prevention.

    • Management depends on specific disorders (e.g., HIV/AIDS).

Antibiotics and Actions

  • Bacterial Infections:

    • Vancomycin:

    • Mechanism: Binds to bacterial cell wall, impairing synthesis.

    • Target: Effective against gram-positive bacilli.

    • Risks: Resistance development, hypersensitivity reactions, GI disturbances, nephrotoxicity, ototoxicity.

    • Amoxicillin:

    • Mechanism: Inhibits bacterial cell membrane synthesis; broad antibacterial spectrum.

    • Risks: Skin rash, potential breathing difficulties.

Viral Infectious Conditions

  • Mononucleosis:

    • Treatment: Antibiotics not first-line; supportive care (rest, fluids) unless secondary bacterial infection occurs.

Antibacterial Resistance

  • Overview:

    • Development of bacterial strains resistant to drugs due to defense mechanisms, enzymatic drug destruction, or genetic mutations.

  • Examples:

    • VRE: Vancomycin-Resistant Enterococcus (serious implications).

    • MRSA: Methicillin-Resistant Staphylococcus Aureus (significance in clinical settings).

  • Prevention Strategies:

    • Avoiding overuse of antibiotics.

    • Utilizing culture tests to select appropriate antibiotics.

    • Practicing sterile techniques and hand hygiene.

    • Patients must complete antibiotic courses to prevent further resistance.