Infection Control — Silvestri Practice Quiz Notes
29 min read
infection-control chain-of-infection transmission-routes standard-precautions transmission-based-precautions contact-precautions droplet-precautions airborne-precautions neutropenic-precautions enteric-precautions tuberculosis anthrax meningitis hepatitis hemodialysis RSV HIV MRSA C-diff syphilis chlamydia gonorrhea toxic-shock-syndrome PID pediculosis conjunctivitis influenza ebola agranulocytosis leukopenia central-venous-line IV-catheter aseptic-technique NCLEX foundations-of-care microbiology pharmacology
Overview
This reference note is derived from a Silvestri Practice Quiz (66 questions) covering Foundations of Care → Infection Control. It is organized to support active study: first by presenting the conceptual framework (chain of infection, precaution types, immunocompromise), then by applying that framework to specific infectious agents.
High-yield exam strategies:
- Know all six components of the chain of infection and be able to identify them in a clinical scenario.
- Given a clinical scenario, identify the transmission route and the appropriate isolation precaution type.
- Identify which nursing intervention breaks the chain of infection for a specific situation.
The Chain of Infection
The chain of infection is a six-link model that describes how a pathogen spreads from one host to another. Breaking any single link interrupts transmission.
| Link | Definition | Examples |
|---|---|---|
| 1. Infectious Agent | The pathogen capable of causing disease | Bacteria, viruses, fungi, parasites |
| 2. Reservoir | The habitat where the agent lives and multiplies | Humans, animals, soil, water, medical equipment |
| 3. Portal of Exit | How the agent leaves the reservoir | Respiratory secretions, wound drainage, blood, feces, urine |
| 4. Mode of Transmission | How the agent travels to a new host | Contact, droplet, airborne, vehicle-borne, vector-borne |
| 5. Portal of Entry | How the agent enters the new host | Mucous membranes, respiratory tract, broken skin, GI tract |
| 6. Susceptible Host | A person who can develop infection | Immunocompromised, elderly, neonates, unvaccinated individuals |
Breaking the Chain — Key Nursing Interventions
- Infectious Agent: antimicrobial therapy, sterilization, disinfection
- Reservoir: treating infected patients, cleaning the environment, proper food storage
- Portal of Exit: covering wounds, containing respiratory secretions (masks, tissues)
- Mode of Transmission: hand hygiene, PPE, isolation precautions, sterilization of equipment
- Portal of Entry: intact skin care, sterile technique, mucous membrane protection
- Susceptible Host: vaccination, adequate nutrition, managing chronic disease, prophylactic therapy
Precaution Systems
Standard Precautions
Standard precautions are applied to the care of all patients regardless of diagnosis or infection status. They are based on the principle that blood, body fluids, non-intact skin, and mucous membranes may be infectious.
Standard precautions include:
- Hand hygiene — the single most effective infection-control measure; performed before and after every patient contact, before donning and after removing gloves, after contact with potentially contaminated surfaces. When performing wound dressing changes, hand hygiene is performed before removing the soiled dressing and again before applying the clean dressing — two separate instances.
- Gloves — worn whenever there is actual or potential contact with blood, body fluids, secretions, excretions, mucous membranes, or non-intact skin.
- Gown — impervious (fluid-resistant) gowns are worn when it is anticipated that clothing or skin will contact splashes of blood or secretions (e.g., wound irrigation).
- Mask and eye protection / face shield — worn during procedures likely to generate splashes or sprays of blood or body fluids. During procedures that aerosolize blood, the nurse wears a mask and protective eyewear or a face shield.
- Safe sharps handling — never recap needles by hand; use safety devices and puncture-resistant sharps containers.
- Respiratory hygiene/cough etiquette — patients with respiratory symptoms should cover their mouth and nose and perform hand hygiene.
- Safe injection practices — use aseptic technique; use a sterile syringe and needle for each injection; never reuse syringes.
- Safe handling of potentially contaminated equipment or surfaces — proper cleaning, disinfection, and sterilization of patient-care equipment.
Transmission-Based Precautions
Transmission-based precautions are used in addition to standard precautions for patients known or suspected to be infected with pathogens that require additional control measures. There are three categories.
Contact Precautions
Used for infections or colonization spread by direct or indirect contact with the patient or the patient’s environment.
- Private room (or cohort with patient with the same infection if a private room is unavailable).
- Gloves and gown — don before entering the room; remove and perform hand hygiene before exiting.
- Patient transport — remove the patient from the room only when absolutely necessary; minimize the risk of transmission during transport.
- Patient-care equipment — dedicate or single-use when possible; if shared, clean and disinfect before use on another patient.
- Examples: MRSA, VRE, C. difficile, wound infections, scabies, conjunctivitis (bacterial), anthrax (cutaneous), pediculosis.
Droplet Precautions
Used for infections spread by large respiratory droplets (>5 µm) expelled during coughing, sneezing, talking, or procedures. Droplets do not remain suspended in air and travel less than 3–6 feet.
- Private room preferred; maintain at least 3 feet (preferably 6 feet) of spatial separation between patients if a private room is unavailable.
- Surgical mask — worn by healthcare workers when within 3–6 feet of the patient.
- Patient transport — have the patient wear a surgical mask.
- Examples: Meningitis (Neisseria meningitidis), influenza, pertussis, rubella, mumps, streptococcal pharyngitis.
Airborne Precautions
Used for infections spread by airborne droplet nuclei (≤5 µm) or dust particles that can remain suspended in air and travel long distances on air currents.
- Airborne Infection Isolation Room (AIIR) — negative-pressure room with at least 6–12 air changes per hour; air exhausted to the outside or through HEPA filtration.
- N95 respirator (or higher) — fitted and worn by healthcare workers entering the room. Standard surgical masks are not sufficient.
- Patient transport — limit transport; have the patient wear a surgical mask during transport.
- Examples: Tuberculosis (TB), varicella (chickenpox), measles (rubeola), disseminated herpes zoster.
Enteric Precautions
Enteric precautions (a subset of contact precautions) are used for infections transmitted by the fecal-oral route — that is, through contaminated food, water, or objects, or through direct contact with fecal material.
- Gloves and gown when contact with feces or fecally contaminated surfaces is anticipated.
- Rigorous hand hygiene with soap and water (alcohol-based hand rub is not effective against C. difficile spores or norovirus; soap and water is preferred).
- Private room or cohort; dedicated bathroom when possible.
- Safe disposal of feces and fecally contaminated materials.
- Patient education on hand hygiene before eating and after toilet use.
- Examples: C. difficile, norovirus, hepatitis A, E. coli O157:H7, Salmonella, Shigella, cholera.
Neutropenic Precautions
Neutropenic precautions (also called protective environment or reverse isolation) are implemented to protect profoundly immunosuppressed patients — particularly those with a severely low neutrophil count — from acquiring infections from the environment or caregivers.
Indications: Absolute neutrophil count (ANC) < 500 cells/mm³, or ANC expected to fall below 500 (e.g., during induction chemotherapy for leukemia, following bone marrow transplant).
Normal reference range: Total WBC 5,000–10,000 cells/mm³. Neutrophils (segs + bands) normally make up 50–70% of the WBC count. An ANC below 1,000 is considered neutropenic; below 500 is severely neutropenic.
Key nursing interventions under neutropenic precautions:
- Private room with positive-pressure airflow (HEPA-filtered air) if available.
- Meticulous hand hygiene by all who enter the room.
- Restrict visitors with signs or symptoms of infection.
- Avoid fresh flowers, plants, and standing water (sources of Pseudomonas and fungi).
- Adhere to a low-microbial (neutropenic) diet: no raw fruits or vegetables, no undercooked meat, no unpasteurized dairy.
- Avoid invasive procedures when possible (rectal temperatures, suppositories, enemas).
- Monitor for subtle signs of infection: fever (often the only sign in a neutropenic patient), chills, changes in vital signs.
- Prompt reporting of fever ≥ 38°C (100.4°F) — febrile neutropenia is a medical emergency.
Agranulocytosis
Agranulocytosis is a severe, acute condition characterized by a profound decrease or near-complete absence of granulocytes (primarily neutrophils) in the peripheral blood, leaving the patient at extreme risk for life-threatening infection.
- Definition: Typically defined as an ANC < 100 cells/mm³ (some sources: < 200 cells/mm³).
- Etiology: Drug-induced (most common) — clozapine, propylthiouracil (PTU), methimazole, carbimazole, certain NSAIDs, chloramphenicol; autoimmune; idiopathic.
- Clinical presentation: High fever, rigors, severe sore throat (pharyngitis, ulcerations), painful mouth sores, signs of systemic infection with no obvious focus, rapid deterioration.
- Nursing priority: Recognize the severity; notify the provider immediately; implement neutropenic precautions; obtain blood cultures before starting antibiotics.
- Management: Discontinue the offending agent; broad-spectrum IV antibiotics; granulocyte colony-stimulating factor (G-CSF; filgrastim) may be used to stimulate neutrophil production; reverse isolation.
Leukopenia
Leukopenia is a decrease in the total white blood cell count below the normal range (< 4,500 cells/mm³ in most adults), indicating a reduced capacity to fight infection. Leukopenia is a broader term than neutropenia (low neutrophils only) or agranulocytosis (near-absent granulocytes).
- Etiology: Bone marrow suppression (chemotherapy, radiation, aplastic anemia), viral infections (HIV, influenza, hepatitis), autoimmune disorders (lupus), nutritional deficiencies (B12, folate), medications (methotrexate, ganciclovir, azathioprine).
- Clinical significance: Degree of risk depends on which WBC type is depleted and by how much. Severe neutropenia carries the greatest infection risk.
- Nursing assessment: Monitor CBC with differential; assess for signs of infection (fever is often the only sign); review medication list for bone marrow–suppressing agents.
- Nursing interventions: Infection prevention (hand hygiene, avoid ill contacts); nutritional support; patient and family education about reporting fever, signs of infection; precautions as indicated by ANC.
Surveillance Methods
Standard (Passive) Surveillance
Relies on routine reporting of disease cases by healthcare providers, laboratories, and public health facilities. Data flow upward (provider → local health department → state → CDC). It is a continuous, ongoing process but may undercount cases due to underreporting.
Active Surveillance
In active surveillance, public health authorities proactively contact healthcare providers, laboratories, and hospitals to solicit reports of specific conditions rather than waiting for providers to report. Active surveillance:
- Produces more complete and timely data than passive surveillance.
- Is used during outbreaks, for rare or high-priority conditions, or to monitor disease trends closely.
- Examples: CDC’s Emerging Infections Program (EIP), sentinel surveillance networks, outbreak investigations.
Community Surveillance
Community surveillance involves monitoring disease occurrence in a defined community population, often using multiple data sources (emergency department visits, school absenteeism, pharmacy sales, social media signals). It is used to detect outbreaks early, track disease trends, and guide public health interventions.
Infectious Agents — Chain of Infection Summaries
Anthrax (Bacillus anthracis)
| Chain Link | Details |
|---|---|
| Infectious Agent | Bacillus anthracis — spore-forming, gram-positive bacillus |
| Reservoir | Soil (spores persist for decades); infected animals (cattle, sheep, goats) |
| Portal of Exit | Soil/environmental release; infected animal hides, meat, or products |
| Mode of Transmission | Contact (cutaneous — direct skin contact with spores); Inhalation (pulmonary — spores aerosolized); Ingestion (gastrointestinal — contaminated undercooked meat) |
| Portal of Entry | Broken skin or mucous membranes (cutaneous); respiratory tract (inhalation); GI tract (ingestion) |
| Susceptible Host | Unvaccinated individuals; agricultural workers; laboratory workers; bioterrorism exposure |
NCLEX key points:
- Three clinical forms: cutaneous (most common, least lethal), inhalation (most lethal), gastrointestinal.
- Cutaneous anthrax: painless black eschar (characteristic ulcer with black center).
- Inhalation anthrax: initially flu-like, then rapid progression to shock and death without early treatment.
- Primary transmission-based precaution: Contact precautions for cutaneous form; standard precautions for inhalation (not person-to-person spread).
Meningitis (Neisseria meningitidis — Bacterial)
| Chain Link | Details |
|---|---|
| Infectious Agent | Neisseria meningitidis (meningococcus); also Streptococcus pneumoniae, Haemophilus influenzae |
| Reservoir | Human nasopharynx (asymptomatic carriers) |
| Portal of Exit | Respiratory secretions from nasopharynx |
| Mode of Transmission | Droplet — large droplets expelled during coughing, sneezing, kissing, close contact (< 3 feet) |
| Portal of Entry | Mucous membranes of the nasopharynx |
| Susceptible Host | Adolescents, college students (dormitory setting), asplenic patients, immunocompromised, unvaccinated |
NCLEX key points:
- Isolation: Droplet precautions for meningococcal meningitis (first 24 hours of effective antibiotic therapy).
- Classic triad: fever, stiff neck (nuchal rigidity), altered mental status.
- Petechial or purpuric rash suggests meningococcemia — a rapidly progressive emergency.
- Close contacts receive prophylaxis (rifampin, ciprofloxacin, or ceftriaxone).
Tuberculosis (Mycobacterium tuberculosis)
| Chain Link | Details |
|---|---|
| Infectious Agent | Mycobacterium tuberculosis — acid-fast bacillus |
| Reservoir | Humans with active pulmonary TB |
| Portal of Exit | Respiratory tract — droplet nuclei generated by coughing, sneezing, singing, speaking |
| Mode of Transmission | Airborne — droplet nuclei (≤ 5 µm) remain suspended in air and travel long distances |
| Portal of Entry | Respiratory tract — inhaled droplet nuclei reach the alveoli |
| Susceptible Host | Immunocompromised (HIV+), malnourished, elderly, homeless, incarcerated populations, close contacts of active cases |
NCLEX key points:
- Isolation: Airborne precautions — negative-pressure AIIR; N95 or HEPA respirator for all healthcare workers entering the room.
- Room requirements: private room with at least 6 air exchanges per hour, negative pressure relative to surrounding areas, air vented to the outside, and ultraviolet lights installed.
- Sputum cultures: collect every 2–4 weeks during active disease.
- Discontinue isolation when: 3 consecutive negative sputum AFB smears are obtained.
- Family members of a newly diagnosed patient: prophylactic isoniazid (INH) for 6–12 months.
- Discharged patient: continues INH therapy for 6–12 months; typically considered non-contagious after 2–3 continuous weeks of effective therapy.
- Noncompliant patients: may be enrolled in directly observed therapy (DOT) — a healthcare worker directly observes the patient swallowing each dose.
- Patient transport: limit movement; if transport is necessary, minimize dispersal of droplet nuclei by placing a surgical mask on the client.
Pediculosis Capitis (Head Lice — Pediculus humanus capitis)
| Chain Link | Details |
|---|---|
| Infectious Agent | Pediculus humanus capitis — ectoparasite |
| Reservoir | Infested humans; fomites (combs, hats, bedding) |
| Portal of Exit | Crawling lice and nits on hair and scalp |
| Mode of Transmission | Contact — direct head-to-head contact; indirect contact via shared fomites |
| Portal of Entry | Scalp and hair (lice attach and lay nits on hair shafts) |
| Susceptible Host | School-age children; crowded environments |
NCLEX key points:
- Contact precautions until 24 hours after treatment initiation.
- Vacuum floors to remove fomites from the environment (carpets, upholstered furniture).
- Wash clothing, bedding, and personal items in hot water (≥ 130°F) and dry on high heat, or seal in plastic bag for 2 weeks.
- Apply pediculicide (permethrin 1% or pyrethrin) per manufacturer instructions; retreat in 9–10 days.
- Notify school/close contacts.
Bacterial Conjunctivitis (“Pink Eye”)
| Chain Link | Details |
|---|---|
| Infectious Agent | Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Neisseria gonorrhoeae |
| Reservoir | Infected humans; contaminated surfaces/fomites |
| Portal of Exit | Purulent eye discharge; hand-to-eye contact |
| Mode of Transmission | Contact — direct contact with infected secretions; indirect contact via fomites (towels, washcloths, contact lenses) |
| Portal of Entry | Conjunctival mucous membrane |
| Susceptible Host | All ages; highest in children; contact lens wearers; neonates (gonococcal) |
NCLEX key points:
- Transmission-based precaution: Contact precautions.
- Frequent handwashing is the most important prevention measure.
- Do not share towels, washcloths, pillowcases, eye makeup, or contact lens cases.
- Antibiotic ophthalmic drops or ointment as prescribed.
- Contagious as long as discharge is present; typically cleared within 24–48 hours of antibiotic treatment.
Viral Conjunctivitis
Viral conjunctivitis is the most common form of conjunctivitis, typically caused by adenovirus. Unlike bacterial conjunctivitis, it produces watery discharge rather than purulent drainage and is highly contagious.
NCLEX key points:
- School exclusion: Keep the child home from school for 24 hours after the start of antibiotic eye drops (even though viral conjunctivitis does not respond to antibiotics, antibiotic drops are sometimes prescribed empirically; the 24-hour exclusion period applies to antibiotic initiation).
- Contact lenses: Clients must discontinue wearing contact lenses until the infection has cleared completely. Obtaining new contact lenses eliminates the risk of reinfection from contaminated lenses and reduces the risk of corneal ulceration.
- Highly contagious; spreads via direct contact with infected secretions and fomites.
- No antibiotic is curative for viral conjunctivitis; management is supportive (cool compresses, artificial tears).
- Standard precautions; contact precautions in healthcare settings.
Hepatitis A (HAV)
| Chain Link | Details |
|---|---|
| Infectious Agent | Hepatitis A virus (HAV) — non-enveloped RNA picornavirus |
| Reservoir | Infected humans |
| Portal of Exit | Feces (high viral load in stool 2 weeks before symptoms appear) |
| Mode of Transmission | Fecal-oral (enteric) — contaminated food or water; person-to-person contact |
| Portal of Entry | GI tract (oral ingestion) |
| Susceptible Host | Unvaccinated individuals; travelers to endemic areas; close contacts of infected persons |
NCLEX key points:
- Enteric/contact precautions during hospitalization.
- Not infectious 1 week after the onset of jaundice — key NCLEX fact.
- No chronic infection; self-limiting; supportive care.
- Prevention: HAV vaccine; hand hygiene; safe food and water handling.
Hepatitis B (HBV)
| Chain Link | Details |
|---|---|
| Infectious Agent | Hepatitis B virus (HBV) — DNA hepadnavirus |
| Reservoir | Infected humans (blood, semen, vaginal secretions, saliva, breast milk) |
| Portal of Exit | Blood and blood products; sexual secretions; breast milk |
| Mode of Transmission | Blood-borne / contact — sexual contact, percutaneous (needlestick, sharing needles), perinatal (mother to neonate), mucous membrane exposure |
| Portal of Entry | Bloodstream via percutaneous route, mucous membranes, or perinatal transmission |
| Susceptible Host | Unvaccinated individuals; healthcare workers; IV drug users; persons with multiple sexual partners; infants of infected mothers |
NCLEX key points:
- Standard precautions (no special isolation required for HBV beyond standard precautions).
- Can progress to chronic hepatitis, cirrhosis, and hepatocellular carcinoma.
- Prevention: HBV vaccine series (standard of care for all infants and unvaccinated adults); hepatitis B immune globulin (HBIG) for post-exposure prophylaxis.
- Needlestick with HBV-positive source: report immediately, check vaccination status, administer HBIG and/or booster as appropriate.
Hemodialysis and Hepatitis B Risk
A significant complication associated with hemodialysis is the acquisition of dialysis-associated hepatitis B. This risk extends to clients receiving dialysis (who may carry the virus), their families (at risk from contact with the client and with environmental surfaces), and dialysis staff (who may acquire the virus from contact with the client’s blood).
NCLEX key points:
- Risk is minimized through consistent use of standard precautions, appropriate handwashing, and rigorous sterilization procedures.
- Eating, drinking, and other hand-to-mouth activities are prohibited in the hemodialysis unit — a critical infection-control rule for this setting.
- Standard precautions are sufficient; no special isolation category is required solely for HBV-positive dialysis clients.
- All hemodialysis staff and at-risk family members should receive the hepatitis B vaccine series.
Respiratory Syncytial Virus (RSV)
| Chain Link | Details |
|---|---|
| Infectious Agent | Respiratory syncytial virus (RSV) — RNA pneumovirus |
| Reservoir | Infected humans |
| Portal of Exit | Respiratory secretions; nasal discharge |
| Mode of Transmission | Contact (primary) — direct and indirect contact with contaminated surfaces and subsequent self-inoculation of mucous membranes; Droplet — large droplets at close range |
| Portal of Entry | Conjunctival and nasal mucous membranes |
| Susceptible Host | Infants < 2 years (especially premature infants, CHD, CLD); immunocompromised adults; elderly |
NCLEX key points:
- Contact + Droplet precautions.
- Antiviral treatment: ribavirin (inhaled) — used in severe RSV disease in high-risk pediatric patients.
- Palivizumab (Synagis) — monthly IM immunoprophylaxis for high-risk infants during RSV season.
- Priority nursing concern in infants: respiratory distress, apnea, hypoxia.
Chlamydia (Chlamydia trachomatis)
| Chain Link | Details |
|---|---|
| Infectious Agent | Chlamydia trachomatis — obligate intracellular bacterium |
| Reservoir | Infected humans (genital tract) |
| Portal of Exit | Genital secretions |
| Mode of Transmission | Sexual contact (most common); perinatal (mother to neonate during delivery) |
| Portal of Entry | Genital/urinary mucous membranes; conjunctival mucosa (neonate) |
| Susceptible Host | Sexually active individuals (highest rates in 15–24 year olds); neonates of infected mothers |
NCLEX key points:
- Standard precautions (no special isolation).
- Most common reportable STI in the United States.
- Often asymptomatic — routine screening recommended (USPSTF: sexually active women ≤ 24, older women at increased risk).
- Untreated: pelvic inflammatory disease (PID), ectopic pregnancy, infertility.
- Treatment: azithromycin (single dose) or doxycycline; treat partner(s).
- Neonatal chlamydial conjunctivitis: erythromycin ophthalmic ointment prophylaxis at birth.
Beta-Hemolytic Streptococcal Infection (Group A Strep — Streptococcus pyogenes)
| Chain Link | Details |
|---|---|
| Infectious Agent | Group A Streptococcus pyogenes — gram-positive coccus |
| Reservoir | Infected or colonized humans (pharynx, skin) |
| Portal of Exit | Respiratory secretions; wound drainage |
| Mode of Transmission | Droplet (pharyngitis); Contact (impetigo, wound infections) |
| Portal of Entry | Respiratory mucous membranes; broken skin |
| Susceptible Host | Children 5–15 years (pharyngitis); any age (skin infections); crowded or institutional settings |
NCLEX key points:
- Droplet precautions for streptococcal pharyngitis; contact precautions for draining wounds.
- Untreated: rheumatic fever, post-streptococcal glomerulonephritis.
- Treatment: penicillin or amoxicillin (drug of choice); erythromycin for penicillin-allergic patients.
- Non-contagious after 24 hours of effective antibiotic therapy.
Pelvic Inflammatory Disease (PID)
PID is an ascending infection of the female upper reproductive tract (uterus, fallopian tubes, ovaries) caused most commonly by Chlamydia trachomatis and Neisseria gonorrhoeae, often polymicrobial.
NCLEX key points:
- Avoid frequent douching — disrupts the natural protective vaginal flora and increases susceptibility to ascending infection.
- Intrauterine devices (IUDs) increase susceptibility to PID, particularly in the weeks after insertion.
- Position: Semi-Fowler’s — gravity assists drainage of purulent material into the pelvic cavity rather than upward toward the diaphragm, preventing abscess formation high in the abdomen. Abscesses near the diaphragm can rupture and cause peritonitis.
- Monitor for complications: tubo-ovarian abscess, ectopic pregnancy, chronic pelvic pain, infertility.
- Treatment: broad-spectrum antibiotics (ceftriaxone + doxycycline ± metronidazole per CDC guidelines).
Toxic Shock Syndrome (TSS)
TSS is a life-threatening, toxin-mediated illness caused by Staphylococcus aureus (or less commonly Streptococcus pyogenes) that can be associated with tampon use, wound infections, and post-surgical infections.
Classic signs and symptoms:
- High fever ≥ 38.9°C (102°F) — sudden onset
- Hypotension (systolic BP < 90 mmHg)
- Diffuse macular erythroderma (sunburn-like rash)
- Desquamation of palms and soles (1–2 weeks after illness onset)
- Vomiting and severe diarrhea
- Multiorgan involvement (renal, hepatic, muscular, mucosal)
NCLEX key point: Vaginal bleeding or discharge is not a sign or symptom of TSS. Do not confuse TSS with other gynecological conditions.
Nursing management: Remove the source (tampon, wound packing); IV fluids; vasopressors for refractory hypotension; antistaphylococcal antibiotics; ICU-level care for multiorgan failure.
Syphilis (Treponema pallidum)
| Chain Link | Details |
|---|---|
| Infectious Agent | Treponema pallidum — spirochete |
| Reservoir | Infected humans |
| Portal of Exit | Syphilitic lesions (chancre); blood; sexual secretions |
| Mode of Transmission | Direct contact — sexual contact with active lesion; transplacental (congenital syphilis) |
| Portal of Entry | Mucous membranes; broken skin |
| Susceptible Host | Sexually active individuals; neonates of infected mothers |
NCLEX key points:
- Standard precautions (contact precautions if active moist lesions are present).
- Primary syphilis: painless, indurated ulcer (chancre) at the site of inoculation — resolves spontaneously.
- Secondary syphilis: diffuse maculopapular rash (including palms and soles), condylomata lata, systemic symptoms.
- Tertiary/late syphilis: gummas, cardiovascular syphilis (aortitis), neurosyphilis.
- Treatment: penicillin G (drug of choice for all stages); doxycycline for penicillin-allergic non-pregnant patients.
- Congenital syphilis: treat with penicillin G; notify public health authorities.
Human Immunodeficiency Virus (HIV)
| Chain Link | Details |
|---|---|
| Infectious Agent | Human immunodeficiency virus — RNA retrovirus |
| Reservoir | Infected humans |
| Portal of Exit | Blood, semen, vaginal secretions, breast milk, cerebrospinal fluid |
| Mode of Transmission | Blood-borne / contact — sexual contact (anal > vaginal); percutaneous (needlestick, sharing needles); perinatal; breast milk |
| Portal of Entry | Bloodstream; mucous membranes; perinatal |
| Susceptible Host | All individuals with exposure risk; immunosuppression worsens prognosis |
NCLEX key points:
- Standard precautions (no special isolation unless a co-infection requires it). Having an HIV-positive status alone does not warrant a special type of precaution.
- HIV destroys CD4+ T lymphocytes — CD4 count < 200 cells/mm³ defines AIDS.
- Antiretroviral therapy (ART) is the cornerstone of management; combination therapy (cART/HAART).
- Post-exposure prophylaxis (PEP): initiated within 72 hours of exposure; 28-day course.
- Pre-exposure prophylaxis (PrEP): daily tenofovir/emtricitabine (Truvada) or tenofovir alafenamide/emtricitabine (Descovy) for high-risk individuals.
- Opportunistic infections: Pneumocystis jirovecii pneumonia (PCP), Toxoplasma, CMV, MAC.
- Nursing: universal precautions; psychosocial support; medication adherence counseling; partner notification.
MRSA (Methicillin-Resistant Staphylococcus aureus)
The CDC places MRSA at Tier 2 of the transmission-based precaution categories. Contact precautions are required.
NCLEX key points:
- Contact precautions — private room, gloves, and gown required.
- If wound irrigation or other procedures may produce splashes from wound drainage, a face shield is worn as well.
- Dedicate or single-use patient-care equipment; clean and disinfect shared equipment between patients.
- Decolonization protocols (e.g., intranasal mupirocin, chlorhexidine bathing) may be implemented per facility policy.
- MRSA surveillance cultures (nares, axillae, groin) are performed per facility protocol on admission to high-risk units.
- Educate the client and family on contact precaution rationale, hand hygiene, and the importance of antibiotic stewardship.
Clostridium difficile (C. difficile / C. diff)
C. difficile is a spore-forming bacterium that disrupts healthy bowel flora, leading to profuse diarrhea ranging from mild colitis to life-threatening pseudomembranous colitis. Because the infection is transmitted through spores in the stool, it is highly persistent in the environment.
NCLEX key points:
- Contact precautions — gloves and gown required; a mask is not necessary unless another condition transmitted by droplet or airborne routes is also present (or agency policy mandates it).
- Hand hygiene with soap and water is required — alcohol-based hand rubs are not effective against C. difficile spores.
- Environmental disinfection: a 10% bleach solution or a sporicidal disinfectant must be used on surfaces and equipment. Soap and water, alcohol-based solutions, and ammonia-based disinfectants do not destroy C. difficile spores.
- Private room or cohort with a client who has the same infection; dedicated bathroom when possible.
- Treatment: metronidazole (mild–moderate disease) or oral vancomycin/fidaxomicin (severe or recurrent disease); discontinue the causative antibiotic if possible.
Influenza
Influenza is an acute respiratory illness caused by influenza A or B viruses, transmitted primarily by large respiratory droplets and, to a lesser extent, by contact with contaminated surfaces.
NCLEX key points:
- Droplet precautions in the healthcare setting.
- Influenza vaccination is recommended annually and developed according to predicted strains for the upcoming season.
- High-risk populations who should receive the vaccine: clients with chronic respiratory disorders, chronic metabolic diseases (e.g., diabetes mellitus), residents of chronic care facilities, elderly adults, and healthcare workers.
- The influenza vaccine does not treat an active influenza infection — it is preventive only.
- Antiviral medications (oseltamivir, zanamivir) are most effective when started within 48 hours of symptom onset.
Ebola Virus Disease (EVD)
Ebola virus disease (EVD) is a severe, often fatal hemorrhagic fever caused by Ebolavirus. Given the high mortality and transmissibility through direct contact with infected body fluids, rapid identification and isolation are the priority nursing actions.
NCLEX key points:
- Isolate first, then assess and notify. When a client meets exposure criteria, the priority is to isolate the client in a private room before other treatment measures are taken.
- Exposure criteria include travel to an endemic region (e.g., West Africa) combined with: fever ≥ 38.0°C (100.4°F) reported at home or in the ED, OR symptoms including headache, fatigue, weakness, muscle pain, vomiting, diarrhea, abdominal pain, or signs of bleeding.
- After isolating, the nurse may then collect additional history, notify the PHCP, and alert state and local public health authorities.
- PPE requirements are strict: full PPE including impervious gown, gloves (double-gloving recommended), face shield, and N95 or PAPR (powered air-purifying respirator).
- Transmission: direct contact with blood and body fluids of an infected symptomatic person — not airborne in typical community or clinical settings.
Clinical Procedures and Infection Control
IV Catheter Insertion — Aseptic Site Preparation
When inserting a peripheral intravenous catheter, the nurse prepares the skin using a circular motion from the center (insertion site) outward. This standard, accepted aseptic technique carries microorganisms away from the insertion site, reducing the risk of introducing pathogens into the bloodstream.
NCLEX key point: Movement is always inward → outward (never back-and-forth or outward → inward) to prevent re-contamination of the cleaned area.
IV Tubing Sterility
The insertion spike of IV tubing must remain sterile throughout preparation and administration.
NCLEX key points:
- If the insertion spike is touched or contaminated during preparation, the tubing must be discarded and replaced with a new sterile set. Using contaminated tubing can introduce infection directly into the client’s bloodstream.
- IV tubing is changed per agency policy and manufacturer recommendations (typically every 72–96 hours for continuous infusions, or per specific product guidelines).
- Maintain sterile technique throughout IV setup; document tubing change dates and times.
Central Venous Line — Suspected Infection
Central line-associated bloodstream infection (CLABSI) is a serious, potentially life-threatening complication. The nurse must recognize signs early and act promptly.
Signs of infection at the catheter site:
- Local: redness (erythema), warmth, swelling, or purulent drainage at the insertion site.
- Systemic: chills, fever, and an elevated white blood cell count.
Nursing actions (in sequence):
- Notify the primary health care provider (PHCP) immediately because of the risk for sepsis.
- Obtain blood cultures before starting antibiotics — starting antibiotics before cultures are drawn may render culture results inaccurate.
- Prepare the client for catheter removal and possible restart at a different site (a trained nurse may remove a central line per approved protocol).
- If requested, send the catheter tip to the laboratory for culture to identify the causative organism.
- Administer IV antibiotics as prescribed; an alternative IV site will be needed.
- Document the occurrence, actions taken, and the client’s response; photograph the infected site per agency protocol.
Antibiotic Treatment Correlations for STIs
| Pathogen / Condition | Drug of Choice |
|---|---|
| Neisseria gonorrhoeae (gonorrhea) | Ceftriaxone (IM) + doxycycline (if chlamydia co-infection not excluded) |
| Genital herpes simplex virus (HSV) | Acyclovir (or valacyclovir, famciclovir) |
| Chlamydia trachomatis | Azithromycin (single dose) or doxycycline |
| Treponema pallidum (syphilis) | Penicillin G benzathine (IM) |
NCLEX tip: Nongonococcal urethritis (NGU) is most commonly caused by Chlamydia trachomatis. Standard precautions are adequate — contact precautions are not required.
Quick-Reference: Transmission Route by Pathogen
| Pathogen / Condition | Transmission Route | Precaution Type |
|---|---|---|
| Anthrax (cutaneous) | Contact | Contact |
| Anthrax (inhalation) | Inhalation of spores | Standard (not person-to-person) |
| Meningitis (N. meningitidis) | Droplet | Droplet |
| Tuberculosis | Airborne (droplet nuclei) | Airborne (N95 or HEPA) |
| Pediculosis capitis | Contact (fomites) | Contact |
| Bacterial conjunctivitis | Contact | Contact |
| Viral conjunctivitis | Contact | Standard / Contact |
| Hepatitis A | Fecal-oral | Contact / Enteric |
| Hepatitis B | Blood-borne | Standard |
| RSV | Contact + Droplet | Contact + Droplet |
| Chlamydia / NGU | Sexual contact | Standard |
| Gonorrhea | Sexual contact | Standard |
| Group A Strep (pharyngitis) | Droplet | Droplet |
| Group A Strep (wound) | Contact | Contact |
| MRSA | Contact | Contact (private room, gown, gloves) |
| C. difficile | Contact (fecal-oral) | Contact (soap & water; sporicidal) |
| Influenza | Droplet | Droplet |
| Mycoplasmal pneumonia | Droplet (>5 µm) | Droplet |
| Ebola virus disease | Direct contact (blood/fluids) | Contact + full PPE |
| PID | Ascending infection | Standard |
| Toxic Shock Syndrome | Toxin-mediated | Standard |
| Syphilis | Contact (lesion/sexual) | Standard (Contact if active lesion) |
| HIV | Blood-borne | Standard |
Study Tips
- NCLEX priority question stem: “Which action by the nurse is most important?” → Hand hygiene is almost always the answer for general infection control.
- Isolation room assignment: TB always requires a negative-pressure room with ≥ 6 air exchanges per hour and UV lights; protective environment (positive-pressure) is for neutropenic patients — do not confuse these.
- Chain of infection: If a question asks how to “break the chain,” identify which link is being targeted by the intervention (e.g., handwashing breaks the mode of transmission link).
- Sputum cultures for TB: Three consecutive negative AFB smears = patient can be removed from airborne isolation.
- TSS: No vaginal bleeding on the signs/symptoms list — this is a classic NCLEX distractor.
- Chancre: Remember — syphilitic chancre is painless (vs. herpes lesions which are painful).
- C. diff disinfection: Only bleach or sporicidal agents destroy spores — alcohol hand rubs and ammonia cleaners are ineffective.
- HIV precautions: Standard precautions only — HIV status alone does not require contact, droplet, or airborne precautions.
- MRSA = Tier 2 Contact: Private room + gloves + gown; add face shield if wound irrigation may cause splash.
- Blood cultures before antibiotics: For CLABSI or any suspected bacteremia, cultures must be drawn before antibiotics are started.
- IV spike: If the insertion spike is contaminated, discard the entire set — never use contaminated IV tubing.
- NGU: Nongonococcal urethritis is most commonly secondary to chlamydia — standard precautions only.
- Antibiotic pearls: Gonorrhea = ceftriaxone; Chlamydia = azithromycin; Syphilis = penicillin G benzathine; Herpes = acyclovir.
- Ebola isolation priority: Isolate the client in a private room first, then assess, collect data, and notify authorities.
- Patient transport on airborne precautions: Place a surgical mask on the client to minimize dispersal of droplet nuclei during transport.
Related Content
Encyclopedia
Courses