2.2 Bacterial Diseases: Pneumococcal, Meningococcal, Tetanus, Diphtheria, and Pertussis
Key Takeaways
- Streptococcus pneumoniae causes both non-invasive infections (otitis media, non-bacteremic pneumonia) and Invasive Pneumococcal Disease (IPD: bacteremia, meningitis); conjugate vaccines (PCV15, PCV20, PCV21) elicit T-cell-dependent mucosal and systemic memory via CRM197 carrier protein, whereas pure polysaccharide PPSV23 elicits T-cell-independent responses.
- Neisseria meningitidis serogroups A, B, C, W, and Y cause fulminant bacteremia and meningitis. MenACWY and MenB products are considered for otherwise healthy adolescents through the current shared clinical decision framework and are recommended for specified high-risk groups such as asplenia and complement deficiency.
- Clostridium tetani produces tetanospasmin, a neurotoxin that blocks inhibitory GABA and glycine release in spinal Renshaw interneurons, producing lockjaw (trismus), risus sardonicus, painful muscle spasms, and autonomic dysfunction.
- Corynebacterium diphtheriae produces an AB exotoxin that inhibits cellular protein synthesis via EF-2 ADP-ribosylation, forming a gray pseudomembrane with risk of airway obstruction, myocarditis, and neuropathies.
- Bordetella pertussis causes whooping cough characterized by severe paroxysmal coughing spasms and post-tussive emesis; pediatric DTaP contains full-dose diphtheria and pertussis antigens, whereas adolescent/adult Tdap contains reduced-quantity antigens to minimize reactogenicity.
Last updated: August 2026
2.2 Bacterial Diseases: Pneumococcal, Meningococcal, Tetanus, Diphtheria, and Pertussis
Bacterial infections and toxoid-mediated diseases account for substantial morbidity and mortality across the human lifespan. A firm grasp of bacterial virulence factors, invasive disease definitions, toxin mechanisms of action, and the immunologic differences between pure polysaccharide, conjugate, and toxoid vaccines is essential for pharmacy technicians.
1. Pneumococcal Disease (Streptococcus pneumoniae)
Streptococcus pneumoniae (the pneumococcus) is an encapsulated, lancet-shaped, gram-positive diplococcus that is alpha-hemolytic under aerobic conditions. The primary virulence factor is its polysaccharide capsule, which interferes with host phagocytosis by preventing opsonization with complement C3b. Over 100 distinct pneumococcal serotypes have been identified based on capsular antigenicity.
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| PNEUMOCOCCAL DISEASE SPECTRUM |
| |
| [ NON-INVASIVE PNEUMOCOCCAL DISEASE ] |
| - Mucosal surface extension from colonized nasopharynx |
| - Acute Otitis Media (middle ear infection; leading cause in infants) |
| - Acute Bacterial Sinusitis |
| - Non-bacteremic Pneumonia (lobar consolidation without bloodstream entry)|
| |
| [ INVASIVE PNEUMOCOCCAL DISEASE (IPD) ] |
| - Isolation of S. pneumoniae from a NORMALLY STERILE body site |
| - Pneumococcal Bacteremia / Sepsis |
| - Pneumococcal Meningitis (high mortality, permanent sensorineural loss) |
| - Bacteremic Pneumonia, Septic Arthritis, Osteomyelitis, Peritonitis |
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Immunology: Pure Polysaccharide vs. Protein-Conjugate Vaccines
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| POLYSACCHARIDE VS. CONJUGATE IMMUNOLOGY |
| |
| PURE POLYSACCHARIDE (PPSV23) CONJUGATE VACCINES (PCV15, PCV20, PCV21) |
| ──────────────────────────── ─────────────────────────────────────── |
| • Antigens: Pure capsular sugars • Antigens: Capsular sugars covalently linked to a |
| • Immune Response: T-CELL INDEPENDENT carrier protein (CRM197 mutant diphtheria toxin) |
| • B-cells cross-link surface IgM • Immune Response: T-CELL DEPENDENT |
| • Poor/No memory B-cell induction • Carrier protein processed and presented by B-cells |
| • NO booster response with re-vaccination to CD4+ T helper cells via MHC Class II |
| • Ineffective in children < 2 years • Robust memory B-cell and T-cell induction |
| • Does NOT reduce mucosal colonization • High IgG affinity maturation and class switching |
| • Effective in infants < 2 years of age |
| • Eradicates nasopharyngeal carriage (herd immunity) |
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Current Pneumococcal Vaccine Formulations
- PCV15 (Vaxneuvance): 15-valent conjugate vaccine covering serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F, and 33F conjugated to CRM197.
- PCV20 (Prevnar 20): 20-valent conjugate covering PCV15 serotypes plus 8, 10A, 11A, 12F, and 15B conjugated to CRM197.
- PCV21 (Capvaxive): Adult 21-valent conjugate containing serotypes 3, 6A, 7F, 8, 9N, 10A, 11A, 12F, 15A, de-O-acetylated 15B, 16F, 17F, 19A, 20A, 22F, 23A, 23B, 24F, 31, 33F, and 35B, each conjugated to CRM197.
- PPSV23 (Pneumovax 23): 23-valent pure unconjugated polysaccharide vaccine covering 23 common serotypes. Administered IM or SC.
ACIP Pneumococcal Guidance Summary
- Routine Pediatric Schedule: 4-dose PCV series at 2, 4, 6, and 12–15 months of age.
- Routine Adult Schedule (Age ≥ 50): For adults with an unknown or no prior pneumococcal conjugate vaccine, give PCV20 or PCV21 alone, or PCV15 followed by PPSV23 (usually ≥1 year later; a minimum 8-week interval applies only to specified high-risk situations).
- Adults Aged 19–64 with Risk Factors: Recommended for individuals with chronic medical conditions (diabetes, chronic lung/heart/liver disease, cigarette smoking) or immunocompromising conditions (asplenia, HIV, chronic renal failure, leukemia, immunosuppressive therapy).
2. Meningococcal Disease (Neisseria meningitidis)
Neisseria meningitidis (the meningococcus) is an aerobic, encapsulated, gram-negative diplococcus. Six capsular serogroups—A, B, C, W, X, and Y—cause virtually all invasive human disease globally.
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| MENINGOCOCCAL PATHOGENESIS |
| |
| 1. Nasopharyngeal Colonization (Asymptomatic carriage in 10% of populace) |
| │ |
| ▼ (Mucosal penetration into subepithelial space) |
| 2. Bloodstream Invasion (Meningococcemia) |
| │ |
| ▼ (Massive shedding of Lipooligosaccharide [LOS] Endotoxin) |
| 3. Endotoxin-Mediated Vascular Collapse & Disseminated Intravascular |
| Coagulation (DIC) |
| - Capillary leakage, petechial and purpuric skin lesions |
| - Purpura fulminans leading to peripheral gangrene and amputation |
| - Bilateral adrenal hemorrhage (Waterhouse-Friderichsen Syndrome) |
| │ |
| ▼ (Seeding across blood-brain barrier) |
| 4. Acute Bacterial Meningitis (Fever, nuchal rigidity, AMS, coma) |
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High-Risk Populations
- Adolescents and young adults living in close congregate quarters (college freshmen residing in residence halls, military recruits)
- Individuals with anatomical or functional asplenia (e.g., sickle cell disease, surgical splenectomy)
- Individuals with persistent complement component deficiencies (C3, C5–C9, properdin, factor D, factor H)
- Patients taking complement inhibitors (e.g., eculizumab [Soliris], ravulizumab [Ultomiris])
- Microbiologists routinely exposed to N. meningitidis isolates
- International travelers to the sub-Saharan African "meningitis belt" or pilgrims attending the Hajj
Meningococcal Vaccine Lineup
| Vaccine Class | Products | Serogroups Covered | Target Population & Routine Schedule |
|---|---|---|---|
| MenACWY Conjugates | Menveo (CRM197 conjugate)<br>MenQuadfi (Tetanus toxoid conjugate) | A, C, W, Y | The January 2026 childhood schedule places vaccination of otherwise healthy adolescents under shared clinical decision-making. When selected, follow the current age schedule and notes; high-risk, outbreak, travel, and certain residential indications remain recommended, with booster timing based on age and ongoing risk. |
| MenB Recombinant / Subunit | Bexsero or Trumenba (same brand throughout): 2 doses at 0 and 6 months for healthy persons under shared decision-making; 3 doses at 0, 1–2, and 6 months for rapid protection or increased risk | B | Shared clinical decision-making for adolescents/young adults aged 16–23 years (preferred 16–18). Recommended for asplenia, complement deficiency, complement inhibitor use, and outbreak risk. |
| MenACWY-MenB Combo | Penbraya | A, B, C, W, Y | Indicated when both MenACWY and MenB are due at the same visit for individuals aged 10 through 25 years. |
[!WARNING] MenB Product Interchangeability: Bexsero and Trumenba are NOT interchangeable. The entire MenB primary series must be completed using the same manufacturer's product because they contain distinct recombinant antigens (Bexsero contains 4 components including factor H binding protein [fHbp], NadA, NHBA, and OMV; Trumenba contains two lipidated fHbp subfamilies A and B).
3. Tetanus, Diphtheria, and Pertussis (Toxoid & Subunit Pathophysiology)
Tetanus (Clostridium tetani)
- Microbiology: Obligate anaerobic, motile, spore-forming gram-positive rod. Spores are ubiquitous in soil, manure, and street dust.
- Pathogenesis: Spores enter necrotic, puncture, or contaminated wounds where low oxygen tension allows germination. Vegetative bacilli produce tetanospasmin (a zinc metalloprotease AB neurotoxin). Tetanospasmin travels retrogradely along motor neurons into the spinal cord and brainstem, where it enters inhibitory Renshaw interneurons and cleaves synaptobrevin (VAMP). This blocks the vesicular release of inhibitory neurotransmitters GABA (gamma-aminobutyric acid) and glycine.
- Clinical Manifestations: Loss of central inhibition leads to unregulated excitatory firing. Results in agonizing tonic muscle spasms, trismus (lockjaw), risus sardonicus (sustained grimace), opisthotonos (severe backward hyperextension of the spine), vocal cord spasms/asphyxia, and profound autonomic instability (labile hypertension, tachycardia, hyperthermia).
- Vaccine: Inactivated tetanus toxoid (formaldehyde-treated tetanospasmin). Non-communicable disease; vaccination confers individual protection only (no herd immunity).
Diphtheria (Corynebacterium diphtheriae)
- Microbiology: Non-motile, pleomorphic, club-shaped gram-positive rod (often arranges in palisades or "Chinese letter" patterns).
- Pathogenesis: Strains infected by a lysogenic bacteriophage (corynephage beta) express diphtheria toxin (an AB exotoxin). The A subunit catalyzes the ADP-ribosylation of Elongation Factor 2 (EF-2), arresting host cellular protein synthesis and causing cell necrosis.
- Clinical Manifestations: Local epithelial necrosis in the pharynx, larynx, or tonsils produces a dense, leathery, adherent gray pseudomembrane surrounded by a fiery red zone. Attempts to dislodge the membrane cause bleeding. Massive cervical lymphadenopathy causes a characteristic "bull neck" appearance. Pseudomembrane aspiration leads to fatal airway obstruction. Systemic toxin absorption causes toxic myocarditis (arrhythmias, heart failure) and demyelinating peripheral polyneuropathy (palatal paralysis, oculomotor dysfunction).
Pertussis (Bordetella pertussis)
- Microbiology: Fastidious, encapsulated, gram-negative coccobacillus.
- Pathogenesis: Transmitted via respiratory droplets. Adheres specifically to ciliated epithelial cells via filamentous hemagglutinin (FHA) and pertactin. Secretes tracheal cytotoxin (which paralyzes and destroys ciliated cells) and pertussis toxin (an AB toxin that ADP-ribosylates inhibitory G proteins [$G_i$], locking them in an inactive state and causing intracellular accumulation of cAMP, dysregulating cellular signaling and causing severe lymphocytosis).
- Clinical Stages of Whooping Cough:
- Catarrhal Stage (1–2 weeks): Rhinorrhea, lacrimation, low-grade fever, mild cough. Peak infectious stage.
- Paroxysmal Stage (2–6+ weeks): Paroxysms of 5 to 15 rapid, staccato, expiratory coughs in a single expiration, followed by a massive, high-pitched inspiratory "whoop" as air is drawn across a narrowed glottis. Accompanied by facial cyanosis, bulging eyes, and post-tussive emesis. Infants often present without whoop, experiencing severe apnea, seizures, and death.
- Convalescent Stage (weeks to months): Gradual recovery; cough paroxysms slowly diminish in frequency ("the 100-day cough").
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| PEDIATRIC (DTaP) VS. ADULT/ADOLESCENT (Tdap / Td) FORMULATIONS |
| |
| CAPITAL LETTERS = Full pediatric antigen quantity |
| LOWER-CASE LETTERS = Reduced antigen quantity (to prevent severe local reactogenicity in older) |
| "a" = Acellular pertussis (purified protein antigens instead of whole-cell bacteria) |
| |
| 1. DTaP (Daptacel, Infanrix) |
| - Full dose diphtheria (D) and pertussis (P). |
| - Indicated ONLY for children aged 6 weeks through 6 years (up to 7th birthday). |
| - Routine 5-dose pediatric series: 2, 4, 6, 15–18 months, and 4–6 years. |
| - CONTRAINDICATED in individuals aged 7 years and older. |
| |
| 2. Tdap (Boostrix, Adacel) |
| - Reduced-dose diphtheria (d) and pertussis (ap); full-dose tetanus (T). |
| - Boostrix approved for ages ≥ 10 years; Adacel approved for ages 10 through 64 (and ≥ 65). |
| - Recommended as a single booster at age 11–12 years. |
| - Recommended during EVERY PREGNANCY at 27 through 36 weeks gestation (optimally early in window)|
| to maximize maternal IgG transplacental transfer for neonatal pertussis protection. |
| - Decennial (every 10 years) booster for adults (or Td). |
| |
| 3. Td (Tenivac) |
| - Full tetanus toxoid (T) + reduced diphtheria toxoid (d). No pertussis component. |
| - Used for decennial boosters and tetanus wound management when pertussis is up to date. |
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Tetanus Wound Management Decision Algorithm
When evaluating a patient with a puncture, contaminated, or tissue-crush wound:
- Clean, Minor Wounds: Administer tetanus-containing toxoid (Tdap or Td) only if ≥ 10 years have elapsed since the last dose (or if < 3 lifetime doses).
- All Other Wounds (Dirty, Soil-Contaminated, Puncture, Animal Bites): Administer tetanus-containing toxoid (Tdap or Td) if ≥ 5 years have elapsed since the last dose. If the patient has had fewer than 3 lifetime tetanus doses or immunization history is unknown, administer both Tdap/Td AND 250 units of Tetanus Immune Globulin (TIG) intramuscularly at separate anatomical sites.
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Test Your Knowledge
A 19-year-old college student who underwent a surgical splenectomy following a motor vehicle collision arrives at the pharmacy for recommended immunizations. Which of the following meningococcal vaccine strategies is indicated for this patient?
A
B
C
D
Test Your Knowledge
When examining vaccine product packaging, a pharmacy technician notes differences in capitalization between 'DTaP' and 'Tdap'. What is the clinical rationale behind this standardized nomenclature?
A
B
C
D
Test Your Knowledge
A 45-year-old construction worker presents to the pharmacy after stepping on a dirty, soil-contaminated nail that pierced deep into his foot 2 hours ago. Pharmacy records indicate his last tetanus booster (Tdap) was administered 7 years ago, and he completed a 5-dose childhood series. What is the correct clinical action?
A
B
C
D