Coccobacilli - aerobes Notes

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Bordetella pertussis (Pertussis/Whooping cough)

Francisella tularensis (Tularemia)

Chapter 2 Acyanotic Defects NOTES COCCOBACILLI: AEROBES MICROBE OVERVIEW ▪ Intermediate shape between cocci (spherical bacteria), bacilli (rod-shaped bacteria) ▪ Gram-negative, obligate aerobe, nonmotile, non-spore forming BORDETELLA PERTUSSIS (PERTUSSIS/WHOOPING COUGH) osms.it/bordetella-pertussis PATHOLOGY & CAUSES ▪ Infectious agent, causes pertussis ▪ Strict human pathogen ▪ Tropism to respiratory epithelium Pathophysiology ▪ Bacteria enters upper respiratory tract, releases toxins ▪ Filamentous hemagglutinin, pertactin, agglutinogen ▫ Anchors to epithelial cells ▪ Tracheal cytotoxin ▫ Paralysis of respiratory cilia → ↑ accumulation of mucus in airways → violent cough reflex ▪ Pertussis toxin ▫ Stimulates T cells to divide, blocks them from leaving blood, migrating into tissues → lymphocytosis ▫ ↑ sensitivity of respiratory tissues to histamine → ↑ vascular permeability → fluid leaks into airway tissues → airway edema → dyspnea OSMOSIS.ORG 345
▪ Adenylate cyclase toxin ▫ ↑ conversion of adenosine triphosphate (ATP) to cyclic adenosine monophosphate (AMP) within phagocytes → disbalance in cellular signaling mechanism → phagocytes unable to correctly respond to infection, undergo apoptosis Stages of infection ▪ Catarrhal: follows incubation period (approx. one week); lasts two weeks, very contagious ▪ Paroxysmal: 1–6 weeks ▪ Convalescent: 2–3 weeks RISK FACTORS ▪ Infants too young to have completed immunization ▪ Unimmunized individuals ▪ Debilitation of immune system COMPLICATIONS ▪ Apparent life-threatening event (ALTE) ▫ Young infants; gasping, cyanosis, apnea ▪ Hypoxia ▫ Seizures, encephalopathy, death ▪ Pneumonia, pneumothorax SIGNS & SYMPTOMS ▪ Catarrhal: nasal congestion; mild cough; sneezing; low-grade fever; red, watery eyes (similar to common cold) ▪ Paroxysmal: high-pitched whooping during inhalation; uncontrollable coughing fits → vomiting, fainting, rib fracture, petechiae in face, subconjunctival hemorrhages, hernias ▪ Convalescent stage: coughing improvement; decreased paroxysm, whooping; healing of airways 346 OSMOSIS.ORG DIAGNOSIS LAB RESULTS ▪ Nasopharyngeal swab culture (Bordet– Gengou agar) ▫ Detects microbe; mercury drop colonies ▪ Polymerase chain reaction (PCR) ▫ Detects microbe ▪ Serology ▫ Detects microbe; antibody levels ▪ Complete blood count (CBC) ▫ Leukocytosis (esp. young infants) OTHER DIAGNOSTICS ▪ History, physical examination ▫ Sudden, dramatic coughing attacks; lung sounds (e.g. whooping) TREATMENT MEDICATIONS ▪ Prophylactic ▫ Diphtheria, tetanus, acellular pertussis (DTaP) vaccine ▪ Macrolide antibiotics OTHER INTERVENTIONS ▪ Compulsory isolation of infected individual
Chapter 63 Coccobacilli: Aerobes FRANCISELLA TULARENSIS (TULAREMIA) osms.it/francisella-tularensis PATHOLOGY & CAUSES ▪ Infectious agent that causes zoonosis tularemia ▪ Facultative, gram-negative intracellular bacteria ▪ Highly infectious, virulent; potential bioterrorism agent Transmission ▪ Direct contact with infected animals (e.g. inoculation of mucous membranes via contaminated hands/infected material) ▪ Ingestion of contaminated water/meat ▪ Airborne spread via contaminated materials (e.g. dust, hay, grass, lab specimens) ▪ Insect vectors ▫ Ticks, mosquitoes, horse flies, fleas, lice Pathophysiology ▪ Francisella tularensis enters body → phagocytosed by macrophages → impairs phagosome-lysosome fusion, rapidly proliferates within macrophage → infected macrophage undergoes apoptosis → bacteria released, infection spread COMPLICATIONS ▪ Lymph node suppuration, sepsis, renal failure, rhabdomyolysis, hepatitis, pneumonia SIGNS & SYMPTOMS ▪ Fever, chills, malaise, lethargy, anorexia, chest/muscle soreness ▪ Ulceroglandular: papulo-ulcerative lesion at point of contact with animal/vector; lymphadenopathy ▪ Glandular: lymphadenopathy (no skin lesions) ▪ Oculoglandular: pain/irritation of eye; periorbital edema/erythema; increased tearing; photophobia; regional adenopathy ▪ Oropharyngeal: sore throat; cervical lymph node enlargement; pharyngitis; tonsillitis ▪ Pneumonic: dry cough; breathing difficulties; substernal chest pain ▪ Typhoidal: very high fever; abdominal pain; diarrhea; vomiting; diffuse abdominal tenderness TYPES ▪ Forms of tularemia: ulceroglandular (75%), glandular, oculoglandular, oropharyngeal, pneumonic, typhoidal RISK FACTORS ▪ Work-related ▫ Lab workers, farmers, veterinarians, gardeners, hunters, butchers ▪ Skin exposure to vectors (esp. in summer) Figure 63.1 An ulcer on the skin of an individual with tularemia. OSMOSIS.ORG 347
DIAGNOSIS LAB RESULTS ▪ Culture ▫ Buffered charcoal yeast extract (BCYE) agar ▪ PCR, direct fluorescent antibody (DFA) test ▫ Detects microbe ▪ Serology ▫ IgM, IgG antibodies appear after 2 weeks OTHER DIAGNOSTICS ▪ History, physical examination 348 OSMOSIS.ORG TREATMENT MEDICATIONS ▪ Antibiotics (e.g. streptomycin, gentamicin, doxycycline)

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