Host Immune Response and Bacterial Pathogens – Supplement and Detail

1. Pertussis (Bordetella pertussis)

1.1 Reservoir:

• Humans only are the sole reservoir for pertussis bacteria.

1.2 Bacterial Name:

• Bordetella pertussis is the scientific name of the bacteria causing whooping cough.

1.3 Morphology and Staining:

• Gram-negative coccobacilli, appearing in a “whooping cough-inducing” form.

• Gram staining:

• Toluidine: Blue-violet

• Methylene blue: Blue

• Shape: Bulb-like, resembling mercury droplets, darker at both ends, resembling a club.

1.4 Structure:

• No flagella, pili, sometimes capsule.

• FHA (filamentous hemagglutinin): Red blood cell agglutination, helps bacteria adhere to respiratory epithelial cilia.

1.5 Resistance:

• Low:

• Does not survive for long in the external environment.

• Susceptible to heat and ultraviolet light.

1.6 Biochemical Properties:

• Obligate aerobe: Does not ferment.

• Utilizes glucose, lactose but does not ferment.

• Unable to break down proteins, but can break down amino acids.

• “Inert” biochemical properties.

1.7 Culture:

• Temperature: 37°C, moist.

• Media:

• Basic medium: Bordet-Gengou (potato-blood-glycerol agar)

• Supplementary media:

• Add 15% sheep blood

• Add activated charcoal => Regan-Lowe charcoal agar

1.8 Developmental Stages:

• Phase I: Virulent phase, containing toxins, possessing antigens.

• Phase II, III: Intermediate phases.

• Phase IV: Non-virulent phase, no toxins, no antigens.

• Conversion: Due to the accumulation of mutations in Bordetella Virulence Gene (BvgA, BvgS), transitioning from phase I to phase IV.

• Vaccine: Phase I bacteria are used to produce pertussis vaccines.

1.9 Antigens:

• Kn O (agglutinogen): Used to determine pertussis serotypes.

• Kn PT (pertussis toxin):

• Kn FHA (hemagglutinin):

1.10 Virulence Factors:

• Adhesion group:

• PT (pertussis toxin – Increased lymphocyte)

• Pertactin

• FHA

• Fimbriae

• Toxins group:

• Tracheal toxin (respiratory epithelial cilia paralysis)

• Dermonecrotic toxin

• Adenylate cyclase (Increased AMPv => Inhibition of neutrophils, neutrophilic white blood cells => Inhibits phagocytosis)

• Pertussis toxin

• Lipopolysaccharide

1.11 Transmission:

• Directly through the respiratory route.

1.12 Pathogenesis:

• Adheres to the respiratory epithelium, multiplies there.

• Secretes toxins but does not invade deeply into the epithelium or enter the bloodstream.

1.13 Complications:

• Pneumonia, bronchitis superinfection.

• Encephalopathy (hypoxia, hypoglycemia).

1.14 Disease Progression:

• 1) Catarrhal (2 weeks): Mild cough, mild runny nose, highly contagious.

• 2) Paroxysmal (3 weeks): Fits of coughing, continuous coughing, inhaling air like a whooping sound.

• 3) Convalescent (3 weeks): Poor appetite, insomnia, congestion, pneumonia, suffocation due to bronchial spasms. The disease subsides naturally after 3 weeks but may recur.

1.15 Specimen Collection:

• Sputum, secretions.

• Ideally, have patients directly cough into a Bordet-Gengou agar plate.

1.16 Diagnosis:

• Staining: Gram, toluidine, methylene blue.

• PCR: Detect pertussis DNA.

• Culture: Results after 5-7 days.

• Fluorescence: Detect antigens.

• Serological diagnosis: Detect antibodies – anti-PT, anti-FHA. Less valuable, takes longer (3 weeks).

1.17 Vaccine:

• DTP: Diphtheria-Tetanus-Pertussis.

• Infanrix hexa (6 in 1): Diphtheria, pertussis, tetanus, HBV, H.influenza, polio.

1.18 Antibiotics:

• Erythromycin: Macrolide group, binds to the 50S subunit of the ribosome.

• Dosage:

• Children: 30-50mg/kg/day

• Adults: 2g/day

2. Enterobacteria

2.1 Classification:

• Gram-negative bacilli.

2.2 Oxygen Requirement:

• Facultative anaerobe.

2.3 Fermentation:

• Ferment glucose but do not produce gas.

2.4 Biochemical Properties:

• Oxidase-negative: No oxidase enzyme.

• Catalase-positive.

2.5 Group causing enteric diseases:

• E. coli:

• Shigella:

• Salmonella:

• Yersinia:

2.6 Motility:

• Motile or non-motile.

• Motility through flagella.

2.7 Surface Antigens:

• K-O-H:

• K: Capsular antigen.

• O: Somatic antigen.

• H: Flagellar antigen.

2.8 Antigen Characteristics:

• Somatic O antigen:

• Located in the cell wall, composed of LPS.

• O polysaccharide: O antigen, determines specificity.

• Core polysaccharide: Determines common antigen.

• Lipid A: Determines virulence.

• Not destroyed by heat at 100°C for 2 hours, 50% alcohol, destroyed by 5% formalin.

• Highly toxic (induces leukopenia in humans and animals).

• Agglutination reaction with anti-O antibodies: Bacteria agglutinate together in small particles, difficult to disperse by shaking.

• Flagellar H antigen:

• Only present in motile bacteria.

• Destroyed by heat, 50% alcohol.

• Not destroyed by 5% formalin.

• Agglutination reaction with anti-H antibodies: IgG.

• H agglutination: Large particles, easily dispersed by shaking, bacteria lose motility antigens.

• Capsular K antigen:

• Composed of polysaccharide or protein depending on the species.

• A virulence factor (Salmonella is called Vi antigen – Virulence).

• Located outside the O antigen.

2.9 Culture:

• Colony morphology: Smooth, rough, mucus.

2.10 Specimen Collection:

• Gastroscopy, colonoscopy, rectal swab, stool.

2.11 Culture Media:

• 1) Non-inhibitory media: General media like blood agar, nutrient agar.

• 2) Differential selective media: Differentiates lactose fermenters from non-lactose fermenters. Some media contain specific inhibitors for the growth of a specific bacterium:

• MacConkey, EMB: Inhibits Gram-positives, Gram-negatives grow.

• SS: Shigella, Salmonella.

• Brilliant green agar: Salmonella.

• 3) Enrichment media: Rapidly multiplies a small amount of bacteria.

• GN: Gram negative

• Selenite F: Salmonella

3. Pseudomonas aeruginosa

3.1 Pathogen of infection:

• Nosocomial infection: Ventilators, catheters,…

• Opportunistic infection: Burns, wounds,…

3.2 Differential diagnosis:

• Gram staining: Gram-negative.

• Oxidase: Positive => Eliminates the enterobacteria group.

• Non-fermenting.

• Blue pus, grape-like odor.

3.3 Growth Temperature:

• 37-42°C. Can grow at 42°C => Distinguishes it from other Pseudomonads.

3.4 Pigmentation:

• Pyocyanin: Bluish-green.

• Pyoverdin: Green.

• Pyorubin: Red.

• Pyomelanin: Black.

3.5 Disease-causing ability:

• Only causes disease when invading areas where the body’s normal defenses are lost:

• Skin and mucous membranes are no longer intact, flaking off.

• Insertion of intravenous catheters, urinary catheters => Biofilm formation in the lumen of the tubes => Resistance to antibiotics.

• Immunocompromised patients.

4. Note:

• Selective culture media for Gram-negative bacteria: MacConkey, EMB.

• Bacteria not yet cultured:

• Leprosy bacteria: Inject into guinea pigs, hamsters, rats.

• Syphilis spirochete: Inject into rabbit testicles.

5. Additional Information:

• Antigen types, virulence factors, pathogenic mechanisms, and disease progression may vary by bacterial species.

• Information on culture, diagnosis, treatment, and disease prevention may change over time and with technology.

Note: Information in this article is for reference only. Please refer to reliable medical literature for the most accurate and complete information.