Airborne, Foodborne, and Waterborne Bacterial Pathogens

Comprehensive vocabulary flashcards covering the etiology, pathophysiology, virulence factors, diagnostic assays, clinical presentations, and treatment of airborne, foodborne, and waterborne bacterial pathogens.

Hemolytic Patterns on Blood Agar Plates

A bacterial classification method where alpha-hemolysis displays partial destruction of red blood cells with a greenish halo, beta-hemolysis causes complete clear lysis of red blood cells, and gamma-hemolysis exhibits no lysis.

Lancefield Classification

A serological system that categorizes streptococci into Groups A through U based on the antigenicity of specific carbohydrate 'C' substances present within their cell walls.

M Protein

A major virulence factor of Streptococcus pyogenes consisting of pili-like surface projections that mediate host tissue adherence, act as superantigens, and resist phagocytosis by interfering with complement component C3b.

Streptococcal Pharyngitis

An upper respiratory tract infection predominantly caused by Streptococcus pyogenes in children aged $5-15$ years, characterized by sudden fever, chills, a red sore throat with white exudate patches, dysphagia, and swollen cervical lymph nodes.

Scarlet Fever

A complication of Streptococcus pyogenes pharyngitis resulting from a bacteriophage T12-encoded erythrogenic exotoxin ($\text{speA}$), presenting with capillary damage, a pink-red blush rash on the neck, chest, and arms, and a strawberry-like tongue.

Rheumatic Fever

A non-suppurative post-streptococcal autoimmune complication (Type II hypersensitivity) driven by molecular mimicry, where cross-reactive antibodies against streptococcal M protein attack cardiac myofiber myosin and connective tissues, resulting in permanent heart valve scarring.

Acute Glomerulonephritis

A rare post-streptococcal inflammatory kidney disorder caused by the deposition of immune complexes containing streptococcal antigens within renal glomeruli and small blood vessels.

Necrotizing Fasciitis

A severe, rapidly progressive destruction of subcutaneous fascia and adjacent muscle tissue mediated by prophage-encoded proteases and superantigens; primary causative agents include Streptococcus pyogenes and Staphylococcus aureus.

Pseudomembrane (Diphtheria)

A tough, adherent, grayish-white inflammatory exudate consisting of dead host epithelial cells, clotted blood, bacteria, and leukocytes that forms over the tonsils and pharynx in Corynebacterium diphtheriae infections, potentially causing airway obstruction.

Diphtheria Toxin

A prophage-encoded A-B exotoxin produced by Corynebacterium diphtheriae in which fragment B mediates cell entry and fragment A catalyzes the ADP-ribosylation of eukaryotic Elongation Factor $2$ (EF2), irreversibly terminating cellular protein synthesis.

Meningococcemia

Fulminant septicemia caused by Neisseria meningitidis marked by rapid capillary breakage, resulting in petechiae ($1-2\,\text{mm}$), purpura ($3-10\,\text{mm}$), ecchymosis ($>10\,\text{mm}$), and potentially fatal shock within $2$ hours.

Waterhouse-Friderichsen Syndrome

A catastrophic complication of severe meningococcal disease characterized by bilateral hemorrhagic necrosis of the adrenal glands, acute adrenal insufficiency, widespread purpura, and cardiovascular collapse.

Haemophilus influenzae type b (HiB)

An encapsulated, non-motile Gram-negative coccobacillus that primarily infects children aged $6\,\text{months}$ to $2\,\text{years}$, spreading from the respiratory mucosa to the bloodstream and meninges; prevented via a capsular polysaccharide conjugate vaccine.

Pertussis Toxin (PTx)

An A-B enterotoxin produced by Bordetella pertussis composed of an enzymatically active toxic A protomer (subunit $1$) and a pentameric B binding oligomer (subunits $2-5$); it catalyzes ADP-ribosylation, inhibits adenylate cyclase regulation, elevates cellular $\text{cAMP}$, paralyzes ciliated cells, and stimulates insulin secretion.

Paroxysmal Phase

The second stage of whooping cough (following the catarrhal stage) characterized by violent, repetitive coughing paroxysms in staccato bursts, ending with an inspiratory, high-pitched stridor or 'whoop'.

Ghon's Complex

A characteristic primary pulmonary tuberculosis lesion visible on chest radiographs consisting of a calcified parenchymal tuberculous granuloma focus combined with an ipsilateral calcified hilar lymph node.

Tuberculous Granuloma

An organized chronic inflammatory aggregate triggered by Mycobacterium tuberculosis consisting of a central core of caseous necrosis surrounded by epithelioid cells, Langhans-type multinucleated giant cells, and an outer rim collar of lymphocytes.

Miliary Tuberculosis

A severe form of disseminated tuberculosis resulting from hematogenous seeding of bacilli throughout the body, forming diffuse, millet-seed-sized ($1-5\,\text{mm}$) granulomatous lesions in multiple organs.

Mantoux Tuberculin Skin Test

A diagnostic intradermal test utilizing Purified Protein Derivative (PPD) to detect Type IV cell-mediated hypersensitivity against Mycobacterium tuberculosis; a firm induration measuring $>10\,\text{mm}$ after $48-72\,\text{hours}$ denotes a positive result.

QuantiFERON-Gold (QFT-G)

An interferon-gamma release blood assay that identifies latent Mycobacterium tuberculosis infection by measuring IFN-gamma output from sensitized T-cells exposed to synthetic ESAT-6 and CFP-10 peptide antigens.

BCG Vaccine (Bacillus of Calmette and Guérin)

An attenuated, live avirulent strain of Mycobacterium bovis designed to prevent tuberculous disease in children; it does not prevent primary infection or late reactivation and is not widely used in the U.S. due to interference with the PPD skin test.

Mycobacterium avium Complex (MAC)

An atypical, highly antibiotic-resistant mycobacterial complex comprising M. avium and M. intracellulare that produces severe pulmonary and disseminated infections in immunocompromised individuals, causing over $95\%$ of mycobacterial isolates in AIDS patients.

Lobar Pneumonia

An acute lower respiratory infection typically caused by encapsulated Streptococcus pneumoniae diplococci in which inflammatory exudate consolidates an entire anatomical lobe of the lung, yielding high fever, pleuritic pain, and rust-colored sputum.

Cold Agglutination Screening Test (CAST)

A serological diagnostic test for primary atypical walking pneumonia caused by Mycoplasma pneumoniae, in which patient serum IgM antibodies agglutinate human type O erythrocytes at $4^{\circ}\text{C}$ but not at $37^{\circ}\text{C}$.

Legionnaires' Disease

An acute pneumonia caused by the motile, Gram-negative rod Legionella pneumophila, contracted via inhalation of contaminated aerosols from cooling towers, whirlpool spas, or air-conditioning systems, with a mortality rate of $15-20\%$.

Q Fever

A zoonotic lower respiratory infection caused by Coxiella burnetii, an obligate intracellular Gram-negative bacterium transmitted by inhaling dust contaminated with birth products, urine, or feces from livestock (cows, sheep, goats).

Psittacosis (Ornithosis)

A zoonotic atypical respiratory infection caused by Chlamydophila psittaci, an obligate intracellular parasite transmitted to humans via desiccated droppings or respiratory secretions from psittacine birds such as parrots, parakeets, and turkeys.

Inhalational Anthrax

Also known as Woolsorters' disease, a life-threatening illness caused by inhaling airborne endospores of Bacillus anthracis, which germinate in alveolar spaces and migrate to mediastinal lymph nodes to produce lethal tripartite toxins.

Dental Plaque

A structured polymicrobial biofilm composed of salivary proteins, food particles, and bacterial species (such as Streptococcus mutans and S. sobrinus) that ferment dietary sucrose into organic acids and insoluble dextran polymers, promoting tooth demineralization.

Infective Endocarditis

Microbial infection of the endocardium and heart valves often seeded by oral commensals (such as viridans streptococci and HACEK group organisms) following dental manipulation or periodontal disease; categorized into subacute (SBE) and acute (ABE) forms.

Foodborne Intoxication

An illness caused by the ingestion of preformed bacterial toxins present within contaminated food, characterized by a rapid onset of symptoms (hours) without requiring in vivo bacterial growth or colonization.

Foodborne Infection

An illness established when viable pathogenic bacteria are ingested with contaminated food or water, survive gastric acid transit, colonize the intestinal mucosa, and replicate over an incubation period of days.

Staphylococcal Food Poisoning

The most common bacterial intoxication, caused by ingestion of heat-stable enterotoxins ($\text{A-E}$) produced by Staphylococcus aureus in unrefrigerated protein-rich foods, triggering vomiting and cramping within $1-6\,\text{hours}$.

Botulinum Toxin

An extremely potent A-B neurotoxin synthesized by anaerobic endospore-forming Clostridium botulinum that binds presynaptic motor neurons and cleaves SNARE complex proteins (SNAP-25, synaptobrevin, syntaxin), permanently inhibiting acetylcholine release and producing flaccid paralysis.

Infant Botulism

An intestinal infection in infants under $1\,\text{year}$ of age caused by the ingestion of Clostridium botulinum endospores (frequently from raw honey) which germinate in the immature colon and elaborate toxin, leading to constipation, slack jaw, and generalized hypotonia ('floppy baby syndrome').

Cholera Toxin

An A-B subunit enterotoxin produced by Vibrio cholerae; the B subunits bind host GM1 gangliosides to allow translocation of subunit A1, which ADP-ribosylates a stimulatory G-protein ($\text{G}_{s\alpha}$), activating adenylate cyclase, elevating intracellular $\text{cAMP}$, and driving massive chloride, bicarbonate, and water secretion through the CFTR channel.

Rice-Water Stools

The hallmark clinical presentation of severe Vibrio cholerae infection (cholera gravis), characterized by voluminous, non-bloody, watery diarrhea flecked with intestinal mucus and epithelial debris, exceeding $1\,\text{L/hour}$ and causing life-threatening hypovolemic shock.

Enterotoxigenic Escherichia coli (ETEC)

A non-invasive E. coli pathotype that adheres to small intestinal enterocytes and produces plasmid-borne heat-labile (LT) and heat-stable (ST) enterotoxins, serving as the principal causative agent of traveler's diarrhea ('Montezuma's revenge').

Enteropathogenic Escherichia coli (EPEC)

A diarrheagenic E. coli pathotype that binds the enterocyte apical membrane via bundle-forming pili and a Type III secretion system, causing effacement of microvilli, malabsorption, and severe dehydration in pediatric patients.

Hemolytic Uremic Syndrome (HUS)

A life-threatening triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure, provoked when Shiga toxins ($\text{Stx1, Stx2}$) produced by STEC/EHEC (such as E. coli O157:H7) enter circulation and bind Gb3 receptors on capillary endothelial cells in the kidneys and brain.

Pseudomembranous Colitis

A severe, opportunistic colonic inflammation caused by Clostridium difficile following antibiotic therapy disruption of normal flora, mediated by Enterotoxin A and Cytotoxin B, which produce raised, yellowish-white mucosal plaques and risk toxic megacolon.

Fecal Microbiota Transplantation (FMT)

A therapeutic procedure for refractory, recurrent Clostridium difficile infection where filtered donor stool is infused via nasogastric tube or colonoscopy to reconstitute microbial diversity and restore colonization resistance in the gut.

Rose Spots

Faint, transient, blanching erythematous maculopapular cutaneous lesions that appear on the abdomen and chest in roughly $30\%$ of patients with enteric (typhoid) fever, representing localized bacterial emboli of Salmonella Typhi.

Salmonella Typhi Carrier State

The chronic persistence of Salmonella enterica serotype Typhi in asymptomatic individuals (exemplified by 'Typhoid Mary'), who harbor the pathogen within the biliary tree and gallbladder and intermittently shed bacilli in feces.

Shigellosis (Bacillary Dysentery)

An acute enteric infection caused by Shigella species with an extremely low infectious dose ($10-200$ bacilli), characterized by high fever, severe tenesmus, and the frequent passage of small-volume, mucopurulent, bloody stools caused by mucosal ulceration and Shiga enterotoxin.

Campylobacter jejuni

A microaerophilic, curved Gram-negative rod colonized in the intestinal tract of poultry and dairy animals; ingestion causes acute enteritis and is recognized as the most common trigger for the post-infectious autoimmune polyneuropathy Guillain-Barré syndrome.

Listeria monocytogenes

A psychrophilic, facultative intracellular Gram-positive bacillus transmitted via unpasteurized dairy, cold cuts, and contaminated produce that can cross the intestinal, blood-brain, and fetoplacental barriers, causing neonatal granulomatosis infantiseptica, septicemia, and spontaneous abortion.

Rapid Urease Test (CLO Test)

A diagnostic gastric biopsy test for Helicobacter pylori infection that detects bacterial urease activity; breakdown of urea into ammonia raises the medium pH, shifting the phenol red indicator from yellow-orange to bright magenta/pink-red.

Helicobacter pylori Pathogenesis

The stepwise colonization and ulcerogenesis in the gastric antrum wherein H. pylori utilizes polar flagella to burrow beneath gastric mucus, generates urease to produce an acid-neutralizing ammonia cloud, and releases cytotoxins that breach epithelial integrity to cause peptic ulcers.

Brucellosis (Undulant Fever)

A systemic zoonotic infection caused by Brucella species (such as B. abortus, B. melitensis, and B. suis) transmitted through unpasteurized milk and cheese, presenting with lymphadenopathy, hepatosplenomegaly, and a classic fluctuating, wave-like diurnal fever curve.