4.2M-bacili
Bacilli Classification
All bacilli are Gram negative except for:
Bacillus
Mycobacterium
Clostridium
Listeria
Corynebacterium
Lactobacillus
Actinomyces
Nocardia
Gardnerella
Erysipelothrix
Arcanobacterium
Corynebacterium diphtheriae
General Information
Always a pathogen
Classification:
GS: Gram (+)
MR: Club-shaped bacilli organized in V or L configurations (mimics Chinese characters)
MT: Nonmotile
AR: Facultative anaerobe
O: Pili presence
Reservoir and Transmission
Reservoir: Human upper respiratory tract (URT)
Transmission:
Respiratory droplets
Indirect contact via fomites
Virulence Factors
Exotoxin production
Catalase enzyme presence
Diphtheria Disease
Symptoms
Mild sore throat with fever
Pseudomembrane formation in the pharynx
Characteristic "Bull's Neck" appearance
Bacteria produce toxins within the pseudomembrane, causing further tissue damage
Management & Prevention
Appropriate antibiotic therapy
Diphtheria antitoxin
Supportive therapy (soft diet, ice collar, adequate hydration)
DPT vaccine
Clostridium botulinum
General Information
Classification:
GS: Gram (+)
MR: Bacilli
MT: Motile
AR: Anaerobe
O: Flagella and subterminal spores
Reservoir and Transmission
Natural habitat: Soil
Transmission:
Ingestion of heat-resistant spores (found in wild/raw honey and bulging canned goods)
Virulence Factors
Botulinum toxin is one of the most potent toxins known, inhibiting the release of Acetylcholine from peripheral nerves, leading to impaired neuromuscular transmission
Botulism Disease
Symptoms
Fatal food poisoning characterized by:
Flaccid paralysis due to potent neurotoxin
Trouble swallowing and slurred speech
Weak muscles and breathing issues
Droopy eyelids and blurry vision
Management & Prevention
Appropriate antibiotic therapy
Botulism Intravenous Immunoglobulin (IG)
Aggressive supportive care
Avoid giving honey to infants, and educate on proper food preparation
Clostridium tetani
General Information
Classification:
GS: Gram (+)
MR: Bacilli with drumstick or tennis racket appearance
MT: Motile
AR: Anaerobe
O: Terminal spores with peritrichous flagella
Reservoir and Transmission
Reservoir: Soil, unsterilized metals, and rusty materials
Transmission: Entry through punctured wounds, also affects umbilical stump of the newborn
Virulence Factors
Spores and toxin (tetanospasmin) inhibit release of GABA and glycine, both inhibitory neurotransmitters, causing excessive stimulation
Tetanus Disease
Symptoms
Acute onset of hypertonia or painful muscular contractions
Characteristic muscle spasms:
Trismus (lockjaw)
Respiratory muscle paralysis
Opisthotonos (spinal arching)
Management & Prevention
Tetanus Immunoglobulin (TIG)
Wound debridement
Appropriate antibiotic therapy
Tetanus Toxoid vaccine and DPT vaccine
Support with airway maintenance and wound care
Vibrio cholerae
General Information
Always a pathogen
Classification:
GS: Gram (-)
MR: Comma-shaped colon bacilli
MT: Motile
AR: Aerobic
O: Presence of pili with a single polar flagellum
Reservoir and Transmission
Reservoir: Human and salt water
Transmission: Fecal-oral route via contaminated water or indirect contact through soiled hands
Virulence Factors
Choleragen toxin stimulates mucosal cells to increase chloride secretion, leading to outpouring of intestinal fluids
Cholera Disease
Symptoms
Acute bacterial disease characterized by:
Severe diarrhea with "rice water stools"
Massive loss of fluid and electrolytes
Management & Prevention
Appropriate antibiotic therapy
Fluid and electrolyte replacement
Proper record keeping of vital signs and intake/output
Sewage disposal and environmental sanitation
Salmonella typhi
General Information
Classification:
GS: Gram (-)
MR: Bacilli
MT: Motile
AR: Facultative anaerobes
O: Encapsulated with pili and peritrichous flagella
Reservoir and Transmission
Reservoir: Human colon
Transmission: Fecal-oral via contaminated shellfish and oysters
Virulence Factors
Presence of peritrichous flagella, capsule, and pili
Typhoid Fever Disease
Symptoms
Infection affecting the GIT, specifically the lymphoid tissues of Peyer's Patches in the ileum, resulting in:
Fever, diarrhea, and rose spots
Potentially leading to bowel perforation and toxin absorption into the bloodstream
Management & Prevention
Appropriate antibiotic therapy
Fluid and electrolyte replacement
Hygiene, sanitation, and proper sewage disposal
Shigella species
General Information
Always a pathogen
Classification:
GS: Gram (-)
MR: Bacilli
MT: Nonmotile
AR: Facultative anaerobes
Reservoir and Transmission
Reservoir: Human
Transmission: Fecal-oral route
Virulence Factors
Produces Shiga toxin along with enterotoxin and neurotoxin
Bacillary Dysentery Disease
Symptoms
Initially presents as watery diarrhea, progressing to bloody diarrhea
Invasion of the submucosa of the intestinal tract by Shiga toxin causes inflammation and ulceration
Management & Prevention
Appropriate antibiotic therapy
Fluid and electrolyte replacement
Hygiene, sanitation, and proper sewage disposal
Escherichia coli
General Information
Opportunistic pathogen and indigenous microbiota of the colon
Classification:
GS: Gram (-)
MR: Bacilli
MT: Motile
AR: Facultative anaerobes
O: Presence of peritrichous flagella, some encapsulated and with pili
Reservoir and Transmission
Reservoir: Human colon
Transmission: Fecal-oral
Virulence Factors
Presence of capsules, flagella, and toxins (endotoxin and enterotoxin)
E. coli Diseases
Types
Urinary Tract Infection
Healthcare-associated infections
Diarrhea, including Traveler's diarrhea (variously known as Montezuma's Revenge, Dehli's belly, etc.)
Management & Prevention
Appropriate antibiotic therapy
Fluid and electrolyte replacement
Hygiene, sanitation, and proper sewage disposal
Traveler's Diarrhea Prevention
Avoid ice
Wash hands with soap and water frequently, especially after using the bathroom
Consume freshly prepared food served hot
Wash or peel raw produce
Drink boiled water or beverages from sealed containers
Pseudomonas aeruginosa
General Information
Opportunistic pathogen and indigenous microbiota of the skin & upper respiratory tract
Classification:
GS: Gram (-)
MR: Bacilli
MT: Motile
AR: Obligate aerobe
O: Encapsulated with a single polar flagellum; produces characteristic blue (pyoverdin) and green (pyocyanin) pigments
Notable sweet, fruity grape-like odor
Reservoir and Transmission
Reservoir: Environmental water sources, humidifiers, and moist environments
Transmission:
Respiratory droplets
Direct contact with skin lesions
Indirect contact through fomites
Virulence Factors
Single polar flagellum, capsule, exoenzyme elastase, endotoxin, and exotoxin
Pseudomonas Diseases
Common Infections
Burn wound infection
Otitis externa
Respiratory infections
Hot tub folliculitis
Healthcare-associated infections, particularly Ventilator-Associated Pneumonia
Management & Prevention
Appropriate antibiotic therapy due to multidrug resistance
Maintenance of hygiene
Haemophilus influenzae
General Information
Opportunistic pathogen, part of indigenous microbiota of the upper respiratory tract
Classification:
GS: Gram (-)
MR: Bacilli
MT: Nonmotile
AR: Facultative anaerobe
O: Encapsulated with pili
Reservoir and Transmission
Reservoir: Human upper respiratory tract
Transmission: Respiratory droplets and indirect contact via fomites
Virulence Factors
Capsule and pili presence
Haemophilus Diseases
Common Infections
Bacterial meningitis (common in children under 5)
Ear infections
Respiratory infections (acute epiglottitis with "cherry red" epiglottis and thumb sign on x-ray)
Management & Prevention
Appropriate antibiotic therapy
Hib vaccine
Bordetella pertussis
General Information
Always a pathogen
Classification:
GS: Gram (-)
MR: Bacilli
MT: Nonmotile
AR: Facultative anaerobe
O: Encapsulated with pili
Reservoir and Transmission
Reservoir: Human upper respiratory tract
Transmission: Respiratory droplets and indirect contact through fomites
Virulence Factors
Capsule and pili presence; produces toxin: tracheal cytotoxin
Pertussis Disease
Symptoms
Known as "whooping cough"; pathogen confined to tracheobronchial mucosa
Tenacious mucus leads to spasmodic coughing
Highly contagious among non-immune individuals, grants lifetime immunity upon recovery
Management & Prevention
Appropriate antibiotic therapy
DPT vaccine
Supportive therapy: adequate nutrition, fluids, oxygen therapy, patient isolation