Gram positive

Diagnosis of Listeriosis

• Culture samples are used to diagnose Listeriosis, depending on symptoms:
  • Stool culture for gastroenteritis
  • Blood culture for bacteremia
  • Cerebrospinal fluid (CSF) culture for meningitis
  • Amniotic fluid culture for trans-placental infection
• Imaging studies like ultrasound or CT scan can identify liver abscesses

Treatment of Listeriosis

• Gastrointestinal Listeriosis: Supportive care (hydration, rest) is used
• Disseminated Listeriosis: Intravenous ampicillin combined with gentamicin is used
• Alternatives: Meropenem is used for those with contraindications to ampicillin (e.g., pregnant individuals, those allergic to ampicillin)

Clostridium Bacteria

• General characteristics:
  • Gram-positive, may appear Gram-negative in older cultures
  • Straight or curved rods, may appear singly, in pairs, or in chains
  • Spore former, with endospores
  • Motile, with peritrichous flagella (except C. ramosum and C. innocuum)
  • Non-encapsulated (except C. perfringens)
  • Obligate anaerobes, strict anaerobes
  • Catalase-negative
• Virulence factors:
  • Exotoxins, varied among species
  • C. perfringens has type A, B, C, D, E toxins

Clostridium difficile

• Growth and laboratory identification:
  • Gram-positive, appearing purple and rod-shaped under the microscope
• Colonization and infection:
  • Fecal-oral route, typically acquired through ingestion of bacteria from fecal matter
  • Asymptomatic carriers, about 5% of the population
  • Disturbance of gut flora, allowing C. difficile overgrowth
• Pathogenic mechanism:
  • Toxin production, main pathogenic mechanism
  • Toxin A (TCDA), a potent enterotoxin
  • Toxin B (TCDB), a cytotoxin
• Symptoms and complications:
  • Diarrhea, abdominal pain, and high fever
  • Severe complications, such as toxic megacolon, intestinal rupture, septic shock, and death if untreated

Foodborne Illness

• Common cause, often called the "cafeteria germ"
• Contamination, spores can contaminate food left out for a while
• Toxin production, produces Clostridium perfringens enterotoxin (CPE) within 24 hours of colonization
• Heat sensitivity, CPE is heat-labile and can be inactivated by cooking at 72°C or above
• Symptoms, abdominal cramping, watery diarrhea, and vomiting
• Symptoms typically improve within a day without the need for antibiotics, hydration is the primary treatment

Wound Infections

• Introduction to wounds, can infect wounds made by dirty, sharp objects in contact with soil
• Myonecrosis, causes clostridial myonecrosis (gas gangrene) via Clostridium perfringens alpha-toxin (CPAT)
• Symptoms, extreme pain, swelling, thin watery pus, blood-filled bullae, and crepitus (crackling sound of gas in tissue)
• Pathogenesis and symptoms of myonecrosis:
  • Cell death, causes necrosis (uncontrolled cell death)
  • Progression, rapidly progresses to fever, tachycardia, hypotension, shock, and potentially death within hours if untreated