Reservoirs Of Microorganisma Flashcards
What is a reservoir?
one or more epidemiologically connected populations or environments in which the pathogen can be permanently maintained and from which infection is transmitted to the defined target population
Discuss the characteristics and epidemiology of Bacillus anthracis
Microbial characteristics: large, gram positive, aerobic, endospore-forming, non- motile, rods occurring in chains
Epidemiology: infrequent and sporadic in most industrial countries
Discuss pathogenicity of bacillus anthracis
Can present in one of three forms (depending on the route of infection ):
- cutaneous anthrax: 95% of cases worldwide, results from infection through skin lesions due to spores traveling through the skin via an opening like a cut
- Pulmonary anthrax results from inhalation of spores
- intestinal anthrax- results from ingestion of spores, usually in infected meat
Endemic in agricultural regions like Africa, asia and Middle East from animals like goats can transfer to humans
Discuss the mode of transmission for cutaneous anthrax
Cutaneous anthrax- infection of skin by contact with infected animal tissues or by contaminated hair, wool, hides or products made from them
Usually gets in skin via cut or Scrape
Most common on the head, neck and forearm of the patient and affects skin and tissue around infect site
Without treatment, 20% die, with treatment nearly everyone lives. The least dangerous form of anthrax
Discuss the mode of transmission of ingestinal anthrax
Ingestinal anthrax- ingestion of contaminated undercooked meat
Discuss the mode of transmission of inhalation of anthrax
Inhalation anthrax- inhalation of spores in contaminated soil areas, dried or processed skins and hides of infected animals
Give the microbial characteristics of Bacillis Cereus
Microbial characteristics: large, gram-positive, aerobic, endospore forming, moitile rod
-produces heat stable and heat labile toxins
Usually results in food poisoning when cooked food is left open and spores germinate and produce toxins
Give the mode of transmission of Bacillus cereus
Ubiquitous organism of the soil
- commonly found in low levels in raw, dried and processed foods
- ingestion of foods kept at ambient conditions after cooking
Give the epidemiology of Bacillus cereus
Worldwide
Discuss pathogenicity of bacillus cereus
Opportunistic pathogen-
Immunocompromised individuals are susceptible
Intoxication characterized by two forms:
- An emetic form with severe nausea and vomiting
- A diarrhea form with abdominal cramps and diahrrea
Give the differential of clostridium and bacillus
Clostridium- obligate anaerobes
Bacillus- facultative aerobes
What are the microbial characteristics of Clostridium perfringens ?
Microbial characteristics: gram-positive , spore forming , non-motile, rods
-obligate anaerobes
What is the mode of transmission of clostridium perfringens?
- Primarily by the ingestion of food contaminated by soil or feces
- Spore transmission into the body via a break in the skin
Give the epidemiology of clostridium perfringens
Widespread and relatively frequent in countries with cooking practices that favor the multiplication of Clostridia
Give the pathogenicity of clostridium of Clostridium perfringens
Pathogenicity:
-food poisoning- intestinal disorder characterized by sudden onset of colic followed by diahrrea, nausea, but vomiting and fever is usually absent; mild, short in during, rarely fatal
-Wound contamination- traumatic or nontraumatic myonecrosis (gas gangrene ) and is specific to muscle tissue as it enters skin with little air, can grow rapidly between 43 and 47 degrees Celsius ; intra-abdominal sepsis, gangrenous cholecystitis
Usually develops hours or days after wound opens as tissues are devitalized which provide the anaerobic conditions and pathogen spreads along tissue, possibly causing sepsis
What is the most common bacterial agent for gas gangrene?
Clostridium perfringes
What are the microbial characteristics of clostridium tetani?
Microbial characteristics:
- Gram-positive, motile, spore forming bacteria (terminal spores with drumstick appearance)
- obligate anaerobes
- catalase and superoxide dismutase negative
What is the mode of transmission of clostridium tetani?
Contamination of wounds with soil or foreign bodies carrying C. Tetani spores
Tend to colonize small wounds, and release tetanus toxins which blocks release of neurotransmitters, glycine, gaba etc, chasing rigid paralysis
The epidemiology of clostridium tetani
Low in developed countries as a result of vaccination
However, For the first time in 30 years a young boy presented with the symptoms of clostridium tetani in Oregon
Discuss the pathogenicity of Clostridium tetanus
- Characterized by spastic paralysis.
- Contamination of a wound with C. Tetani
- the anaerobic tissue environment facilitates C. Tetani replication and secretion of exotoxins