Bacteriology (part 1) Flashcards
Occurs when bacteria, viruses, fungi and parasites change over time and no longer respond to medicines making infections harder to treat and increasing the risk of disease spread, severe illness and death (WHO, 2020).
Antimicrobial resistance
Causes of Antimicrobial Resistance
• Over-prescribing of antibiotics
• Patients not finishing their medications
• Over-use of antibiotics in livestock and fish farming
• Poor infection control in hospitals and clinics
• Lack of hygiene and poor sanitation
• Lack of new antibiotics being developed
2 types of toxins
Exotoxin & Endotoxin
Produced by Gram (+) and Gram (-) and Has killed 50,000 soldiers by Clostridium tetani during WWII
Exotoxin
Vaccines made from exotoxins
Toxoids
Produced by Gram (-) bacteria
Endotoxin
Endotoxin produces
fever
hypotension
hypoglycemia
early leukopenia
Contact transmissions
- Direct – person-to-person
- Indirect – Fomite
- Congenital – mother to fetus or newborn at birth
- Droplet – Mucus droplet that only travels short distances
Vehicle transmissions
- Airborne – droplet nuclei in dust that travels more than 1 meter
- Waterborne – contaminated water
- Foodborne – incompletely cooked food, poorly refrigerated or prepared under
unsanitary conditions - Fecal-oral – Microbes enter the water or food after being shed in the feces of
people or animals
Vector transmissions
- Mechanical - fly
- Biological - mosquito & fleas
Types of transmission
Contact
Vehicle
Vector
Spore forming gram (+) bacilli
Bacillus anthracis
Bacillus cereus
Clostridium perfringens
Clostridium difficile
Clostridium botulinum
Clostridium tetani
large, aerobic; strikes primarily grazing animals
Bacillus anthracis
Virulence factors of Bacillus anthracis
Edema toxin
Lethal toxin
Causes local edema and interferes with phagocytosis by macrophages
Edema toxin
targets and kills macrophages
Lethal toxin
Diseases caused by Bacillus anthracis
Cutaneous
•Endospore enters at the minor skin lesion
•Papule appears and then eventually vesicles, which rupture and form a depressed, ulcerated area that is covered by a black eschar
•Mortality rate: 1%
Gastrointestinal
•Ingestion of undercooked food containing anthrax endospores
•S/S: Nausea, abdominal pain , bloody diarrhea
•Mortality rate: 50%
Inhalational
•S/S:
1st day: mild fever, coughing, some chest pain
2nd-3rd day: bacteria enter the bloodstream and proliferate; septic shock that usually kills the patient within 24 to 36 hrs.
•Mortality rate: 100%
Treatment for anthrax
Doxycycline
Ciprofloxacin
Raxibacumab
large, endospore-forming bacterium that commonly contaminates rice; when large amounts of rice are cooked and allowed to cool slowly, the B. cereus germinate and the vegetative cells produce toxin during sporulation
Bacillus cereus
Two Distinct Forms of Bacillus cereus
Emetic type: NV, abdominal cramps, occasionally diarrhea and is self- limiting with recovery occurring within 24 hours
Diarrheal type: profuse diarrhea with abdominal pain and cramps; fever and vomiting are uncommon; due to enterotoxins
Tx for Bacillus cereus
•Vancomycin and Clindamycin
•Ciprofloxacin for wound infections
Bacillus cereus is resistant to a variety of antimicrobial agents such as
Penicillins and Cephalosporins
Prevention for B. cereus
cook food thoroughly and cool rapidly
endospore-forming, obligately anaerobic rod; endospore survive most routine heating; grows in the intestinal tract and produces exotoxin that causes the typical symptoms of abdominal pain and diarrhea
Clostridium perfringens
Disease caused by Clostridium perfringens
Gas Gangrene
Causes of Clostridium perfringens
Improperly performed abortions
Contaminated wound
S/S: spreads in 1-3 days, crepitation in the SC tissue and muscle, foul-smelling discharge, rapidly progressing necrosis, fever, hemolysis, toxemia, shock, death
Clostridium perfringens