Microbiology Analyse Flashcards
What pathogen causes cholera, and what is its key symptom?
Vibrio cholerae; profuse watery ‘rice-water’ diarrhea due to toxin reversing intestinal water absorption.
Cholera is a severe diarrheal disease that can lead to dehydration and death if untreated.
Name the causative agent and critical complication of typhoid fever.
Salmonella typhi; septicemia from endotoxin release, leading to severe fever and abdominal pain.
Typhoid fever is often associated with poor sanitation and contaminated food or water.
Which bacterium is used as a fecal contamination indicator in water?
Escherichia coli (E. coli), due to its abundance in intestines and resistance in water.
E. coli is commonly used in water quality testing to indicate potential contamination by fecal matter.
How is Legionella pneumophila transmitted?
Inhalation of aerosols from warm water systems (e.g., showers, AC units).
Legionnaires’ disease is a severe form of pneumonia caused by this bacterium.
What characterizes Hepatitis A transmission and viral structure?
Fecal-oral route; non-enveloped Picornaviridae virus.
Hepatitis A is often spread through contaminated food or water.
Which parasite causes chronic diarrhea in immunocompromised individuals?
Cryptosporidium parvum; resistant to chlorine, spreads via fecal-oral route.
Cryptosporidiosis can be particularly severe in individuals with weakened immune systems.
What is the NPP method used for?
Estimating coliform density statistically via tube dilution series and Mac Grady tables.
The NPP method helps assess water quality and safety.
What pore size is used in membrane filtration for bacterial concentration?
0.45 µm or 0.22 µm membranes; traps bacteria for colony counting.
Membrane filtration is a common technique for detecting bacteria in water samples.
Why fill water sample flasks to the brim?
To prevent air contamination and preserve sample integrity.
Air exposure can lead to changes in the sample that affect analysis.
How should water samples be transported for microbiological analysis?
At ≤4°C in ice boxes, analyzed within 24 hours to inhibit microbial growth.
Timely analysis is crucial for accurate microbiological assessment.
If 3/3 tubes at 10² and 2/3 at 10³ dilutions are positive, how is NPP calculated?
Use Mac Grady tables; e.g., 5-2-1 pattern → 70 NPP/100 mL.
This pattern helps determine the most probable number of coliforms in the sample.
A canned food’s pH rises from 4.5 to 5.5 after incubation. What does this indicate?
Microbial fermentation (e.g., Clostridium), producing gas and metabolic byproducts.
Changes in pH can signal spoilage or fermentation processes.
What is the danger of improper canned food sterilization?
C. botulinum spores survive, producing lethal neurotoxins in anaerobic conditions.
Botulism is a serious foodborne illness that can result from consuming improperly processed canned foods.
What are the phases of giardiasis?
Acute phase (cramps, diarrhea); chronic phase (milder symptoms, malabsorption).
Giardiasis is caused by the parasite Giardia lamblia and can lead to long-term digestive issues.
How does cholera toxin cause dehydration?
Binds duodenal cells, reverses water absorption → 8-10 L/day fluid loss.
This mechanism highlights the severity of cholera and the importance of rehydration.
Name two bacteria in Enterobacteriaceae.
Escherichia coli, Salmonella, Shigella, Klebsiella (any two).
The Enterobacteriaceae family includes many important pathogens and indicators of fecal contamination.
