Questions and Answers
What is the color of Gram (+) bacteria after applying Safranin?
Which of the following is a characteristic of Gram (-) bacteria?
What is the virulence factor associated with Shigella spp.?
Flagella
The typical temperature range for the growth of Staphylococcus aureus is ______ °C.
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What type of hemolysis does Streptococcus pyogenes produce?
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The antibiotic treatment for Clostridium botulinum is ______.
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Match the following bacterial species with their corresponding diseases:
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All Streptococcus species are catalase-positive.
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S.epidermidis is coagulase-positive.
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What is the mechanism of action (MOA) of endotoxins?
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What is a major cause of nosocomial infections associated with Staphylococcus aureus?
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What treatment is commonly used for Haemophilus influenza infections?
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What is the primary disease caused by Bordetella pertussis?
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Haemophilus ducreyi causes soft chancres.
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The DOC for treating Haemophilus vaginalis infections is ___.
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Which organism is known to cause cat-scratch disease?
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What is the vector for Leishmania tropica?
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Yersinia pestis does not cause plague.
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What is the primary mode of transmission for Brucella spp.?
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What is the treatment for Enterocolitis caused by Yersinia enterocolitica?
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Coccidioidomycosis is also known as ___.
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Cryptococcus neoformans can be identified using India ink staining.
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Study Notes
Basics of Microbial Diversity in Prokaryotes
- Prokaryotes are classified into two main groups based on their cell wall characteristics: Gram-positive and Gram-negative.
- Gram staining involves a series of steps that differentiate bacteria based on their cell wall structure.
Gram Staining Procedures
- Crystal Violet: Stains both Gram-positive and Gram-negative bacteria violet.
- Iodine: Acts as a mordant, intensifying the violet color in all bacteria.
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Alcohol:
- For Gram-positive: retains violet color.
- For Gram-negative: results in colorless outcome.
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Safranin:
- For Gram-positive: retains violet color.
- For Gram-negative: stains red or pink.
Features of Cell Wall
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Gram-positive:
- Thick peptidoglycan layer.
- Contains teichoic acids for rigidity.
- Higher resistance to physical disruption.
- More sensitive to penicillin and lysozyme.
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Gram-negative:
- Thin peptidoglycan layer.
- Contains an outer membrane with lipopolysaccharides (LPS).
- Less sensitive to antibiotics like penicillin.
Microbial Morphology
- Morphology includes shapes like cocci (spherical), bacilli (rod-shaped), spirilla (spiral), and pleomorphic.
Virulence Factors
- Motility: Flagella provide mobility in pathogens such as Shigella, Campylobacter, and Helicobacter.
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Toxins:
- Endotoxins: Part of the Gram-negative outer membrane; stable at high temperatures, generally less potent, pyrogenic.
- Exotoxins: Secreted by both Gram-positive and Gram-negative; unstable at high temperatures, highly potent, and target specific cells.
Bacterial Spores
- Dormant structures allowing survival in extreme conditions.
- Highly resistant to environmental stressors such as heat and desiccation, can germinate under favorable conditions.
Gram-positive Cocci
- Catalase test: Identifies Staphylococcus spp. (+) produce bubbles; Streptococcus spp. (-) do not.
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Staphylococcus aureus:
- Characteristics: Forms grape-like clusters; coagulase-positive.
- Associated with nosocomial infections and Toxic Shock Syndrome.
- Key diseases: Scalded Skin Syndrome and Food Poisoning.
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Staphylococcus epidermidis:
- Coagulase-negative; opportunistic pathogen.
- Common infections: Prosthetic valve endocarditis, UTIs.
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Staphylococcus saprophyticus:
- Novobiocin-resistant; common cause of UTIs in sexually active women.
Streptococcus Characteristics
- Morphology: Spherical, appear in chains; catalase-negative.
- Alpha-hemolytic: Partial hemolysis, includes S. pneumoniae (causes pneumonia) and S. viridans (part of oral flora).
- Beta-hemolytic: Complete hemolysis; includes S. pyogenes (causes strep throat) and S. agalactiae (neonatal infections).
- Gamma-hemolytic: Non-hemolytic; includes enterococci linked to UTIs and endocarditis.
Lancefield Grouping
- A method for classifying streptococci based on cell wall antigens.
- Group A: S. pyogenes, causes pharyngitis and scarlet fever.
- Group B: S. agalactiae, significant in neonatal infections.
Gram-positive Bacilli
- Includes spore-forming (Bacillus, Clostridium) and non-spore-forming genera.
- Bacillus anthracis: Causes anthrax, has unique amino acid capsule; used in biowarfare.
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Clostridium spp.:
- C. botulinum: Causes flaccid paralysis, produces lethal neurotoxin.
- C. tetani: Causes spastic paralysis; preventative vaccines available.
Non-spore Forming Gram-positive Bacilli
- Corynebacterium diphtheriae: Aerobic, non-motile, causes diphtheria.
- Listeria monocytogenes: Can cause serious infections during pregnancy.
Conclusion
- Understanding the classification, morphology, pathogenic mechanisms, and associated diseases of prokaryotic microorganisms is essential for identifying and treating bacterial infections effectively.### Diphtheria
- Produces diphtheria toxin and commonly infects the upper respiratory tract.
- Symptoms include a sore throat and can be screened using the Schick test.
- Diagnosed using Loeffler’s slant medium.
- Prophylactic treatment includes the DTP vaccine.
- Treatment options: Erythromycin and Penicillin G.
Listeria monocytogenes
- Exhibits tumbling motility and is facultatively anaerobic.
- Produces hemolysin and ferments sugars, resulting in acid production.
- Causes listeriosis and neonatal meningitis.
- Treatment: Cotrimoxazole and Ampicillin.
Lactobacillus
- Located in the vagina, intestinal tract, and oral cavity.
- Commercially used in the production of sauerkraut, pickles, buttermilk, and yogurt.
Non-Sporing Forming Bacteria
- Erysipelothrix rhusiopathiae: Occupational pathogen; causes seal finger disease; treated with Penicillin.
- Actinomyces israelii: Causes actinomycosis; noted for skin lesions and pus; treat with surgical removal.
- Nocardia asteroides: Causes chronic pulmonary infections and mycetoma; treated with Co-trimoxazole.
- Propionibacterium acne: Main cause of acne; involved in Swiss cheese fermentation.
Gram (-) Cocci
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Neisseria spp.:
- N.meningitidis: Causes meningitis and meningococcemia; prophylaxis with Rifampicin and Ciprofloxacin; treatment with Ciprofloxacin.
- N.gonorrhea: Causes gonorrhea and PID; grows in enriched media; treated with Ceftriaxone and Doxycycline.
- Moraxella catarrhalis: Causes otitis media and respiratory infections; a Gram-negative diplococcus.
Gram (-) Bacilli
Enterobacteriaceae
- Includes E. coli, Klebsiella pneumoniae, Salmonella spp., Shigella dysenteriae, etc.
- E.coli: Gram-negative, motile; causes UTI, neonatal meningitis, and hospital-acquired pneumonia; treated with Cotrimoxazole and Quinolones.
- E.coli classified into different pathotypes like EPEC, ETEC, EIEC, and EHEC.
Salmonella
- Salmonella typhi: Causes typhoid fever; diagnosed with the Widal test; treated with Ciprofloxacin or Ceftriaxone.
- Salmonella enteritidis: Causes gastroenteritis; Salmonella choleraesius: associated with septicemia.
Shigella dysenteriae
- Non-motile, non-spore forming; known for causing dysentery; treated with Cotrimoxazole and Quinolones.
Vibrio
- Vibrio cholerae: Responsible for cholera; virulence factor includes cholera toxin; treated with Tetracycline and Oral Rehydration Salt.
- Helicobacter pylori: Microaerophilic organism; causes gastritis and ulcers; treated with multidrug therapy including Bismuth compounds.
Pseudomonas aeruginosa
- Gram-negative rod, opportunistic pathogen; characterized by a sweet grape-like odor; detected based on blue-green fluorescing colonies.
- Treatment includes anti-pseudomonal penicillins and aminoglycosides.
Fungi
- Fungi are eukaryotic, acquiring nutrients through absorption; reproduce sexually and asexually.
- Classified into Zygomycota, Microsporidia, Ascomycota, and Basidiomycota.
Fungal Diseases
- Superficial Mycoses: Include diseases such as Black Piedra and Pityriasis versicolor.
- Cutaneous Mycoses: Dermatophytes such as Tinea pedis and Tinea corporis.
- Systemic Mycoses: Diseases like Coccidioidomycosis and Cryptococcosis; treated with Amphotericin B or Fluconazole.
Algae
- Algae are unicellular or multicellular photosynthetic organisms; can reproduce sexually and asexually.
- Thallus refers to the body of multicellular algae; seaweeds have structures such as holdfasts for anchoring.
Conclusions
- Importance of understanding various bacterial and fungal pathogens, their disease manifestations, and treatment modalities.
- Knowledge of microbial diversity helps in diagnostics and preventing infectious diseases in clinical settings.### Algae Structure and Support
- Stipes are stem-like, hollow structures providing support, unlike woody plant stems.
- Blades are leaf-like structures extending from the stipe.
- Surrounding water supports the algae; some have gas-filled bladders called pneumatocysts for buoyancy.
Algae Reproduction
- Asexual reproduction occurs through mitosis, producing identical offspring.
- Sexual reproduction involves the fusion of gametes, promoting genetic diversity.
Protozoa Overview
- Protozoa belong to the kingdom Protista, mostly unicellular but some form colonies.
- Classified by locomotion:
- Amebas use pseudopodia (false feet).
- Flagellates utilize whiplike flagella.
- Ciliates employ hairlike cilia.
- Sporozoans lack motility, having no specialized locomotion structures.
Protozoan Infections and Lifecycle
- Diagnosed by observing various developmental stages including trophozoites (motile, feeding stage) and dormant cysts.
- Infections generally acquired through ingestion/inhalation of cysts, or bites from infected arthropods.
- Rarely, trophozoites serve as the infective stage due to fragility.
Protozoa Reproduction
- Asexual reproduction includes:
- Fission: simple cell division.
- Budding: new organism forms from a part of a cell.
- Schizogony: multiple fission, leading to several daughter cells.
- Sexual reproduction involves the formation of gametes and zygote formation (fusion of two gametes).
Types of Hosts in Protozoa
- Definitive host harbors the sexually mature form of a parasite.
- Paratenic host carries the parasite in a non-developing form, keeping it viable for infection.
- Intermediate host supports the asexual or larval stage of the parasite.
Groups of Protozoa
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Amoebas: Free-living in water; move by pseudopods.
- Entamoeba histolytica causes amebiasis via fecal-oral transmission; diagnosed through fecalysis.
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Flagellates: Lack mitochondria and possess multiple flagella.
- Giardia lamblia causes giardiasis; commonly transmitted fecal-orally.
- Trichomonas vaginalis causes trichomoniasis; transmitted sexually.
- Leishmania spp. are zoonotic; transmitted by sandflies causing various leishmaniasis forms.
- Trypanosoma cruzi causes Chagas' disease, vector is the kissing bug.
- Trypanosoma brucei causes sleeping sickness; transmitted by tsetse fly.
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Ciliates: Notable for their cilia.
- Balantidium coli, largest protozoan parasite, causes balantidiasis; reservoirs include pigs.
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Sporozoans: Lifecycle involves sexual and asexual cycles.
- Mosquito is the definitive host for Plasmodium spp., which cause malaria:
- P.falciparum: deadliest and most common.
- P.vivax: benign tertian malaria.
- P.ovale and P.malariae also cause malaria.
- Mosquito is the definitive host for Plasmodium spp., which cause malaria:
Malaria Prophylaxis and Treatment
- Prophylactic drugs include chloroquine; alternatives for drug-resistant strains are quinine + fansidar.
- Severe P.falciparum malaria treatment involves quinidine.
Other Protozoal Infections
- Toxoplasma gondii: causes toxoplasmosis; associated with cat feces.
- Isospora belli: causes isosporiasis; particularly harmful in immunocompromised individuals.
- Blastocystis hominis: resembles protozoan yeast; transmitted fecal-orally and treated with metronidazole.
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Test your knowledge on Gram staining techniques and bacterial characteristics with this microbiology quiz. It covers important details like the color changes in Gram-positive and Gram-negative bacteria, virulence factors, and growth conditions for notable bacteria. Perfect for students studying microbiology!
