Microbiology: Parasitology and Antimicrobial Drugs

Comprehensive practice flashcards covering medical parasitology, fungi, algae, protozoa, helminths, and antimicrobial chemotherapy based on lecture notes.

What notebook brand and model information is recorded on the title notebook page in Source 1?

KOKUYO Campus, marked with "W 80 -108WM".

What proportion of the global population is affected by parasitic diseases caused by pathogenic eukaryotes?

$\frac{1}{3}$ of the world's population.

Of the more than $100{,}000$ classified fungal species, approximately how many are considered pathogenic to humans?

Around $200$ species.

What carbohydrate polymer makes up the cell walls of fungi?

Chitin.

How are the body and filaments of a mold or fleshy fungus defined?

The body of a mold or fleshy fungus is called the thallus, which consists of long filaments of joined cells called hyphae.

What structural difference distinguishes septate hyphae from coenocytic hyphae?

Septate hyphae contain cross-walls (septa) dividing them into distinct uninucleate units, whereas coenocytic hyphae lack septa and form continuous, multinucleate filaments.

What are the primary functional differences between vegetative hyphae and aerial (reproductive) hyphae?

Vegetative hyphae obtain nutrients from the growth medium, whereas aerial (reproductive) hyphae project above the surface and carry out reproduction.

How do budding yeasts such as Saccharomyces reproduce asexually?

They divide unevenly: the parent cell produces an external protuberance (bud), the nucleus divides and sends one daughter nucleus into the bud, cell wall material forms, and the bud breaks away.

What metabolic pathways allow yeasts to grow under different environmental conditions, and what are their fermentation end products?

Yeasts are facultative anaerobes that use aerobic respiration in the presence of oxygen and carbohydrate fermentation in the absence of oxygen, producing ethanol and $CO_2$.

How does temperature regulate morphological growth in dimorphic fungi?

At $37\,^\circ\text{C}$, they grow in a yeastlike form (reproducing by budding), whereas at $25\,^\circ\text{C}$, they grow in a moldlike form (producing vegetative and aerial hyphae).

How do fungal spores differ functionally from bacterial endospores?

Fungal spores are reproductive and infectious units produced sexually or asexually, whereas bacterial endospores are non-reproductive structures designed purely for survival in harsh conditions.

What are the five categories used to classify mycoses based on tissue depth and route of host entry?

1. Systemic, 2. Subcutaneous, 3. Cutaneous, 4. Superficial, and 5. Opportunistic.

What is the typical origin and route of transmission for systemic mycoses?

They are typically caused by soil fungi whose spores are inhaled deep into the body; they are not contagious from animal to animal.

How do subcutaneous fungal infections enter the host, and what is a classic example seen in gardeners?

They enter through deep implantation of spores into a puncture wound beneath the skin; sporotrichosis is a common example.

What anatomical structures are colonized by cutaneous mycoses (dermatophytes), and what enzyme do they secrete to obtain nutrients?

They colonize the epidermis, hair, and nails, and secrete keratinase to degrade keratin proteins.

Which two opportunistic fungi are prominent causes of disease in immunocompromised hosts and individuals with AIDS?

Pneumocystis (causing life-threatening pneumonia in AIDS patients) and Candida albicans (causing candidiasis / yeast infections).

Why is "algae" not considered a formal taxonomic grouping?

It is an informal descriptive term for eukaryotic photoautotrophs that lack the true roots, stems, and leaves of plants.

What four principal vegetative structures of a kelp thallus are highlighted in this diagram?

Blade (leaflike structure), Gas bladder, Stipe (stem-like, hollow structure), and Holdfast (branched root-like anchor).

What commercially important substances are harvested from brown algae and red algae cell walls?

Algin is extracted from brown algae, and agar is extracted from red algae.

What are the structural components of diatom cell walls, and what toxin can they produce?

Their cell walls contain pectin and a layer of silica; they produce domoic acid, which causes diarrhea and neurological damage/memory loss upon ingestion.

What neurotoxin is produced by planktonic dinoflagellates, and which genus causes red tide phenomena?

They produce saxitoxins (responsible for paralytic shellfish poisoning); Alexandrium spp. are responsible for red tide events.

What percentage of the Earth’s oxygen supply is generated by planktonic algae?

$80\%$ of the Earth's oxygen.

What is a protozoan trophozoite, and what role does a pellicle serve?

A trophozoite is the vegetative, feeding, and growing stage of a protozoan; a pellicle is a protective outer covering surrounding the plasma membrane.

How do ciliates and amebae differ in their mechanisms for capturing food particles?

Ciliates sweep food into a mouth-like cytostome using cilia, whereas amebae extend pseudopods around food particles to ingest them via phagocytosis.

What cellular characteristics and transmission route distinguish Trichomonas vaginalis?

It lacks mitochondria, has flagella bordered by an undulating membrane, lacks a protective cyst form, and is transmitted sexually.

What organ does Giardia intestinalis colonize, and how is it transmitted between hosts?

It colonizes the small intestine of humans and mammals, survives outside the host as an environmental cyst, and is transmitted via the fecal-oral route.

What hemoflagellate genus is depicted here, and what two diseases are caused by its insect-borne transmission?

Trypanosoma; it causes African sleeping sickness (transmitted by the tsetse fly) and Chagas disease (transmitted by the kissing bug).

How does Entamoeba histolytica establish intestinal infection and damage human cells?

It uses surface lectin proteins to bind galactose residues on intestinal cell membranes, causing host cell lysis and amebic dysentery.

What animal serves as the definitive host for Toxoplasma gondii, and why is infection critical during pregnancy?

Domestic cats are the definitive host; maternal infection during pregnancy can cause dangerous congenital infections in utero.

Where in the human body does Cryptosporidium multiply, and what clinical sign does it produce?

It lives inside epithelial cells lining the small intestine and causes watery diarrhea.

In the malaria parasite Plasmodium vivax, which hosts represent the definitive and intermediate stages?

The mosquito is the definitive host (harboring sexual reproduction), and the human is the intermediate host (harboring asexual reproduction).

What physiological organ systems are typically reduced or missing in parasitic helminths compared to free-living worms?

Their digestive system, nervous system, and locomotory systems are typically reduced or absent, while their reproductive system is highly complex.

What is the difference between dioecious and monoecious helminths?

Dioecious helminths have distinct male and female reproductive organs in separate individuals, whereas monoecious (hermaphroditic) helminths contain both male and female reproductive systems within a single worm.

What morphological characteristics define trematodes (flukes)?

They have flat, leaf-shaped bodies equipped with oral and ventral suckers, and they absorb host nutrients directly through a protective, nonliving cuticle.

What intestinal parasite is shown here, and what are its three labeled morphological sections?

A cestode (tapeworm), showing the scolex (head with attachment hooks/suckers), the neck, and repeating segments called proglottids.

What distinguishing digestive feature do nematodes possess, and how many global infections are attributed to Ascaris?

Nematodes have a complete digestive system (mouth, intestine, and anus); Ascaris infections affect more than $2\text{ billion}$ people worldwide.

How do blood-sucking arthropod vectors typically utilize their hosts, and which insect represents a notable exception?

Most arthropod vectors (such as ticks, fleas, and mosquitoes) reside on the host only while taking a blood meal; the human louse is the exception because it remains on the host continuously.

Which historical scientist is shown here, and what major concepts did he contribute to antimicrobial therapy?

Paul Ehrlich; he coined the term "chemotherapy" and originated the principles of selective toxicity and the "magic bullet".

What distinguishes natural antibiotics from synthetic antimicrobial drugs?

Antibiotics are naturally synthesized by microorganisms to inhibit other microbes in small concentrations, whereas antimicrobial drugs encompass fully synthetic chemical substances (such as sulfa drugs).

Which bacterial genus produces more than half of all known clinical antibiotics?

Streptomyces.

Why is developing drugs with selective toxicity significantly more challenging against fungi, protozoa, and helminths than bacteria?

Fungi, protozoa, and helminths are eukaryotes whose cellular and metabolic pathways closely resemble those of human host cells, leaving fewer unique drug targets.

What structural feature of Gram-negative bacteria serves as a primary physical barrier to antibiotic penetration?

The lipopolysaccharide (LPS) outer membrane containing narrow porin channels, which restrict the entry of large antibiotic molecules.

What is the clinical difference between bactericidal and bacteriostatic agents?

Bactericidal agents directly kill bacterial cells, whereas bacteriostatic agents reversibly arrest bacterial growth, allowing host immune mechanisms to clear the infection.

How does sulfanilamide act as a competitive antimetabolite in bacterial cells?

It structurally mimics para-aminobenzoic acid (PABA) and competitively binds the enzyme dihydropteroate synthase (DHPS), halting folic acid biosynthesis.

What common chemical moiety do beta-lactams possess, and what specific enzymatic step in cell wall assembly do penicillins disrupt?

They possess a core beta-lactam ring; penicillins block transpeptidase cross-linking of peptidoglycan chains, leading to osmotic cell lysis.

What is penicillinase (beta-lactamase), and which bacterial genus is well known for producing it?

Penicillinase is an enzyme that hydrolyzes the beta-lactam ring, inactivating penicillins; it is notably produced by Staphylococcus species.

How do bacitracin and vancomycin differ in their clinical usage and spectrum?

Bacitracin interferes with early peptidoglycan strand synthesis and is limited to topical application, whereas vancomycin is a glycopeptide reserved for severe systemic infections such as MRSA.

How do chloramphenicol, aminoglycosides, and tetracyclines differ in their bacterial ribosomal binding sites and actions?

Chloramphenicol binds the $50\text{S}$ subunit inhibiting peptide bond formation; aminoglycosides alter the $30\text{S}$ subunit causing mRNA misreading; tetracyclines bind the $30\text{S}$ subunit blocking tRNA attachment.

How do the membrane-disrupting lipopeptide daptomycin and the polypeptide polymyxin differ in their target organisms?

Daptomycin selectively targets Gram-positive bacterial plasma membranes to form pores, while polymyxin disrupts the outer membrane and LPS of Gram-negative bacteria.

What four cellular mechanisms of bacterial antibiotic resistance are illustrated in this diagram?

1. Blocking entry, 2. Inactivating enzymes, 3. Alteration of target molecule, and 4. Efflux of antibiotic.