Microbial Identification and Protozoan Parasitology

Vocabulary flashcards covering diagnostic flowcharts for bacterial identification and fundamental concepts in eukaryotic protozoan morphology, reproduction, and human pathogenesis.

Selective toxicity

The ability of a therapeutic agent to target and eliminate a pathogen without damaging host cells, which is challenging when treating eukaryotic protozoa because their cellular machinery and structures closely resemble those of human cells.

Schizogony

An asexual reproductive method in protozoa where a cell undergoes multiple nuclear divisions to become multinucleated before bursting to produce multiple individual daughter cells.

Intermediate host

The host organism within a multi-host parasitic life cycle in which the parasite replicates strictly through asexual methods rather than sexual reproduction.

Definitive host

The specific host organism in a complex parasitic life cycle within which the parasite undergoes sexual reproduction.

Protozoan cyst

A protective survival structure formed by certain protozoa that allows them to endure harsh conditions outside a host and serves as a transmission vehicle to infect new hosts via feces.

Protozoan conjugation

A sexual reproductive process observed in ciliates like Paramecium involving the reciprocal exchange of haploid micronuclei to generate genetic diversity, distinct from bacterial conjugation via sex pili.

Excavata

A eukaryotic protozoan group characterized by organisms that lack standard functional mitochondria and must generate ATP through alternative cellular pathways.

Giardia

A flagellated protozoan parasite that lacks mitochondria and forms resilient cysts surviving in cold mountain streams, causing diarrheal illness when ingested through unfiltered water.

Trichomonas

A flagellated parasite equipped with an undulating membrane that cannot form protective cysts and is transmitted exclusively by direct human-to-human sexual contact.

Naegleria

A waterborne amoebic protozoan that enters the human body through the nasal passages during swimming, migrates to destroy brain tissue, and is typically fatal.

Plasmodium

The complex protozoan parasite that causes malaria, using mosquitoes as definitive hosts and humans as intermediate hosts where it multiplies inside liver and blood cells by schizogony.

Phototaxis

The directional cellular movement toward a light source exhibited by photosynthetic protozoa containing chloroplasts.

Helminths

Multicellular parasitic worms that are classified apart from unicellular microbes and are typically diagnosed clinically by finding eggs in patient stool specimens.

Clostridium

A genus of Gram-positive, endospore-forming, anaerobic rod bacteria that fail to grow in normal air and can cause gas accumulation under the skin following puncture wounds.

Mycobacterium tuberculosis

A slow-growing, acid-fast positive, non-endospore-forming Gram-positive rod bacterium that causes chronic cough, weight loss, and takes weeks to form visible colonies on culture media.

Urease test

A biochemical identification step used on diagnostic keys to separate Salmonella (which tests negative) from Proteus (which tests positive).

Hydrogen sulfide production test

A diagnostic procedure checking for black precipitation caused by bacterial reduction of sulfate as an alternative terminal electron acceptor in anaerobic respiration, used to distinguish Shigella from Proteus.

Listeria

A Gram-positive rod-shaped bacterium identified along a diagnostic key by a positive catalase test, a negative acid-fast test, and an absence of endospores.