In the beginning, God created heaven and hell.
In heaven, He created all living things.
The living things were classified bacteria, archaea, and eukaryota. Man He created him on Day 6. While the other beasts were created before. So the primitive eukaryota (and the bacteria and archaea) He created before before. Created He them according to their likeness; each according to its likeness He created them.
- symbiont: mutual benefit
- commensal: surface contact only (no disease)
- pathogen: macromolecular interaction (microbe in close contact with host immune defence)
- frank pathogen — probable agent of disease
- opportunistic pathogen — organism isolated from a host with impaired defences
- non-pathogenic — organism that rarely cause disease
A non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host.
- Bacteriology — constitutes a large domain of prokaryotic microorganisms with a cell wall, classified according to the following, non-mutually exclusive, manner
- Gram positive and Gram negative
- Aerobic and anaerobic
- Facultative and obligate
- Virology — most precisely classified according to genomic type
- Fungi — eukaryotic
- Yeasts — single-celled
- Moulds — grow hyphae
- Dimorphic fungi — can exist as either single-celled or hyphenated
- Protists (Protozoa)
- Amoebae
- Flagellates
- Ciliates
- Sporozoa
- Helminths (Worm)
- Nematode (roundworms)
- Cestode (tapeworms)
- Trematode (flukes)
- Arthropods
- Insects
- Arachnids
Medically important fungi are of four phyla:
- Ascomycota —sexual reproduction in a sack called an ascus (→ ascospores)
- Basidiomycota — sexual reproduction in a sack called a basidium (→ basidiospores)
- Zygomycota — sexual reproduction by gametes and asexual reproduction (→ zygospores)
- Mitosporic Fungi [Fungi Imperfecti] — no recognizable form of sexual reproduction; includes most pathogenic fungi
| Organism | Natural Habitat | Infectious Form | Mode of Transmission | Common Sites of Infection | Clinical Form |
| Aspergillus spp. | Ubiquitous, plants | Conidia | Inhalation | Lungs, eyes, skin, nails | Hyphae |
| Blastomyces dermatitidis | Unknown(?), soil/wood | Probably conidia | Usually inhalation | Lungs, skin, long bones | Yeast |
| Candida spp. | Human flora | Yeast, pseudohyphae, and true hyphae | Direct invasion/dissemination | GI and GU tracts, nails, viscera, blood | Yeast, pseudohyphae, and true hyphae |
| Coccidioides immitis | Soil of many arid regions | Arthroconidia | Inhalation | Lungs, skin, meninges | Spherules, endospores |
| Cryptococcus neoformans complex | Bird faeces, soil | Yeast* | Inhalation | Lungs, skin, meninges | Yeast |
| Histoplasma capsulatum | Bat and bird faeces | Conidia | Inhalation | Lungs, bone marrow, blood | Yeast |
| Paracoccidioides brasiliensis | (?)Soil, plants | Conidia | Inhalation/trauma | Lungs, skin, mucous membranes | Yeast |
| Sporothrix schenckii | Soil, plants | Conidia/hyphae | Trauma/rarely inhalation | Skin and lymphatics, lungs, meninges | Yeast |
| Dermatophytes | Human disease, animals, soil | Conidia/hyphae | Contact | Skin, hair, or nails | Hyphae |
Helminth infection and infestation in humans is under-recognised and their systemic effect goes underappreciated. In acute infection the immune system is ramped up and can over-react to other antigens but in the chronic setting it can also reduce the severity of harmful autoinflammatory predispositions and autoimmunity. This is as T-cell dynamics change over time and often decline during chronic infection. In evolutionary biological terms, the constant pressure of helminth infections has played a strong role in shaping the mammalian immune response. This bystander effect of helminth infection is in contrast to and above and beyond the extensive tissue damage and repair response induced upon helminthic epithelial penetration.
For instance, Chetty and colleagues looked at the effect of remote tissue helminth infection on female reproductive tract health. An immune imprinting on the infected host can effect other organ systems. As Chetty and colleagues show: “Host immune control of STIs is strongly correlated with the pattern of cytokine production in the host. Differential activation of Th1 cells, producing IL-2 and IFN-γ, mediate cellular immune responses, whereas Th2-like cells producing IL-4, IL-5, and IL-13, facilitate humoral immunity.” Other cytokines, like IL-10, have been associated with STI viral persistence, for instance. Helminth infections can skew the immune system towards a type-2 response that impacts the body over. This can impair rather than facilitate the type-1 mediated mechanism utilised to control, for instance, a HPV infection.
Pork tapeworm: Taenia solium.
Bovine tapeworm: Taenia saginata.
Whipworm: Trihcuris trichiuria.
Liver fluke: Fasciola hepatica and Fasciola gigantica. At least three species of snail, known to be intermediate hosts for liver fluke, occur in Australia. The most important is the freshwater snail, Lymnaea tomentosa. Infection is most commonly transmitted to humans from the consumption of infected freshwater fish, or the drinking of contaminated water.
General classification of metazoa: helminths of the animal kingdom (Meglitsch and Schram, 1991).
Infection with large metazoan parasites (helminths) typically induces a type 2 immune response, orchestrated by the CD4+ T helper 2 cell.
Hugot, Jean-Pierre & Baujard, Pierre & Morand, Serge. (2001). Biodiversity in helminths and nematodes as a field of study: An overview. Nematology. 3. 199-208. 10.1163/156854101750413270.
Identification of helminth species:
Helminths are triploblastic organisms that possess a skin and a mouth of sorts and a body system mainly of alimentary and a reproductive system. They possess also a primitive nervous and excretory system. Sexes may be separate, but hermaphroditism is frequent in helminth systems. There are two main groups of helminth in classification, the flattened or platyhelminths and the nemathelminths that house a cavity within an unsegmented body.
Helminth class:
Of the Platyhelminthes:
- Cestoda – tape worms
- segmented
- possess scolex, neck, and proglottids
- hermaphroditic
- reproduce by oviparous or by the multiplication within the larval forms
Cestode infection is generally by the ingestion of the encysted larvae.
- Trematoda – flukes
- unsegmented
- leaf-like or cylindrical
- hermaphroditic (generally)
- oviparous reproduction and also from the multiplication within the larval forms
Fluke infestations mainly occur from the larval stages entering the intestinal tract and sometimes through the skin.
Of the Nemathelminths:
- Nematoda – round worms:
- unsegmented
- mouth, oesophagus, anus
- sexes separate
- oviparous and larviparous reproduction
Nematode infection is from ingestion of eggs (or encysted larvae) or the penetration of the larvae through the skin or from the bite of an arthropod vector.
