The Streptococcal Infections

This scanning electron micrograph of Streptococcus pyogenes shows the characteristic cellular phenotype resembling chains of cocci. (credit: modification of work by U.S. Centers for Disease Control and Prevention - Medical Illustrator) OpenStax Microbiology A common upper respiratory infection, streptococcal pharyngitis (strep throat) is caused by Streptococcus pyogenes. This gram-positive bacterium appears as chains of cocci. Rebecca Lancefield serologically classified streptococci in the … Continue reading The Streptococcal Infections

Defenses of the Respiratory System

This micrograph shows the structure of the mucous membrane of the respiratory tract. (credit: modification of micrograph provided by the Regents of University of Michigan Medical School © 2012) OpenStax Microbiology The inner lining of the respiratory system consists of mucous membranes and is protected by multiple immune defenses. The goblet cells within the respiratory epithelium secrete … Continue reading Defenses of the Respiratory System

Anatomy of the Upper Respiratory System

(a) The ear is connected to the upper respiratory tract by the eustachian tube, which opens to the nasopharynx. (b) The structures of the upper respiratory tract.Source: OpenStax Microbiology OpenStax Microbiology The respiratory system can be conceptually divided into upper and lower regions at the point of the epiglottis, the structure that seals off the lower respiratory system … Continue reading Anatomy of the Upper Respiratory System

Acanthamoeba Infections

(a) An Acanthamoeba cyst. (b) An Acanthamoeba trophozoite (c) The eye of a patient with Acanthamoeba keratitis. The fluorescent color, which is due to sodium fluorescein application, highlights significant damage to the cornea and vascularization of the surrounding conjunctiva. (credit a: modification of work by Centers for Disease Control and Prevention; credit b, c: modification of work by Jacob Lorenzo-Morales, Naveed … Continue reading Acanthamoeba Infections

The Sporotrichosis

Cytology of exudate from feline Sporotrichosis; numerous intracellular yeast forms; Dif-Quik stainBy self - Own work, CC BY-SA 3.0, OpenStax Microbiology Whereas cutaneous mycoses are superficial, subcutaneous mycoses can spread from the skin to deeper tissues. In temperate regions, the most common subcutaneous mycosis is a condition called sporotrichosis, caused by the fungus Sporothrix schenkii and commonly known as rose gardener’s … Continue reading The Sporotrichosis

Candidiasis of the Skin and Nails

(a) This red, itchy rash is the result of cutaneous candidiasis, an opportunistic infection of the skin caused by the yeast Candida albicans. (b) Fungal infections of the nail (tinea unguium) can be caused by dermatophytes or Candida spp. The nail becomes yellow, brittle, and prone to breaking. This condition is relatively common among adults. (c) C. albicans growing on Sabouraud … Continue reading Candidiasis of the Skin and Nails

The Tineas

Tineas are superficial cutaneous mycoses and are common. (a) Tinea barbae (barber’s itch) occurs on the lower face. (b) Tinea pedis (athlete’s foot) occurs on the feet, causing itching, burning, and dry, cracked skin between the toes. (c) A close-up view of tinea corporis (ringworm) caused by Trichophyton mentagrophytes. (credit a, c: modification of work by … Continue reading The Tineas

The Chronic Edema

Elephantiasis (chronic edema) of the legs due to filariasis. (credit: modification of work by Centers for Disease Control and Prevention) OpenStax Microbiology In addition to granulomas, chronic inflammation can also result in long-term edema. A condition known as lymphatic filariasis (also known as elephantiasis) provides an extreme example. Lymphatic filariasis is caused by microscopic nematodes (parasitic worms) whose … Continue reading The Chronic Edema