The Oral Thrush

Overgrowth of Candida in the mouth is called thrush. It often appears as white patches. (credit: modification of work by Centers for Disease Control and Prevention) OpenStax Microbiology The yeast Candida is part of the normal human microbiota, but overgrowths, especially of Candida albicans, can lead to infections in several parts of the body. When Candida  infection develops in the oral … Continue reading The Oral Thrush

The Dental Caries

Tooth decay occurs in stages. When bacterial biofilms (plaque) develop on teeth, the acids produced gradually dissolve the enamel, followed by the dentin. Eventually, if left untreated, the lesion may reach the pulp and cause an abscess. (credit: modification of work by “BruceBlaus”/Wikimedia Commons) Cavities of the teeth, known clinically as dental caries, are microbial lesions … Continue reading The Dental Caries

Anatomy and Normal Microbiota of the Oral Cavity

(a) When food enters the mouth, digestion begins. (b) Salivary glands are accessory digestive organs. (credit: modification of work by National Cancer Institute) OpenStax Microbiology Food enters the digestive tract through the mouth, where mechanical digestion (by chewing) and chemical digestion (by enzymes in saliva) begin. Within the mouth are the tongue, teeth, and salivary glands, including the parotid, sublingual, and … Continue reading Anatomy and Normal Microbiota of the Oral Cavity

Protozoan Infections of the Urogenital System

Trichomonas vaginalis is visible in this Gram stained specimen. (credit: modification of work by American Society for Microbiology) OpenStax Microbiology Only one major protozoan species causes infections in the urogenital system.  Trichomoniasis, or “trich,” is the most common nonviral STI and is caused by a flagellated protozoan Trichomonas vaginalis. T. vaginalis has an undulating membrane and, generally, an amoeboid … Continue reading Protozoan Infections of the Urogenital System

The Human Papillomas

Genital warts may occur around the anus (left) or genitalia (right). (credit left, right: modification of work by Centers for Disease Control and Prevention) OpenStax Microbiology Warts of all types are caused by a variety of strains of human papillomavirus (HPV). Condylomata acuminata, more commonly called genital warts or venereal warts, are an extremely prevalent STI caused by … Continue reading The Human Papillomas

The Chancroid

(a) A soft chancre on the penis of a man with chancroid. (b) Chancroid is caused by the gram-negative bacterium Haemophilus ducreyi, seen here in a gram-stained culture of rabbit blood. (credit a, b: modification of work by Centers for Disease Control and Prevention) OpenStax Microbiology The sexually transmitted infection chancroid is caused by the gram-negative rod Haemophilus ducreyi. … Continue reading The Chancroid

The Chlamydia

(a) Chlamydia trachomatis inclusion bodies within McCoy cell monolayers. Inclusion bodies are distinguished by their brown color. (b) Lymphogranuloma venereum infection can cause swollen lymph nodes in the groin called buboes. (credit a: modification of work by Centers for Disease Control and Prevention; credit b: modification of work by Herbert L. Fred and Hendrik A. van Dijk) … Continue reading The Chlamydia

The Cryptococcosis

(a) The micrograph shows stained budding Cryptococcus yeast cells from the lungs of a patient with AIDS. (b) The large capsule of Cryptococcus neoformans is visible in this negative stain micrograph. (credit a, b: modification of work by Centers for Disease Control and Prevention) OpenStax Microbiology Infection by the encapsulated yeast Cryptococcus neoformans causes cryptococcosis. This fungus is ubiquitous in the soil … Continue reading The Cryptococcosis

The Gonorrhea

(a) Clinical photograph of gonococcal discharge from penis. The lesions on the skin could indicate co-infection with another STI. (b) Purulent discharge originating from the cervix and accumulating in the vagina of a patient with gonorrhea. (c) A micrograph of urethral discharge shows gram-negative diplococci (paired cells) both inside and outside the leukocytes (large cells … Continue reading The Gonorrhea