Escherichia coli
Classification General Characteristics Features: Stain: gram-negative Morphology: bacillus (rod) Facultative anaerobic Either nonmotile or motile (flagellated) Catalase-positive Ferments lactose Special media and biochemical test: MacConkey agar: grows as pink colonies Eosin–methylene blue (EMB) agar: grows as metallic, green colonies Indole test–positive Pathogenesis and Virulence Factors Virulence Antigenic structures: O antigen: component of the lipopolysaccharide (LPS) […]
Coxsackievirus
Classification General Characteristics and Epidemiology General features of Coxsackievirus Family: Picornaviridae Genus: Enterovirus RNA virus: Linear Single stranded Positive sense Functions as mRNA Diameter: approximately 30 nm Icosahedral symmetry Lacks a lipid envelope Acid-stable viruses Clinically relevant species Coxsackie group A virus (23 serotypes): Herpangina Hand, foot, and mouth disease (HFMD): most frequently implicated is […]
Poliovirus/Poliomyelitis
Classification General Characteristics and Epidemiology General characteristics of poliovirus Family: Picornaviridae Genus: Enterovirus Classified as a strain of Enterovirus C RNA virus: Linear Single-stranded Positive-sense Functions as mRNA Diameter: 25–30 nm Icosahedral symmetry Lacks a lipid envelope Acid-stable Clinically relevant species Poliomyelitis is caused by 3 serotypes of poliovirus: Wild type 1 (most common) Wild […]
Malassezia Fungi
General Characteristics and Epidemiology General features of Malassezia Formerly known as Pityrosporum Taxonomy: Family: Malasseziaceae Genus: Malassezia Dimorphic: Yeast: spherical or oval Mycelial form: short hyphae Colonies are cream or yellowish in color. Lipophilic Most species are lipid-dependent. Not a dermatophyte Reproduce by unipolar budding Clinically relevant species There are a number of recognized species: […]
Aspergillus/Aspergillosis
General Characteristics of Aspergillus Characteristics: Exists only as a mold (not dimorphic) Highly aerobic Grows on plants, soil, household dust, and food Obtains nutrients from dead and decaying matter Best visualized with silver stains Morphology: Hyphae Long, filamentous structures Frequent septae Form dichotomous branches (45-degree angles) Walls are typically parallel Conidia Asexual, nonmotile spores Spherical […]
Toxoplasma/Toxoplasmosis
General Characteristics and Epidemiology General features of Toxoplasma General characteristics: Morphologic forms: Clinically relevant species Toxoplasmosis is caused by Toxoplasma gondii. Epidemiology Pathogenesis Hosts Transmission Life cycle and pathophysiology Life cycle: Life cycle and pathophysiology in humans: Clinical Presentation The clinical presentation of toxoplasmosis can vary depending on the host’s immune function and organs involved. […]
Ascaris/Ascariasis
General Characteristics and Epidemiology General features of Ascaris Ascaris is a genus of parasitic nematodes (roundworms). Adults: Eggs: Clinically relevant species Ascariasis is caused by: Epidemiology Ascariasis is one of the most common parasitic infections in humans. Pathogenesis Reservoirs A. lumbricoides: A. suum: Transmission Life cycle Pathophysiology Effect of larvae migration in the lungs → […]
Equine Encephalitis Viruses
Classification General Characteristics and Epidemiology General features of equine encephalitis virus (EEV) Family: Togaviridae Genus: Alphavirus Genome: Positive-sense, ssRNA 11–12 kb in size Properties: Enveloped Lipid bilayer envelope has viral-encoded glycoproteins E1 and E2. Small icosahedral capsid Clinically relevant viruses and geographic distribution: Eastern equine encephalitis virus (EEEV) complex: Eastern equine encephalitis (EEE) virus: North […]
Schistosoma/Schistosomiasis
General Characteristics and Epidemiology General features of Schistosoma Clinically relevant species Epidemiology Geographic distribution Pathogenesis Reservoir Transmission Transmission occurs through skin contact with infected fresh water. Host risk factors Schistosoma occupies freshwater environments in areas with poor sewerage management. Life cycle Pathophysiology Clinical disease is caused by: Clinical Presentation Most patients are asymptomatic. Symptomatic individuals […]
Helicobacter
Classification Characteristics Features: Stains: Gram-negative Detected with silver stain Morphology: Motile rod Curved shape Contains multiple flagella Growth and culture: Microaerophilic Complex growth requirements (special transport media required) Oxidase-positive, catalase-positive Urease-positive production: creates alkaline environment that permits survival of bacteria in acidic mucosa Helicobacter genus contains about 35 species, with H. pylori being the most […]