Medical Microbiology and Infection

Neisseria and Moraxella (Bacteriology) (Medical Microbiology and Infection)

Neisseria gonorrhoeae Infection with Neisseria gonorrhoeae, a Gram-negative diplococ-cus, is most common in individuals between 15 and 35 years of age. It is almost exclusively spread by sexual contact. Pathogenesis The organism adheres to the genitourinary epithelium via pili, then invades the epithelial layer and provokes a local acute inflammatory response. Variation in the proteins […]

Small Gram-negative coccobacilli: Haemophilus, Brucella, Francisella, Yersinia and Bartonella (Bacteriology) (Medical Microbiology and Infection)

Haemophilus Haemophilus spp. are fastidious Gram-negative coccobacilli that colonize mucosal surfaces. H. influenzae and H. ducreyi are the main pathogenic species. Haemophilus influenzae Haemophilus influenzae expresses an antiphagocytic polysaccharide capsule of which there are six types (a-f). It also expresses a lipopolysaccharide (LPS) and an IgA1 protease. Septicaemia, meningitis and osteomyelitis are usually associated with […]

Pathogenicity of enteric Gram-negative bacteria (Medical Microbiology and Infection)

The Enterobacteriaceae are a large family (>20 genera and 100 species) of facultatively anaerobic Gram-negative bacilli that are easily cultured, reduce nitrate and ferment glucose. The wide diversity of named species is in part because they are easy to grow and study in the laboratory, but also because they are capable of causing a wide […]

Enterobacteriaceae clinical syndromes (Bacteriology) (Medical Microbiology and Infection)

Salmonella There are two Salmonella species that account for the majority of human and animal infections: S. enterica and S. bongori. Salmonellosis Salmonella are host-adapted to animals and humans. Infection is usually confined to the bowel, appearing as acute self-limiting diarrhoea. Less commonly invasive disease develops, which may be complicated by bacteraemia, life-threatening septicaemia or […]

Vibrio, Campylobacter and Helicobacter (Bacteriology) (Medical Microbiology and Infection)

Vibrio spp Vibrios are Gram-negative, curved, motile bacilli. There are more than eight species; V. cholerae and V. parahaemolyticus being the main human pathogens. Vibrio cholerae The organism is subdivided by the somatic O antigens; O1 and O139 being the main types associated with cholera. They are able to survive the gastric acidity, burrowing through […]

Environmental pathogens: Pseudomonas, Burkholderia and Legionella (Bacteriology) (Medical Microbiology and Infection)

Pseudomonas spp. Most Pseudomonas spp. are environmental organisms that can cause opportunistic infections in a healthcare environment. Pseudomonas aeruginosa This organism is widespread in the environment, but rare in the flora of healthy individuals. Its carriage increases with hospitalization. Moist places such as sink-traps, drains and flower vases can harbour Pseudomonas. Pathogenesis • Produces cytotoxins […]

Chlamydia, Mycoplasma and Rickettsia (Bacteriology) (Medical Microbiology and Infection)

Chlamydia There are three species: Chlamydia trachomatis, which infects the eye and the genital tract; and two respiratory pathogens, C. pneumonia and a related species Chlamydophila psittaci. They are obligate, intracellular bacteria that exist in two forms: the reticulate body (a non-infective, intracellular, vegetative form) and the elementary body (an extracellular form that permits the […]

Spiral bacteria (Medical Microbiology and Infection)

Leptospira There are two main species: Leptospira interrogans, which contains all of the pathogenic strains, and L. biflexa, a non-pathogen. L. interrogans has more than 200 serovariants that may be written as if they are separate species. Epidemiology Leptospira interrogans have different preferred mammalian hosts, for example the rat is the reservoir of L. interrogans […]

Virus structure, classification and antiviral therapy (Virology) (Medical Microbiology and Infection)

Viral classification Viral classification is based on the nucleotides in the virus, its mode of replication, the structure and symmetry of the structural proteins (capsids) and the presence or absence of an envelope. Genetic material and replication DNA viruses • Double-stranded DNA viruses include poxviruses, herpesvi-ruses, adenoviruses, papovaviruses and polyomaviruses. • Single-stranded DNA viruses include […]

Herpesviruses I (Virology) (Medical Microbiology and Infection)

Herpesviruses are enveloped, double-stranded DNA viruses (120— 240 kb) encoding for more than 35 proteins. After an acute infection, lifelong latency follows with the potential for relapse to occur later in life, especially if the individual becomes immunocompromised. Classification Herpesviruses are divided into three groups: • α-herpesviruses are fast-growing cytolytic viruses that establish latent infections […]

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