Biomedical Engineering Reference
In-Depth Information
Moraxella catarrhalis is an opportunistic pathogen that often targets
young children, the elderly, and immune-compromised individuals. It can
cause a wide range of infections. In adults it tends to cause pneumonia,
bronchitis, sinusitis, and can lead to sepsis. In young children, it can cause
otitis media. The organism seems to live in humans exclusively, colonizing
the respiratory tracts of infected individuals [40].
Much like Genus Acinetobacter, members of Genus Pseudomonas are
opportunistic infections that are often nosocomial (i.e., hospital-acquired).
Pseudomonas species can grow as biofilms. The biofilms contain an excreted
exopolysaccharide that interferes with disinfection of colonized surfaces.
Patients in a weakened condition are particularly vulnerable to infections.
The most common Pseudomonas species involved in human infections is
Pseudomonas aeruginosa, which causes some of the same kinds of infections
observed with Acinetobacter species (pneumonia, bacteremia, urinary tract
infections, burn infections).
Several species, formerly assigned to Genus Pseudomonas, are now
assigned to Genus Burkholderia (Beta Proteobacteria, Chapter 6). These include
species now known as Burkholderia mallei and Burkholderia pseudomallei.
Gamma Proteobacteria
Thiotrichales
Francisellaceae
*Francisella
Class Thiotrichales has received scientific attention as it contains the largest
known species of bacteria, Thiomargarita namibiensis. This ocean-dwelling
non-pathogen can reach a size of 0.75 millimeter, visible to the unaided eye
(see Glossary item, Largest species).
In contrast, Genus Francisella contains small organisms, under a micron
in size. Francisella tularensis is the cause of tularemia, also known as rabbit
fever. The species occurs in two serotypes (A and B), with Type B producing
milder disease. The organism's reservoir is infected rodents (including rabbits
and beavers), and is usually transmitted to humans via arthropod bites, particu-
larly tick bites. Human infections can also follow ingestion of contaminated water
or soil or by handling infected animals. Tularemia is a serious disease, that can
produce a wide variety of symptoms. A common presentation involves lymph
nodes (glandular form) and infection of the facial skin. The enlargement of lymph
nodes is similar to the buboes (ulcerating enlarged lymph nodes) associated with
plague. Other species of Genus Francisella, Francisella novicida and Francisella
philomiragia, previously assigned to Genus Yersinia, can produce sepsis.
Gamma Proteobacteria
Vibrionales
Vibrionaceae
*Vibrio
