Biomedical Engineering Reference
In-Depth Information
Readers should remember that despite its name, Haemophilus parain-
fluenzae is not the cause of the disease known as parainfluenza.
Parainfluenza is a type of croup (laryngotracheobronchitis), and about
75% of the cases of croup are caused by the parainfluenza virus, a Group
V virus (Chapter 43).
Haemophilus ducreyi is the cause of chancroid, a sexually transmitted
disease. Chancroid produces painful genital ulcers. It must not be confused
with other diseases that cause genital ulcers: syphilis and granuloma ingui-
nale. Klebsiella granulomatis, in Class Enterobacteriaceae causes granuloma
inguinale, and was described previously in this chapter. Syphilis is caused by
a spirochete (Chapter 9). Adding to the confusion, the syphilitic genital ulcer
is known as a chancre.
Genus Pasteurella contains Pasteurella multocida, the cause of pasteurellosis,
a zoonosis. Pasteurella multocida lives as a commensal or as a pathogen in a
variety of animals. Infection in humans usually results from close contact with
infected animals. Infections may arise through bites or scratches from pets,
particularly cats. Infection can result in sepsis, pneumonia, or skin infections.
Skin infections often occur at the site of a cat scratch.
Gamma Proteobacteria
Pseudomonadales
Moraxellaceae
*Acinetobacter
*Moraxella
Pseudomonadaceae
*Pseudomonas
Class Pseudomonadales contains organisms that cause opportunistic infec-
tions. Several grow as surface biofilms, making them hard to disinfect from
contaminated medical devices, and thus potential sources of nosocomial
(hospital-acquired) infections. Biofilm infections in hospitals will be
described again when we discuss the gliding bacteria (Chapter 10).
Members of Genus Acinetobacter are found in soil. The organisms grow as
coccobacillary forms, sometimes clumped in pairs. Species of Acinetobacter
are found in hospitals, particularly as surface colonies. Though Acinetobacter
species are generally non-pathogenic in healthy individuals, serious infections
may occur in weakened individuals in intensive care units, on ventilatory sup-
port, or recovering from wounds. Outbreaks of Acinetobacter infections have
occurred in military hospitals. Acinetobacter baumanii is often associated with
pneumonia in hospital patients, particularly in patients receiving ventilator
support. Infections may lead to bacteremia, meningitis, and skin infections.
Bacteria and disseminated infections are often associated with another species,
Acinetobacter lwoffi.
Readers should not confuse Genus Acinetobacter (Gamma Proteobacteria,
Chapter 7), with Class Actinobacteria (Chapter 14).
