Opportunistic Enterobacteriaceae
Many Enterobacteriaceae with minimum pathogenicity are classic opportunists. The most frequent opportunistic infections caused by them are: urinary tract infections, respiratory tract infections, wound infections,
Table 4.9 Overview of the Most Important Enterobacteriaceae That Cause Opportunistic Infections
Bacterial species
Properties
Escherichia coli
Citrobacter freundii; C. divs.; C. amalonaticus
Klebsiella pneumoniae; K. oxytoca and others
Klebsiella ozaenae
Klebsiella rhinoscleromatis
Enterobacter cloace; E. aerogenes; E. agglomerans; E. sakazakii, and others
Serratia marcescens and others
Proteus mirabilis Proteus vulgaris
Morganella morganii Providencia rettgeri; P. stuartii
Can use citrate as its sole source of C; delayed breakdown of lactose; nonmotile
Lactose-positive; nonmotile; many strains have a polysaccharide capsule. Cause approx. 10% of nosocomial infections. Causative organism in so-called Friedlander's pneumonia in predisposed persons, especially in the presence of chronic pulmonary diseases.
Causative pathogen in ozena; atrophy of nasal mucosa
Causative pathogen in rhinoscleroma; granuloma in the nose and pharynx
Lactose-positive; motile; frequent multiple resistance to antibiotics
Lactose-positive; motile; frequent multiple resistance to antibiotics, some strains produce red pigment at 20 °C
Lactose-negative; highly motile; wanders on surface of nutrient agar (swarming). O antigens OX-2, OX-19, and OX-K from P. vulgaris are identical to rickettsiae antigens. For this reason, antibodies to rickettsiae were formerly identified using these strains (Weil-Felix agglutination test)
Lactose-negative; frequent multiple resistance to antibiotics
Lactose-negative; frequent multiple resistance to antibiotics
dermal and subcutaneous infections, and sepsis. Such infections only occur in predisposed hosts, they are frequently seen in patients with severe primary diseases. Another reason why opportunistic Enterobacteriaceae have become so important in hospital medicine is the frequent development of resistance to anti-infective agents, which ability enables them to persist at locations where use of such agents is particularly intensive, i.e., in hospitals. Occurrence of multiple resistance in Enterobacteriaceae is due to the impressive genetic variability of these organisms (p. 170). Table 4.9 provides an overview of the most important opportunistic Enterobacteriaceae.
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