Epidemiology

The organisms discussed in this chapter most often inhabit environmental niches (eg, water soil) (Table 20-1), Spe- cies of Acinetobacter were initially recovered in patient specimens from humid climates, but by the late 1970s, they began to emerge as nosocomial pathogens in more temperate  climates, and clinical infections with Acinetobacter seem to be higher in the summer months compared with other seasons. It is likely that the humid conditions are more favor- able for growth. Stenutrophomonas maltophilia is ubiquitous in nature and is closely related to the genus Pendamanan. It was first isolated from a human in 1943 and has under- gone several taxonomic updates throughout the years before finally being given in own geous organisms are capable of survival on inanimate objects for extended pe- riods (weeks to months), and this makes them problematic in health care settings, where they frequently colonize the patient environment and health care equipment. In addition to inanimate objects, species of Acinetobacter have been re ported of the general population and have been identified from number of human sources, including sputum, urine, feces, and vaginal secretions. Both Acimenbacter spp. and S. maltophilia can contaminate potable or chlorinated water. Although none of these organisms are considered normal human microbiota, the relatively high prevalence of Acinetobacter spp. and S. mabophilia in in hospitals frequently results in colonization of the and respiratory tract of patients. The prevalence of these organiums is evidenced by the fact that, excluding the Enterobacteriaceae and Peudomonas aeruginosa. Acineto bacter spp. and S. maltophilia are the third and fourth most common gram-negative bacilli, respectively, encountered in clinical specimens.