Oropharyngeal and fecal carriage of Pseudomonas aeruginosa in hospital patients

This prospective study was designed to determine the incidence of rectal and/or oropharyngeal colonization rates of patients with Pseudomonas aeruginosa upon admission to a general hospital and the risk of becoming colonized while hospitalized. Consecutive 186 admissions (180 patients) to one medical ward, one surgical ward, and the intensive care unit were studied over a period of 5 months. Rectal and oropharyngeal swabs for P. aeruginosa were obtained on admission, weekly thereafter, and/or upon discharge. Forty-two patients (22.6%) were colonized on admission, 20 patients (10.8%) acquired P. aeruginosa during hospitalization. Colonization on admission was observed twice as frequently on the surgical ward and in the intensive care unit as on the medical ward. Positive rectal cultures were more frequent than oropharyngeal cultures throughout the study (P less than 0.01). For patients admitted culture positive or culture negative, the probabilities of remaining culture positive or culture negative, respectively, remained at 44 and 72% after 35 days of hospitalization. The most common P. aeruginosa serotypes were 1, 6, and 10, and pyocin types 1, 3, and 10 were predominant. There was no statistical difference in the serotypes or pyocin types detected on admission or acquired during hospitalization. Except for two hospital-acquired first isolates which were resistant to moxalactam, all first isolates were susceptible to the four antibiotics tested. During the study, one isolate became resistant to azlocillin, gentamicin, and tobramycin, while two isolates became resistant to moxalactam. A statistical analysis was performed for 13 risk factors for all colonized and noncolonized patients. Colonization detected at the time admission was positively associated with age ( > 65 years), previous surgery of the gastrointestinal tract for neoplasm, and anemia ( P< 0.05). In contrast, for patients who entered the study culture negative, none of the analyzed 13 risk factors was associated with an increased probability for colonization. This observation included the administration of antimicrobial agents singly or in combination or both.

Nosocomial Mycobacterium fortuitum colonization from a contaminated ice machine

Between October 15 and November 18, 1985, 5 patients on a medical ward of the Albany VA Medical Center (Ward 8A) became colonized with Mycobacterium fortuitum. Because other patients in Ward 8A were at risk of developing disease with M. fortuitum, microbiologic surveillance to identify colonization in sputum was begun. By February 15, 1986, 30 colonized patients had been identified in this ward but none in another ward with a comparable patient population, which suggests a source unique to Ward 8A. Because water has been recognized as a source of opportunistic mycobacterial pathogens, we conducted a retrospective case-control study using a telephone survey questionnaire to examine a number of water exposures in 10 patients and 20 control subjects. Exposure to ice from the Ward 8A ice machine, but not to potable water, was associated with colonization with M. fortuitum. Large-volume water samples from a variety of sources were cultured for acid-fast bacilli. M. fortuitum was isolated only from the ice machine in Ward 8A. The ice machine was disconnected, and no additional patients became colonized. Although ice machines are infrequently implicated in nosocomial outbreaks, they represent a potential source for pathogens that survive or replicate in water.