Pseudomonas aeruginosa is the most common pathogen of Pseudomonas species. One of the most virulent organisms pathogenic to man, P aeruginosa can cause a variety of infections in humans. Despite the introduction of many new antimicrobial agents with enhanced activity against P aeruginosa, the high mortality rate associated with the organism over the past two decades continues.

During a 13-month period, 25 residents of a nursing home were found to have positive cultures for methicillin-resistant Staphylococcus aureus (MRSA), including 17 with clinically significant infections. The outbreak came to attention in February 1985 when pneumonia was diagnosed in five residents during a 10-day period, and sputum cultures from all five were positive for MRSA. A survey revealed that nine (12%) of a sample of 74 residents and nine (7%) of 130 personnel had positive cultures for MRSA. Six of nine residents with MRSA detected in the culture survey had not been hospitalized for 6 or more months before the survey, suggesting acquisition of MRSA in the nursing home. Implementation of control measures was associated with a decreased occurrence but not complete elimination of new cases. MRSA in nursing homes is of concern because these institutions might serve as reservoirs for MRSA in the community. Further studies are required to define the magnitude of the problem, as well as optimal control measures.

Molecular laboratory techniques were used to study the epidemiology of an outbreak of nosocomial Legionnaires' disease. All patient isolates were Legionella pneumophila serogroup 1 and showed identical plasmid profiles and reactions with serogroup-specific monoclonal antibodies. L pneumophila was also cultured from four of five cooling tower water samples; however, the isolate from only one tower was serogroup 1 of the same sub-type as patient isolates. Since the cases were temporally clustered and epidemiologically associated with exposure to cooling tower aerosols, the single cooling tower implicated by molecular analysis was the most likely source of the outbreak. Chlorination of cooling tower ponds has eradicated the epidemic strain. Since potable water also harbored the infecting organism and was the probable source for cooling tower contamination, decontamination of the hospital water system was also undertaken. Superchlorination of hot water holding tanks to 17 ppm on a weekly basis has effectively eradicated L pneumophila from the potable water system and appears to be a reasonable, simple, and relatively inexpensive alternative to previously described methods of control.

In a prospective 12-month study at a university-affiliated pediatric hospital, isolation usage was quantitated by ward/service, season, isolation category and type of infection (community-acquired vs nosocomial). Such information may be helpful in designing hospitals, recognizing time utilization of the pediatric infection control nurse, and defining educational and isolation needs. Hospitals with multiple bed rooms and inadequate numbers of single rooms may be unable to meet current federal isolation guidelines.

The mean number of isolation days was 153 per 1000 patient days or 15.3% of bed days used. This ranged from 18.5% on the infant/toddler/preschool medical ward to 2.8% on child/teenage orthopedic surgery. Isolation requirements vary seasonally and rose to 32% in winter on one ward. Proportional frequencies of isolation category included enteric—29%, protective—28%, strict—16%, barrier (contact)—10%, multiply resistant organism (MRO)—8%, wound—5%, pregnant women (careful handwashing)—3%, blood and body fluid precautions—1%. Isolation of patients with and contacts of nosocomial infections account for 32% of isolation usage. During one third of the 365-day year, the hospital is unable to provide adequate numbers of single rooms for one to 20 patients.

At the Ann Arbor Veterans Administration Medical Center, 30 patients over a 6-month period became nosocomially infected or colonized by methicillin-resistant Staphylococcus aureus. Immediate institution of strict infection control measures, in conjunction with surveillance cultures of personnel and treatment of carriers, did not limit spread of the outbreak strain of MRSA. Multiple nonoutbreak strains, phenotypically exhibiting heteroresistance, were also uncovered. Thirteen hospital personnel were identified as MRSA carriers. Trimethoprim-sulfamethoxazole (TMP-SMX) and rifampin initially eradicated the carrier state, documented by anterior nares cultures in 13 courses of treatment in 11 employees. However, three employees were recolonized, one at one month, one at both one and four months, and one at four months. Treatment of the carrier state reservoir among personnel appeared to have no effect on the emergence and spread of nosocomial MRSA.

During a 6-month period, term infants underwent nasal and umbilical swabbing within 96 hours of delivery and again at 1 to 18 (mean 3.8) weeks after discharge. Swabs were inoculated onto horse blood agar and all S aureus isolates were phage typed. Two hundred three infants were enrolled and follow-up was obtained for 181 (89%). Thirty-two of 181 (17.6%) were initially colonized, of whom 12 (37.5%) were colonized on follow-up. Thirty-two of 181 became colonized subsequent to hospital discharge. No single phage type predominated. Twenty-five patients were diagnosed to have clinical illness—omphalitis (11), conjunctivitis (10), and pustulosis (5). Six of these were colonized with 5 aureus initially, although organisms of the same phage type were not recovered from cultures obtained at the time of clinical illness. There was no significant difference in the rate of infections in colonized (19%) versus noncolonized (12%) infants. In five patients where S aureus was recovered at the time of symptoms, all organisms were acquired subsequent to discharge. We conclude that nursery colonization with S aureus did not lead to clinical illness, and clinical illnesse s previously ascribed to S aureus frequently occur in the absence of these bacteria.

Five clusters of pseudobacteremias over a seven-month period were traced to a BACTEC® radiometric device. Four episodes were due to enterococcus and one involved Staphylococcus aureus. Each cluster began with multiple positive blood cultures from a patient with clinical evidence of bacteremia. On subsequent days each bottle in sequence yielded growth of the identical organism, as shown by phage typing and antibiograms. Cultures from patients believed to be infected with the organisms tested positive earlier (mean = 1.4 days) than those patients believed to be pseudobacteremic (mean = 4.8 days). Investigation pointed toward the BACTEC device as the most likely source. Resin beads were found in the needle on several occasions and were shown to be transferred from bottle to bottle. We postulated that contaminated resin beads or liquid from a positive bottle remained in the needle above the portion that was heat-sterilized, contaminating the next bottle when it was sampled.

We describe circumstances at the Hospital Rosales, located in San Salvador, El Salvador, and some salient observations from an infection control program begun in 1978. Findings include overuse of antibiotics, especially of penicillin and chloramphenicol; a predominance of gram-negative rod infections, especially Pseudomonas aeruginosa; a relative infrequency of Staphylococcus aureus infections; an apparent doubling of the mean duration of hospitalization for patients with nosocomial infections compared with other patients (22.1 days versus 11.0 days); documentation and partial correction of deficiencies in aseptic and antiseptic practices; an outbreak of Pseudomonas aeruginosa endophthalmitis traced to the hospital's factory for the manufacturing of intravenous fluids; and attitudinal problems such as the care of patients with rabies on open wards. Prevalence surveys conducted during 1981 and 1986 suggest a dramatic increase in the recent incidence of surgical wound infection (44% v 28%, P < 0.001). This latter observation suggests a direct relationship between infection rates and the hardships imposed by poverty and civil war.