The economic techniques of cost-effectiveness and cost-benefit analysis have provided useful insights into the potential advantages of vaccination against pneumococcal pneumonia. They suggest that the cost of vaccinating persons 65 years and older and perhaps younger persons with high risk conditions would be reasonable when compared with the cost of treatment for pneumococcal pneumonia. These findings, together with other considerations, may guide physicians and health care policymakers in deciding which individuals might be expected to benefit from pneumococcal vaccination.

Many patients hospitalized for or dying of pneumococcal bacteremia have been discharged from a hospital with in the previous five years. In addition to age and underlying medical condition, previous hospital care, particularly for high risk conditions, is a useful marker for identifying individuals who are destined to develop serious pneumococcal infections. Relatively few patients, especially those with high risk conditions, would need to receive pneumococcal vaccine at the time of hospital discharge to prevent, within the next five years, each subsequent readmission or death from pneumococcal pneumonia. Although pneumococcal vaccine has not been widely used in the hospital setting, there are sound epidemiologic reasons to expect that organized programs for vaccine delivery in hospitals would be an effective approach to preventing many serious pneumococcal infections.

Inter- and intrahospital epidemics of nosocomial infections due to gram-negative bacilli resistant to many antimicrobials have been well-documented. Prospective studies on the use of isolation along with epidemiologic analysis and appropriate environmental control have been lacking. In the six-month period from November 1978 to April 1979 Pseudomonas aeruginosa (MDR) resistant to all antibiotics except amikacin was isolated from 15 patients. This organism had not previously been seen in our hospital. Epidemiologic assessment of infected patients revealed that nine of 15 patients had contact either with a previously infected case or contaminated area. All strains of P. aeruginosa were identical by pyocin typing and antibiogram. The organism was present in an environmental reservoir, the urine graduated cylinder, and was found in three of eight receptacles (p = 0.002 vs. other environmental cultures). A case control study of patient risk factors showed aminoglycoside use, other antibiotic use, surgery, intravenous lines, Foley catheter use and mechanical ventilation to be no more frequent in cases than controls. The use of aminoglycosides in only 40% of cases suggests that antibiotic pressure was not the sole factor in perpetuating the epidemic.

A methicillin/aminoglycoside-resistant strain of Staphylococcus aureus (MARS) was likely introduced by transfer of a patient from another hospital. Over the next year, 20 other patients were colonized or infected with MARS of the same phage type, although antibiograms varied. Affected patients usually had serious underlying disease and were in intensive care units. Vancomycin therapy was frequently delayed and MARS may have contributed to the death of some patients. The mode of spread was not definitively delineated, but two nurses were found to be colonized. Institution of isolation procedures was difficult, but the problem gradually waned.

Susceptibility testing showed vancomycin to be the most active agent. Synergy studies showed no consistent effect of combining methicillin with an aminoglycoside. This experience illustrates the problem of MARS spread between hospitals and wards, the need for institution of effective control measures, and consideration of early empiric use of vancomycin.

Between March and December of 1979, an outbreak of infections due to multiply antibiotic resistant Serratia marcescens took place in a 50-bed neonatal intensive care unit. Fifteen neonates suffered major infections (sepsis, meningitis and pneumonia) with one death, and 20 suffered minor infections (conjunctivitis, cystitis, wound infections). Epidemiologic investigation failed to reveal a common source; S. marcescens, however, was isolated from an employee's hand, emollient skin cleanser, suction tubing, and three in-use manual infant resuscitation bags. The skin cleanser and equipment-cleaning agents were ineffective against S. marcescens. Asymptomatic, colonized infants were the major reservoir of S. marcescens. These infants were identified by daily cultures of the nose, umbilicus and rectum. The rectal swab most commonly (76%) yielded first-positive cultures in previously uncolonized infants, and was ultimately positive in 92% of colonized infants. A control program was begun by: 1) removing all inanimate sources of S. marcescens; and 2) cohorting patients and staff into a S. marcescens-exposed group and a new patient group. The new patient group of infants was surveyed by daily triple-site cultures for colonization and subsequent transfer to the S. marcescens-exposed group. After four months, the epidemic was controlled and the organism eradicated from the neonatal intensive care unit.

An infection control program was instituted at The Victoria General Hospital, an 800-bed acute care hospital, in July 1977. Serratia marcescens had infected or colonized (I/C) 225 to 232 patients yearly for each of the three previous years. Since this organism is usually acquired nosocomially, we decided to use Serratia I/C as a marker for our infection control program. During the years 1977 to 1980, we identified and eliminated several reservoirs of Serratia (contaminated urine measuring containers, urometers, diabetic urine testing equipment and in-use contamination of 2% Hibitane). Readmission of previously I/C patients proved to be an increasingly important reservoir. During 1980, only 120 patients were I/C, and gentamicin-resistant isolates of S. marcescens had dropped from 44% in 1977 to 4.4% in 1980. Use of Serratia as a marker enabled us to monitor the efficacy of our infection control program and allowed us to prove to our health care workers the usefulness of many of the measures we introduced.

We retested 2,181 bacteria-antibiotic combinations with the Kirby-Bauer disc-diffusion technique and found interpretive changes with 120 (5.5%). Most changes (101 of 120) were single steps (i.e. from R to I, I to R or S, or S to I). Of the 19 remaining, 10 of them were from R to Sand nine from S to R. These changes were significantly more frequent for combinations with zone diameters clustered near interpretive breakpoints (within 2mm) than for other combinations, and there was a linear relationship between decreased reproducibility and increased clustering near interpretive breakpoints.

Based on an analysis of all susceptibility testing results performed in 1978, combinations most commonly clustered near interpretive breakpoints included: Ampicillin with Klebsiella pneumoniae; erythromycin with enterococci; chloramphenicol with Serratia marcescens; gentamicin with Pseudomonas aeruginosa and enterocci; and tetracycline with Enterobacter spp., Escherichia coli, and K. pneumoniae.

Q fever (Query Fever) is a zoonosis caused by the rickettsia Coxiella burnetii. Domestic ungulates such as sheep, cattle, and goats serve as the reservoir of infection for humans and shed the desiccation-resistant organism in urine, feces, milk, and especially in birth products. In humans the illness is generally mild; however, Q fever hepatitis is often seen and Q fever endocarditis is an uncommon, but frequently fatal complication. Q fever long has been recognized as an occupational hazard among persons working with animals or animal products, and in laboratories working with C. burnetii. Recently, Q fever outbreaks have occurred in medical research facilities using sheep as research animals. Recommendations are presented for reducing the risk of exposure to Q fever in persons not working with sheep in research facilities that use sheep. In addition, recommendations are presented for reducing the risk of infection in persons who work with sheep in research facilities.

The Congress has authorized the Medicare program to pay for the cost of pneumococcal vaccine and its administration. The history of this legislation demonstrates that chance and political considerations quite separate from the scientific issues on vaccination played an important role in the development of this policy. It demonstrates both the need for and the difficulty of achieving more effective coordination of the activities related to national policies on vaccines and immunization.