During a 24-month period, 5,625 blood culture specimens were collected at the Seattle Veterans Administration Medical Center in 20-ml volumes and divided into separate 10-ml aliquots. The two aliquots were processed as duplicate sets (set 1, set 2) by the BACTEC system (Johnston Laboratories, Inc., Towson, Md.). Specimens (5 ml) from each set were inoculated into aerobic (6B) and anaerobic (7C/7D) vials. A total of 434 significantly positive blood cultures were found. In 342 of these positive cultures, yielding 379 isolates (112 members of the family Enterobacteriaceae, 104 staphylococci, 87 streptococci, 27 anaerobes, 20 yeasts, 14 pseudomonads, and 15 miscellaneous organisms), there was adequate specimen volume to fill all four vials. The utilization of set 1 would have resulted only in the failure to detect 65 of 379 (17.2%) significant isolates, 52 of 342 (15.2%) positive cultures, and 20 of 198 (10.1%) bacteremic episodes. There were no significant differences in the recovery of individual species in sets 1 and 2. Although the range of isolates recovered by the aerobic and anaerobic vials of each set differed, the percent yield of total isolates was similar, indicating total isolate yield was predominantly a function of specimen volume. The addition of set 2 most dramatically increased the recovery of Escherichia coli (30%), yeasts (33%), and anaerobes (42%).

Antimicrobial use varied significantly across these hospitals, but generally was higher in ICUs. These results suggest that concomitant surveillance of both antimicrobial resistance and antimicrobial use is helpful in interpreting antimicrobial resistance in a hospital or ICU and that further analysis is required to determine the role of variables other than antimicrobial use in a statistical model for predicting antimicrobial resistance.

The development of antimicrobial drugs, and particularly of antibiotics, has played a considerable role in substantially reducing the morbidity and mortality rates ofmany infectious diseases. However, thefact that bacteria can develop resistance to antibiotics has produced a situation where antimicrobial agents are losing their effectiveness because of the spread and persistence of drug-resistant organisms. To combat this, more and more antibiotics with increased therapeutic and prophylactic action will need to be developed. This article is concerned with antibiotic resistance in bacteria which are pathogenic to man and animals. The historical background is given, as well as some information on the present situation and trends of antibiotic resistance to certain bacteria in different parts of the world. Considerable concern is raised over the use of antibiotics in man and animals. It is stated that antibiotic resistance in human pathogens is widely attributed to the "misuse" of antibiotics for treatment and prophylaxis in man and to the administration of antibiotics to animals for a variety of purposes (growth promotion, prophylaxis, or therapy), leading to the accumulation of resistant bacteria in their flora. Factors favouring the development of resistance are discussed.

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