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A total of 6,253 cases of Staphylococcus aureus bacteremia, including 274 (4.4%) endocarditis cases, were registered in Denmark in the period 1975-1984. Patients with hematological malignancies and/or agranulocytosis accounted for 479 of the bacteremia cases. The incidence of endocarditis in this group of patients was only 0.4% as compared to 4.7% in other patients with staphylococcal bacteremia (p less than 0.01). The lower incidence of endocarditis complicating bacteremia in these patients may justify a shorter course of therapy than usually recommended for suspected endocarditis. Patients with hematological malignancies and other patients with agranulocytosis had a higher mortality (49 and 46%, respectively) than other patients with S. aureus bacteremia (33%). The highest mortality was found in patients with multiple myeloma (71%, p less than 0.01), the lowest in patients with acute lymphocytic leukemia (28%, p less than 0.01). The higher mortality in these patients may indicate that empiric antibiotic regimens in granulocytopenic patients should include a specific anti-staphylococcal agent.

In the period 1975-1981, 4060 cases of Staphylococcus aureus bacteremia were recorded in Denmark, and the corresponding strains were examined. The percentage of strains, resistant to penicillin only, rose to 82, and the percentage of multiply-resistant strains fell to five. Newer phage types (94, 96 and 95) increased from 10% to 27% of the material. These strains were usually resistant only to penicillin, but produced large amounts of penicillinase. The ample penicillinase production has also been characteristic for previous epidemic strains, and it is furthermore correlated to mortality. The overall mortality of 34.6% was lower than that of the preceding period. Mortality rates were highest in elderly patients, nosocomial cases, patients with serious primary diseases and endocarditis cases.

During the years 1966-1974, 167,297 strains isolated from 167,297 patients or staff members in Danish hospitals were registered at Staten Seruminstitu. All the strains were phage-typed and examined for production of a 'Tween'-80-splitting enzyme and resistance to mercuric chloride. 158,236 strains were examined for resistance to antibiotics. Since 1968, a steep decrease in the number of strains resistant to three or more antibiotics (multiple-resistant) and in strains of the 83A complex was noticed. In recent years an increase in strains belonging to phage-group I and in those referred to as miscellaneous and non-identified was registered. The increase in the non-typable strains might be explained by the shift of the concentration of the typing phages from 1000 X RTD to 100 X RTD. It is concluded that at least two factors may have contributed to the reduction of the multiple-resistant strains: an altered antibiotic policy, restricting the use of streptomycin and tetracyclines, and an improved hospital hygiene, diminishing the spread of identical strains within the various departments. However, it is emphasized that the consumption of methicillin is still increasing.

Three hundred and seventy-one penicillin-resistant Staphylococcus aureus strains of phage type 95 isolated in the years 1977-1983 were investigated. They had characteristic resistance patterns to cadmium (Cd), arsenate (As) and mercury (Hg). Most were susceptible to all three heavy metals; 25 strains were resistant to As only and one to Cd and As. The susceptible strains had a uniform medium level of penicillinase production, whereas the As-resistant strains produced large amounts of penicillinase. In most of the strains, penicillin resistance was located on a very unstable penicillinase plasmid. The combination of rare properties found in Danish type-95 strains seems to point to the spread of one or two clones. Co-reactions with other phage groups or complexes and results of lysogenisation experiments suggest that the Danish type-95 strains are derived from strains of the 52, 52A, 80, 81 complex.

In the period 1969-1974 a decreasing number of Danish hospital departments recorded epidemic occurrences of Staphylococcus aureus strains, and the local spread of strains was less extensive. Multiple-resistant strains of the 83 A complex were succeeded by type 94 strains, resistant to penicillin only. The level of methicillin resistance fell from 19 to 6%. 12% of methicillin resistant strains are now sensitive to streptomycin and/or tetracyclines; they do not represent a few clones, but belong to a wide spectrum of phage types. The changes follow a reduction in the consumption of streptomycin and tetracyclines not of methicillin or other penicillins. As a contrast to the general reduction of combined resistance to streptomycin and tetracyclines, the strains in dermatological departments, where tetracyclines are commonly used, maintain a high degree of resistance to tetracyclines alone.

Hypotheses for the origin of multiply-resistant coagulase-negative staphylococci from 146 patients undergoing cardiac surgery were tested. All received cephalothin per-operatively. Antibiotic susceptibility testing, phage-typing, bio-typing, and test for Tween-80-splitting enzyme were used to characterize 132 isolates from nose swabs. Seventy-five percent of the pre-operative susceptible isolates were of biotype 1, while biotypes 3 and 4 made up 59% of the post-operative, multiply-resistant isolates. Fifty-three percent of the isolates were typable by phage-typing. Typability of isolates of biotype 1 was high (56%) while almost 75% of biotype 4 were untypable. Susceptible isolates were more often typable than multiply-resistant ones. Of the 146 patients, 105 (72%) carried coagulase-negative staphylococci pre-operatively, only two of them carried multiply-resistant strains. Fifty-nine patients (41%) were colonized with multiply-resistant coagulase-negative staphylococci post-operatively. By combining the results of bio-typing, phage-typing, and test for Tween-splitting enzyme the study made it probable that a maximum of ten patients (6.8%) already carried multiply-resistant strains on admission to the hospital or were carriers of initially susceptible strains which developed multiple-resistance during administration of antibiotics. It therefore seemed likely that most of the patients were deprived of their natural bacterial flora by antibiotic treatment and subsequently colonized post-operatively with multiply-resistant coagulase-negative staphylococci from the environment.

Clinical and bacteriological information on Staphylococcus aureus endocarditis from hospitals all over Denmark in the period 1976-1981 was reviewed in 119 cases, 61 females and 58 males. Patient ages ranged from 16 days to 85 years, with a median age of 63 years. The overall mortality was 71%. The mortality correlated significantly with such factors as age, hospital-acquired infections and resistance to penicillin in infecting strains. Hospital-acquired infections occurred in 38% of the patients. The distribution of phage types among strains isolated from blood cultures from patients with endocarditis corresponded to that of strains from other septicaemia cases. Group I and group III strains and strains of the 94, 96 complex comprised 74% of the phage types of the present material. Infections of the skin were the most common portal of entry for the infecting strains. Apart from drug addicts, of which 11 cases were included, mortality did not correlate with the presence of any underlying diseases.