Changes in resistance traits of Staphylococcus epidermidis isolated in the preoperative and postoperative phases from patients undergoing open heart surgery were studied in a two-step prospective investigation. Period 1 comprised 32 patients. All received streptomycin for five days and methicillin for seven days, starting the evening before operation. None of the patients was colonized with multiresistant (MR) strains before or immediately after operation. Two days after operation, in the intensive care unit (ICU) 79% of the patients carried MR S. epidermidis in the nose. Air analyses showed that 30% of the bacteria isolated from the ICU were MR, while such strains were seldom found in the operating theatre. Nose swabs from the staff showed that 26% at the ICU and none in the operating theatre carried MR strains. In an attempt to counteract the selection for MR strains, all patients in period 2 received methicillin alone for only 3 days, and disinfection of the ICU was then performed after each patient. Period 2 comprised 105 patients. The frequency of MR S. epidermidis in the patient material declined from 80% to 40% and from 26% to 15% in the staff members. No changes were found concerning the frequency of postoperative complications. The conclusion is that methicillin alone for three days gives as good a protection against postoperative infections as a more broad-spectrum treatment and that reduced use of antibiotics will reduce the risk of early colonization with resistant strains.
Thirty‐six strains of yellow‐pigmented Pseudomonas from clinical as well as non‐clinical material and 11 reference strains of Pseudomonas were investigated by means of conventional bacteriological methods (a total of 53 different tests). Eighteen of the 36 yellow‐pigmented strains could be classified as P. paucimobilis. Apart from the presence of lipid inclusions on β‐hydroxybutyrate, hydrolysis of DNA, and Tween 80 our results showed a high degree of accordance with other investigations. Eight strains showed characteristics compatible with inclusion in the CDC VE group; one orange‐yellow strain showed the characteristics of P. vesicularis, and one was a pyoverdin negative, yellow P. putida. Eight strains remained unidentified. Strains of P. paucimobilis were most often resistant to antibiotics used for P. aeruginosa infections (viz. piperacillin, cefsulodin, ceftazidime) while the strains of the CDC VE group were often susceptible. Most strains were susceptible to the aminoglycosides. The difficulties in distinguishing yellow‐pigmented strains of Pseudomonas from Flavobacterium spp. or Xanthomonas spp. are discussed.
Coagulase‐negative Micrococcaceae from blood cultures were classified biochemically according to Baird‐Parker and to Kloos & Schleifer and by means of antibiotic susceptibility testing, in an attempt to distinguish between bacterial growth due to contamination and growth due to bacteremia. S. epidermidis biotype 1 (according to Baird‐Parker) accounted for c. 60% of the isolates and for c. 85% of the isolates considered to be of clinical importance. The more time‐ and resource‐demanding classification of Kloos & Schleifer provided no further clinically useful information, as the predominant number of isolates turned out to be S. epidermidis. Isolates other than S. epidermidis (according to Kloos & Schleifer) accounted for c. 45% of the total number of isolates but for only 20% of the isolates considered of clinical importance. Resistance to multiple antibiotics was recorded more often in isolates from patients with positive clinical information than in isolates thought to be contaminators. The frequency of blood cultures contaminated with coagulase‐negative Micrococcaceae was estimated at c. 1.5%. Records from 91 patients were reviewed. By correlating the clinical findings to biochemical classification, resistance types, and the massiveness of growth it was suggested that the quantitative rather than the qualitative findings are suitable for determining clinical significance of isolates of coagulase‐negative Micrococcaceae from blood cultures.
A total of 965 strains of Micrococcaceae isolated from 200 patients, personnel, and air in a department of cardiac surgery were classified by means of Baird‐Parker's scheme. The majority of strains were identified as Staphylococcus epidermidis (S. epidermidis) biotype 1, but S. epidermidis biotype 4 accounted for c. 25% of isolates from patients post‐operatively. Pre‐operative isolates were generally sensitive to most antibiotics tested while post‐operative strains of coagulase‐negative Micrococcaceae from patients and isolates from personnel and air were frequently multiply‐resistant. Strains of Staphylococcus aureus (S. aureus) were sensitive or resistant only to penicillin. More patients were colonized with coagulase‐negative Micrococcaceae after operation than at admission to the hospital (p <0.001), while the frequency of S. aureus carriers was the same before and after operation and equal to the frequency found earlier. The frequency of S. aureus carriers among the personnel, however, was lower than reported earlier (10%). Multiply‐resistant strains of S. epidermidis seem to have replaced resistant strains of S. aureus as the predominant hospital saprophyte among Micrococcaceae.
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