This study analysed patterns of requests for repeated blood cultures and the microorganisms isolated in follow-up cultures.
The frequencies and intervals of repeated blood cultures performed during January and Feb-ruary of 2010 at seven university-affiliated hospitals in Korea were evaluated. Results of microbiological cultures at follow-up were analysed with respect to pathogen replication, immune clearance, appearance of new pathogens, and skin contaminants.
Among 3,072 patients who received repeated blood cultures, the average number of requests was 3.2. Of the 5,241 follow-up blood culture events recorded, durations of 1, 2, and 3 days between cultures were identified for 23.1%, 21.4%, and 15.0% of events, respectively. Relative to each initial culture, persistent pathogen growth in subsequent culture(s) accounted for 2.3% of events, whereas immune clearance was confirmed in 8.5% of events. Previously undetected pathogens were isolated in 5.2% of the follow-up cultures, the majority of which grew after an interval of six days. Skin contaminants were detected in 7.6% of the repeated cultures, and 76.1% of the follow-ups displayed no growth of microorganisms.
The most common numbers of repeat culture requests were two and three, and these were typically performed within three days of the initial culture. Among the follow-up cultures, new pathogens were identified in 5.2%, and the majority of this group likely presented for follow-up during a new disease episode.
Summary of initial and follow-up blood culture results (%) by hospital
| Initial/follow-up culture | Hospitals | |||||||
|---|---|---|---|---|---|---|---|---|
| A (82) |
B (279) | C (334) | D (424) | E (447) | F (533) | G (973) | Total (3,072) | |
| Growth |
7.3 | 2.2 | 1.2 | 2.6 | 1.3 | 3.0 | 3.1 | 2.3 (70) |
| No growth/growth | 14.6 | 5.0 | 4.5 | 2.1 | 4.5 | 4.7 | 6.8 | 5.2 (161) |
| Growth/no growth | 12.2 | 7.2 | 4.8 | 5.7 | 11.0 | 6.0 | 11.3 | 8.5 (261) |
| Contaminants |
13.4 | 11.8 | 2.1 | 5.0 | 7.4 | 8.6 | 8.3 | 7.6 (232) |
| No growth/no growth | 52.5 | 73.8 | 87.4 | 84.6 | 75.8 | 77.7 | 70.5 | 76.4 (2,348) |
Number of patients;
Detection of pathogens;
Normal skin flora detected in only one set.
Culture intervals for patients harboring persistently growing microorganisms
| Microorganism | Interval days | |||||
|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4-6 | 7 | Total (%) | |
| 7 | 3 | 2 | 3 | 1 | 16 (22.9) | |
| 8 | 1 | 1 | 1 | 11 (15.7) | ||
| 4 | 1 | 1 | 1 | 7 (10.0) | ||
| 2 | 5 | 7 (10.0) | ||||
| 1 | 2 | 2 | 5 (7.1) | |||
| Other Gram (+) bacteria | 6 | 2 | 1 | 1 | 2 | 12 (17.1) |
| Other Gram (‒) bacteria | 6 | 2 | 4 | 12 (17.1) | ||
| Total (%) | 34 (48.6) | 14 (20.0) | 11 (15.7) | 7 (10.0) | 4 (5.7) | 70 (100) |
Intervals between blood cultures for cases in which pathogens were identified only upon follow-up culture
| Microorganism | Interval days | |||||||
|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | Total (%) | |
| 4 | 4 | 3 | 2 | 4 | 1 | 10 | 28 (17.4) | |
| 2 | 1 | 2 | 2 | 1 | 1 | 5 | 14 (8.9) | |
| 2 | 1 | 1 | 1 | 8 | 13 (8.1) | |||
| 3 | 1 | 1 | 2 | 4 | 11 (6.8) | |||
| 1 | 4 | 4 | 9 (5.6) | |||||
| 1 | 1 | 3 | 4 | 9 (5.6) | ||||
| 2 | 2 | 1 | 3 | 8 (5.0) | ||||
| Other Gram (+) bacteria | 7 | 8 | 3 | 5 | 3 | 1 | 13 | 38 (23.6) |
| Other Gram (‒) bacteria | 1 | 6 | 1 | 1 | 3 | 10 | 22 (13.7) | |
| Non-albicans |
2 | 1 | 4 | 7 (4.3) | ||||
| Total (%) | 23 (14.3) | 31 (19.3) | 11 (6.8) | 12 (7.5) | 10 (6.2) | 9 (5.6) | 65 (40.4) | 161 (100) |