860 LIMMATHUROTSAKUL AND OTHERS Table 2 Prognostic significance of a respiratory secretion, urine, throat swab, and pus/surface swab culture positive for Burkholderia pseudo- mallei on admission, adjusted for blood culture positive for B. pseudomallei* Sample type Patients with positive blood culture (%) Patients with negative blood culture (%) Adjusted OR† (95% CI) P‡ Positive respira- 224/386 (58.0) 276/393 (70.2) 2.3 (1.4–3.7) 0.001 tory secretions Positive urine 152/564 (27.0) 82/545 (15.1) 1.9 (1.3–2.7) 0.001 Positive 149/361 (41.3) 171/497 (34.4) 3.1 (2.0–4.9) < 0.001 throat swab Positive pus/ 205/257 (79.8) 392/462 (84.9) 0.7 (0.4–1.2) > 0.1 surface swab *OR = odds ratio; CI = confidence interval; Positive = positive for B. pseudomallei; Negative = negative for B. pseudomallei. †OR was adjusted for blood culture positive for B. pseudomallei, sex, age, history of dia- betes, pneumonia, hypotension, and duration of in-hospital intravenous antimicrobial treat- ment received. ‡P value for adjusted OR. Follow-up blood cultures were performed during days 4–10 in 321 patients and after day 10 in 190 patients. Patients who had a blood culture positive for B. pseudomallei on admission were more likely to have a positive follow-up blood culture than patients who had a negative admission blood culture (31% [50 of 159] versus 10% [16 of 162]; P < 0.001).The median duration of antimicrobial drugs received in patients who had a positive follow-up blood culture was not different from that of patients who had a negative follow-up blood culture (7 days [IQR = 5–7 days] versus 7 days [IQR = 4–7 days]; P > 0.1). Multivariable logistic regression demonstrated that follow-up blood cultures positive for B. pseudomallei were strongly asso- ciated with death (adjusted odds ratio = 4.2, 95% confidence interval = 2.1–8.7, P < 0.001 and adjusted odds ratio = 2.6, 95% confidence interval = 1.1–6.0, P = 0.03, respectively). However, this association was not observed in follow-up culture of other specimen types (Table 1). The prognostic value of follow-up blood culture was evalu- ated further in a subset of patients who had quantitative blood culture. Thirteen patients had quantitative blood culture on admission and one or more follow-up cultures (Figure 1). All 13 patients received ceftazidime or a carbapenem drug within the first two days after admission, and a decrease in bacterial count in blood was observed in all patients. Most patients with a positive quantitative follow-up blood culture (80%, 4 of 5 patients) had an admission bacterial count in blood greater than 1 colony-forming unit (CFU)/mL, and most patients with a negative quantitative follow-up blood culture (88%, 7 of 8 patients) had an admission bacterial count in blood of less than 1 CFU/mL (P = 0.03). Of these 13 patients, two patients who had a bacterial count in blood ≤ 100 CFU/mL at admis- sion (patients A and B), and one patient who had persistent bacteremia (0.2 CFU/mL on day 2, 0.1 CFU/mL on day 17, and 0.1 CFU/mL on day 26; patient D) died (Figure 1). Patient D was a 66-year old man with diabetes mellitus and non-Hodgkin lymphoma, and was post-chemotherapy. The patient who had a follow-up blood culture of 4.7 CFU/mL on day 9 (patient C) improved and was transferred to continue parenteral therapy at a community hospital. Our study shows that follow-up blood culture is an impor- tant predictor of late in-patient death from melioidosis. This finding agrees with observations for other infectious dis- eases.11,12 Response to antimicrobial therapy for melioidosis is often slow (mean duration of fever of 9 days),13 and markers Figure 1. Quantitative Burkholderia pseudomallei count in blood specimens obtained from 13 patients who had follow-up quantita- tive hemoculture performed. Each line represents the results of one patient. Solid lines represent five patients who had follow-up hemocul- ture positive for B. pseudomallei (patients A–E), and broken lines represent eight patients who had follow-up hemoculture negative for B. pseudomallei. Of 13 patients, three patients (A, B, and D) died. Patient C improved and was transferred to continue parenteral anti- microbial therapy at a community hospital. Patient E had a positive follow-up blood culture of 0.1 colony-forming units/mL on day 16, but negative blood cultures on days 19 and 28. for patients who survive the first week of in-patient care but remain at risk of death are not well established. Our study indicates that patients with melioidosis should receive weekly follow-up blood culture until clearance of the organism from blood Our results from a small subset of patients who had follow- up quantitative blood culture indicated that positive follow- up blood culture was associated with several factors, including high bacterial load on admission and an immunocompromise condition associated with a presumed failure to eradicate the infecting bacterium. We found that most of the patients who had follow-up positive blood culture had a bacterial count in blood of more than 1 CFU/mL on admission. However, one patient who had a bacterial count in blood of 0.2 CFU/mL failed to clear the organism from the blood (patient D). This finding could have been caused by his markedly impaired immune function and defective phagocytic cell function asso- ciated with chemotherapy. This finding emphasizes that in the clinical setting, intensive and detailed management is required of patients with positive follow-up blood culture, even without data on quantitative count. Although a positive culture of respiratory secretions, urine, or sputum on admission was associated with death, this asso- ciation was not observed for follow-up cultures of these speci- men types. Positive cultures of respiratory secretions and urine on admission represent organ involvement, including pneu- monia and urinary tract infection, which have been shown to be independent prognostic factors for death.3 This study extends previous findings by describing the value of a throat swab on admission as a prognostic factor, an observation that was independent of blood and urine culture results (as demonstrated by multivariable logistic regression). Furthermore, a throat swab is better than a sputum culture because it can be performed in every patient and not only patients with respiratory symptoms and sputum production.