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Detection of Fungemia from Blood Cultures Using the BACTEC 9240 Instrument
Zent.bI. Bakterioi. 287, 53-59 (1998) © Gustav Fischer Verlag
Zentralblatt fur
Blkterioloaie
Detection of Fungemia from Blood Cultures Using the BACTEC 9240 Instrument M. Siemann and G. Rabenhorst Pathologisch-Bakteriologisches Institut, Stiidtisches Krankenhaus Kiel, Germany
Received February 28,1997· Revision received April 14, 1997· Accepted May 26,1997
Summary From January 1995 to November 1996, 14623 resin-containing blood culture vials were tested with the BACTEC fluorescent series instrument. A total of 1560 microor ganisms were recovered. 48 of the microorganisms were fungi. We could demonstrate the ability of the BACTEC 9240 to detect cases of fungaemia with Candida species and moulds such as Aspergillus fumigatus (4 cases) and Fusarium solani (1 case).
Introduction The purpose of the study was to prove the ability of the BACTEC 9240 system to detect fungemia. The most important predisposing factors for systemic fun gal infections are broad-spectrum antibiotic or corticoid therapy, indwelling intravenous catheters, chemotherapy, diabetes mellitus, solid organ or bone marrow transplantation (3). Patients with a systemic fungal infection have a poor prognosis if therapy is started too late or not at all. Diagnosis of systemic fungal infections is problematic. The sensitivity of serological methods such as Candida or Aspergillus antigen assays is unsatisfactory (4,5, 13). False-positive results may occur. Cultural methods for fungi are time-consuming and sensitiv ity is poor when respiratory specimens are cultured. Colonization of the respir atory tract with Aspergillus species without infection is possible in healthy as well as in hospitalized individuals. The availability of a fast, sensitive and spe cific diagnostic instrument for the detection of systemic fungal infections would be desirable. Blood cultures are the most important kind of specimen processed in a routine laboratory for detection of microorganisms that cause septicaemia. Reports about the detection of moulds in blood cultures are rare (1, 9). In con trolled clinical evaluations of automated blood culture systems, detection of
54
M. Siemann and G. Rabenhorst
Candida sp. is common but detection moulds was not reported (2, 6, 7, 8, 10, 11,14), with the exception of one strain in one study (12).
Materials and Methods Patient Population. The City Hospital of Kiel is a 700-bed teaching hospital of the Uni versity of Kiel. It consists of three medical departments (ICU 15 beds), surgery (ICU 8 beds), obstetrics, gynecology, urology, dialysis and paediatrics. The second department of internal medicine is part of the University of Kiel and specialized in haematologic disorders and immune-complex diseases. Patients with a predisposition for systemic fungal infections are frequent. Blood cultures. From January 1995 to November 1996, 14623 resin-containing blood culture vials were tested with the BACTEC fluorescent series instrument. A total of 1560 microorganisms were recovered, 48 of which were fungi. Blood culture media used were BACTEC PLUS Aerobic/F and PLUS Anaerobic/F (Becton Dickinson, Sparks, MD, USA). Both media contain resins and were monitored by the BACTEC 9240 instrument. Blood culture vials were inoculated at the bedside by the ward per sonnel. Most blood cultures arrive at our laboratory within 4 hours. Before transport, the vials are incubated in decentralized incubators at 35°C. As a rule, the preincuba tion period is not more than 12 hours. Nevertheless, we use Delayed Vial Entry soft ware and culture media. Blood cultures flagged negative by the instrument after 7 days of incubation were subcultured if they looked like being positive (bulging septum, cho colatized blood) or if we disposed of a positive culture from a sterile body site of this patient (CSfluid, CVCtips, biopsies) or suspected an Aspergillus infection. Blood cul tures flagged positive by the instrument were processed according to the manufacturer's instructions. Appropriate subculture media were selected on the basis of gram staining. Blood culture vials resulting in a negative gram stain were subcultured on Columbia Blood Agar (CBA) and Chocolate Agar for aerobic vials and CBA and Schaedler's Agar for anaerobic vials. Subculturing was performed in a safety cabinet under laminar flow conditions. The plates were inoculated and sealed with Parafilm to prevent contamina tion during incubation. All subcultures were inspected daily for growth. Chocolate Agar was incubated in a COz-enriched atmosphere for 14 days. Incubation was per formed at 35°C for 18 hours, followed by 14 days at room temperature. Differentia tion down to species level was done by macro and micromorphology characteristics for moulds, and using the Auxacolor system (Sanofi-Pasteur, Freiburg, Germany) for Can dida species. Moulds in the subcultures were considered a contaminant if there were no additional sources of the same isolate or if there was no clinical correlation.
Results Patient characteristics. Fungemia was detected in 14 patients (2.2 %), including 9 patients with systemic candidiasis, four patients with a systemic Aspergillus fumigatus infection and one patient with Fusarium solani mycosis. Bacteraemia was detected in 636 patients (97.8%). One subculture yielded Aspergillus fu migatus that was considered a contaminant (no clinical correlation and no addi tional source of the same isolate). Patient characteristics are shown in Table 1.
52
Male
Male Female
Female Female
Male
8
9
10
12 13
14
54
20 50
Medical
ICU ICU
ICU Medical
ICU
ICU ICU Medical Medical ICU ICU ICU ICU
Unit
Abbreviations: ALL acute lymphoblastic leukemia AML acute myelogenous leukemia BAL bronchoalveolar lavage BMT bone marrow transplant CVC central venous catheter
11
51 47
26 47 44 41 34 46 56 31
Male Male Male Female Female Female Female Male
1 2 3 4 5 6 7
Age (yrs)
Sex
Patient No.
FUO ICU RAEB SLE
SLE, steroid therapy Heart failure, adiposity (>200 kg) Alcoholism
SLE, steroid therapy Pancreatitis
AML
ALL, BMT NHL SLE, steroid therapy SLE, steroid therapy RAEB Alcoholism, meningitis AML ALL, BMT
Underlying disease and/or condition
Table 1. Summary of patient characteristics
venous venous venous venous venous
line line line line line
Lung
Central venous line Lung
Lung, central venous line Lung Pancreas
FUO FUO Central Central Central Central Central Lung
Infection site
fever of unknown origin intensive care unit refractory anemia with excess blasts systemic lupus erythematosus
Aspergillus fumigatus
Candida albicans Candida albicans
Aspergillus fumigatus Candida albicans
Aspergillus fumigatus
Aspergillus fumigatus Candida tropicalis Candida albicans Candida albicans Candida albicans Candida albicans Candida pseudotropicalis Fusarium solani
Isolate
BAL, autopsy pancreatic abscess CVC BAL, skin lesions
CVC CVC CVC CVC CVC BAL, skin lesions, aqueous humour BAL,CVC
Additional sample source other than blood
v, v,
0
~
N
\.0
> n ...., tTl n
OJ
I1Q
;5'
C V>
~.
'"
~
"'" "Tj
0
:::
0'
'"~
tJ
.... '"
56
M. Siemann and G. Rabenhorst
Blood culture data. From 38 sets of blood cultures (76 vials), the BACTEC instrument detected 38 positive bottles (12 patients). Terminal subcultures (38 subcultures of negative companion bottles of positive vials, 496 subcultures of bottles from patients with possible fungal infection and 3 subcultures of vials that looked like a positive vial) of the vials flagged negative by the in strument after seven days of incubation detected 11 additional positive vials and two additional patients. Blood culture data are shown in Table 2. Detection time. The detection time for Candida species in our blood cul ture media was not different from the detection time for bacteremia. The av erage detection time for the first positive blood bulture with Candida species was 14.03 h (n =8 patients). The average detection time for the first positive blood culture for bacteraemia was 14.06 h (n = 636 patients). Table 3 shows the recovery times of all cases of fungemia detected with BACTEC blood cul ture media in our laboratory.
Table 2. Number of positive blood culture vials Patient No.
Isolate
No. of blood cultures (sets)
Blood cultures flagged positive by the instrument aerobic
anaerobic
Instrumentnegative vials with positive subcultures aerobic
anaerobic
1
Aspergillus fumigatus
11
0
0
2
Candida tropicalis
1
0
0
3
Candida albicans
11
0
0
4
Candida albicans
44
1
2
5
Candida albicans
444
6
Candida albicans
44
0
0
7
Candida pseudotropicalis
8
Fusarium solani
1 33
0
0
0
0
9
Aspergillus fumigatus
20
022
10
Aspergillus fumigatus
20
012
11
Candida albicans
9
12
Candida albicans
11
13
Candida albicans
4
1
00
0
14
Aspergillus fumigatus
1
1
0
0
38
31
73
8
92
2 0
0
Detection of Fungi Using BACTEC 9240
57
Table 3. Recovery times of fungi in BACTEC PLUS blood culture media Recovery time (days)
Patient Isolate No. dO* dl I 2 3 4 5 6
Aspergillus fumigatus
7
Candida pseudotropicalis
8
Fusarium solani
Candida tropicalis
d2
d3
d4 d5 d6
Detected in the subculture d7
1 1
Candida albicans Candida albicans
1
Candida albicans
7I
I 22
2 2I
Candida albicans
I
I I2
9 10
Aspergillus fumigatus
11
Candida albicans
52
12
Candida albicans
1
13 14
Candida albicans
1
4 3 2
Aspergillus fumigatus
1
Aspergillus fumigatus 9
12 7
5
2
1
11
* detected by the instrument on the day the blood culture was drawn.
Discussion The BACTEC PLUS Aerobic/F medium and the BACTEC 9240 instrument have shown a good ability to detect candidaemia, as reported above. Some of the anaerobic vials had a positive subculture when the companion aerobic bottle was positive. The BACTEC PLUS anaerobiclF medium is not designed for the detection of aerobic bacteria or fungi and therefore sensitivity is low. All positive subcultures of instrument-negative bottles showed however heavy growth after 18 hours of incubation. No additional patient, with candidae mia could be detected by blind subculturing of aerobic or anaerobic vials in our laboratory. A study to determine the value of terminal subcultures (n = 13,471) of vials flagged negative by the instrument yielded five additional pa tients with fungaemia: 3 with Candida glabrata, 1 with Candida albicans and 1 with Cryptococcus neoformans, but none with moulds (10). Reports on a detection of Aspergillus sp., Fusarium sp. and other moulds in blood cultures are rare. In high-risk patient populations, blood cultures
58
M. Siemann and G. Rabenhorst
could be a helpful tool for confirmation of a suspected aspergillosis. A posi tive culture on material from a sterile body site (blood) is of high value if there is only a positive culture on material from a non-sterile body site, where colonization without infection may occur. In patient 1, the blood culture confirmed a suspected aspergillosis. Patient 8 was suspected of having a systemic fungal infection during an episode of FUO. The blood cultures from this patient were the first confirmation of the diagnosis. Later we were able to isolate Fusarium so/ani from all specimens we had except for urine and CVC tips (8 specimens). In patient 9, the culture of the evc tip was positive and contamination was suspected. All subcultures of the four blood culture vials were positive within 18 hours. In patient 10, several pulmonary speci mens grew Aspergillus fumigatus and so did, later on, three of four blood cultures drawn before starting the therapy. Patient 14 suffered from community-acquired pneumonia and was treated with macrolides for sus pected legionnaire's disease. This blood culture was the only specimen that grew Aspergillus fumigatus. Contamination of the blood culture could not be excluded.
Conclusion In the diagnosis of systemic fungal infection, BACTEC PLUS AerobiclF blood cultures are a helpful tool. An effective therapy can be initiated early in cases of candidemia. Suspected systemic infections with moulds could be confirmed by blood cultures, but subcultures are often necessary. All aerobic blood cul tures from patients suspected of having a systemic fungal infection should be subcultured after seven days of incubation in the instrument. The best time for subculturing has to be determined. Further studies will be necessary to de termine the sensitivity of BACTEC PLUS AerobiclF blood culture vials for moulds. Subcultures should be incubated for a sufficient period of time and must be handled carefully to prevent contamination. Acknowledgements. We would like to thank Dr. R. A. Samson of the Centraalbureau voor Schimmelcultures, Baarn, The Netherlands, for identification of the Fusarium sp. and G. Joly for critical reading of the manuscript.
References 1. Bille, j., L. Stockman, and G. D. Roberts: Detection of yeasts and filamentous fun gi in bloodcultures during a 10-year period (1972 to 1981). J. Clin. Microbiol. 16 (1982) 968-970 2. Cockerill III, C. A., Torgerson, G. S. Reed, E. A. Vetter, A. L. Weaver, j. C. Dale, G. D. Roberts, N. K. Henry, D. M. Ilstrup, and j. E. Rosenblatt: Clinical compari son of Difco ESP, Wampole Isolator, and Becton Dickinson aerobic blood culturing systems. J. Clin. Microbiol. 34 (1996) 20-24
Detection of Fungi Using BACTEC 9240
59
3. Edwards,]. E., Jr.: Candida species. In: G. L. Mandell,]. E. Bennett, and R. Dolin, Principles and practice of infectious diseases, 4th ed. Churchill Livingstone, New York (1995) 4. Fung, J. c., S. T. Donta, and R. C. Tilton: Candida Detection System (CAND-TEC) to differentiate between Candida albicans colonization and disease. J. Clin. Micro bioI. 24 (1986) 542-547 5. Gutierrez, J., C. Maroto, G. Piedrola, E. Martin, and J. A. Perez: Circulating Can dida antigens and antibodies: useful markers of candidemia. J. Clin. Microbiol. 31 (1993) 2550-2552 6. Hellinger, W c., J.]. Cawley, S. Alvarez, S. F. Hogan, W S. Harmsen, D. M. Ilstrup, and F. R. Cockerill III.: Clinical comparison of the Isolator and BacT/Alert aero bic blood culture systems. J. Clin. Microbiol. 33 (1995) 1787-1790 7. Pohlman, ]. K., B. A. Kirkley, K. A. Easley, B. A. Basilie, and]. A. Washington: Controlled clinical evaluation of BACTEC Plus AerobiclF and Bact/alert aerobic FAN bottles for detection of bloodstream infections. J. Clin. Microbiol. 33 (1995) 2856-2858 8. Pohlman, ]. K., B. A. Kirkley, K. A. Easley, and]. A. Washington: Controlled clin ical comparison of Isolator and BACTEC AerobiclF resin bottle for detection of bloodstream infections. J. Clin. Microbiol. 33 (1995) 2525-2529 9. Schell, WA. and]. R. Perfect: Fatal, disseminated Acremonium strictum infection in a neutropenic host. J. Clin. Microbiol. 34 (1996) 1333-1336 10. Shigei, J. T., J. A. Shimabukuro, M. T. Pezzlo, L. M. De La Maza, and E. M. Peter son: Value of terminal subcultures for blood cultures monitored by BACTEC 9240. J. Clin. Microbiol. 33 (1995) 1385-1388 11. Smith, ]. A., E. A. Bryce, ]. H. Ngui- Yen, and F.]. Roberts: Comparison of BAC TEC 9240 and BacT/Alert blood culture systems in an adult hospital. J. Clin. Microbiol. 33 (1995) 1905-1908 12. Snyder,]. Wand S. K. Lude: Comparison of BacT/Alert FAN medium with BAC TEC NR660 Plus 26A medium. J. Clin. Microbiol. 34 (1996) 1327-1329 13. Sulahian, A., M. Tabouret, P. Ribaud, J. Sarfati, E. Gluckman, ]. P. Latge, and F. Derouin: Comparison of an enzyme immunoassay and latex agglutination test for detection of galactomannan in the diagnosis of invasive aspergillosis. Eur. J. Clin. Microbiol. Infect. Dis. 15 (1996) 139-145 14. Wilson, M. L., M. P. Weinstein, S. Mirret, L. G. Reimer, R.J. Feldman, C. R. Chuard, and L. B. Relier: Controlled evaluation of Bact/Alert anaerobic and FAN anaerobic blood culture bottles for the detection of bacteriemia and fungemia. J. Clin. Microbiol. 33 (1995) 2265-2270 Corresponding author: Dr. Michael Siemann, Stadtisches Krankenhaus Kiel, Patholo gisch-Bakteriologisches Institut, ChemnitzstralSe 33, D-24116 Kiel, Germany
Zentralblatt fur
Blkterioloaie
Detection of Fungemia from Blood Cultures Using the BACTEC 9240 Instrument M. Siemann and G. Rabenhorst Pathologisch-Bakteriologisches Institut, Stiidtisches Krankenhaus Kiel, Germany
Received February 28,1997· Revision received April 14, 1997· Accepted May 26,1997
Summary From January 1995 to November 1996, 14623 resin-containing blood culture vials were tested with the BACTEC fluorescent series instrument. A total of 1560 microor ganisms were recovered. 48 of the microorganisms were fungi. We could demonstrate the ability of the BACTEC 9240 to detect cases of fungaemia with Candida species and moulds such as Aspergillus fumigatus (4 cases) and Fusarium solani (1 case).
Introduction The purpose of the study was to prove the ability of the BACTEC 9240 system to detect fungemia. The most important predisposing factors for systemic fun gal infections are broad-spectrum antibiotic or corticoid therapy, indwelling intravenous catheters, chemotherapy, diabetes mellitus, solid organ or bone marrow transplantation (3). Patients with a systemic fungal infection have a poor prognosis if therapy is started too late or not at all. Diagnosis of systemic fungal infections is problematic. The sensitivity of serological methods such as Candida or Aspergillus antigen assays is unsatisfactory (4,5, 13). False-positive results may occur. Cultural methods for fungi are time-consuming and sensitiv ity is poor when respiratory specimens are cultured. Colonization of the respir atory tract with Aspergillus species without infection is possible in healthy as well as in hospitalized individuals. The availability of a fast, sensitive and spe cific diagnostic instrument for the detection of systemic fungal infections would be desirable. Blood cultures are the most important kind of specimen processed in a routine laboratory for detection of microorganisms that cause septicaemia. Reports about the detection of moulds in blood cultures are rare (1, 9). In con trolled clinical evaluations of automated blood culture systems, detection of
54
M. Siemann and G. Rabenhorst
Candida sp. is common but detection moulds was not reported (2, 6, 7, 8, 10, 11,14), with the exception of one strain in one study (12).
Materials and Methods Patient Population. The City Hospital of Kiel is a 700-bed teaching hospital of the Uni versity of Kiel. It consists of three medical departments (ICU 15 beds), surgery (ICU 8 beds), obstetrics, gynecology, urology, dialysis and paediatrics. The second department of internal medicine is part of the University of Kiel and specialized in haematologic disorders and immune-complex diseases. Patients with a predisposition for systemic fungal infections are frequent. Blood cultures. From January 1995 to November 1996, 14623 resin-containing blood culture vials were tested with the BACTEC fluorescent series instrument. A total of 1560 microorganisms were recovered, 48 of which were fungi. Blood culture media used were BACTEC PLUS Aerobic/F and PLUS Anaerobic/F (Becton Dickinson, Sparks, MD, USA). Both media contain resins and were monitored by the BACTEC 9240 instrument. Blood culture vials were inoculated at the bedside by the ward per sonnel. Most blood cultures arrive at our laboratory within 4 hours. Before transport, the vials are incubated in decentralized incubators at 35°C. As a rule, the preincuba tion period is not more than 12 hours. Nevertheless, we use Delayed Vial Entry soft ware and culture media. Blood cultures flagged negative by the instrument after 7 days of incubation were subcultured if they looked like being positive (bulging septum, cho colatized blood) or if we disposed of a positive culture from a sterile body site of this patient (CSfluid, CVCtips, biopsies) or suspected an Aspergillus infection. Blood cul tures flagged positive by the instrument were processed according to the manufacturer's instructions. Appropriate subculture media were selected on the basis of gram staining. Blood culture vials resulting in a negative gram stain were subcultured on Columbia Blood Agar (CBA) and Chocolate Agar for aerobic vials and CBA and Schaedler's Agar for anaerobic vials. Subculturing was performed in a safety cabinet under laminar flow conditions. The plates were inoculated and sealed with Parafilm to prevent contamina tion during incubation. All subcultures were inspected daily for growth. Chocolate Agar was incubated in a COz-enriched atmosphere for 14 days. Incubation was per formed at 35°C for 18 hours, followed by 14 days at room temperature. Differentia tion down to species level was done by macro and micromorphology characteristics for moulds, and using the Auxacolor system (Sanofi-Pasteur, Freiburg, Germany) for Can dida species. Moulds in the subcultures were considered a contaminant if there were no additional sources of the same isolate or if there was no clinical correlation.
Results Patient characteristics. Fungemia was detected in 14 patients (2.2 %), including 9 patients with systemic candidiasis, four patients with a systemic Aspergillus fumigatus infection and one patient with Fusarium solani mycosis. Bacteraemia was detected in 636 patients (97.8%). One subculture yielded Aspergillus fu migatus that was considered a contaminant (no clinical correlation and no addi tional source of the same isolate). Patient characteristics are shown in Table 1.
52
Male
Male Female
Female Female
Male
8
9
10
12 13
14
54
20 50
Medical
ICU ICU
ICU Medical
ICU
ICU ICU Medical Medical ICU ICU ICU ICU
Unit
Abbreviations: ALL acute lymphoblastic leukemia AML acute myelogenous leukemia BAL bronchoalveolar lavage BMT bone marrow transplant CVC central venous catheter
11
51 47
26 47 44 41 34 46 56 31
Male Male Male Female Female Female Female Male
1 2 3 4 5 6 7
Age (yrs)
Sex
Patient No.
FUO ICU RAEB SLE
SLE, steroid therapy Heart failure, adiposity (>200 kg) Alcoholism
SLE, steroid therapy Pancreatitis
AML
ALL, BMT NHL SLE, steroid therapy SLE, steroid therapy RAEB Alcoholism, meningitis AML ALL, BMT
Underlying disease and/or condition
Table 1. Summary of patient characteristics
venous venous venous venous venous
line line line line line
Lung
Central venous line Lung
Lung, central venous line Lung Pancreas
FUO FUO Central Central Central Central Central Lung
Infection site
fever of unknown origin intensive care unit refractory anemia with excess blasts systemic lupus erythematosus
Aspergillus fumigatus
Candida albicans Candida albicans
Aspergillus fumigatus Candida albicans
Aspergillus fumigatus
Aspergillus fumigatus Candida tropicalis Candida albicans Candida albicans Candida albicans Candida albicans Candida pseudotropicalis Fusarium solani
Isolate
BAL, autopsy pancreatic abscess CVC BAL, skin lesions
CVC CVC CVC CVC CVC BAL, skin lesions, aqueous humour BAL,CVC
Additional sample source other than blood
v, v,
0
~
N
\.0
> n ...., tTl n
OJ
I1Q
;5'
C V>
~.
'"
~
"'" "Tj
0
:::
0'
'"~
tJ
.... '"
56
M. Siemann and G. Rabenhorst
Blood culture data. From 38 sets of blood cultures (76 vials), the BACTEC instrument detected 38 positive bottles (12 patients). Terminal subcultures (38 subcultures of negative companion bottles of positive vials, 496 subcultures of bottles from patients with possible fungal infection and 3 subcultures of vials that looked like a positive vial) of the vials flagged negative by the in strument after seven days of incubation detected 11 additional positive vials and two additional patients. Blood culture data are shown in Table 2. Detection time. The detection time for Candida species in our blood cul ture media was not different from the detection time for bacteremia. The av erage detection time for the first positive blood bulture with Candida species was 14.03 h (n =8 patients). The average detection time for the first positive blood culture for bacteraemia was 14.06 h (n = 636 patients). Table 3 shows the recovery times of all cases of fungemia detected with BACTEC blood cul ture media in our laboratory.
Table 2. Number of positive blood culture vials Patient No.
Isolate
No. of blood cultures (sets)
Blood cultures flagged positive by the instrument aerobic
anaerobic
Instrumentnegative vials with positive subcultures aerobic
anaerobic
1
Aspergillus fumigatus
11
0
0
2
Candida tropicalis
1
0
0
3
Candida albicans
11
0
0
4
Candida albicans
44
1
2
5
Candida albicans
444
6
Candida albicans
44
0
0
7
Candida pseudotropicalis
8
Fusarium solani
1 33
0
0
0
0
9
Aspergillus fumigatus
20
022
10
Aspergillus fumigatus
20
012
11
Candida albicans
9
12
Candida albicans
11
13
Candida albicans
4
1
00
0
14
Aspergillus fumigatus
1
1
0
0
38
31
73
8
92
2 0
0
Detection of Fungi Using BACTEC 9240
57
Table 3. Recovery times of fungi in BACTEC PLUS blood culture media Recovery time (days)
Patient Isolate No. dO* dl I 2 3 4 5 6
Aspergillus fumigatus
7
Candida pseudotropicalis
8
Fusarium solani
Candida tropicalis
d2
d3
d4 d5 d6
Detected in the subculture d7
1 1
Candida albicans Candida albicans
1
Candida albicans
7I
I 22
2 2I
Candida albicans
I
I I2
9 10
Aspergillus fumigatus
11
Candida albicans
52
12
Candida albicans
1
13 14
Candida albicans
1
4 3 2
Aspergillus fumigatus
1
Aspergillus fumigatus 9
12 7
5
2
1
11
* detected by the instrument on the day the blood culture was drawn.
Discussion The BACTEC PLUS Aerobic/F medium and the BACTEC 9240 instrument have shown a good ability to detect candidaemia, as reported above. Some of the anaerobic vials had a positive subculture when the companion aerobic bottle was positive. The BACTEC PLUS anaerobiclF medium is not designed for the detection of aerobic bacteria or fungi and therefore sensitivity is low. All positive subcultures of instrument-negative bottles showed however heavy growth after 18 hours of incubation. No additional patient, with candidae mia could be detected by blind subculturing of aerobic or anaerobic vials in our laboratory. A study to determine the value of terminal subcultures (n = 13,471) of vials flagged negative by the instrument yielded five additional pa tients with fungaemia: 3 with Candida glabrata, 1 with Candida albicans and 1 with Cryptococcus neoformans, but none with moulds (10). Reports on a detection of Aspergillus sp., Fusarium sp. and other moulds in blood cultures are rare. In high-risk patient populations, blood cultures
58
M. Siemann and G. Rabenhorst
could be a helpful tool for confirmation of a suspected aspergillosis. A posi tive culture on material from a sterile body site (blood) is of high value if there is only a positive culture on material from a non-sterile body site, where colonization without infection may occur. In patient 1, the blood culture confirmed a suspected aspergillosis. Patient 8 was suspected of having a systemic fungal infection during an episode of FUO. The blood cultures from this patient were the first confirmation of the diagnosis. Later we were able to isolate Fusarium so/ani from all specimens we had except for urine and CVC tips (8 specimens). In patient 9, the culture of the evc tip was positive and contamination was suspected. All subcultures of the four blood culture vials were positive within 18 hours. In patient 10, several pulmonary speci mens grew Aspergillus fumigatus and so did, later on, three of four blood cultures drawn before starting the therapy. Patient 14 suffered from community-acquired pneumonia and was treated with macrolides for sus pected legionnaire's disease. This blood culture was the only specimen that grew Aspergillus fumigatus. Contamination of the blood culture could not be excluded.
Conclusion In the diagnosis of systemic fungal infection, BACTEC PLUS AerobiclF blood cultures are a helpful tool. An effective therapy can be initiated early in cases of candidemia. Suspected systemic infections with moulds could be confirmed by blood cultures, but subcultures are often necessary. All aerobic blood cul tures from patients suspected of having a systemic fungal infection should be subcultured after seven days of incubation in the instrument. The best time for subculturing has to be determined. Further studies will be necessary to de termine the sensitivity of BACTEC PLUS AerobiclF blood culture vials for moulds. Subcultures should be incubated for a sufficient period of time and must be handled carefully to prevent contamination. Acknowledgements. We would like to thank Dr. R. A. Samson of the Centraalbureau voor Schimmelcultures, Baarn, The Netherlands, for identification of the Fusarium sp. and G. Joly for critical reading of the manuscript.
References 1. Bille, j., L. Stockman, and G. D. Roberts: Detection of yeasts and filamentous fun gi in bloodcultures during a 10-year period (1972 to 1981). J. Clin. Microbiol. 16 (1982) 968-970 2. Cockerill III, C. A., Torgerson, G. S. Reed, E. A. Vetter, A. L. Weaver, j. C. Dale, G. D. Roberts, N. K. Henry, D. M. Ilstrup, and j. E. Rosenblatt: Clinical compari son of Difco ESP, Wampole Isolator, and Becton Dickinson aerobic blood culturing systems. J. Clin. Microbiol. 34 (1996) 20-24
Detection of Fungi Using BACTEC 9240
59
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