Nosocomial bacteremia caused by biofilm-forming Bacillus cereus and Bacillus thuringiensis.
OBJECTIVE
Bacterial biofilms cause serious problems, such as antibiotic resistance and medical device-related infections. Recent reports indicate that Bacillus species potentially form biofilms and cause nosocomial bacteremia via catheter infection. Our objective was to investigate the relationship between nosocomial bacteremia caused by Bacillus species and biofilm formations.


METHODS
Between 2001 and 2006, Bacillus cereus and Bacillus thuringiensis were isolated from blood samples of 21 patients with nosocomial bacteremia in two hospitals. The patients had underlying diseases such as cerebrovascular damage, malignant disease, or chronic obstructive lung disease and had high fever at the onset of bacteremia. After investigation, B. cereus and B. thuringiensis were isolated from patient's catheter tip, gauze, and hospital environment. Pulsed-field gel electrophoresis (PFGE) on 32 B. cereus and 7 B. thuringiensis isolates, microtiter biofilm assay and scanning electron microscopy (SEM) on 22 B. cereus isolates from patient's blood were performed.


RESULTS
Molecular analysis by PFGE showed that 32 B. cereus strains had 21 patterns and 7 B. thuringiensis strains had 3 patterns. The PFGE patterns of B. thuringiensis and B. cereus in blood samples from 2 patients blood were similar to those from the same patient's catheter tip. The PFGE pattern of B. cereus from a hospital environment was similar to that from 2 patients' blood samples, and the PFGE pattern of B. thuringiensis from 2 hospital environments was similar to that from 2 patients' blood. The biofilm formations by 22 B. cereus isolates from patients' blood were confirmed by microtiter biofilm assay and SEM even at 24 hours.


CONCLUSIONS
Our data indicate that various types of Bacillus species exist in hospital environments and the biofilm-forming strains potentially cause nosocomial bacteremia by catheter infection.
Kuroki
Reiki
R
Department of Internal Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki.
Kawakami
Kenji
K
Qin
Liang
L
Kaji
Chiharu
C
Watanabe
Kiwao
K
Kimura
Yumiko
Y
Ishiguro
Chiaki
C
Tanimura
Shinobu
S
Tsuchiya
Yukiko
Y
Hamaguchi
Ichiro
I
Sakakura
Mitsuru
M
Sakabe
Shigetoshi
S
Tsuji
Kota
K
Inoue
Masakazu
M
Watanabe
Hiroshi
H
D000368:Aged; D000369:Aged, 80 and over; D001409:Bacillus cereus / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D001413:Bacillus thuringiensis / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D016470:Bacteremia / Q000382:microbiology*; D018441:Biofilms / Q000254:growth & development*; D055499:Catheter-Related Infections / Q000382:microbiology; D003428:Cross Infection / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D016521:Electrophoresis, Gel, Pulsed-Field; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology*; D006801:Humans; D008855:Microscopy, Electron, Scanning
D004269:DNA, Bacterial