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Kang and Kim: Characteristics of Microorganisms Isolated from Blood Cultures at a University Hospital Located in an Island Region During 2003∼2007

Abstract

Background

The referral hospital is somewhat isolated from the mainland due to its island status; thus, microorganisms isolated from blood cultures might have a distinct pattern in their frequency and anti-biogram. We attempted to uncover these characteristics.

Methods

The isolates from blood cultures at the Cheju University Hospital during 2003∼2007 were analysed. After inoculation in aerobic and anaerobic bottles, blood specimens were cultured using BacT/ Alert system, and the isolates were identifieded and antimicrobial susceptibilities were tested using Vitek II system.

Results

The overall positive rate of blood cultures was 9.6% and contamination rate was 3.6%. The most commonly isolated pathogens were Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae. Gram positive rod, gram negative cocci, and anaerobes were not isolated, but fungi were isolated in 0.6% of blood cultures. The prevalence of methi-cillin-resistant S. aureus (MRSA) was 68.0% in 2003, 41.4% in 2004, 48.1% in 2005, 54.5% in 2006, and 65.2% in 2007. The prevalence of vancomycin-resistant enterococcus (VRE) was 0% in 2003 and 2004, 16.7% in 2005, 10.0% in 2006, and 9.5% in 2007.

Conclusion

The most commonly isolated pathogens were similar to those from other hospitals, but the isolation rates of MRSA and VRE by year showed different patterns. Also, gram positive rods, gram negative cocci and anaerobes were not isolated. To help the choice of empirical antibiotic treatments, we need complementary measures to upgrade microorganism isolation systems and further studies in-cluding the monitoring of antibiotic use.

References

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Fig. 1.
Trend of antimicrobial resistance of S. aureus, S. pneumoniae and E. faecalis by year. Abbreviations: OXS R SAU, oxacillin-resistant S. aureus; SXT SAU, trimethoprim-sulfamethoxazole-resistant S. aureus; TET R SPN, tetracycline-resistant S. pneumoniae; SXT R SPN, trimethoprim-sulfamethoxazole-resistant S. pneumoniae; TET R EFC, tetracycline-resistant E. faecalis; VAN R EFC, vancomycin-resistant E. faecalis.
kjcm-11-11f1.tif
Fig. 2.
Trend of antimicrobial resistance of E. coli and K. pneumoniae by year. Abbreviations: FOX R ECO, cefoxitin-resistant E. coli; TAX R ECO, cefotaxime-resistant E. coli; SXT R ECO, trimethoprim-sulfamethoxazole-resistant E. coli; FOX R KPN, cefoxitin-resistant K. pneumoniae; TAX R KPN, cefotaxime-resistant K. pneumoniae; SXT R KPN, trimethoprim-sulfamethoxazole-resistant K. pneumoniae.
kjcm-11-11f2.tif
Fig. 3.
Trend of antimicrobial resistance of A. baumannii and P. aeruginosa by year. Abbreviations: CIP R ABA, ciprofloxacin-resistant A. baumannii; IMI R ABA, imipenem-resistant A. baumannii; PIP R PAE, piperacillin-resistant P. aeruginosa; CIP R PAE, ciprofloxacin-resistant P. aeruginosa; IMI R PAE, imipenem-resistant P. aeruginosa; AZM R PAE, aztreonam-resistant P. aeruginosa.
kjcm-11-11f3.tif
Table 1.
Microorganisms isolated from blood in an island region during 2003∼2007
Organisms Yr N of positive isolates and patients by year
2003  2004 2005 2006 2007 Total
  I P I P I P I P I P I P
Aerobic and facultative
Gram-positive cocci 135 103 249 192 242 188 369 273 373 256 1,368 1,012
Staphylococcus aureus 36 25 61 29 50 27 68 33 97 40 312 154
CNS 67 57 146 133 146 124 218 189 198 164 775 667
Others 32 21 42 30 46 37 83 51 78 52 281 191
Gram-positive bacilli NE NE NE NE NE NE NE NE NE NE NE NE
Gram-negative cocci NE NE NE NE NE NE NE NE NE NE NE NE
Gram-negative bacilli 152 101 180 122 242 156 295 179 296 174 1,165 732
Enterobacteriaceae 129 85 131 89 202 128 226 137 246 143 934 582
Glucose-nonfermenting 15 11 43 29 34 24 59 36 44 28 195 128
Others 8 5 6 4 6 4 10 6 6 3 36 22
Subtotal 287 204 429 314 484 344 664 452 669 430 2,533 1,744
Anaerobic NT NT NT NT NT NT 0 0 0 0 0 0
Fungi NT NT NT NT NT NT 4 3 16 8 20 11
Total 287 204  429 314 484 344 668 455 685 438 2,553 1,755

Abbreviations: Yr, year; I, isolates; P, patients; CNS, Coagulase Negative Staphylococci; NE, not estimated; NT, not tested.

Table 2.
Species of aerobic gram-positive cocci, bacilli and gram-negative cocci from blood in an island region during 2003∼2007
Organisms N (%) of positive results
Isolates Patients
N (%) N (%)
Gram-positive cocci
Staphylococcus aureus 312 (22.8) 154 (15.2)
Coagulase negative staphylococci 775 (56.7) 667 (65.9)
Streptococcus pneumoniae 70 (5.1) 45 (4.4)
Streptococcus agalactiae 20 (1.5) 18 (1.8)
Streptococcus pyogenes 10 (0.7) 7 (0.7)
Viridans streptococci 5 (0.4) 5 (0.5)
Other Streptococcus spp. 46 (3.4) 33 (3.3)
Enterococcus faecalis 60 (4.4) 34 (3.4)
Enterococcus faecium 42 (3.1) 28 (2.8)
Other Enterococcus spp. 26 (1.9) 19 (1.9)
Micrococcus spp. 2 (0.1) 2 (0.2)
Other gram-positive cocci 0 (0.0) 0 (0.0)
Subtotal 1,368 (100.0) 1,012 (100.0)
Gram-positive bacilli NE (NE) NE (NE)
Gram-negative cocci NE (NE) NE (NE)
Total 1,368 (100.0)  1,012 (100.0)

Abbreviations: See Table 1.

Table 3.
Species of aerobic and facultative anaerobic gram-negative bacilli from blood in an island region during 2003∼2007
Organisms N (%) of positive results
Isolates Patients
N (%) N (%)
Enterobacteriaceae    
Escherichia coli 581 (59.9) 363 (60.1)
Citrobacter spp. 21 (2.2) 16 (2.6)
Enterobacter aerogenes 12 (1.2) 8 (1.3)
Enterobacter cloacae 37 (3.8) 22 (3.6)
Other Enterobacter spp. 1 (0.1) 1 (0.2)
Klebsiella oxytoca 20 (2.1) 15 (2.5)
Klebsiella pneumoniae 186 (19.2) 103 (17.1)
Other Klebsiella spp. 5 (0.5) 4 (0.7)
Morganella spp. 6 (0.6) 4 (0.7)
Proteus spp. 8 (0.8) 6 (1.0)
Salmonella typhi 4 (0.4) 3 (0.5)
Other Salmonella spp. 10 (1.0)) 7 (1.2)
Serratia spp. 34 (3.5) 23 (3.8)
Others 9 (0.9) 7 (1.2)
Subtotal 934 (96.3) 582 (96.4)
Other gram-negative bacilli    
Aeromonas hydrophilia 22 (2.3) 13 (2.2)
Other Aeromonas spp. 4 (0.4) 2 (0.3)
Haemophilus influenzae 3 (0.3) 1 (0.2)
Other Haemophilus spp. 0 (0.0) 0 (0.0)
Vibrio parahaemolyticus 1 (0.1) 1 (0.2)
Vibrio vulnificus 0 (0.0) 0 (0.0)
Others 6 (0.6) 5 (0.8)
Subtotal 36 (3.7) 22 (3.6)
Total 970 (100.0) 604 (100.0)
Table 4.
Species of glucose-nonfermenting gram-negative bacilli solated from blood in an island region during 2003∼2007
Organisms N (%) of positi ve results
Isolates Patients
N (%) N (%)
Acinetobacter baumannii 51 (26.2) 35 (27.3)
Other Acinetobacter spp. 14 (7.2) 12 (9.4)
Alcaligenes spp. 0 (0.0) 0 (0.0)
Burkholderia cepacia 17 (8.7) 11 (8.6)
Other Burkholderia spp. 4 (2.1) 3 (2.3)
Flavobacterium spp. 0 (0.0) 0 (0.0)
Moraxella spp. 0 (0.0) 0 (0.0)
Pseudomonas aeruginosa 72 (36.9) 42 (32.8)
Other Pseudomonas spp. 31 (15.9) 21 (16.4)
Others 6 (3.1) 4 (3.1)
Others 6 (3.1) 4 (3.1)
Total 195 (100.0) 128 (100.0)
Table 5.
Species of fungi isolated from blood in an island region during 2003∼2007
Fungi N (%) of positive results
Total isolates Total patients
N (%) N (%)
Candida albicans 1 (5.0) 1 (9.1)
Candida glabrata 1 (5.0) 1 (9.1)
Candida krusei 2 (10.0) 1 (9.1)
Candia lusitaniae 1 (5.0) 1 (9.1)
Candida parapsilosis 15 (75.0) 7 (63.6)
Other yeast 0 (0.0) 0 (0.0)
Other mold 0 (0.0) 0 (0.0)
Total 20 (100.0) 11 (100.0)
Table 6.
Annual isolation rate of relatively common bacteria isolated from blood in an island region during 2003∼2007
Organisms Yr N (%) of positive patients by year
2003 2004 2005 2006 2007 Total
N (%) N (%) N (%) N (%) N (%) N (%)
Staphylococcus aureus 25 (13.9) 29 (10.7) 27 (9.1) 33 (8.1) 40 (10.4) 154 (10.0)
CNS 57 (31.7) 133 (49.1) 124 (41.8) 189 (46.4) 164 (42.5) 667 (43.3)
Streptococcus pneumoniae 3 (1.7) 4 (1.5) 10 (3.4) 14 (3.4) 14 (3.6) 45 (2.9)
Enterococcus faecalis 5 (2.8) 2 (0.7) 5 (1.7) 11 (2.7) 11 (2.8) 34 (2.2)
Enterococcus faecium 4 (2.2) 3 (1.1) 1 (0.3) 9 (2.2) 11 (2.8) 28 (1.8)
Bacillus spp. 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)
Neisseria spp. 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)
Escherichia coli 56 (31.1) 50 (18.5) 76 (25.6) 86 (21.1) 95 (24.6) 363 (23.6)
Klebsiella pneumoniae 11 (6.1) 24 (8.9) 25 (8.4) 21 (5.2) 22 (5.7) 103 (6.7)
Enterobacter spp. 5 (2.8) 4 (1.5) 5 (1.7) 12 (2.9) 5 (1.3) 31 (2.0)
Proteus spp. 0 (0.0) 1 (0.4) 2 (0.7) 2 (0.5) 1 (0.3) 6 (0.4)
Salmonella spp. 2 (1.1) 1 (0.4) 1 (0.3) 1 (0.2) 5 (1.3) 10 (0.6)
Serratia spp. 1 (0.6) 5 (1.8) 10 (3.4) 4 (1.0) 3 (0.8) 23 (1.5)
Acinetobacter baumannii 6 (3.3) 4 (1.5) 2 (0.7) 17 (4.2) 6 (1.6) 35 (2.3)
Pseudomonas aeruginosa 5 (2.8) 11 (4.1) 9 (3.0) 8 (2.0) 9 (2.3) 42 (2.7)
Total 180 (100.0) 271 (100.0) 297 (100.0) 407 (100.0) 386 (100.0) 1,541 (100.0)

Abbreviations: See Table 1.

Table 7.
Distribution of relatively common bacteria isolated from blood in an island region by age group of patients
Organisms Yo N (%) of patients by age group
<1/12 1/12∼1 2∼5 6∼9 10∼19 20∼29 30∼39 40∼49 50∼59 60∼69 >70 Total
Staphylococcus aureus N 4 3 0 2 5 3 3 20 22 42 50 154
(%) (2.6) (1.9) 0.0 (1.3) (3.2) (1.9) (1.9) (13.0) (14.3) (27.3) (32.5) (100.0)
CNS N 74 35 25 3 7 23 23 53 79 119 226 667
(%) (11.1) (5.2) (3.7) (0.4) (1.0) (3.4) (3.4) (7.9) (11.8) (17.8) (33.9) (100.0)
Streptococcus pneumoniae N 0 8 2 1 0 0 2 4 5 13 10 45
(%) (0.0) (17.8) (4.4) (2.2) (0.0) (0.0) (4.4) (8.9) (11.1) (28.9) (22.2) (100.0)
Enterococcus faecalis N 2 0 0 0 0 0 1 1 6 7 17 34
(%) (5.9) (0.0) (0.0) (0.0) (0.0) (0.0) (2.9) (2.9) (17.6) (20.6) (50.0) (100.0)
Enterococcus faecium N 0 0 0 0 1 0 1 3 0 11 12 28
(%) (0.0) (0.0) (0.0) (0.0) (3.6) (0.0) (3.6) (10.7) (0.0) (39.3) (42.9) (100.0)
Escherichia coli N 10 0 0 1 6 11 16 35 42 78 164 363
(%) (2.8) (0.0) (0.0) (0.3) (1.7) (3.0) (4.4) (9.6) (11.6) (21.5) (45.2) (100.0)
Klebsiella pneumoniae N 2 3 1 0 0 1 1 10 18 24 43 103
(%) (1.9) (2.9) (1.0) (0.0) (0.0) (1.0) (1.0) (9.7) (17.5) (23.3) (41.7) (100.0)
Enterobacter spp. N 1 1 1 0 0 1 1 5 7 8 6 31
(%) (3.2) (3.2) (3.2) (0.0) (0.0) (3.2) (3.2) (16.1) (22.6) (25.8) (19.4) (100.0)
Proteus spp. N 0 0 0 0 0 0 0 0 1 2 3 6
(%) (0.0) (0.0) (0.0) (0.0) (0.0) (0.0) (0.0) (0.0) (16.7) (33.3) (50.0) (100.0)
Salmonella spp. N 0 0 2 1 2 2 0 1 0 2 0 10
(%) (0.0) (0.0) (20.0) (10.0) (20.0) (20.0) (0.0) (10.0) (0.0) (20.0) (0.0) (100.0)
Serratia spp. N 3 1 1 1 1 1 1 3 1 5 5 23
(%) (13.0) (4.3) (4.3) (4.3) (4.3) (4.3) (4.3) (13.0) (4.3) (21.7) (21.7) (100.0)
Acinetobacter baumannii N 1 2 0 0 1 1 2 4 3 10 11 35
(%) (2.9) (5.7) (0.0) (0.0) (2.9) (2.9) (5.7) (11.4) (8.6) (28.6) (31.4) (100.0)
Pseudomonas aeruginosa N 1 1 0 0 0 0 2 0 5 15 18 42
(%) (2.4) (2.4) (0.0) (0.0) (0.0) (0.0) (4.8) (0.0) (11.9) (35.7) (42.9) (100.0)

Abbreviations: Yo, years old; see Table 1.

Table 8.
Association between the number of blood culture and blood culture-positive patients and CNS and BCP isolated from blood
Year N of blood culture N (%) of positive patients N (%) of CNS and BCP
N (%) N (%)
2003 1,886 204 (10.8) 57 (3.0)
2004 3,437 314 (9.1) 133 (3.9)
2005 3,687 344 (9.3) 124 (3.4)
2006 4,455 455 (10.2) 189 (4.2)
2007 4,879 438 (9.0) 164 (3.4)
Total 18,344 1,755 (9.6) 667 (3.6)

Abbreviations: CNS, Coagulase Negative Staphylococcus; BCP, Bacillus spp., Corynebacterium spp. and Propionibacterium spp.

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