Sung Ha Kang; Young Ree Kim

doi:10.5145/kjcm.2008.11.1.11

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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

Original Article

Korean J Clin Microbiol 2008;11(1):11-17.

Published online: 20 April 2008

DOI: https://doi.org/10.5145/kjcm.2008.11.1.11

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

Sung Ha Kang, Young Ree Kim

Department of Laboratory Medicine, College of Medicine, Cheju National University, Jeju, Korea

Department of Laboratory Medicine, College of Medicine, Cheju National University, 154, Samdo 2-dong, Jeju 690-716, Korea. (Tel) 82-64-750-1257, (Fax) 82-64-750-1257, (E-mail) namu8790@empal.com

Received 3 January 2008 Accepted 26 February 2008

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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.

Keywords: Blood culture, Positive rate, Contamination, Antimicrobial susceptibility

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.

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.

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.

Table 1.

Microorganisms isolated from blood in an island region during 2003∼2007

Organisms Yr	N of positive isolates and patients by year
Organisms Yr	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
Organisms	Yo	＜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
Staphylococcus aureus	(%)	(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
CNS	(%)	(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
Streptococcus pneumoniae	(%)	(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
Enterococcus faecalis	(%)	(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
Enterococcus faecium	(%)	(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
Escherichia coli	(%)	(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
Klebsiella pneumoniae	(%)	(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
Enterobacter spp.	(%)	(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
Proteus spp.	(%)	(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
Salmonella spp.	(%)	(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
Serratia spp.	(%)	(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
Acinetobacter baumannii	(%)	(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
Pseudomonas aeruginosa	(%)	(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
Year	N of blood culture	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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