Evaluation of MicroScan and Phoenix System for Rapid Identification and Susceptibility Testing Using Direct Inoculation from Positive BACTEC Blood Culture Bottles

Jae-Woo Chung; Hong-Seon Jeon; Heungsup Sung; Mi-Na Kim

doi:10.3343/kjlm.2009.29.1.25

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Chung, Jeon, Sung, and Kim: Evaluation of MicroScan and Phoenix System for Rapid Identification and Susceptibility Testing Using Direct Inoculation from Positive BACTEC Blood Culture Bottles

Original Article

Korean J Leg Med 2009;29(1):25-34.

Published online: 14 February 2009

DOI: https://doi.org/10.3343/kjlm.2009.29.1.25

Evaluation of MicroScan and Phoenix System for Rapid Identification and Susceptibility Testing Using Direct Inoculation from Positive BACTEC Blood Culture Bottles

Jae-Woo Chung, M.D., Hong-Seon Jeon, M.S., Heungsup Sung, M.D., Mi-Na Kim, M.D.

Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea

Corresponding author: Mi-Na Kim, M.D. Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, 388-1 Pungnap-2dong, Songpa-gu, Seoul 138-736, Korea Tel: +82-2-3010-4511, Fax: +82-2-478-0884 E-mail: mnkim@amc.seoul.kr

Received 28 August 200810 December 2008 Accepted 10 December 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

Procedures for rapid identification and susceptibility testing by direct inoculation (DI) from positive blood culture bottles into an automated system have not been standardized. This study was purposed to evaluate DI from BACTEC 9240 blood culture system (BD, USA) into MicroScan (Dade Behring, USA) or Phoenix (BD, USA).

Methods

From May to June 2006, bacterial pellets from positive aerobic bottles showing gram-positive cocci (GPC) or gram-negative rods (GNR) of single morphology were directly inoculated to MicroScan PosCombo1A and NegCombo32 and to Phoenix PMIC/ID-107 and NMIC/ID-53. In addition, the automated instruments were also inoculated from subcultures (standard inoculations, SI). Species identification and susceptibilities were compared between DI and SI and between MicroScan and Phoenix.

Results

A total of 108, 104, and 78 specimens were tested with MicroScan, Phoenix, and both, respectively. When DI and SI were matched, 94.8% of GPC were correctly identified with MicroScan, compared to 80.7% with Phoenix, and 93.9% of GNR were correctly identified with MicroScan, compared to 95.7% with Phoenix. DI with MicroScan and Phoenix showed correct susceptibilities in 94.6% of 1,150 and 96.5% of 660 tests (with very major error [VME] of 1.1% and 1.1%), respectively, among GPC and in 94.4% of 942 and 96.3% of 781 tests (with VME of 0.6% and 0%), respectively, of GNR. Correlation of identification/susceptibilities between MicroScan and Phoenix using DI were 81.8%/98.0% for Staphylococcus aureus and 100.0%/95.6% for Escherichia coli.

Conclusions

DI warrants a reliable method for identification and susceptibility testing of both GPC and GNR in MicroScan, and those of only GNR in Phoenix.

Keywords: Blood culture, Direct inoculation, Identification, Susceptibility, MicroScan, Phoenix

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Table 1.

Concordance rate of species identification between direct inoculation and standard inoculation methods in Micro-Scan and Phoenix

Organisms	MicroScan		Phoenix
Organisms	N of isolates	N (%) of concordant results	N of isolates	N (%) of concordant results
Gram positive cocci
Staphylococcus acureus	12	12 (100.0)	11	9 (81.8)
CoNS	29	29/25^∗ (100.0/86.2^∗)	29	28/18^∗ (96.6/62.1^∗)
Streptococci	9	8 (88.9)	7	3 (42.9)
Enterococci	6	5 (83.3)	7	5 (71.4)
Others	2^†	1 (50.0)	3^‡	1 (33.3)
Total	58	55/51^∗ (94.8/87.9^∗)	57	46/36^∗ (80.7/63.2^∗)
Gram negative rods
Escherichia coli	16	16 (100.0)	18	18 (100.0)
Klebsiella spp.	15	15 (100.0)	14	14 (100.0)
Acinectobacter spp.	7	5 (71.4)	5	5 (100.0)
Pseudomonas spp.	4	4 (100.0)	4	4 (100.0)
Stenotrophomonas maltophilia	2	2 (100.0)	1	1 (100.0)
Others	5^§	4 (80.0)	4^‖	2 (50.0)
Total	49	46 (93.9)	46	44 (95.7)

^∗ Based on species level;

^† including Leuconostoc spp. and Micrococcus spp.;

^‡ including Leuconostoc spp., Kocuria spp. and Micrococcus spp.;

^§ including Salmonella Typhi, Citrobacter freundii, Burkholderia cepacia, Vibrio cholerae, Achromobacterspp.;

^‖ including Achromobacter spp, Ochrobactrum anthropi, Burkholderia cepacia, Aeromonas sobria.

Abbreviation: CoNS, coagulase negative staphylococci.

Table 2.

36 discrepant results of species identification between direct inoculation and standard inoculation methods in MicroScan and Phoenix

Species	MicroScan		Phoenix
Species	Direct	Standard	Direct	Standard
Gram positive cocci
Staphylococus aureus	S. aureus	S. aureus	Alloiococcus otitidis	S. aureus
	S. aureus	S. aureus	A. otitidis	S. aureus
CoNS	Staphylococus auricularis	Staphylococus lugdunensis	Staphylococus haemolyticus	S. haemolyticus
	Staphylococus capitis	S. capitis	Staphylococus hominis	Staphylococus warneri
	S. capitis	S. capitis	Staphylococus kloosii	S. capitis
	S. capitis	S. capitis	S. capitis	Staphylococus cohnii
	Staphylococus epidermidis	NT	Bacillus cereus	S. epidermidis
	S. epidermidis	S. epidermidis	NT	NT
	S. epidermidis	Staphylococus simulans	NT	NT
	S. epidermidis	S. epidermidis	S. hominis	S. hominis
	S. epidermidis	NT	S. hominis	S. hominis
	S. epidermidis	S. epidermidis	Staphylococus saprophyticus	S. epidermidis
	S. epidermidis	S. epidermidis	S. saprophyticus	S. epidermidis
	S. epidermidis	S. epidermidis	S. saprophyticus	S. epidermidis
	S. epidermidis	NT	S. saprophyticus	S. saprophyticus
	S. haemolyticus	S. haemolyticus	S. haemolyticus	S. lugdunensis
	S. hominis	S. hominis	S. epidermidis	S. epidermidis
	S. hominis	S. hominis	S. saprophyticus	S. hominis
	S. hominis	S. hominis	S. saprophyticus	S. hominis
	S. warneri	S. capitis	S. warneri	S. lugdunensis
Streptococcus pneumoniae	Streptococcus anginosus group	S. pneumoniae	NT	NT
	S. pneumoniae	S. pneumoniae	Streptococcus mitis group	S. pneumoniae
Group C streptococci	Streptococcus agalactiae	S. agalactiae	Streptococcus pyogenes	S. pyogenes
Viridans streptococci	S. viridans group	S. viridans group	S. acidominimus	S. mitis group
Streptococcus mutans group	S. mutans group	S. mutans group	Streptococcus chromogenes	S. mutans group
Streptococcus anginosus group	S. anginosus group	NT	S. pyogenes	Streptococcus dysgalactiae subsp. equisimilis
Enterococcus faecium	E. faecium	Enterococcus gallinarum	Aerococcus spp.	E. faecium
	E. faecium	E. faecium	Aerococcus spp.	E. faecium
Leuconostoc spp.	Leuconostoc spp.	Leuconostoc spp.	Bacillus circulans	Leuconostoc spp.
Micrococcus spp.	Staphylococcus sciuri	Micrococcus spp.	S. capitis	Kocuria spp.
Gram negative rods
Klebsiella spp.	Klebsiella oxytoca	NT	Klebsiella pneumoniae	K. pneumoniae
Acinetobacter spp.	Acinetobacter baumannii	Acinetobacter lwoffii	NT	NT
	K. oxytoca	A. baumannii/haemolyticus	Acinetobacter spp.	Acinetobacter spp.
Achromobacter spp.	Achromobacter xylosoxidans	A. xylosoxidans	Moraxella spp.	Achromobacter spp.
Ochrobactrum spp.	Ochrobactrum anthropi	NT	Pasteurella pneumotropica	O. anthropi
Unidentified	Aeromonas hydrophila group	Vibrio cholerae	Aeromonas sobria	A. sobria

Abbreviations: CoNS, coagulase negative staphylococci; NT, not tested.

Table 3.

Results for antimicrobial susceptibilities with low correlation (<95%) between direct inoculation and standard inoculation method in MicroScan and Phoenix

	MicroScan					Phoenix
	N of strains tested	Correct (%)	VME (%)	ME (%)	mE (%)	N of strains tested	Correct (%)	VME (%)	ME (%)	mE (%)
Gram positive cocci
Teicoplanin	47	42 (89.4)	0 (0.0)	0 (0.0)	5 (10.6)	36	33 (91.7)	0 (0.0)	1 (2.8)	2 (5.6)
Gentamicin	41	34 (82.9)	1 (2.4)	0 (0.0)	6 (14.6)	34	33 (97.1)	0 (0.0)	0 (0.0)	1 (2.9)
Ciprofloxacin	47	46 (97.9)	0 (0.0)	0 (0.0)	1 (2.1)	38	36 (94.7)	0 (0.0)	0 (0.0)	2 (5.3)
Levofloxacin						37	35 (94.6)	0 (0.0)	0 (0.0)	2 (5.4)
Trimethoprim/sulfamethoxazole	41	38 (92.7)	2 (4.9)	1 (2.4)	0 (0.0)	33	32 (97.0)	0 (0.0)	1 (3.0)	0 (0.0)
Rifampin	47	44 (93.6)	1 (2.1)	1 (2.1)	1 (2.1)	33	31 (93.9)	0 (0.0)	1 (3.0)	1 (3.0)
Gram negative rods
Ampicillin	33	25 (75.8)	0 (0.0)	7 (21.2)	1 (3.0)	33	33 (100.0)	0 (0.0)	0 (0.0)	0 (0.0)
Piperacillin	44	40 (90.9)	1 (2.3)	0 (0.0)	3 (6.8)
Piperacillin/tazobactam	38	35 (92.1)	1 (2.6)	1 (2.6)	1 (2.6)	41	39 (95.1)	0 (0.0)	0 (0.0)	2 (4.9)
Cefazolin	33	30 (90.9)	0 (0.0)	0 (0.0)	3 (9.1)
Cefepime	44	40 (90.9)	1 (2.3)	1 (2.3)	2 (4.5)	41	38 (92.7)	0 (0.0)	0 (0.0)	3 (7.3)
Aztreonam	38	36 (94.7)	0 (0.0)	0 (0.0)	2 (5.3)	36	33 (91.7)	0 (0.0)	0 (0.0)	3 (8.3)
Levofloxacin	47	44 (93.6)	0 (0.0)	0 (0.0)	3 (6.4)	42	40 (95.2)	0 (0.0)	2 (4.8)	0 (0.0)

Abbreviations: VME, very major error; ME, major error; mE, minor error.

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