- Email: [email protected]
Can the rmpA gene predict metastatic meningitis among patients with primary Klebsiella pneumoniae liver abscess?
166
Letters to the Editor
4. Marty FM, Koo S. Role of (1–>3)-beta-D-glucan in the diagnosis of invasive aspergillosis. Med Mycol 2009;47(Suppl. 1): S233e40. 5. Mennink-Kersten MA, Ruegebrink D, Verweij PE. Pseudomonas aeruginosa as a cause of 1,3-beta-D-glucan assay reactivity. Clin Infect Dis 2008 Jun 15;46(12):1930e1. 6. Osmon S, Ward S, Fraser VJ, Kollef MH. Hospital mortality for patients with bacteremia due to Staphylococcus aureus or Pseudomonas aeruginosa. Chest 2004 Feb;125(2):607e16. 7. Koya J, Nannya Y, Ichikawa M, Kurokawa M. The clinical role of procalcitonin in hematopoietic SCT. Bone Marrow Transplant 2012 Oct;47(10):1326e31.
Junji Koya Yasuhito Nannya Department of Hematology & Oncology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan Hisayuki Kobayashi Shu Okugawa Kyoji Moriya Department of Infection Control and Prevention, The University of Tokyo Hospital, Tokyo, Japan Mineo Kurokawa* Department of Hematology & Oncology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan Department of Cell Therapy and Transplantation, The University of Tokyo Hospital, Tokyo, Japan *Corresponding author. Department of Hematology & Oncology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. Tel.: þ81 3 5800 9092; fax: þ81 3 5840 8667. E-mail address: [email protected] Accepted 26 March 2013 ª 2013 The British Infection Association. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jinf.2013.03.017
Can the rmpA gene predict metastatic meningitis among patients with primary Klebsiella pneumoniae liver abscess? A newly distinct invasive syndrome of Klebsiella pneumoniae liver abscess (KLA) is well known and that would follows metastatic infections, particularly meningitis and endophthalmitis.1 In 2007, Chung and colleagues, writing in this Journal, reported that metastatic infection at distant sites occurred in 8.7% of 263 KLA cases.2 The metastatic infections mainly comprised of septic pneumonia and others like meningitis, endophthalmitis, cerebral abscess, and prostatic abscess, etc.2 In a recent nationwide
population-based study, a greater longitudinal risk for developing prostatic abscess following pyogenic liver abscess (69.2% KLA) was identified when compared with the comparison population.3 However, the microbiological risk factors for the development of the disastrous metastatic infections have not well been elucidated. Among the invasive nature of some K. pneumoniae isolates, serotypes K1 and K2 strains had a hypermucoviscous phenotype strongly associated with the regulator of mucoid phenotype A gene (rmpA).1 In 2008, Lee and colleagues reported 110 patients with KLA and found 17 metastatic infections, mainly including 11 meningitis and 4 endophthalmitis.4 Among them, complete microbiological data were available for only 49 (44.5%) of 110 cases. Only 27 isolates (55.1%) were rmpA-positive and 26 isolates (53.1%) had hypermucoviscous phenotype. Furthermore, among 17 patients with metastatic infections associated with primary KLA, only 8 strains were available for rmpA test and 7 (87.5%) strains were positive. Thereby the authors recognized rmpA as one of the significant risk factors for metastatic infections of the KLA cases. However, Yeh et al. reported a prevalence rate of 93.9% (31 of 33 isolates) for rmpA in KLA strains from northern Taiwan.5 We found rmpA in 96% (48 of 50 isolates) of primary KLA strains from southern Taiwan.6 Because of the high prevalence of rmpA in the KLA strains, rmpA would be difficult to predict metastatic meningitis among the patients with KLA. Lee et al.4 reported the lowest rates of rmpA and hypermucoviscous phenotype among those of various primary KLA studies in Taiwan (Table 1). Thus in Lee’s report, the lower rate (55.1%) of rmpA in KLA stains and relative higher rate (87.5%) of rmpA in metastatic strains might reach a plausible significance for rmpA as a predictor for metastatic infections.4 Besides, Fang et al. have reported insignificant difference in rmpA copy numbers between isolates from KLA patients with and without ocular or central nervous system infections.7 Therefore, we concern that rmpA might not really be able to predict distant metastatic infections for KLA cases. Notably, K. pneumoniae is capable of causing infected meningitis not metastatic from liver or other focus. Therefore, we tried to elucidate whether rmpA could really be a predictor of K. pneumoniae to infected meningitis. We collected 22 K. pneumoniae isolates from cerebrospinal fluid (CSF) among meningitis patients without liver abscess. These CSF K. pneumoniae isolates were collected from Taipei Veterans General Hospital in Taipei (n Z 7), Chi Mei Medical Center in Tainan (n Z 4), and National Cheng Kung University Hospital in Tainan (n Z 11). For comparison, we collected 33 KLA isolates from patients without meningitis. Plasmid DNA was extracted by QIAprep Spin Miniprep (Qiagen, Hilden, Germany) for detection of rmpA gene. Polymerase chain reaction analysis was performed by using specific rmpA primers (forward, 50 -TAC ATA TGA AGG AGT AGT TAA T-30 ; reverse, 50 -GAG CCA TCT TTC ATC AAC-30 ). The rmpA gene was positive for 18 isolates (81.8%) among CSF strains versus 32 isolates (97.0%) among KLA strains (p Z 0.077). Our study suggested that the rmpA gene is highly prevalent among both CSF and KLA strains without statistically significant difference. Therefore, the rmpA gene could not predict metastatic meningitis among patients with primary KLA.
Letters to the Editor
167
Table 1 The prevalence of plasmid-carried rmpA gene and hypermucoviscosity phenotype of Klebsiella pneumoniae causing liver abscess in Taiwan studies. Studies in Taiwan
Case number
rmpA prevalence
Hypermucoviscosity prevalence
Reference
Fang et al. (2004) Lee et al. (2006) Yu et al. (2006) Yeh et al. (2007) Yu et al. (2008) Lee et al. (2008) Lee et al. (2010) Hsu et al. (2011)
53 35 16 33 50 110 19a 43c
53 (100%) Not available 14 (87.5%) 31 (93.9%) 48 (96%) 27/49 (55.1%) 17 (89.5%)b 42 (97.7%)
52 (98%) 27 (77.1%) 13 (81.3%) Not available 45 (90%) 26/49 (53.1%) 18 (84.7%) Not available
7 8 9 5 6 4 10 11
a Invasive syndrome included at least one of the following focal infections: liver abscess, meningitis, empyema, mycotic aneurysm, and endophthalmitis. b Positive for rmpA or rmpA2. c Clinical isolates from Asia (including Taiwan, Hong Kong and Japan).
In addition, the prevalence of rmpA in the hypermucoviscous and magA-positive strains by Lee et al. was 57.7% and 62%, respectively.4 These rates were also inconsistent with existing data in the literature. Yu et al. have showed a high correlation between mucoidity of K. pneumoniae and the rmpA gene, as of 77 mucoid isolates, 86% were rmpA-positive.12 We also reported that rmpA occurred in 97.8% of the hypermucoviscous strains.6 In addition, the rmpA was present in all KLA strains with K1 (magA-positive) serotypes.5,6 Serotype K1 isolates negative for rmpA and hypermucoviscous phenotype were less virulent in mouse lethality tests.6 In Lee’s study,4 the reasons for such a low prevalence of rmpA in magA-positive and hypermucoviscous KLA strains remain unknown. In conclusion, rmpA seems to be one of the common virulence factors of K. pneumoniae strains for infected meningitis and primary liver abscess. Although rmpA might be essential in metastatic strains, it is almost ubiquitous in primary KLA strains, thus rmpA could hardly predict metastatic infections among patients with primary KLA.
Financial disclosure This work was supported by a research grant (grant number CMFHR10208) from Chi Mei Medical Center, Tainan, Taiwan.
Conflicts of interest We declare that we have no conflicts of interest.
Acknowledgements We thank Ching-Chien Lee and Chi-Chung Chen, Department of Medical Research, Chi Mei Medical Center (Tainan, Taiwan), for technical assistance.
2. Chung DR, Lee SS, Lee HR, Kim HB, Choi HJ, Eom JS, et al. Emerging invasive liver abscess caused by K1 serotype Klebsiella pneumoniae in Korea. J Infect 2007;54:578e83. 3. Chung SD, Keller J, Lin HC. Greatly increased risk for prostatic abscess following pyogenic liver abscess: a nationwide population-based study. J Infect 2012;64:445e7. 4. Lee SS, Chen YS, Tsai HC, Wann SR, Lin HH, Huang CK, et al. Predictors of septic metastatic infection and mortality among patients with Klebsiella pneumoniae liver abscess. Clin Infect Dis 2008;47:642e50. 5. Yeh KM, Kurup A, Siu LK, Koh YL, Fung CP, Lin JC, et al. Capsular serotype K1 or K2, rather than magA and rmpA, is a major virulence determinant for Klebsiella pneumoniae liver abscess in Singapore and Taiwan. J Clin Microbiol 2007;45: 466e71. 6. Yu WL, Ko WC, Cheng KC, Lee CC, Lai CC, Chuang YC. Comparison of prevalence of virulence factors for Klebsiella pneumoniae liver abscesses between isolates with capsular K1/K2 and non-K1/K2 serotypes. Diagn Microbiol Infect Dis 2008;62:1e6. 7. Fang CT, Lai SY, Yi WC, Hsueh PR, Liu KL, Chang SC. Klebsiella pneumoniae genotype K1: an emerging pathogen that causes septic ocular or central nervous system complications from pyogenic liver abscess. Clin Infect Dis 2007;45: 284e93. 8. Lee HC, Chuang YC, Yu WL, Lee NY, Chang CM, Ko NY, et al. Clinical implications of hypermucoviscosity phenotype in Klebsiella pneumoniae isolates: association with invasive syndrome in patients with community-acquired bacteraemia. J Intern Med 2006;259:606e14. 9. Yu WL, Ko WC, Cheng KC, Lee HC, Ke DS, Lee CC, et al. Association between rmpA and magA genes and clinical syndromes caused by Klebsiella pneumoniae in Taiwan. Clin Infect Dis 2006;42:1351e8. 10. Lee CH, Liu JW, Su LH, Chien CC, Li CC, Yang KD. Hypermucoviscosity associated with Klebsiella pneumoniae-mediated invasive syndrome: a prospective cross-sectional study in Taiwan. Int J Infect Dis 2010;14:e688e92. 11. Hsu CR, Lin TL, Chen YC, Chou HC, Wang JT. The role of Klebsiella pneumoniae rmpA in capsular polysaccharide synthesis and virulence revisited. Microbiology 2011;157:3446e57. 12. Yu VL, Hansen DS, Ko WC, Sagnimeni A, Klugman KP, von Gottberg A, et al. Virulence characteristics of Klebsiella and clinical manifestations of K. pneumoniae bloodstream infections. Emerg Infect Dis 2007;13:986e93.
References 1. Siu LK, Yeh KM, Lin JC, Fung CP, Chang FY. Klebsiella pneumoniae liver abscess: a new invasive syndrome. Lancet Infect Dis 2012;12:881e7.
Yin-Ching Chuang Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
168
Letters to the Editor Department of Internal Medicine, Chi Mei Medical Center-Liou Ying, Tainan, Taiwan Mei-Feng Lee Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan Che-Kim Tan Department of Intensive Care Medicine, Chi Mei Medical Center, Tainan, Taiwan Wen-Chien Ko Department of Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan Fu-Der Wang Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
Wen-Liang Yu* Department of Intensive Care Medicine, Chi Mei Medical Center, Tainan, Taiwan Department of Medicine, Taipei Medical University, Taipei, Taiwan *Corresponding author. Department of Intensive Care Medicine, Chi Mei Medical Center, No. 901 Zhonghua Road, Yongkang District, 710 Tainan, Taiwan. Tel.: þ886 6 281 2811x52605; fax: þ886 6 2517849. E-mail address: [email protected] Accepted 26 March 2013 ª 2013 The British Infection Association. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jinf.2013.03.016
Letters to the Editor
4. Marty FM, Koo S. Role of (1–>3)-beta-D-glucan in the diagnosis of invasive aspergillosis. Med Mycol 2009;47(Suppl. 1): S233e40. 5. Mennink-Kersten MA, Ruegebrink D, Verweij PE. Pseudomonas aeruginosa as a cause of 1,3-beta-D-glucan assay reactivity. Clin Infect Dis 2008 Jun 15;46(12):1930e1. 6. Osmon S, Ward S, Fraser VJ, Kollef MH. Hospital mortality for patients with bacteremia due to Staphylococcus aureus or Pseudomonas aeruginosa. Chest 2004 Feb;125(2):607e16. 7. Koya J, Nannya Y, Ichikawa M, Kurokawa M. The clinical role of procalcitonin in hematopoietic SCT. Bone Marrow Transplant 2012 Oct;47(10):1326e31.
Junji Koya Yasuhito Nannya Department of Hematology & Oncology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan Hisayuki Kobayashi Shu Okugawa Kyoji Moriya Department of Infection Control and Prevention, The University of Tokyo Hospital, Tokyo, Japan Mineo Kurokawa* Department of Hematology & Oncology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan Department of Cell Therapy and Transplantation, The University of Tokyo Hospital, Tokyo, Japan *Corresponding author. Department of Hematology & Oncology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. Tel.: þ81 3 5800 9092; fax: þ81 3 5840 8667. E-mail address: [email protected] Accepted 26 March 2013 ª 2013 The British Infection Association. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jinf.2013.03.017
Can the rmpA gene predict metastatic meningitis among patients with primary Klebsiella pneumoniae liver abscess? A newly distinct invasive syndrome of Klebsiella pneumoniae liver abscess (KLA) is well known and that would follows metastatic infections, particularly meningitis and endophthalmitis.1 In 2007, Chung and colleagues, writing in this Journal, reported that metastatic infection at distant sites occurred in 8.7% of 263 KLA cases.2 The metastatic infections mainly comprised of septic pneumonia and others like meningitis, endophthalmitis, cerebral abscess, and prostatic abscess, etc.2 In a recent nationwide
population-based study, a greater longitudinal risk for developing prostatic abscess following pyogenic liver abscess (69.2% KLA) was identified when compared with the comparison population.3 However, the microbiological risk factors for the development of the disastrous metastatic infections have not well been elucidated. Among the invasive nature of some K. pneumoniae isolates, serotypes K1 and K2 strains had a hypermucoviscous phenotype strongly associated with the regulator of mucoid phenotype A gene (rmpA).1 In 2008, Lee and colleagues reported 110 patients with KLA and found 17 metastatic infections, mainly including 11 meningitis and 4 endophthalmitis.4 Among them, complete microbiological data were available for only 49 (44.5%) of 110 cases. Only 27 isolates (55.1%) were rmpA-positive and 26 isolates (53.1%) had hypermucoviscous phenotype. Furthermore, among 17 patients with metastatic infections associated with primary KLA, only 8 strains were available for rmpA test and 7 (87.5%) strains were positive. Thereby the authors recognized rmpA as one of the significant risk factors for metastatic infections of the KLA cases. However, Yeh et al. reported a prevalence rate of 93.9% (31 of 33 isolates) for rmpA in KLA strains from northern Taiwan.5 We found rmpA in 96% (48 of 50 isolates) of primary KLA strains from southern Taiwan.6 Because of the high prevalence of rmpA in the KLA strains, rmpA would be difficult to predict metastatic meningitis among the patients with KLA. Lee et al.4 reported the lowest rates of rmpA and hypermucoviscous phenotype among those of various primary KLA studies in Taiwan (Table 1). Thus in Lee’s report, the lower rate (55.1%) of rmpA in KLA stains and relative higher rate (87.5%) of rmpA in metastatic strains might reach a plausible significance for rmpA as a predictor for metastatic infections.4 Besides, Fang et al. have reported insignificant difference in rmpA copy numbers between isolates from KLA patients with and without ocular or central nervous system infections.7 Therefore, we concern that rmpA might not really be able to predict distant metastatic infections for KLA cases. Notably, K. pneumoniae is capable of causing infected meningitis not metastatic from liver or other focus. Therefore, we tried to elucidate whether rmpA could really be a predictor of K. pneumoniae to infected meningitis. We collected 22 K. pneumoniae isolates from cerebrospinal fluid (CSF) among meningitis patients without liver abscess. These CSF K. pneumoniae isolates were collected from Taipei Veterans General Hospital in Taipei (n Z 7), Chi Mei Medical Center in Tainan (n Z 4), and National Cheng Kung University Hospital in Tainan (n Z 11). For comparison, we collected 33 KLA isolates from patients without meningitis. Plasmid DNA was extracted by QIAprep Spin Miniprep (Qiagen, Hilden, Germany) for detection of rmpA gene. Polymerase chain reaction analysis was performed by using specific rmpA primers (forward, 50 -TAC ATA TGA AGG AGT AGT TAA T-30 ; reverse, 50 -GAG CCA TCT TTC ATC AAC-30 ). The rmpA gene was positive for 18 isolates (81.8%) among CSF strains versus 32 isolates (97.0%) among KLA strains (p Z 0.077). Our study suggested that the rmpA gene is highly prevalent among both CSF and KLA strains without statistically significant difference. Therefore, the rmpA gene could not predict metastatic meningitis among patients with primary KLA.
Letters to the Editor
167
Table 1 The prevalence of plasmid-carried rmpA gene and hypermucoviscosity phenotype of Klebsiella pneumoniae causing liver abscess in Taiwan studies. Studies in Taiwan
Case number
rmpA prevalence
Hypermucoviscosity prevalence
Reference
Fang et al. (2004) Lee et al. (2006) Yu et al. (2006) Yeh et al. (2007) Yu et al. (2008) Lee et al. (2008) Lee et al. (2010) Hsu et al. (2011)
53 35 16 33 50 110 19a 43c
53 (100%) Not available 14 (87.5%) 31 (93.9%) 48 (96%) 27/49 (55.1%) 17 (89.5%)b 42 (97.7%)
52 (98%) 27 (77.1%) 13 (81.3%) Not available 45 (90%) 26/49 (53.1%) 18 (84.7%) Not available
7 8 9 5 6 4 10 11
a Invasive syndrome included at least one of the following focal infections: liver abscess, meningitis, empyema, mycotic aneurysm, and endophthalmitis. b Positive for rmpA or rmpA2. c Clinical isolates from Asia (including Taiwan, Hong Kong and Japan).
In addition, the prevalence of rmpA in the hypermucoviscous and magA-positive strains by Lee et al. was 57.7% and 62%, respectively.4 These rates were also inconsistent with existing data in the literature. Yu et al. have showed a high correlation between mucoidity of K. pneumoniae and the rmpA gene, as of 77 mucoid isolates, 86% were rmpA-positive.12 We also reported that rmpA occurred in 97.8% of the hypermucoviscous strains.6 In addition, the rmpA was present in all KLA strains with K1 (magA-positive) serotypes.5,6 Serotype K1 isolates negative for rmpA and hypermucoviscous phenotype were less virulent in mouse lethality tests.6 In Lee’s study,4 the reasons for such a low prevalence of rmpA in magA-positive and hypermucoviscous KLA strains remain unknown. In conclusion, rmpA seems to be one of the common virulence factors of K. pneumoniae strains for infected meningitis and primary liver abscess. Although rmpA might be essential in metastatic strains, it is almost ubiquitous in primary KLA strains, thus rmpA could hardly predict metastatic infections among patients with primary KLA.
Financial disclosure This work was supported by a research grant (grant number CMFHR10208) from Chi Mei Medical Center, Tainan, Taiwan.
Conflicts of interest We declare that we have no conflicts of interest.
Acknowledgements We thank Ching-Chien Lee and Chi-Chung Chen, Department of Medical Research, Chi Mei Medical Center (Tainan, Taiwan), for technical assistance.
2. Chung DR, Lee SS, Lee HR, Kim HB, Choi HJ, Eom JS, et al. Emerging invasive liver abscess caused by K1 serotype Klebsiella pneumoniae in Korea. J Infect 2007;54:578e83. 3. Chung SD, Keller J, Lin HC. Greatly increased risk for prostatic abscess following pyogenic liver abscess: a nationwide population-based study. J Infect 2012;64:445e7. 4. Lee SS, Chen YS, Tsai HC, Wann SR, Lin HH, Huang CK, et al. Predictors of septic metastatic infection and mortality among patients with Klebsiella pneumoniae liver abscess. Clin Infect Dis 2008;47:642e50. 5. Yeh KM, Kurup A, Siu LK, Koh YL, Fung CP, Lin JC, et al. Capsular serotype K1 or K2, rather than magA and rmpA, is a major virulence determinant for Klebsiella pneumoniae liver abscess in Singapore and Taiwan. J Clin Microbiol 2007;45: 466e71. 6. Yu WL, Ko WC, Cheng KC, Lee CC, Lai CC, Chuang YC. Comparison of prevalence of virulence factors for Klebsiella pneumoniae liver abscesses between isolates with capsular K1/K2 and non-K1/K2 serotypes. Diagn Microbiol Infect Dis 2008;62:1e6. 7. Fang CT, Lai SY, Yi WC, Hsueh PR, Liu KL, Chang SC. Klebsiella pneumoniae genotype K1: an emerging pathogen that causes septic ocular or central nervous system complications from pyogenic liver abscess. Clin Infect Dis 2007;45: 284e93. 8. Lee HC, Chuang YC, Yu WL, Lee NY, Chang CM, Ko NY, et al. Clinical implications of hypermucoviscosity phenotype in Klebsiella pneumoniae isolates: association with invasive syndrome in patients with community-acquired bacteraemia. J Intern Med 2006;259:606e14. 9. Yu WL, Ko WC, Cheng KC, Lee HC, Ke DS, Lee CC, et al. Association between rmpA and magA genes and clinical syndromes caused by Klebsiella pneumoniae in Taiwan. Clin Infect Dis 2006;42:1351e8. 10. Lee CH, Liu JW, Su LH, Chien CC, Li CC, Yang KD. Hypermucoviscosity associated with Klebsiella pneumoniae-mediated invasive syndrome: a prospective cross-sectional study in Taiwan. Int J Infect Dis 2010;14:e688e92. 11. Hsu CR, Lin TL, Chen YC, Chou HC, Wang JT. The role of Klebsiella pneumoniae rmpA in capsular polysaccharide synthesis and virulence revisited. Microbiology 2011;157:3446e57. 12. Yu VL, Hansen DS, Ko WC, Sagnimeni A, Klugman KP, von Gottberg A, et al. Virulence characteristics of Klebsiella and clinical manifestations of K. pneumoniae bloodstream infections. Emerg Infect Dis 2007;13:986e93.
References 1. Siu LK, Yeh KM, Lin JC, Fung CP, Chang FY. Klebsiella pneumoniae liver abscess: a new invasive syndrome. Lancet Infect Dis 2012;12:881e7.
Yin-Ching Chuang Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
168
Letters to the Editor Department of Internal Medicine, Chi Mei Medical Center-Liou Ying, Tainan, Taiwan Mei-Feng Lee Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan Che-Kim Tan Department of Intensive Care Medicine, Chi Mei Medical Center, Tainan, Taiwan Wen-Chien Ko Department of Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan Fu-Der Wang Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
Wen-Liang Yu* Department of Intensive Care Medicine, Chi Mei Medical Center, Tainan, Taiwan Department of Medicine, Taipei Medical University, Taipei, Taiwan *Corresponding author. Department of Intensive Care Medicine, Chi Mei Medical Center, No. 901 Zhonghua Road, Yongkang District, 710 Tainan, Taiwan. Tel.: þ886 6 281 2811x52605; fax: þ886 6 2517849. E-mail address: [email protected] Accepted 26 March 2013 ª 2013 The British Infection Association. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jinf.2013.03.016