- Email: [email protected]
Antimicrobial susceptibility of pneumococcal isolates causing bacteraemic pneumococcal pneumonia: analysis using current breakpoints and fluoroquinolone pharmacodynamics
Letters to the Editor / International Journal of Antimicrobial Agents 36 (2010) 90–98
95
Table 1 Univariate association of patient variables with risk of ototoxicity. Variable
Ototoxicity
P-value a
OR (95% CI)
No (n = 32)
Yes (n = 7)
Age (years) [mean (95% CI)] Male sex [n (%)] Caucasian [n (%)] Hispanic [n (%)] Other race [n (%)] Diabetes mellitus [n (%)] Renal dysfunction [n (%)] b Concomitant vancomycin [n (%)] Concomitant NSAIDs [n (%)]
27.8 (25.9–29.6) 15 (46.9) 19 (59.4) 1 (3.1) 12 (37.5) 8 (25.0) 8 (25.0) 6 (18.8) 10 (31.3)
26.0 (21.2–30.8) 2 (28.6) 3 (42.9) 2 (28.6) 2 (28.6) 2 (28.6) 3 (42.9) 4 (57.1) 5 (71.4)
Elevated troughs [n (%)] >10 mg/L (AMK) or >2 mg/L (GEN and TOB) >5 mg/L (AMK) or >1 mg/L (GEN and TOB) >0 mg/L (AMK, GEN and TOB)
1 (3.1) 1 (3.1) 22 (68.8)
No. of courses AMKc GENc TOBc All aminoglycoside coursesc Mean aminoglycoside courses [mean (95% CI)]
13 4 58 75 2.34 (1.89–2.80)
8 1 20 29 4.14 (0.2–8.08)
– – – – –
0.41 0.92 0.30 0.31
Cumulative dose (g) [mean (95% CI)] AMK GEN TOB
59.1 (17.0–101) 6.8 (–14.4 to 28.0) 32.3 (24.4–40.1)
74.4 (−198 to 347) 12.6 (N/A) 51.6 (20.8–82.4)
– – –
0.75 0.62 0.06
3 (42.9) 3 (42.9) 6 (85.7)
– 0.45 (0.08–2.69) 0.51 (0.10–2.69) 12.40 (0.94–164) 0.67 (0.11–3.99) 1.20 (0.19–7.44) 2.25 (0.41–12.30) 5.78 (1.01–32.90) 5.50 (0.91–33.35)
0.41 0.44 0.68 0.08 1.00 1.00 0.38 0.06 0.09
23.25 (1.93–280) 23.25 (1.93–280) 2.73 (0.29–25.75)
0.01 0.01 0.65
OR, odds ratio; CI, confidence interval; NSAID, non-steroidal anti-inflammatory drug; AMK, amikacin; GEN, gentamicin; TOB, tobramycin; N/A, not applicable. a Calculated by Student’s t-test for continuous variables or by Fisher’s exact test for categorical variables. b Rise in serum creatinine of >0.5 mg/dL or 50% above baseline. c Reported as absolute number of courses per group.
However, the results of this study give rise to the hypothesis that Hispanic CF patients may be predisposed to aminoglycosideassociated ototoxicity and further study of a genetic predisposition is warranted. Despite the fact that this was a small, limited study, we were able to identify two factors that may predispose adult CF patients to aminoglycoside ototoxicity, namely elevated trough concentrations and Hispanic race. Funding: No funding sources. Competing interests: None declared. Ethical approval: Ethical approval was obtained through the Northwestern University Institutional Review Board (project # 0273-023); informed consent was not required due to the retrospective de-identified nature of the study.
Kimberly K. Scarsi Northwestern University Feinberg School of Medicine, Division of Infectious Diseases, 645 N. Michigan Avenue, Suite 900, Chicago, IL 60611, USA Marc H. Scheetz a,b Midwestern University, Chicago College of Pharmacy, 555 31st Street, Downers Grove, IL 60515, USA b Northwestern Memorial Hospital, 251 E. Huron Street, Feinberg LC-700, Chicago, IL 60611, USA a
Michael J. Postelnick Northwestern Memorial Hospital, 251 E. Huron Street, Feinberg LC-700, Chicago, IL 60611, USA Joanne Cullina Cystic Fibrosis Center, Children’s Memorial Hospital, 2300 Children’s Plaza, #43, Chicago, IL 60614, USA
References [1] Tan KH, Mulheran M, Knox AJ, Smyth AR. Aminoglycoside prescribing and surveillance in cystic fibrosis. Am J Respir Crit Care Med 2003;167:819–23. [2] Touw DJ. Clinical pharmacokinetics of antimicrobial drugs in cystic fibrosis. Pharm World Sci 1998;20:149–60. [3] Wood PJ, Ioannides-Demos LL, Li SC, Williams TJ, Hickey B, Spicer WJ, et al. Minimisation of aminoglycoside toxicity in patients with cystic fibrosis. Thorax 1996;51:369–73. [4] Mulheran M, Degg C, Burr S, Morgan DW, Stableforth DE. Occurrence and risk of cochleotoxicity in cystic fibrosis patients receiving repeated high-dose aminoglycoside therapy. Antimicrob Agents Chemother 2001;45:2502–9. [5] Mulherin D, Fahy J, Grant W, Keogan M, Kavanagh B, FitzGerald M. Aminoglycoside induced ototoxicity in patients with cystic fibrosis. Ir J Med Sci 1991;160:173–5. [6] Tang HY, Hutcheson E, Neill S, Drummond-Borg M, Speer M, Alford RL. Genetic susceptibility to aminoglycoside ototoxicity: how many are at risk? Genet Med 2002;4:336–45. [7] Fischel-Ghodsian N, Prezant TR, Chaltraw WE, Wendt KA, Nelson RA, Arnos KS, et al. Mitochondrial gene mutation is a significant predisposing factor in aminoglycoside ototoxicity. Am J Otolaryngol 1997;18:173–8.
E. Paul O’Donnell ∗ Midwestern University, Chicago College of Pharmacy, 555 31st Street, Downers Grove, IL 60515, USA
Manu Jain Northwestern University Division of Pulmonary & Critical Care Medicine, 240 E. Huron Street, McGaw M300, Chicago, IL 60611, USA ∗ Corresponding author. Tel.: +1 630 515 7264. E-mail address: [email protected] (E.P. O’Donnell)
17 January 2010 doi:10.1016/j.ijantimicag.2010.02.018
Antimicrobial susceptibility of pneumococcal isolates causing bacteraemic pneumococcal pneumonia: analysis using current breakpoints and fluoroquinolone pharmacodynamics Sir, We undertook a prospective, observational study in the public sector (Charlotte Maxeke Johannesburg Academic Hospital) and the private sector (private hospitals in Johannesburg and Preto-
96
Letters to the Editor / International Journal of Antimicrobial Agents 36 (2010) 90–98
Table 1 Comparative pharmacokinetic/pharmacodynamic parameters for intravenous (i.v.) and oral (p.o.) levofloxacin and moxifloxacin for pneumococcal isolates causing bacteraemic community-acquired pneumonia in the public and private sectors in Gauteng, South Africa. Antibiotic
Levofloxacin Levofloxacin Levofloxacin Moxifloxacin
MIC90 (mg/L) 0.75 0.75 0.75 0.125
Dosage
AUC0–∞ (g h/mL)
500 mg OD 500 mg BID 750 mg OD 400 mg OD
i.v. 55a,b 110c 110d 48e
AUIC90 p.o. 48a,b 96c 101d 48e
i.v. 73 147 147 384
p.o. 64 128 135 384
MIC90 , minimum inhibitory concentration inhibiting 90% of the pneumococcal isolates; OD, once daily; BID, twice daily; AUC0–∞ , mean area under the plasma concentration–time curve from 0 h to infinity; AUIC90 , area under the inhibitory curve for 90% of the isolates. a Reference [2]. b Reference [3]. c Reference [4]. d Reference [5]. e Reference [6].
ria referring specimens to Ampath Laboratories) in Gauteng, South Africa, between January 2004 and December 2006 to determine the prevalence and patterns of antimicrobial susceptibility in pneumococcal isolates causing radiologically confirmed bacteraemic pneumonia, with the primary aims of defining the prevalence of fluoroquinolone resistance and/or mutations among the isolates and calculating and comparing the area under the inhibitory curves (AUICs) of levofloxacin at varying dosages and of moxifloxacin at standard dosages. The prevalence of penicillin resistance using the new Clinical and Laboratory Standards Institute (CLSI) (2008) breakpoints and of macrolide resistance and its mechanisms were also determined. Consecutive adult patients aged ≥18 years, hospitalised with radiologically confirmed bacteraemic pneumococcal communityacquired pneumonia were recruited. Various demographic and clinical data for the patients were recorded. Minimum inhibitory concentrations (MICs) of the isolates to penicillin, erythromycin, clindamycin, trimethoprim/sulfamethoxazole (SXT), ceftriaxone, levofloxacin, moxifloxacin, linezolid, teicoplanin and telithromycin were determined by broth microdilution according to CLSI guidelines and by Etest (AB BIODISK, Solna, Sweden). Isolates were defined as non-susceptible if they were intermediately resistant or fully resistant to the antibiotic. Isolates with levofloxacin MICs ≥ 1 mg/L were screened for quinolone resistance-determining region (QRDR) mutations. DNA was prepared by boiling bacterial cultures and the QRDR regions of parC, parE, gyrA and gyrB were amplified and sequenced [1]. Fluoroquinolone-susceptible pneumococcal strain R6 was used as a reference strain for identification of mutations. The comparative AUIC for 90% of the isolates (AUIC90 ) for different dosages of intravenous (i.v.) and oral levofloxacin versus moxifloxacin were calculated based on pharmacokinetic studies in healthy volunteers [2–6]. Erythromycin non-susceptible isolates (MIC ≥ 0.5 mg/L) were screened for the presence of ermB and/or mefA by a duplex polymerase chain reaction (PCR) [7]. For statistical analyses, continuous variables were analysed by Mann–Whitney U-test (two-tail) and categorical variables by Fisher’s exact test (two-tail). A P-value of <0.05 was considered statistically significant. A total of 175 patients fulfilling the inclusion criteria were analysed. The main differences when comparing public and private sector cases were as follows: the median age was lower in public sector patients [median 32 years, 95% confidence interval (CI) 32.6–36.6 years] compared with private sector patients (median 50 years, 95% CI 46.8–54.7 years) (P < 0.0001); fewer public sector patients had co-morbid illnesses other than human immunodeficiency virus (HIV) infection (P = 0.008); and more of the private sector patients had received prior antibiotic therapy in the past 3 months (P < 0.0001). No levofloxacin-resistant strains were detected in this study and therefore isolates with the highest levofloxacin MIC (1 mg/L; n = 9) were screened for first-
step QRDR mutations. Six isolates were found to have mutations in ParC and/or ParE. Only one isolate had a first-step mutation (Ser 79 → Phe) that has previously been associated with the development of fluoroquinolone resistance. The comparative pharmacokinetic/pharmacodynamic parameters for different doses of i.v. and oral levofloxacin and moxifloxacin are depicted in Table 1. AUIC90 values of 73, 147 and 147 were calculated for i.v. levofloxacin doses of 500 mg once daily, 500 mg twice daily and 750 mg once daily, respectively, whilst for moxifloxacin 400 mg once daily an AUIC90 of 384 was reported. Using the historical breakpoints, 32.6% of isolates tested (57/175) were non-susceptible to penicillin, with the majority of these in the intermediate range (52/175; 29.7%). Using the updated 2008 CLSI pneumonia (non-meningeal) breakpoints, only three isolates were identified as penicillin non-susceptible. There were no differences in the prevalence of penicillin and SXT resistance when comparing isolates from patients in the two sectors. Overall resistance to erythromycin, clindamycin and SXT was 13% (23/175), 9% (16/175) and 37% (65/175), respectively. There was more erythromycin resistance [18/79 (23%) vs. 5/96 (5%); P = 0.0007] and more clindamycin resistance [13/79 (16%) vs. 3/96 (1%); P = 0.0004] in isolates from patients in the private versus the public sector, respectively. None of the isolates were resistant to ceftriaxone, moxifloxacin, linezolid, teicoplanin or telithromycin. All isolates that were macrolide-resistant remained fully susceptible to telithromycin. Twenty-three isolates (13%) were non-susceptible to erythromycin, of which 13 (56.5%) contained ermB, 6 (26.1%) contained mefA, 3 (13.0%) contained both resistance determinants and 1 isolate (4.3%) contained neither ermB nor mefA. In this study of clinically significant isolates of Streptococcus pneumoniae from Gauteng, South Africa, no fluoroquinolone resistance was noted among the isolates and although six isolates were documented to have first-step fluoroquinolone mutations, only one carried a mutation that has previously been linked to subsequent development of fluoroquinolone resistance. Both levofloxacin (in higher dosages of 750 mg daily or 500 mg twice daily) and moxifloxacin (400 mg daily) in currently recognised dosages achieved AUIC90 levels greater than those recommended in the current literature (>125) [6]. Negligible levels of penicillin resistance were documented among the isolates when defined using the new CLSI breakpoint definition for pneumonia.
Acknowledgments The authors thank all laboratory and clinical staff who contributed to this surveillance. They also acknowledge the Group for Enteric, Respiratory and Meningeal Disease Surveillance in South Africa (GERMS-SA) for their efforts in collecting the data and isolates used in this study.
Letters to the Editor / International Journal of Antimicrobial Agents 36 (2010) 90–98
Funding: This study was supported by an unrestricted grant from Sanofi-aventis (Midrand, South Africa). In addition, routine surveillance isolate characterisation was funded by the National Institute for Communicable Diseases, a division of the National Health Laboratory Service; and molecular characterisation was funded for in part by the Medical Research Council, South Africa. The funding sources had no role in the collection, analysis and interpretation of data, in the writing of the manuscript or in the decision to submit the manuscript for publication. Competing interests: CF serves on advisory boards for MSD, Janssen-Cilag and Wyeth/Pfizer and acts as a speaker for Abbott, Sanofi-aventis, Winthrop, GlaxoSmithKline, MSD, Bayer, Cipla and Sandoz; AJB serves on advisory boards for Wyeth, GlaxoSmithKline and Jansen, on a speaker’s bureau for Wyeth and has received a research grant from Sanofi-aventis and MSD; AvG serves on advisory boards for Wyeth/Pfizer, GlaxoSmithKline and Novartis and has received grant funds from Sanofi-aventis and Wyeth/Pfizer; KPK serves on advisory boards for Bayer, Pfizer, Merck and GlaxoSmithKline. All other authors declare no competing interests. Ethical approval: This study was approved by the Human Research Ethics Committee of the University of the Witwatersrand, Johannesburg, South Africa (protocol number 40435). References [1] Von Gottberg A, Klugman KP, Cohen C, Wolter N, de Gouveia L, du Plessis M, et al. Emergence of levofloxacin-non-susceptible Streptococcus pneumoniae and treatment for multidrug-resistant tuberculosis in children in South Africa: a cohort observational surveillance study. Lancet 2008;371:1108–13. [2] Lacy MK, Lu W, Xu X, Tessier PR, Nicolau DP, Quintiliani R, et al. Pharmacodynamic comparisons of levofloxacin, ciprofloxacin and ampicillin against Streptococcus pneumoniae in an in vitro model of infection. Antimicrob Agents Chemother 1999;43:672–7. [3] Chien S-C, Rogge MC, Gisclon LG, Curtin C, Wong F, Natarajan J, et al. Pharmacokinetic profile of levofloxacin following once-daily 500-milligram oral or intravenous doses. Antimicrob Agents Chemother 1997;41:2256–60. [4] Fish DN, Chow AT. The clinical pharmacokinetics of levofloxacin. Clin Pharmacokinet 1997;32:101–19. [5] Chien SC, Wong FA, Fowler CL, Callery-D’Amico SV, Williams RR, Nayak R, et al. Double-blind evaluation of the safety and pharmacokinetics of multiple oral once-daily 750-milligram and 1-gram doses of levofloxacin in health volunteers. Antimicrob Agents Chemother 1998;42:885–8. [6] Schentag JJ, Gilliland KK, Paladino JA. What have we learned from pharmacokinetic and pharmacodynamic theories? Clin Infect Dis 2001;32(Suppl. 1):S39–46. [7] Wolter N, von Gottberg A, du Plessis M, de Gouveia L, Klugman KP; Group for Enteric, Respiratory and Meningeal Surveillance in South Africa. Molecular basis and clonal nature of increasing pneumococcal macrolide resistance in South Africa, 2000–2005. Int J Antimicrob Agents 2008;32:62–7.
C. Feldman ∗ Division of Pulmonology, Department of Internal Medicine, Charlotte Maxeke Johannesburg Academic Hospital and Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa A.J. Brink Ampath National Laboratory Services, Milpark Hospital, Johannesburg, South Africa A. von Gottberg N. Wolter L. de Gouveia Respiratory and Meningeal Pathogens Research Unit, National Institute for Communicable Diseases, Johannesburg, South Africa O. Perovic External Quality Assessment Reference Unit, National Institute for Communicable Diseases, Johannesburg, South Africa K.P. Klugman a,b Respiratory and Meningeal Pathogens Research Unit, National Institute for Communicable Diseases, Johannesburg, South Africa b Hubert Department of Global Health, Rollins School of Public Health, and Division of Infectious Diseases, School of Medicine, Emory University, Atlanta, GA, USA a
97
∗ Corresponding
author. Tel.: +27 11 488 3840; fax: +27 11 488 4675. E-mail address: [email protected] (C. Feldman) 3 December 2009
doi:10.1016/j.ijantimicag.2010.02.021
DNA gyrase and topoisomerase IV are dual targets of zabofloxacin in Streptococcus pneumoniae Sir, Quinolone resistance in Streptococcus pneumoniae is related to mutations in the DNA gyrase and topoisomerase IV genes [1]. The quinolone resistance-determining regions (QRDRs), point mutation spots in discrete regions of the DNA gyrase and topoisomerase IV genes, are responsible for the development of resistance [2]. Zabofloxacin (DW-224a) has been shown to have excellent in vitro activity both against Gram-negative and Gram-positive pathogens, including ciprofloxacin-resistant S. pneumoniae [3–5]. Zabofloxacin has also demonstrated rapid bactericidal activity and a long post-antibiotic effect against S. pneumoniae [6]. In this study, we report a detailed analysis of QRDRs in gyrA, gyrB, parC and parE of S. pneumoniae mutants selected stepwise for resistance to zabofloxacin. Mutants were selected by plating ca. 109 –1010 colony-forming units of S. pneumoniae c9211 or its mutant derivatives on brain–heart infusion plates containing 10% sheep blood and zabofloxacin. Plates were incubated aerobically at 37 ◦ C for 48 h. Mutant frequencies were determined by comparing the number of colonies that grew on plates containing the drug with the number of colonies growing in the absence of the drug. Genomic DNA was used as a template in polymerase chain reaction (PCR) amplification of the QRDRs of the gyrA, gyrB, parC and parE genes. The PCR products were sequenced and analysed. Minimum inhibitory concentrations (MICs) were determined by an agar dilution method with Mueller–Hinton agar supplemented with 5% sheep blood following Clinical and Laboratory Standards Institute guidelines [7]. MICs of zabofloxacin against c9211 and its mutants are presented in Table 1. Streptococcus pneumoniae 1CM1 and 1GM1 were obtained by first-step selection for resistance to ciprofloxacin and gemifloxacin, respectively. For strain 1CM1 bearing the S79F mutation in ParC, the MIC of zabofloxacin was 0.125 mg/L, a four-fold increase over that for c9211 (MIC = 0.03 mg/L). For strain 1GM1 bearing the S81F mutation in GyrA, the MIC of zabofloxacin was 0.5 mg/L, a 16-fold increase over that for the wild-type. These observations indicate that DNA gyrase and topoisomerase IV were each targeted by zabofloxacin and that a mutation in a single enzyme was not able to register a significant increase in resistance. To examine the primary intracellular target, S. pneumoniae c9211 mutants were generated by stepwise challenge using increasing concentrations of zabofloxacin. The frequency of firststep mutants selected at 0.125 mg/L zabofloxacin (4× MIC) was 5.0 × 10−8 –1.0 × 10−8 . Five of the first-step zabofloxacin mutants were chosen for analysis. For each of the first-step mutants 1DWM1 to 1DWM3, there was an eight-fold increase in the MIC of zabofloxacin. Using DNA sequence analysis of the PCR products from the three mutants, the presence of mutations in gyrA leading to the alteration Ser81Phe was observed. Strains 1DWM4 and 1DWM5 increased the MIC of zabofloxacin to 0.125 mg/L, but there was no alteration in GyrA, GyrB, ParC or ParE. For the second-step selection, strain 1DWM3 (zabofloxacin MIC = 0.25 mg/L) was challenged with the drug at 0.5 mg/L (2× MIC), yielding second-step mutants 2DWM1 to 2DWM4. The frequency of the second-step mutants was 6.67 × 10−8 . Strains
95
Table 1 Univariate association of patient variables with risk of ototoxicity. Variable
Ototoxicity
P-value a
OR (95% CI)
No (n = 32)
Yes (n = 7)
Age (years) [mean (95% CI)] Male sex [n (%)] Caucasian [n (%)] Hispanic [n (%)] Other race [n (%)] Diabetes mellitus [n (%)] Renal dysfunction [n (%)] b Concomitant vancomycin [n (%)] Concomitant NSAIDs [n (%)]
27.8 (25.9–29.6) 15 (46.9) 19 (59.4) 1 (3.1) 12 (37.5) 8 (25.0) 8 (25.0) 6 (18.8) 10 (31.3)
26.0 (21.2–30.8) 2 (28.6) 3 (42.9) 2 (28.6) 2 (28.6) 2 (28.6) 3 (42.9) 4 (57.1) 5 (71.4)
Elevated troughs [n (%)] >10 mg/L (AMK) or >2 mg/L (GEN and TOB) >5 mg/L (AMK) or >1 mg/L (GEN and TOB) >0 mg/L (AMK, GEN and TOB)
1 (3.1) 1 (3.1) 22 (68.8)
No. of courses AMKc GENc TOBc All aminoglycoside coursesc Mean aminoglycoside courses [mean (95% CI)]
13 4 58 75 2.34 (1.89–2.80)
8 1 20 29 4.14 (0.2–8.08)
– – – – –
0.41 0.92 0.30 0.31
Cumulative dose (g) [mean (95% CI)] AMK GEN TOB
59.1 (17.0–101) 6.8 (–14.4 to 28.0) 32.3 (24.4–40.1)
74.4 (−198 to 347) 12.6 (N/A) 51.6 (20.8–82.4)
– – –
0.75 0.62 0.06
3 (42.9) 3 (42.9) 6 (85.7)
– 0.45 (0.08–2.69) 0.51 (0.10–2.69) 12.40 (0.94–164) 0.67 (0.11–3.99) 1.20 (0.19–7.44) 2.25 (0.41–12.30) 5.78 (1.01–32.90) 5.50 (0.91–33.35)
0.41 0.44 0.68 0.08 1.00 1.00 0.38 0.06 0.09
23.25 (1.93–280) 23.25 (1.93–280) 2.73 (0.29–25.75)
0.01 0.01 0.65
OR, odds ratio; CI, confidence interval; NSAID, non-steroidal anti-inflammatory drug; AMK, amikacin; GEN, gentamicin; TOB, tobramycin; N/A, not applicable. a Calculated by Student’s t-test for continuous variables or by Fisher’s exact test for categorical variables. b Rise in serum creatinine of >0.5 mg/dL or 50% above baseline. c Reported as absolute number of courses per group.
However, the results of this study give rise to the hypothesis that Hispanic CF patients may be predisposed to aminoglycosideassociated ototoxicity and further study of a genetic predisposition is warranted. Despite the fact that this was a small, limited study, we were able to identify two factors that may predispose adult CF patients to aminoglycoside ototoxicity, namely elevated trough concentrations and Hispanic race. Funding: No funding sources. Competing interests: None declared. Ethical approval: Ethical approval was obtained through the Northwestern University Institutional Review Board (project # 0273-023); informed consent was not required due to the retrospective de-identified nature of the study.
Kimberly K. Scarsi Northwestern University Feinberg School of Medicine, Division of Infectious Diseases, 645 N. Michigan Avenue, Suite 900, Chicago, IL 60611, USA Marc H. Scheetz a,b Midwestern University, Chicago College of Pharmacy, 555 31st Street, Downers Grove, IL 60515, USA b Northwestern Memorial Hospital, 251 E. Huron Street, Feinberg LC-700, Chicago, IL 60611, USA a
Michael J. Postelnick Northwestern Memorial Hospital, 251 E. Huron Street, Feinberg LC-700, Chicago, IL 60611, USA Joanne Cullina Cystic Fibrosis Center, Children’s Memorial Hospital, 2300 Children’s Plaza, #43, Chicago, IL 60614, USA
References [1] Tan KH, Mulheran M, Knox AJ, Smyth AR. Aminoglycoside prescribing and surveillance in cystic fibrosis. Am J Respir Crit Care Med 2003;167:819–23. [2] Touw DJ. Clinical pharmacokinetics of antimicrobial drugs in cystic fibrosis. Pharm World Sci 1998;20:149–60. [3] Wood PJ, Ioannides-Demos LL, Li SC, Williams TJ, Hickey B, Spicer WJ, et al. Minimisation of aminoglycoside toxicity in patients with cystic fibrosis. Thorax 1996;51:369–73. [4] Mulheran M, Degg C, Burr S, Morgan DW, Stableforth DE. Occurrence and risk of cochleotoxicity in cystic fibrosis patients receiving repeated high-dose aminoglycoside therapy. Antimicrob Agents Chemother 2001;45:2502–9. [5] Mulherin D, Fahy J, Grant W, Keogan M, Kavanagh B, FitzGerald M. Aminoglycoside induced ototoxicity in patients with cystic fibrosis. Ir J Med Sci 1991;160:173–5. [6] Tang HY, Hutcheson E, Neill S, Drummond-Borg M, Speer M, Alford RL. Genetic susceptibility to aminoglycoside ototoxicity: how many are at risk? Genet Med 2002;4:336–45. [7] Fischel-Ghodsian N, Prezant TR, Chaltraw WE, Wendt KA, Nelson RA, Arnos KS, et al. Mitochondrial gene mutation is a significant predisposing factor in aminoglycoside ototoxicity. Am J Otolaryngol 1997;18:173–8.
E. Paul O’Donnell ∗ Midwestern University, Chicago College of Pharmacy, 555 31st Street, Downers Grove, IL 60515, USA
Manu Jain Northwestern University Division of Pulmonary & Critical Care Medicine, 240 E. Huron Street, McGaw M300, Chicago, IL 60611, USA ∗ Corresponding author. Tel.: +1 630 515 7264. E-mail address: [email protected] (E.P. O’Donnell)
17 January 2010 doi:10.1016/j.ijantimicag.2010.02.018
Antimicrobial susceptibility of pneumococcal isolates causing bacteraemic pneumococcal pneumonia: analysis using current breakpoints and fluoroquinolone pharmacodynamics Sir, We undertook a prospective, observational study in the public sector (Charlotte Maxeke Johannesburg Academic Hospital) and the private sector (private hospitals in Johannesburg and Preto-
96
Letters to the Editor / International Journal of Antimicrobial Agents 36 (2010) 90–98
Table 1 Comparative pharmacokinetic/pharmacodynamic parameters for intravenous (i.v.) and oral (p.o.) levofloxacin and moxifloxacin for pneumococcal isolates causing bacteraemic community-acquired pneumonia in the public and private sectors in Gauteng, South Africa. Antibiotic
Levofloxacin Levofloxacin Levofloxacin Moxifloxacin
MIC90 (mg/L) 0.75 0.75 0.75 0.125
Dosage
AUC0–∞ (g h/mL)
500 mg OD 500 mg BID 750 mg OD 400 mg OD
i.v. 55a,b 110c 110d 48e
AUIC90 p.o. 48a,b 96c 101d 48e
i.v. 73 147 147 384
p.o. 64 128 135 384
MIC90 , minimum inhibitory concentration inhibiting 90% of the pneumococcal isolates; OD, once daily; BID, twice daily; AUC0–∞ , mean area under the plasma concentration–time curve from 0 h to infinity; AUIC90 , area under the inhibitory curve for 90% of the isolates. a Reference [2]. b Reference [3]. c Reference [4]. d Reference [5]. e Reference [6].
ria referring specimens to Ampath Laboratories) in Gauteng, South Africa, between January 2004 and December 2006 to determine the prevalence and patterns of antimicrobial susceptibility in pneumococcal isolates causing radiologically confirmed bacteraemic pneumonia, with the primary aims of defining the prevalence of fluoroquinolone resistance and/or mutations among the isolates and calculating and comparing the area under the inhibitory curves (AUICs) of levofloxacin at varying dosages and of moxifloxacin at standard dosages. The prevalence of penicillin resistance using the new Clinical and Laboratory Standards Institute (CLSI) (2008) breakpoints and of macrolide resistance and its mechanisms were also determined. Consecutive adult patients aged ≥18 years, hospitalised with radiologically confirmed bacteraemic pneumococcal communityacquired pneumonia were recruited. Various demographic and clinical data for the patients were recorded. Minimum inhibitory concentrations (MICs) of the isolates to penicillin, erythromycin, clindamycin, trimethoprim/sulfamethoxazole (SXT), ceftriaxone, levofloxacin, moxifloxacin, linezolid, teicoplanin and telithromycin were determined by broth microdilution according to CLSI guidelines and by Etest (AB BIODISK, Solna, Sweden). Isolates were defined as non-susceptible if they were intermediately resistant or fully resistant to the antibiotic. Isolates with levofloxacin MICs ≥ 1 mg/L were screened for quinolone resistance-determining region (QRDR) mutations. DNA was prepared by boiling bacterial cultures and the QRDR regions of parC, parE, gyrA and gyrB were amplified and sequenced [1]. Fluoroquinolone-susceptible pneumococcal strain R6 was used as a reference strain for identification of mutations. The comparative AUIC for 90% of the isolates (AUIC90 ) for different dosages of intravenous (i.v.) and oral levofloxacin versus moxifloxacin were calculated based on pharmacokinetic studies in healthy volunteers [2–6]. Erythromycin non-susceptible isolates (MIC ≥ 0.5 mg/L) were screened for the presence of ermB and/or mefA by a duplex polymerase chain reaction (PCR) [7]. For statistical analyses, continuous variables were analysed by Mann–Whitney U-test (two-tail) and categorical variables by Fisher’s exact test (two-tail). A P-value of <0.05 was considered statistically significant. A total of 175 patients fulfilling the inclusion criteria were analysed. The main differences when comparing public and private sector cases were as follows: the median age was lower in public sector patients [median 32 years, 95% confidence interval (CI) 32.6–36.6 years] compared with private sector patients (median 50 years, 95% CI 46.8–54.7 years) (P < 0.0001); fewer public sector patients had co-morbid illnesses other than human immunodeficiency virus (HIV) infection (P = 0.008); and more of the private sector patients had received prior antibiotic therapy in the past 3 months (P < 0.0001). No levofloxacin-resistant strains were detected in this study and therefore isolates with the highest levofloxacin MIC (1 mg/L; n = 9) were screened for first-
step QRDR mutations. Six isolates were found to have mutations in ParC and/or ParE. Only one isolate had a first-step mutation (Ser 79 → Phe) that has previously been associated with the development of fluoroquinolone resistance. The comparative pharmacokinetic/pharmacodynamic parameters for different doses of i.v. and oral levofloxacin and moxifloxacin are depicted in Table 1. AUIC90 values of 73, 147 and 147 were calculated for i.v. levofloxacin doses of 500 mg once daily, 500 mg twice daily and 750 mg once daily, respectively, whilst for moxifloxacin 400 mg once daily an AUIC90 of 384 was reported. Using the historical breakpoints, 32.6% of isolates tested (57/175) were non-susceptible to penicillin, with the majority of these in the intermediate range (52/175; 29.7%). Using the updated 2008 CLSI pneumonia (non-meningeal) breakpoints, only three isolates were identified as penicillin non-susceptible. There were no differences in the prevalence of penicillin and SXT resistance when comparing isolates from patients in the two sectors. Overall resistance to erythromycin, clindamycin and SXT was 13% (23/175), 9% (16/175) and 37% (65/175), respectively. There was more erythromycin resistance [18/79 (23%) vs. 5/96 (5%); P = 0.0007] and more clindamycin resistance [13/79 (16%) vs. 3/96 (1%); P = 0.0004] in isolates from patients in the private versus the public sector, respectively. None of the isolates were resistant to ceftriaxone, moxifloxacin, linezolid, teicoplanin or telithromycin. All isolates that were macrolide-resistant remained fully susceptible to telithromycin. Twenty-three isolates (13%) were non-susceptible to erythromycin, of which 13 (56.5%) contained ermB, 6 (26.1%) contained mefA, 3 (13.0%) contained both resistance determinants and 1 isolate (4.3%) contained neither ermB nor mefA. In this study of clinically significant isolates of Streptococcus pneumoniae from Gauteng, South Africa, no fluoroquinolone resistance was noted among the isolates and although six isolates were documented to have first-step fluoroquinolone mutations, only one carried a mutation that has previously been linked to subsequent development of fluoroquinolone resistance. Both levofloxacin (in higher dosages of 750 mg daily or 500 mg twice daily) and moxifloxacin (400 mg daily) in currently recognised dosages achieved AUIC90 levels greater than those recommended in the current literature (>125) [6]. Negligible levels of penicillin resistance were documented among the isolates when defined using the new CLSI breakpoint definition for pneumonia.
Acknowledgments The authors thank all laboratory and clinical staff who contributed to this surveillance. They also acknowledge the Group for Enteric, Respiratory and Meningeal Disease Surveillance in South Africa (GERMS-SA) for their efforts in collecting the data and isolates used in this study.
Letters to the Editor / International Journal of Antimicrobial Agents 36 (2010) 90–98
Funding: This study was supported by an unrestricted grant from Sanofi-aventis (Midrand, South Africa). In addition, routine surveillance isolate characterisation was funded by the National Institute for Communicable Diseases, a division of the National Health Laboratory Service; and molecular characterisation was funded for in part by the Medical Research Council, South Africa. The funding sources had no role in the collection, analysis and interpretation of data, in the writing of the manuscript or in the decision to submit the manuscript for publication. Competing interests: CF serves on advisory boards for MSD, Janssen-Cilag and Wyeth/Pfizer and acts as a speaker for Abbott, Sanofi-aventis, Winthrop, GlaxoSmithKline, MSD, Bayer, Cipla and Sandoz; AJB serves on advisory boards for Wyeth, GlaxoSmithKline and Jansen, on a speaker’s bureau for Wyeth and has received a research grant from Sanofi-aventis and MSD; AvG serves on advisory boards for Wyeth/Pfizer, GlaxoSmithKline and Novartis and has received grant funds from Sanofi-aventis and Wyeth/Pfizer; KPK serves on advisory boards for Bayer, Pfizer, Merck and GlaxoSmithKline. All other authors declare no competing interests. Ethical approval: This study was approved by the Human Research Ethics Committee of the University of the Witwatersrand, Johannesburg, South Africa (protocol number 40435). References [1] Von Gottberg A, Klugman KP, Cohen C, Wolter N, de Gouveia L, du Plessis M, et al. Emergence of levofloxacin-non-susceptible Streptococcus pneumoniae and treatment for multidrug-resistant tuberculosis in children in South Africa: a cohort observational surveillance study. Lancet 2008;371:1108–13. [2] Lacy MK, Lu W, Xu X, Tessier PR, Nicolau DP, Quintiliani R, et al. Pharmacodynamic comparisons of levofloxacin, ciprofloxacin and ampicillin against Streptococcus pneumoniae in an in vitro model of infection. Antimicrob Agents Chemother 1999;43:672–7. [3] Chien S-C, Rogge MC, Gisclon LG, Curtin C, Wong F, Natarajan J, et al. Pharmacokinetic profile of levofloxacin following once-daily 500-milligram oral or intravenous doses. Antimicrob Agents Chemother 1997;41:2256–60. [4] Fish DN, Chow AT. The clinical pharmacokinetics of levofloxacin. Clin Pharmacokinet 1997;32:101–19. [5] Chien SC, Wong FA, Fowler CL, Callery-D’Amico SV, Williams RR, Nayak R, et al. Double-blind evaluation of the safety and pharmacokinetics of multiple oral once-daily 750-milligram and 1-gram doses of levofloxacin in health volunteers. Antimicrob Agents Chemother 1998;42:885–8. [6] Schentag JJ, Gilliland KK, Paladino JA. What have we learned from pharmacokinetic and pharmacodynamic theories? Clin Infect Dis 2001;32(Suppl. 1):S39–46. [7] Wolter N, von Gottberg A, du Plessis M, de Gouveia L, Klugman KP; Group for Enteric, Respiratory and Meningeal Surveillance in South Africa. Molecular basis and clonal nature of increasing pneumococcal macrolide resistance in South Africa, 2000–2005. Int J Antimicrob Agents 2008;32:62–7.
C. Feldman ∗ Division of Pulmonology, Department of Internal Medicine, Charlotte Maxeke Johannesburg Academic Hospital and Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa A.J. Brink Ampath National Laboratory Services, Milpark Hospital, Johannesburg, South Africa A. von Gottberg N. Wolter L. de Gouveia Respiratory and Meningeal Pathogens Research Unit, National Institute for Communicable Diseases, Johannesburg, South Africa O. Perovic External Quality Assessment Reference Unit, National Institute for Communicable Diseases, Johannesburg, South Africa K.P. Klugman a,b Respiratory and Meningeal Pathogens Research Unit, National Institute for Communicable Diseases, Johannesburg, South Africa b Hubert Department of Global Health, Rollins School of Public Health, and Division of Infectious Diseases, School of Medicine, Emory University, Atlanta, GA, USA a
97
∗ Corresponding
author. Tel.: +27 11 488 3840; fax: +27 11 488 4675. E-mail address: [email protected] (C. Feldman) 3 December 2009
doi:10.1016/j.ijantimicag.2010.02.021
DNA gyrase and topoisomerase IV are dual targets of zabofloxacin in Streptococcus pneumoniae Sir, Quinolone resistance in Streptococcus pneumoniae is related to mutations in the DNA gyrase and topoisomerase IV genes [1]. The quinolone resistance-determining regions (QRDRs), point mutation spots in discrete regions of the DNA gyrase and topoisomerase IV genes, are responsible for the development of resistance [2]. Zabofloxacin (DW-224a) has been shown to have excellent in vitro activity both against Gram-negative and Gram-positive pathogens, including ciprofloxacin-resistant S. pneumoniae [3–5]. Zabofloxacin has also demonstrated rapid bactericidal activity and a long post-antibiotic effect against S. pneumoniae [6]. In this study, we report a detailed analysis of QRDRs in gyrA, gyrB, parC and parE of S. pneumoniae mutants selected stepwise for resistance to zabofloxacin. Mutants were selected by plating ca. 109 –1010 colony-forming units of S. pneumoniae c9211 or its mutant derivatives on brain–heart infusion plates containing 10% sheep blood and zabofloxacin. Plates were incubated aerobically at 37 ◦ C for 48 h. Mutant frequencies were determined by comparing the number of colonies that grew on plates containing the drug with the number of colonies growing in the absence of the drug. Genomic DNA was used as a template in polymerase chain reaction (PCR) amplification of the QRDRs of the gyrA, gyrB, parC and parE genes. The PCR products were sequenced and analysed. Minimum inhibitory concentrations (MICs) were determined by an agar dilution method with Mueller–Hinton agar supplemented with 5% sheep blood following Clinical and Laboratory Standards Institute guidelines [7]. MICs of zabofloxacin against c9211 and its mutants are presented in Table 1. Streptococcus pneumoniae 1CM1 and 1GM1 were obtained by first-step selection for resistance to ciprofloxacin and gemifloxacin, respectively. For strain 1CM1 bearing the S79F mutation in ParC, the MIC of zabofloxacin was 0.125 mg/L, a four-fold increase over that for c9211 (MIC = 0.03 mg/L). For strain 1GM1 bearing the S81F mutation in GyrA, the MIC of zabofloxacin was 0.5 mg/L, a 16-fold increase over that for the wild-type. These observations indicate that DNA gyrase and topoisomerase IV were each targeted by zabofloxacin and that a mutation in a single enzyme was not able to register a significant increase in resistance. To examine the primary intracellular target, S. pneumoniae c9211 mutants were generated by stepwise challenge using increasing concentrations of zabofloxacin. The frequency of firststep mutants selected at 0.125 mg/L zabofloxacin (4× MIC) was 5.0 × 10−8 –1.0 × 10−8 . Five of the first-step zabofloxacin mutants were chosen for analysis. For each of the first-step mutants 1DWM1 to 1DWM3, there was an eight-fold increase in the MIC of zabofloxacin. Using DNA sequence analysis of the PCR products from the three mutants, the presence of mutations in gyrA leading to the alteration Ser81Phe was observed. Strains 1DWM4 and 1DWM5 increased the MIC of zabofloxacin to 0.125 mg/L, but there was no alteration in GyrA, GyrB, ParC or ParE. For the second-step selection, strain 1DWM3 (zabofloxacin MIC = 0.25 mg/L) was challenged with the drug at 0.5 mg/L (2× MIC), yielding second-step mutants 2DWM1 to 2DWM4. The frequency of the second-step mutants was 6.67 × 10−8 . Strains