Doi:10.1016/j.ijantimicag.2006.07.010

International Journal of Antimicrobial Agents 28 (2006) 532–536 Activity of tigecycline against clinical isolates of Staphylococcus aureus and extended-spectrum ␤-lactamase-producing Escherichia coli in Granada, Spain A. Sorl´ozano , J. Guti´errez , A. Salmer´on , J.D. Luna , F. Mart´ınez-Checa , J. Rom´an , G. Pi´edrola a Department of Microbiology, University of Granada, Spain b Pharmacy Services, Hospital Universitario San Cecilio, Granada, Spain c Department of Biostatistics, University of Granada, Spain d Microbiology Services, Hospital Universitario San Cecilio, Granada, Spain Received 2 June 2006; accepted 17 July 2006 Abstract
We evaluated the in vitro activity of tigecycline using the Etest and disk diffusion method according to Clinical and Laboratory Standards Institute guidelines against clinical isolates of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus(MRSA) as well as for CTX-M-9 extended-spectrum ␤-lactamase (ESBL)-producing Escherichia coli and SHV ESBL-producing E. coli.
All isolates were susceptible to tigecycline according to US Food and Drug Administration cut-off points. There were no differences in theactivity of tigecycline between MSSA and MRSA isolates or between the presence of either type of ESBL. For each type of microorganismstudied, we established the equation relating the minimum inhibitory concentration to the diameter of the zone of inhibition.
2006 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
Keywords: Tigecycline; Staphylococcus aureus; Escherichia coli; ESBL 1. Introduction
tetracycline- and minocycline-resistant microorganisms anddoes not present cross-resistance with other antibiotics Tigecycline is a semi-synthetic tetracycline (glycylcy- such as ␤-lactams or fluoroquinolones Nevertheless, cline) derived from minocycline It is active against in vitro studies show that it is not active against Pseu- Gram-positive cocci and Gram-negative rods, includ- domonas aeruginosa, Proteus mirabilis or Providencia spp.
ing methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus spp., macrolide- or Tigecycline crosses the external membrane of bacteria penicillin-resistant Streptococcus pneumoniae, extended- through porins via passive diffusion and reaches the cyto- spectrum ␤-lactamase (ESBL)-producing Enterobacteri- plasm by an energy-dependent mechanism. It binds to the aceae and carbapenem-resistant Acinetobacter spp. It is ribosome thereby inhibiting protein synthesis. This effect is also active against anaerobic bacteria (Bacteroides spp., produced by blocking binding of the tRNA aminoacyl site Clostridium perfringens and Peptostreptococcus spp.), intra- to the 30 S ribosomal subunit. The association is reversible, cellular microorganisms and non-tuberculous mycobac- which explains its bacteriostatic effect The absence of teria Furthermore, tigecycline is active against anti-eukaryotic activity means that it has selective antibacte-rial properties.
Several cases of reduced sensitivity to this antibiotic have Corresponding author. Present address: Departamento de Microbiolog´ıa, Facultad de Medicina, Avda. de Madrid 11, E-18012 Granada, Spain.
been reported in Enterobacteriaceae owing to induction of E-mail address: (J. Guti´errez).
0924-8579/$ – see front matter 2006 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
doi: A. Sorl´ozano et al. / International Journal of Antimicrobial Agents 28 (2006) 532–536 Tigecycline is administered parenterally as a 1 h infusion cisco Soria Melguizo S.A., Madrid, Spain) the clinical twice daily and is only available as an injectable formulation.
microbiology laboratory of Hospital ‘San Cecilio’, Granada, It crosses the placental barrier and is generally eliminated in high concentrations in breast milk. It is metabolised in the One hundred and five isolates were identified as S. liver and the main routes of elimination are via the biliary aureus. Resistance to methicillin was confirmed using the Mueller–Hinton agar diffusion procedure (bioM´erieux, To date, the indications approved by the US Food and Drug Marcy l’Etoile, France) with 1 ␮g oxacillin disks, as recom- Administration (FDA) are treatment of complicated skin and mended by the Clinical and Laboratory Standards Institute soft tissue infections and complicated intra-abdominal infec- (CLSI) Fifty-four MSSA and 51 MRSA isolates were In recent years in Spain we have observed a marked The remaining 115 isolates were ESBL-producing E. increase in the number of infections produced by multiresis- coli in which the presence of the enzyme in each isolate tant microorganisms as well as in the morbidity and mortality was confirmed by the diffusion method with disks con- of infections caused by MRSA and ESBL-producing Enter- taining cefotaxime (30 ␮g), cefotaxime/clavulanic acid (30/10 ␮g), ceftazidime (30 ␮g) and ceftazidime/clavulanic In Spain, the increased incidence of MRSA (from acid (30/10 ␮g), as recommended by the CLSI ollow- 1.5% in 1986 to 31.2% in 2002) was accompanied by ing phenotypic confirmation, determination of the existing a marked increase in resistance to other antibiotics such ␤-lactamase and clonality was carried out by means of as macrolides, lincosamides, aminoglycosides or fluoro- biochemical (determination of the isoelectric point) and quinolones Although this is not currently a significant molecular (polymerase chain reaction) studies following problem in Europe, there have been reports of infections the procedures previously described by our group caused by S. aureus with reduced susceptibility to glycopep- Sixty-seven isolates produced the CTX-M-9 enzyme and 48 tides (glycopeptide-intermediate S. aureus (GISA)) This situation is particularly problematic given the lack of avail- Isolates were stored at −40 ◦C until the susceptibility ESBLs are plasmid-borne enzymes produced by Gram- negative rods that confer resistance to all the penicillins, cephalosporins (with the exception of cephamycins) andmonobactams. The plasmids encoding these enzymes can After checking the purity of the isolates, a 0.5 also carry genes for resistance to other antibiotics such as co- McFarland suspension was prepared and inoculated onto trimoxazole, aminoglycosides and tetracyclines and cross- Mueller–Hinton agar plates (bioM´erieux). An agar plate was used for each isolate and the Etest and disk diffusion proce- isms are also resistant to fluoroquinolones more frequently than other non-ESBL-producing isolates Therefore, Tigecycline Etest strips (AB Biodisk, Solna, Sweden) sometimes the only possibility of treatment is using carbapen- were used to determine the minimum inhibitory concentra- ems However, these should be used in moderation as tion (MIC) of tigecycline. To determine the diameter of the they have been associated with an increase in infections by zone of inhibition, the agar diffusion method was used with carbapenem-resistant Acinetobacter baumannii or P. aerug- 15 ␮g tigecycline disks (BBL, Becton Dickinson, Franklin inosa with the result that treatment of these infections The control strains used in all procedures were K. pneu- Tigecycline may therefore be an alternative in the treat- moniae ATCC 700603, E. coli ATCC 25922 and S. aureus ment of skin and soft tissue infections caused by S. aureus and intra-abdominal infections caused by Enterobacteriaceae(especially ESBL-producing Escherichia coli and Klebsiellapneumoniae) in hospitalised patients. This study used dif- 3. Results
ferent methods to describe the activity of tigecycline againstclinical isolates of methicillin-sensitive S. aureus (MSSA), MRSA and ESBL-producing E. coli.
Using the cut-off established by the FDA in 2005 for S. aureus (MIC ≤ 0.5 ␮g/mL), 100% of the S. aureus isolates 2. Material and methods
were susceptible to tigecycline. They were all inhibited by aconcentration of ≤0.19 ␮g/mL and presented a zone of inhi- bition around the disk ≥18 mm. For S. aureus ATCC 29213,the values were 0.125 ␮g/mL and 20 mm, respectively.
We evaluated the in vitro activity of tigecycline against 220 The MIC range and the MIC for 50% and 90% of the clinical isolates identified using the WIDER system (Fran- organisms (MIC50 and MIC90, respectively) obtained by the A. Sorl´ozano et al. / International Journal of Antimicrobial Agents 28 (2006) 532–536 Table 1MIC range and MIC for 50% and 90% of the organisms (MIC50 and MIC90, respectively) obtained by the Etest, and range, mean and S.D. of the diameter ofthe zone of inhibition obtained by the disk diffusion method for Staphylococcus aureus isolates MIC, minimum inhibitory concentration; S.D., standard deviation; MRSA, methicillin-resistant S. aureus; MSSA, methicillin-susceptible S. aureus.
Table 2Percentage of clinical isolates at each minimum inhibitory concentration (MIC) of tigecycline obtained by the Etest ESBL, extended-spectrum ␤-lactamase; MSSA, methicillin-susceptible S. aureus; MRSA, methicillin-resistant S. aureus.
Table 3MIC range and MIC for 50% and 90% of the organisms (MIC50 and MIC90, respectively) obtained by the Etest, and range, mean and S.D. of the diameter ofthe zone of inhibition obtained by the disk diffusion method for isolates of extended-spectrum ␤-lactamase (ESBL)-producing Escherichia coli MIC, minimum inhibitory concentration; S.D., standard deviation.
Etest, and the range, mean and standard deviation (S.D.) were 0.5 ␮g/mL and 23 mm, and for E. coli ATCC 25922 they of the diameter of the zone of inhibition obtained by the were 0.38 ␮g/mL and 22 mm, respectively.
disk diffusion method for the 105 S. aureus isolates are The range, MIC50 and MIC90 obtained by the Etest, and shown in The MIC values obtained by Etest show the range, mean and S.D. of the diameter of the zone of inhibi- the excellent activity of tigecycline against these clinical tion obtained by disk diffusion for the 115 ESBL-producing isolates (range 0.047–0.19 ␮g/mL, MIC50 = 0.094 ␮g/mL, E. coli isolates are shown in The MIC values MIC90 = 0.125 ␮g/mL). These values were observed both inthe MSSA and MRSA isolates.
ws the percentage of S. aureus isolates at each tigecycline MIC determined by the Etest.
Finally, we studied the relationship between the MIC val- ues and the zone of inhibition around the 15 ␮g disks for S.
aureus. The equation relating MIC (y) and the diameter ofthe zone of inhibition (x) was y = 0.4566–0.0162x and thecorrelation coefficient was r = −0.808, which demonstrates asignificant relationship between both variables ( Using the cut-off established by the FDA in 2005 for Enterobacteriaceae (MIC ≤ 2 ␮g/mL), 100% of the ESBL-producing E. coli isolates were susceptible to tigecy-cline. All the isolates were inhibited by a concentration Fig. 1. Scattergram comparing zones of inhibition around 15 ␮g tigecycline ≤0.75 ␮g/mL and presented a zone of inhibition around the disks (x) with the tigecycline minimum inhibitory concentration (MIC) (y) disk ≥19 mm. For K. pneumoniae ATCC 700603, the values determined by the Etest method for all the isolates of Staphylococcus aureus.
A. Sorl´ozano et al. / International Journal of Antimicrobial Agents 28 (2006) 532–536 Table 4Activity of tigecycline against species of Staphylococcus aureus (MRSA and MSSA) and Escherichia coli (ESBL-producing and non-ESBL-producing) indifferent studies Minimum inhibitory concentration (␮g/mL) MRSA, methicillin-resistant S. aureus; MSSA, methicillin-susceptible S. aureus; ESBL, extended-spectrum ␤-lactamase.
obtained by the Etest show the excellent activity of tigecy- studies show that tigecycline is as active as imipenem in the cline against these clinical isolates (range 0.047–0.75 ␮g/mL, treatment of intra-abdominal infections (where it is neces- MIC50 = 0.125 ␮g/mL, MIC90 = 0.38 ␮g/mL). Similar val- sary to cover the presence of Gram-negative pathogens such ues were obtained for isolates producing CTX-M-9 or SHV as Enterobacteriaceae) and as active as the combination of vancomycin and aztreonam in skin and soft tissue infections shows the percentage of isolates of ESBL- (where it is necessary to cover the presence of MRSA and producing E. coli for each tigecycline MIC determined by shows the results of susceptibility to tigecy- The equation relating the MIC value (y) and the diam- cline among S. aureus isolates (MRSA and MSSA) and eter of the zone of inhibition around the 15 ␮g disks (x)was y = 1.8656–0.0674x and the correlation coefficient wasr = −0.845, which, once again, shows a significant relation-ship between both variables ( 4. Discussion
Staphylococcus aureus and ESBL-producing E. coli are two important causes of nosocomial and community-acquired infections. Carbapenems are sometimes the onlytherapeutic alternative against infections caused by ESBL-producing pathogens owing to the resistance associated withother groups of antibiotics Glycopeptides such as van-comycin or teicoplanin are generally the antibiotics of choice Fig. 2. Scattergram comparing zones of inhibition around 15 ␮g tigecycline for the treatment of MRSA infections. The emergence of disks (x) with the tigecycline minimum inhibitory concentration (MIC) (y) GISA that the use of glycopeptides may be lim- determined by the Etest method for all the isolates of extended-spectrum ited and it may be necessary to look for alternatives. Several ␤-lactamase-producing Escherichia coli.
A. Sorl´ozano et al. / International Journal of Antimicrobial Agents 28 (2006) 532–536 ESBL-producing E. coli in different studies [10] Sorl´ozano A, Guti´errez J, Luna J,D, et al. High presence of extended- spectrum ␤-lactamases and resistance to quinolones in clinical isolates 50 and MIC90 values for MRSA isolates range from 0.12 ␮g/mL to 0.25 ␮g/mL and from 0.25 ␮g/mL to of Escherichia coli. Microbiol Res 2006 Mar 23 [Epub ahead of print].
[11] Johnson DM, Biedenbach DJ, Jones RN. Potency and antimicrobial 0.5 ␮g/mL, respectively (compared with 0.094 ␮g/mL and spectrum update for piperacillin/tazobactam (2000): emphasis on its 0.125 ␮g/mL in the present study). For MSSA isolates, activity against resistant organism populations and generally untested the MIC50 and MIC90 values range from 0.12 ␮g/mL to species causing community-acquired respiratory tract infections. Diagn 0.25 ␮g/mL and from 0.125 ␮g/mL to 0.5 ␮g/mL, respec- Microbiol Infect Dis 2002;43:49–60.
tively (compared with 0.094 ␮g/mL and 0.125 ␮g/mL in the [12] Lee SO, Kim NJ, Choi SH, et al. Risk factors for acquisition of imipenem-resistant Acinetobacter baumannii: a case–control study.
present study). For E. coli isolates (ESBL-producing and Antimicrob Agents Chemother 2004;48:224–8.
non-ESBL-producing), the MIC50 and MIC90 values in the [13] Canton R, Perez-Vazquez M, Oliver A, et al. Evaluation of the different studies range from 0.12 ␮g/mL to 1 ␮g/mL and Wider system, a new computer-assisted image-processing device for from 0.25 ␮g/mL to 1 ␮g/mL, respectively (compared with bacterial identification and susceptibility testing. J Clin Microbiol 0.125 ␮g/mL and 0.38 ␮g/mL in the present study). Our [14] Clinical and Laboratory Standards Institute. Performance standards results are therefore similar to those of other studies.
for antimicrobial susceptibility testing. 15th informational supplement.
Given the importance of these microorganisms in intra- abdominal infections and infections of the skin and soft [15] Sorl´ozano A, Guti´errez J, Fern´andez F, Soto MJ, Pi´edrola G. A pre- tissues as well as the initial indications for therapy with liminary study on the presence of extended-spectrum beta-lactamases tigecycline, our results show that tigecycline has excellent (ESBL) in clinical isolates of Escherichia coli in Granada (Spain). AnnMicrobiol 2004;54:227–32.
activity. Furthermore, in our series this activity is maintained [16] Livermore DM. Tigecycline: what is it, and where should it be used? J regardless of the presence of methicillin resistance or type of Antimicrob Chemother 2005;56:611–4.
[17] Biedenbach DJ, Beach ML, Jones RN. In vitro antimicrobial activ- To conclude, tigecycline is a therapeutic alternative ity of GAR-936 tested against antibiotic-resistant gram-positive blood against infections caused by S. aureus (including MRSA iso- stream infection isolates and strains producing extended-spectrum ␤-lactamases. Diagn Microbiol Infect Dis 2001;40:173–7.
lates) and ESBL-producing E. coli.
[18] Betriu C, Rodriguez-Avial I, Sanchez BA, et al. In vitro activities of tige- cycline (GAR-936) against recently isolated clinical bacteria in Spain.
Antimicrob Agents Chemother 2002;46:892–5.
References
[19] Milatovic D, Schmitz FJ, Verhoef J, Fluit AC. Activities of the glycylcycline tigecycline (GAR-936) against 1,924 recent European [1] Petersen PJ, Jacobus NV, Weiss WJ, Sum PE, Testa RT. In vitro clinical bacterial isolates. Antimicrob Agents Chemother 2003;47: and in vivo antibacterial activities of a novel glycylcycline, the 9-t- butylglycylamido derivative of minocycline (GAR-936). Antimicrob [20] Zhang YY, Zhou L, Zhu DM, et al. In vitro activities of tigecycline against clinical isolates from Shanghai, China. Diagn Microbiol Infect [2] Zinner SH. Overview of antibiotic use and resistance: setting the stage for tigecycline. Clin Infect Dis 2005;41:289–92.
[21] Reynolds R, Potz N, Colman M, Williams A, Livermore D, Mac- [3] Noskin GA. Tigecycline: a new glycylcycline for treatment of serious Gowan A. Antimicrobial susceptibility of the pathogens of bacteraemia infections. Clin Infect Dis 2005;41:303–14.
in the UK and Ireland 2001–2002: the BSAC Bacteraemia Resis- [4] Gales AC, Jones RN. Antimicrobial activity and spectrum of the new tance Surveillance Programme. J Antimicrob Chemother 2004;53: glycylcycline, GAR-936 tested against 1,203 recent clinical bacterial isolates. Diagn Microbiol Infect Dis 2000;36:19–36.
[22] Fritsche TR, Kirby JT, Jones RN. In vitro activity of tigecycline [5] Projan SJ. Preclinical pharmacology of GAR-936, a novel glycylcycline (GAR-936) tested against 11,859 recent clinical isolates associated antibacterial agent. Pharmacotherapy 2000;20:219–23.
with community-acquired respiratory tract and gram-positive cuta- [6] Hirata T, Saito A, Nishino K, Tamura N, Yamaguchi A. Effects of efflux neous infections. Diagn Microbiol Infect Dis 2004;49:201–9.
transporter genes on susceptibility of Escherichia coli to tigecycline [23] Fritsche TR, Sader HS, Stilwell MG, Dowzicky MJ, Jones RN. Potency (GAR-936). Antimicrob Agents Chemother 2004;48:2179–84.
and spectrum of tigecycline tested against an international collection [7] Cuevas O, Cercenado E, Vindel A, et al. Evolution of the antimicrobial of bacterial pathogens associated with skin and soft tissue infections resistance of Staphylococcus spp. in Spain: five nationwide prevalence (2000–2004). Diagn Microbiol Infect Dis 2005;52:195–201.
studies, 1986 to 2002. Antimicrob Agents Chemother 2004;48:4240–5.
[24] Sader HS, Jones RN, Dowzicky MJ, Fritsche TR. Antimicrobial activ- [8] Cartolano GL, Cheron M, Benabid D, Leneveu M, Boisivon A.
ity of tigecycline tested against nosocomial bacterial pathogens from Methicillin-resistant Staphylococcus aureus (MRSA) with reduced sus- patients hospitalized in the intensive care unit. Diagn Microbiol Infect ceptibility to glycopeptides (GISA) in 63 French general hospitals. Clin [25] Fritsche TR, Strabala PA, Sader HS, Dowzicky MJ, Jones RN. Activity [9] Bradford PA. Extended-spectrum ␤-lactamases in the 21st century: of tigecycline tested against a global collection of Enterobacteriaceae, characterization, epidemiology, and detection of this important resis- including tetracycline-resistant isolates. Diagn Microbiol Infect Dis tance threat. Clin Microbiol Rev 2001;14:933–51.

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