Tigecycline antimicrobial activity tested against clinical bacteria from Latin American medical centres: results from SENTRY Antimicrobial Surveillance Program (2011–2014)

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Highlights

  • 13,494 bacterial organisms were consecutively collected in 2011–2014 from 21 medical centres.

  • Bacterial isolates were tested by reference broth microdilution methods at a central laboratory.

  • Tigecycline was very active against Gram-positive organisms, with MIC50/90 values of ≤0.03–0.06/≤0.03–0.12 µg/mL.

  • Among Enterobacteriaceae strains (n = 4543), tigecycline MIC50/90 values were 0.25/1 µg/mL.

  • Tigecycline remains active against clinically relevant species isolated from Latin American hospitals.

Abstract

Bacterial organisms (n = 13,494) were consecutively collected in 2011–2014 from 21 Latin American medical centres (11 nations). Antimicrobial susceptibility was determined by broth microdilution at a central laboratory. Tigecycline was very active against Gram-positive organisms, with MIC50/90 values of 0.06/0.06 µg/mL for Staphylococcus aureus (n = 2878), 0.06/0.12 µg/mL for coagulase-negative staphylococci (n = 880), 0.06/0.06 µg/mL for enterococci (n = 708) and ≤0.03/≤0.03–0.06 µg/mL for streptococci (n = 1352). All Gram-positive species exhibited 100.0% susceptibility (FDA and/or EUCAST criteria), except for Streptococcus pneumoniae (99.8% susceptible). The S. aureus oxacillin resistance rate varied from 28.0% (Brazil) to 55.0% (Argentina), and the overall vancomycin resistance rate was 15.5% (Enterococcus faecium, 50.3%; and Enterococcus faecalis, 2.3%). The E. faecium vancomycin resistance rate varied from a low (26.3%) in Argentina to a high (71.7%) in Brazil. Against Enterobacteriaceae (n = 4543), tigecycline MIC50/90 values were 0.25/1 µg/mL; 98.3% and 94.2% of strains were considered susceptible according to FDA and EUCAST breakpoints, respectively. Overall, 37.7% and 57.3% of Escherichia coli and Klebsiella pneumoniae exhibited the CLSI ESBL screening phenotype. The highest CLSI ESBL screening phenotype rates among E. coli and Klebsiella spp. strains were observed for isolates collected from Mexico (69.9%) and Chile (69.9%), respectively. Occurrence of carbapenem-resistant Enterobacteriaceae was substantially higher in Brazil (9.0%) and Argentina (6.3%) compared with Chile and Mexico (0.4–0.7%). Tigecycline was also active against Acinetobacter spp. (MIC50/90, 1/2 µg/mL; 92.3/72.1% inhibited at ≤2/≤1 µg/mL) and Stenotrophomonas maltophilia (MIC50/90, 0.5/2 µg/mL; 91.5/83.0% inhibited at ≤2/≤1 µg/mL).

Introduction

Tigecycline was the first of a class of antimicrobials named glycylcyclines and has been active in vitro against a variety of Gram-positive and Gram-negative organisms, including meticillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), Enterobacteriaceae strains that produce extended-spectrum β-lactamases (ESBLs) and carbapenemases, such as Klebsiella pneumoniae carbapenemases (KPC) and metallo-β-lactamases, and multidrug-resistant (MDR) Acinetobacter spp. [1]. Tigecycline was initially approved by the US Food and Drug Administration (FDA) in 2005 for the treatment of adults with complicated skin and skin-structure infections and complicated intra-abdominal infections [2]. In 2009, tigecycline also received FDA approval for the treatment of community-acquired bacterial pneumonia [1], [2]. This minocycline derivative has provided clinicians with an alternative treatment option for infections caused by these ‘difficult-to-treat’ pathogens [3], [4], [5], [6], [7].

A limited number of Latin American countries possess a nationwide surveillance programme for monitoring antimicrobial resistance [8], [9]. Data from monitoring surveillance programmes, such as the SENTRY Antimicrobial Surveillance Program, have provided information on the continuing activity of most clinically relevant antimicrobial agents against a wide spectrum of clinically important Gram-positive and Gram-negative pathogens from Latin America [10], [11], [12]. The objective of this investigation was to evaluate the in vitro activity of tigecycline tested against contemporary clinical isolates causing bacterial infections in Latin American medical centres. The prevalence of the most clinically important resistance phenotypes in the main Latin American countries was also evaluated.

Section snippets

Bacterial strains

A total of 13,494 bacterial organisms, including 5818 (43.1%) Gram-positive cocci and 7676 (56.9%) Gram-negative bacilli, were collected between January 2011 and December 2014 from 21 Latin American medical centres located in 11 nations as part of the SENTRY Antimicrobial Surveillance Program. The number of isolates from each species/organism group collected from each country is listed in Table 1. Of note, Argentina, Brazil, Chile and Mexico contributed 78.9% of the isolates. The organisms were

Results

The in vitro activity of tigecycline tested against clinical bacteria collected from Latin American countries during the 4-year period (2011–2014) of this investigation is summarised in the format of MIC distributions (Table 2). Tigecycline was active against Gram-positive organisms, with MIC50/90 values of 0.06/0.06 µg/mL for S. aureus (2878 strains), 0.06/0.12 µg/mL for coagulase-negative staphylococci (CoNS) (880 strains), 0.06/0.06 µg/mL for enterococci (including 477 E. faecalis, 197

Discussion

The results of this investigation provide valuable information on the activity of tigecycline and various comparator agents tested against a large longitudinal collection (2011–2014) of bacterial isolates collected from Latin American medical centres, including MDR organisms that are prevalent in the region such as MRSA, VRE, ESBL-producing strains and CRE [8], [10], [11], [12], [17], [18]. However, the limitations of the study should be considered when interpreting the data, with the small

Acknowledgements

The authors would like to thank all the participants of the SENTRY Antimicrobial Surveillance Program for providing bacterial isolates.

Funding: JMI Laboratories, Inc. (North Liberty, IA) received funding for this study from Pfizer Inc. in connection with the development of this manuscript. This study was supported by Pfizer Inc. via the SENTRY Program platform.

Competing interests: JMI Laboratories, Inc. has also received research and educational grants in 2014–2015 from Achaogen, Actavis,

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