Antimicrobial Susceptibility Studies
Antimicrobial resistance among Gram-negative bacilli isolated from Latin America: results from SENTRY Antimicrobial Surveillance Program (Latin America, 2008–2010)

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Abstract

This study updates the frequency and resistance rates of Gram-negative bacilli isolated from Latin American medical centers enrolled in the SENTRY Antimicrobial Surveillance Program. A total of 12,811 bacterial organisms, including 5704 Gram-negative bacilli (44.5%), were consecutively collected (1 per patient) between January 2008 and December 2010 from 10 Latin American medical centers located in Argentina, Brazil, Chile, and Mexico. Antimicrobial susceptibility testing was performed and interpreted by the Clinical and Laboratory Standards Institute broth microdilution method at a central laboratory. All Gram-negative organisms with reduced susceptibility to imipenem or meropenem (MIC, ≥ 2 μg/mL) were screened for carbapenemase production by the modified Hodge test and by polymerase chain reaction. ESBL rates were 18.1%, 12.8%, 23.8%, and 48.4% among Escherichia coli and 60.4%, 49.9%, 59.2%, and 33.3% among Klebsiella spp. from Argentina, Brazil, Chile, and Mexico, respectively. Meropenem-nonsusceptible Klebsiella spp. rate was highest in Brazil (11.1%), followed by Argentina (8.2%), Chile (5.0%), and Mexico (0.8%). Klebsiella pneumoniae carbapenemase (KPC)–producing K. pneumoniae was not detected in 2008, but emerged in 2009 (10 strains) and increased significantly in 2010 (44; P < 0.0001). blaKPC-2 was detected in 54 (65.9%) of 85 carbapenem-nonsusceptible K. pneumoniae. Meropenem-nonsusceptible P. aeruginosa was observed in 53.8%, 46.7%, 33.3%, and 28.8% of strains from Argentina, Brazil, Chile, and Mexico, respectively. Imipenem-resistant Acinetobacter spp. rates increased from 6.4%, 12.6%, and 0.0% in the 1997–1999 period to 84.9%, 71.4%, and 50.0% in 2008–2010 in Argentina, Brazil, and Chile, respectively. Oxacillinase (OXA)-producing Acinetobacter spp. was documented in Argentina (OXA-23 and -24), Brazil (OXA-23), Chile (OXA-58), and Mexico (OXA-24). Only colistin showed > 77% overall coverage against the 5 most frequently isolated Gram-negative bacilli from Latin American Medical centers participating in the SENTRY Program.

Introduction

Infections caused by multidrug-resistant isolates are associated with increased costs, length of hospitalization, and, especially, morbidity and mortality rates (Evans et al., 2007). Resistance among Gram-negative organisms is of great concern, since few antimicrobial agents are effective to treat infections caused by these pathogens and a limited number of antimicrobial agents are in late stage of development. Surveillance studies are undertaken to help direct antimicrobial use, particularly empiric therapy, based on the local resistance patterns of organisms, and implementation of infection control measures (Jones, 1996). From a public health perspective, surveillance data can be employed to identify points for intervention to control bacterial resistance and, subsequently, to assess the effectiveness of these interventions (Jones, 1996).

A limited number of Latin American countries possess a nationwide surveillance programs for monitoring antimicrobial resistance like Argentina, Chile, and Colombia (Briceno et al., 2010, Garcia, 2003, Rossi et al., 1999). Unfortunately, other countries like Brazil and Mexico do not have a national program for monitoring antimicrobial resistance in the hospital setting yet, making it even more difficult to estimate the real prevalence and burden of disease caused by antimicrobial resistant bacteria (Okeke et al., 2005). The SENTRY Antimicrobial Surveillance Program has been monitoring the predominant pathogens and antimicrobial resistance patterns of nosocomial- and community-acquired infections via a broad network of sentinel hospitals since 1997 (Pfaller et al., 1998). The monitored infections include bloodstream infections (20 consecutive isolates per month), pneumonia (100 consecutive isolates collected in a 6-month period each year), and skin and soft tissue infections including surgical wound infections (100 consecutive isolates collected in a 6-month period each year).

More recently, with broader dissemination of Klebsiella pneumoniae carbapenemase (KPC)–producing Enterobacteriaceae and oxacillinase (OXA)-carbapenemase–producing Acinetobacter spp. isolates, a rapid decrease in the susceptibility to carbapenems has been noticed in many parts of the world, including Latin America. The objective of this study was to update the frequency and resistance rates of Gram-negative pathogens isolated from Latin American sites enrolled in the SENTRY Program between 2008 and 2010 and summarize molecular characterization data for subsets of carbapenemase-producing strains.

Section snippets

Bacterial strains

A total of 12,811 bacterial isolates, including 5704 (44.5%) Gram-negative bacilli, from hospitalized patients with serious community-acquired or nosocomial-acquired infections were recovered between January 2008 and December 2010 and submitted to the SENTRY Program. The organisms were consecutively collected from various infection sites and only 1 isolate per patient was included in the study. The medical centers were guided by common protocols. All isolates were identified in the participant

Results

A total of 5704 (44.5%) of 12,811 bacterial isolates collected from Latin American medical centers were identified as Gram-negative bacilli. They were collected from Argentina (19.6%), Brazil (40.9%), Chile (18.4%), and Mexico (18.4%). Most of these isolates were collected from patients diagnosed with bloodstream infections (BSI; 52.6%); skin and soft tissue infections, including surgical wound infections (SSTI; 22.9%); and pneumonia (13.1%). The most common causes of BSI were Staphylococcus

Discussion

In this study, we have confirmed that Gram-negative bacilli account for a significantly higher proportion of etiologic agents of infections in Latin America compared to the USA and Canada. An even more striking difference is the very high percentage of infections caused by P. aeruginosa and Acinetobacter spp. compared to North American medical centers (Pfaller et al., 1998). This difference could be explained by the geographic location of Latin America since most of it lies in the tropical zone

Acknowledgments

The authors would like to thank the following investigators for kindly contributing strains to the study: José M. Casellas (Sanatorio Parque y Niño, Rosario, Santa Fe, Argentina); Jorgelina Smayevsky (Laboratorio CEMIC, Buenos Aires, Argentina); Ana C. Gales (Federal University of São Paulo, São Paulo, Brazil); Cássia Zoccoli (Laboratório Médico Santa Luzia, Florianópolis, Brazil); Afonso Barth (Hospital de Clínicas, Porto Alegre, Brazil); Julival Ribeiro (Hospital de Base, Brasília, Brazil);

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