Characterization of carbapenem-resistant Acinetobacter baumannii in Brazil (2008-2011): countrywide spread of OXA-23-producing clones (CC15 and CC79).

The study investigated the genetic relationship of carbapenem-resistant Acinetobacter baumannii clinical isolated from inpatients during 2008-2011 from 11 Brazilian states. Antimicrobial susceptibility profile was determined by disc diffusion method and Etest. Polymerase chain reaction was applied for carbapenemase genes, and ISAba1. Isolates were subjected to pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) for molecular typing. Most of the isolates showed high resistance rates to antibiotics tested. The blaOXA-51-like gene was found in all isolates, and 146 (94.2%) isolates were positive for blaOXA-23-like. In the most OXA-23-producing isolates, the blaOXA-23-like gene was accompanied by ISAba1. A total of 146 OXA-23-producing isolates were clustered into 28 genotypes by PFGE. Molecular analysis by MLST identified 13 sequence types (STs). The most prevalent PFGE profiles were designated as ST15 (CC15), ST1 (CC1), and ST79 (CC79). This study showed the widespread of clonal complexes of A. baumannii harboring the blaOXA-23-like gene in different Brazilian states.

Occurrence of blaOXA-23 gene in imipenem-susceptible Acinetobacter baumannii.

The aim of the current study was to describe the occurrence of the blaOXA-23 gene and the ISAba1 element in imipenem-susceptible Acinetobacter baumannii strains. By performing the polymerase chain reaction mapping using combinations of ISAba1 forward primers and the blaOXA-23-like gene reverse primers, we demonstrated that the ISAba1 element did not occur upstream of the blaOXA-23 gene in five of 31 isolates, which explained the lack of resistance to imipenem despite the presence of the blaOXA-23 gene. All of the blaOXA-23-positive isolates were susceptible to imipenem and meropenem with minimal inhibitory concentration ≤ 4 µg/mL. Pulsed-field gel electrophoresis analysis revealed four genotypes among the five blaOXA-23-positive isolates. The current report of the blaOXA-23 gene in imipenem-susceptible isolates provided evidence that this gene may be silently spread in a hospital environment and highlighted the threat of undetected reservoirs of carbapenemase genes.

Metallo-ß-lactamase and genetic diversity of Pseudomonas aeruginosa in intensive care units in Campo Grande, MS, Brazil.

Infection by Pseudomonas aeruginosa has spread worldwide, with limited options for treatment. The purpose of this study was to investigate metallo-ß-lactamase-producing P. aeruginosa strains and compare their genetic profile using samples collected from patients in intensive care units. Forty P. aeruginosa strains were isolated from two public hospitals in Campo Grande, Mato Grosso do Sul State, from January 1st, 2007 to June 31st, 2008. Profiles of antimicrobial susceptibility were determined using the agar diffusion method. Metallo-ß-lactamase was investigated using the double-disk diffusion test and PCR. Molecular typing was performed by pulsed-field gel electrophoresis (PFGE). Respiratory and urinary tracts were the most common isolation sites. Of the 40 samples tested, 72.5% (29/40) were resistant to ceftazidime and 92.5% (37/40) to imipenem, whereas 65% (26/40) were resistant to both antimicrobials. Fifteen pan-resistant samples were found. Five percent (2/40) of samples were positive for metallo-ß-lactamase on the phenotype test. No metallo-ß-lactamase subtype was detected by PCR. Macrorestriction analysis revealed 14 distinct genetic patterns. Based on the superior accuracy of PCR, it can be inferred that P. aeruginosa isolates from the investigated hospitals have alternative mechanisms of carbapenem resistance. The results also suggest clonal spread of P. aeruginosa between the studied hospitals.

Occurrence of blaOXA-23 gene in imipenem-susceptible Acinetobacter baumannii

The aim of the current study was to describe the occurrence of the blaOXA-23 gene and the ISAba1 element in imipenem-susceptible Acinetobacter baumannii strains. By performing the polymerase chain reaction mapping using combinations of ISAba1 forward primers and the blaOXA-23-like gene reverse primers, we demonstrated that the ISAba1 element did not occur upstream of the blaOXA-23 gene in five of 31 isolates, which explained the lack of resistance to imipenem despite the presence of the blaOXA-23 gene. All of the blaOXA-23-positive isolates were susceptible to imipenem and meropenem with minimal inhibitory concentration < 4 µg/mL. Pulsed-field gel electrophoresis analysis revealed four genotypes among the five blaOXA-23-positive isolates. The current report of the blaOXA-23 gene in imipenem-susceptible isolates provided evidence that this gene may be silently spread in a hospital environment and highlighted the threat of undetected reservoirs of carbapenemase genes.

Metallo-β-lactamase and genetic diversity of Pseudomonas aeruginosa in intensive care units in Campo Grande, MS, Brazil

Infection by Pseudomonas aeruginosa has spread worldwide, with limited options for treatment. The purpose of this study was to investigate metallo-β-lactamase-producing P. aeruginosa strains and compare their genetic profile using samples collected from patients in intensive care units. Forty P. aeruginosa strains were isolated from two public hospitals in Campo Grande, Mato Grosso do Sul State, from January 1st, 2007 to June 31st, 2008. Profiles of antimicrobial susceptibility were determined using the agar diffusion method. Metallo-β-lactamase was investigated using the double-disk diffusion test and PCR. Molecular typing was performed by pulsed-field gel electrophoresis (PFGE). Respiratory and urinary tracts were the most common isolation sites. Of the 40 samples tested, 72.5 percent (29/40) were resistant to ceftazidime and 92.5 percent (37/40) to imipenem, whereas 65 percent (26/40) were resistant to both antimicrobials. Fifteen pan-resistant samples were found. Five percent (2/40) of samples were positive for metallo-β-lactamase on the phenotype test. No metallo-β-lactamase subtype was detected by PCR. Macrorestriction analysis revealed 14 distinct genetic patterns. Based on the superior accuracy of PCR, it can be inferred that P. aeruginosa isolates from the investigated hospitals have alternative mechanisms of carbapenem resistance. The results also suggest clonal spread of P. aeruginosa between the studied hospitals.

OXA-23-producing Acinetobacter baumannii: a new hotspot of diversity in Rio de Janeiro?

OBJECTIVES: this study focused on the population structure of OXA-23-producing Acinetobacter baumannii clinical isolates from Rio de Janeiro, Brazil. METHODS: the analysis included several genomic typing methods, including PFGE, two multilocus sequence typing (MLST) schemes, sequence group (SG) determination and bla(OXA-51-like) sequencing. The genomic context of the bla(OXA-23) gene was also evaluated using I-CeuI hybridizations and PCR assays. RESULTS: congruent clustering was obtained revealing four lineages. In accordance, four new sequence types (STs) (ST131, ST132, ST133 and ST134) were obtained with the MLST-OD scheme (associated with the Oxford Database) and four (ST79, ST15 and two new allelic profiles) with the MLST-IP scheme (developed by the Institute Pasteur). Four SGs (SG1, SG4 and two new profiles) were identified, allowing the association of 70% of the isolates with European clone II. bla(OXA-51-like) sequencing revealed the presence of bla(OXA-66), bla(OXA-69), bla(OXA-95) and bla(OXA-132). CONCLUSIONS: identification of new STs together with new SG profiles are findings suggestive of a local diversity hotspot that is worth exploring.

Dissemination of multidrug-resistant Acinetobacter baumannii genotypes carrying bla(OXA-23) collected from hospitals in Rio de Janeiro, Brazil.

The present study reports the dissemination of multidrug-resistant (MDR) OXA-23-producing Acinetobacter baumannii clones throughout hospitals in Rio de Janeiro, Brazil. A total of 110 imipenem-resistant A. baumannii isolates were obtained from January 2006 to September 2007 in eight hospitals. The modified Hodge test was performed to screen for carbapenemase production. Polymerase chain reaction (PCR) and DNA sequencing were performed for the detection of bla(IMP), bla(VIM), bla(OXA-23-like), bla(OXA-24-like), bla(OXA-58) and the class 1 integron. Isolates were typed by pulsed-field gel electrophoresis (PFGE) following digestion with ApaI. All the isolates were MDR and 96 (87.3%) produced the carbapenemase OXA-23. No isolates produced OXA-24, OXA-58 or the metallo-beta-lactamases IMP and VIM. The class 1 integron was absent in all isolates. The A. baumannii isolates were separated into five genotypes, with the highest prevalence of genotype A (71.8%) followed by genotype B (22.7%). Genotype A was present in seven hospitals, whilst genotype B had spread in five hospitals. The OXA-23-producing isolates belonged to all genotypes. The presence of MDR OXA-23-producing A. baumannii in different hospitals in Rio de Janeiro emphasises the need to control the use of carbapenems and to prevent the spread of these organisms in Rio de Janeiro.