ABSTRACT
Se estudiaron 100 aislados consecutivos y no epidemiológicamente relacionados de Acinetobacter baumannii resistentes a los carbapenems, recuperados entre enero y agosto de 2016 de muestras clínicas en 11 hospitales de 10 provincias de la Argentina, ubicadas en distintas regiones del país. Los genes que codifican las carbapenemasas de Ambler clase D y clase B se investigaron mediante la técnica de PCR utilizando cebadores específicos. Todos los aislados se agruparon mediante las técnicas de 3-locus sequence typing y la secuenciación del gen blaOXA-51-like. El gen blaOXA-23 se recuperó en todos los aislados estudiados. La población de A. baumannii resistente a carbapenems en Argentina estuvo asociada, principalmente, con ST1 (45%), ST25 (34%) y ST79 (15%). ST25 se recuperó en todas las regiones estudiadas y no se detectó CC2.
One hundred sequential, epidemiologically unrelated carbapenem-resistant- Acinetobacter baumannii isolates from 11 hospitals in 10 Argentine provinces were collected between January and August 2016. Genes coding for Ambler class D and B carbapenemases were investigated by PCR using specific primers. All isolates were typed using the 3-locus sequence typing and b/aOXA-51-like sequence-based typing techniques. The blaOXA-23 gene was recovered in all isolates studied. The population of carbapenem-resistant- A. baumannii in Argentina was principally associated with ST1 (45%), ST25 (34%) and ST79 (15%). ST25 was recovered in all the regions studied and CC2 was not detected.
Subject(s)
Humans , Bacterial Proteins/genetics , beta-Lactamases/genetics , Acinetobacter Infections/microbiology , Carbapenems/pharmacology , Cross Infection/microbiology , beta-Lactam Resistance , Acinetobacter baumannii/isolation & purification , Argentina/epidemiology , Acinetobacter Infections/epidemiology , Cross Infection/epidemiology , Acinetobacter baumannii/drug effects , Acinetobacter baumannii/enzymology , Acinetobacter baumannii/geneticsABSTRACT
The increasing use of polymyxins as last-resort drugs for managing infections by Acinetobacter baumannii has led to the emergence of resistance. This study aimed to determine the resistance mechanisms in Acinetobacter baumannii isolates with colistin MIC ≥ 4 mg/L and to relate the mechanisms of resistance with the difficulties in detecting them. Absolute agreement among the different methodologies (Phoenix automatized system, broth and agar dilution, and a rapid colorimetric test) in the 140 colistin-susceptible isolates was observed; whereas in the 25 resistant isolates, the performance varied according to the colistin MIC value. Most of the discrepancies (irrespective of the methodology that was used) were observed in isolates with an MIC value close to the breakpoint. The number of errors in each method in the resistant isolates was as follows: rapid test, four of 25 (16%); agar dilution, eight of 25 (32%); Phoenix system, 13 of 25 (52%) and its manual reading at 24 h, eight of 25 (32%). Categorical errors were detected in 13 isolates: slow growth was the main reason in five isolates, whereas in the remaining eight isolates, slow growth was detected together with a low proportion of colistin-resistant subpopulations and the colistin MIC value was close to the breakpoint value. To understand the probable reason for the observed MIC values, sequencing of genes associated with colistin resistance was performed. Mutations at lpxA, lpxC, and pmrB genes were detected and it was observed that isolates carrying mutations in lpxC presented slow growth at killing curves.
Subject(s)
Acinetobacter baumannii/drug effects , Acinetobacter baumannii/genetics , Anti-Bacterial Agents/pharmacology , Colistin/pharmacology , Drug Resistance, Multiple, Bacterial/genetics , Acinetobacter Infections/drug therapy , Acinetobacter baumannii/isolation & purification , Acyltransferases/genetics , Amidohydrolases/genetics , Humans , Microbial Sensitivity TestsABSTRACT
One hundred sequential, epidemiologically unrelated carbapenem-resistant- Acinetobacter baumannii isolates from 11 hospitals in 10 Argentine provinces were collected between January and August 2016. Genes coding for Ambler class D and B carbapenemases were investigated by PCR using specific primers. All isolates were typed using the 3-locus sequence typing and blaOXA-51-like sequence-based typing techniques. The blaOXA-23 gene was recovered in all isolates studied. The population of carbapenem-resistant- A. baumannii in Argentina was principally associated with ST1 (45%), ST25 (34%) and ST79 (15%). ST25 was recovered in all the regions studied and CC2 was not detected.
Subject(s)
Acinetobacter Infections/microbiology , Acinetobacter baumannii/isolation & purification , Bacterial Proteins/genetics , Carbapenems/pharmacology , Cross Infection/microbiology , beta-Lactam Resistance , beta-Lactamases/genetics , Acinetobacter Infections/epidemiology , Acinetobacter baumannii/drug effects , Acinetobacter baumannii/enzymology , Acinetobacter baumannii/genetics , Argentina/epidemiology , Cross Infection/epidemiology , HumansABSTRACT
One hundred and twenty-six epidemiologically sequential, unrelated, carbapenem-resistant Acinetobacter baumannii isolates from nine hospitals in six countries of South America were collected between July 2013 and June 2014. Genes coding for Ambler class D and B carbapenemases were sought by PCR. All isolates were typed using the 3-locus sequence typing and blaOXA-51-like sequence-based typing techniques. The blaOXA-23 gene was recovered in all the participating hospitals and in all the isolates of seven of nine medical centres. The blaOXA-72 gene was only recovered in the two medical centres from Guayaquil city, Ecuador. Trilocus sequence typing revealed the presence of sequence groups SG2, SG4 and SG5. blaOXA-51-like sequence-based typing revealed the presence of blaOXA-132, blaOXA-65, blaOXA-69 and blaOXA-64. Our results showed that the population of carbapenem-resistant A. baumannii in South America was principally associated with ST79, ST25 and ST15 (92 %) and harboured the blaOXA-23 gene mainly. CC2 was not detected.