José Di Conza

Novel Class 1 Integron (InS21) Carrying blaCTX-M-2 in Salmonella enterica Serovar Infantis

ABSTRACT The genetic organization of the region coding for CTX-M-2 in Salmonella enterica serovar Infantis was determined by PCR mapping. This gene seems to have been mobilized from the Kluyvera ascorbata chromosome to a complex sulI-type integron, similar to In6 and In7.

Biochemical Characterization of PER-2 and Genetic Environment of blaPER-2

ABSTRACT PER-2 was the first detected and the second most prevalent extended-spectrum β-lactamase in clinical pathogens isolated in Argentina and was also reported only in other South American countries. Citrobacter freundii 33587 was isolated in 1999 in Buenos Aires and was resistant to all tested β-lactams except cephamycins and carbapenems. The strain produced both plasmid-borne TEM-1 and PER-2 (pI 5.4), which could be transferred by conjugation. By PCR screening, thermal asymmetric interlaced PCR, and DNA sequencing, we detected an ISPa12/IS1387a insertion sequence upstream of blaPER-2, previously reported as also being associated with blaPER-1. The presence of similar structures upstream of blaPER-1 and blaPER-2 suggests a common origin and mobilization. Compared to blaPER-1 genes, an additional putative promoter for blaPER-2 was found. PER-2 kinetic analysis showed its high hydrolysis efficiencies toward both CTX and CAZ (kcat/Km, 0.76 and 0.43 μM−1·s−1, respectively).

Antibiotic resistance and integrons in Shiga toxin-producing Escherichia coli (STEC)

Shiga toxin-producing Escherichia coli (STEC) cause hemorrhagic colitis (HC) and hemolytic-uremic syndrome in humans (HUS). Cattle are the main reservoir of STEC and transmission to humans occurs through contaminated food and water. Antibiotics are used in pig production systems to combat disease and improve productivity and play a key role in the dissemination of antibiotic resistance genes to the bacteria. Integrons have been identified in resistant bacteria allowing for the acquisition and dissemination of antibiotic resistance genes. STEC strains isolated from humans and animals have developed antibiotic resistance. In our laboratory, 21 non-157 STEC strains isolated from pigs were analyzed to detect class 1 and 2 integrons by PCR. Eight carried integrons, 7 of them harbored intl2. In another study 545 STEC strains were also analyzed for the presence of intl1 and intl2 . Strains carrying intl1 belonged to isolates from environment (n = 1), chicken hamburger (n = 2), dairy calves (n = 4) and pigs (n = 8). Two strains isolated from pigs harbored intl2 and only one intl1 / intl2 , highlighting the presence of intl2 in pigs. The selection for multiresistant strains may contribute to the emergence of antibiotic resistant pathogens and facilitate the spreading of the mobile resistance elements to other bacteria.

Plasmid-mediated colistin resistance in Escherichia coli recovered from healthy poultry

Fil: Dominguez, Johana Elizabeth. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Houssay; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro de Investigacion en Ciencias Veterinarias y Agronomicas. Instituto de Patobiologia; Argentina

Transcriptional Analysis of the blaCTX-M-2 Gene in Salmonella enterica Serovar Infantis

ABSTRACT Transcriptional organization of blaCTX-M-2 present in a multiresistance plasmid of Salmonella enterica serovar Infantis suggests the presence of more than one promoter involved in the expression of the β-lactamase gene. At least two blaCTX-M-2-specific mRNAs (near to 1 kb and 5 kb) were evidenced. Two +1 signals were detected at −22 bp and −59 bp of blaCTX-M-2 defining two putative promoters.

A novel OXA-10–like β-lactamase is present in different Enterobacteriaceae

OXA 101, a novel OXA-10 like enzyme, was found forming part of a class 1 integron located in a conjugative plasmid in three different species of Enterobacteriaceae. This beta-lactamase is related to OXA-35 and OXA-56 and displays a narrow substrate hydrolysis profile.

Molecular characterization of InJR06, a class 1 integron located in a conjugative plasmid of Salmonella enterica ser. Typhimurium

Poster, XXIII General Assembly. European Geophysical Society. Nice, Francia, 20-24 Abril 1998.12 paginas, 3 tablas y 7 figuras.- Contribucion en el VI Seminario de Judia y en el Seminario sobre la eficiencia del sistema simbiotico Phaseolus-Rhizobium celebrado en la Estacion Experimental del Zaidin (CSIC, Granada) los dias 25 y 26 de Octubre de 2016.

Comparación de tres métodos microbiológicos para la detección de betalactamasas de espectro extendido en enterobacterias aisladas en Santa Fe (Argentina)

Introduccion. Las betalactamasas de espectro extendido (BLEE) son la principal causa de resistencia a las oxiiminocefalosporinas y monobactamas en enterobacterias. La mayoria de las BLEE derivan de TEM o SHV, sin embargo se ha incrementado la incidencia de otras familias como CTX-M, OXA y PER. En Argentina, CTX-M-2 es la BLEE mas frecuente en enterobacterias. Esta situacion particular, diferente a la del hemisferio norte, ha motivado el estudio de nuevas estrategias diagnosticas que permitan detectar la mayor parte de las BLEE de nuestra region. Metodos. La deteccion microbiologica de las BLEE se realizo comparando los metodos de sinergia de doble disco, discos de cefotaxima y ceftazidima con y sin el agregado de acido clavulanico (National Committee for Clinical Laboratory Standards, NCCLS) y discos de cefotaxima y ceftazidima en placas de agar Mueller-Hinton suplementado con clavulanato de litio (MH-cla). Las betalactamasas fueron caracterizadas mediante isoelectroenfoque, perfil de hidrolisis y amplificacion por reaccion en cadena de la polimerasa. Resultados. Sobre 575 enterobacterias, el 14% fueron resistentes a oxiiminocefalosporinas. En 31 aislados resistentes se detectaron dos tipos diferentes de BLEE: grupo CTX-M-2 (28) y PER-2 (3). El metodo de sinergia presento menor sensibilidad en la deteccion de BLEE que los otros dos metodos. Con ellos se detecto la presencia de BLEE en todos los aislados empleando discos de cefotaxima, sin embargo no ocurrio lo mismo al emplear discos de ceftazidima. Conclusion. El metodo microbiologico que emplea MH-cla con disco de cefotaxima tuvo una sensibilidad y especificidad equivalentes a la tecnica de confirmacion propuesta por el NCCLS para la deteccion de las BLEE empleando el mismo antibiotico.

β-lactamases produced by amoxicillin-clavulanate-resistant enterobacteria isolated in Buenos Aires, Argentina: A new blaTEM gene

Resistance to β-lactam/β-lactamase inhibitors in enterobacteria is a growing problem that has not been intensively studied in Argentina. In the present work, 54/843 enterobacteria collected in a teaching hospital of Buenos Aires city were ampicillin-sulbactam-resistant isolates remaining susceptible to second- and third-generation cephalosporins. The enzymatic mechanisms present in the isolates, which were also amoxicillin-clavulanic acid (AMC)-resistant (18/54) were herein analyzed. Sequencing revealed two different variants of blaTEM-1, being blaTEM-1b the most frequently detected allelle (10 Escherichia coli, 3 Klebsiella pneumoniae, 2 Proteus mirabilis and 1 Raoultella terrigena) followed by blaTEM-1a (1 K. pneumoniae). Amoxicillin-clavulanate resistance seems to be mainly associated with TEM-1 overproduction (mostly in E. coli) or co-expressed with OXA-2-like and/or SHV β-lactamases (K. pneumoniae and P. mirabilis). A new blaTEM variant (TEM-163) was described in an E. coli strain having an AMC MIC value of 16/8μg/ml. TEM-163 contains Arg275Gln and His289Leu amino acid substitutions. On the basis of the high specific activity and low IC50 for clavulanic acid observed, the resistance pattern seems to be due to overproduction of the new variant of broad spectrum β-lactamase rather than to an inhibitor-resistant TEM (IRT)-like behavior.

INQ-1, a chromosome-encoded AmpC β-lactamase from Inquilinus limosus

Fil: Pino, Marylu. Universidad de Buenos Aires. Facultad de Farmacia y Bioquimica. Departamento de Microbiologia, Inmunologia y Biotecnologia. Catedra de Microbiologia; Argentina