Antimicrobial resistance in bacterial isolates from companion animals in Buenos Aires, Argentina: 2011-2017 retrospective study.

The widespread use of antimicrobial therapy in companion animals could lead to increased levels of resistance. Monitoring these levels is critical to understand not only the zoonotic threat of resistant bacteria but also the interspecies transmission of resistance mechanisms. However, data on resistance levels in companion animals of urban areas in Latin America are lacking. In this retrospective study, we analysed 23,922 isolates recovered from clinical samples of dogs and cats between 2011 and 2017. Growing trends of resistance to fluoroquinolones were observed in most bacterial species of veterinary importance with zoonotic potential (Enterobacterales, Pseudomonas and Staphylococcus). Furthermore, an increase of resistance levels to third-generation cephalosporins was also detected in Enterobacterales. Currently, Pseudomonas aeruginosa, Enterococcus spp. and Streptococcus spp. did not seem to represent a clinical challenge. A high proportion of multidrug-resistant (MDR) Enterobacterales isolated from urine was reported. It is interesting to outline that resistance to amikacin was exceptional. This study might be considered as a baseline for prospective antimicrobial resistance surveillance in companion animals in our region.

Co-occurrence of clinically relevant ß-lactamases and MCR-1 encoding genes in Escherichia coli from companion animals in Argentina.

Extended-spectrum ß-lactamase (ESBL), plasmid-mediated AmpC (pAmpC) and MCR-1 phosphoethanolamine transferase enzymes have been pointed out as the main plasmid-mediated mechanisms of resistance to third generation cephalosporins (TGC) and colistin, respectively, and are currently considered a major concern both in human and veterinary medicine. Little data on these resistance determinants prevalence in companion animal infections is available. The aim of this study was to determine the resistance profile of Escherichia coli isolated from pet infections, in Argentina, and to characterize the resistance mechanisms to TGC, as well as the presence of the plasmid-borne colistin resistance gene, mcr-1. A total of 54 E. coli isolates were collected from clinical samples in dogs and cats; from them, 20/54 (37%, CI95: [24%; 51%]) displayed resistance to TGC. In this regard, thirteen pAmpC-producing isolates were positive for blaCMY-2 genes, whereas seven ESBL- producers harboured blaCTX-M-2 (n = 4), blaCTX-M-15 (n = 2) and blaCTX-M-14 (n = 1) genes. One E. coli strain (V80), isolated from a canine urinary tract infection, showed resistance to colistin (MIC = 8 µg/ml) and whole-genome sequencing analysis revealed co-occurrence of mcr-1.1, blaCTX-M-2, aadA1, ant(2'')-Ia, catA1 and sul1 genes; the former being carried by a 60,587-bp IncI2 plasmid, previously reported in human colistin-resistant E. coli. E. coli V80 belonged to ST770 and the highly virulent phylogenetic group B2. In general, most of these multidrug-resistant isolates belonged to the phylogenetic group F (11/20) and to a lesser extent B2 (5/20), B1 (2/20), D (1/20) and E (1/20). In summary, CMY- and CTX-M-type ß-lactamases may constitute the main TGC resistance mechanism in E. coli isolated from pet infections in Argentina, whereas dissemination of colistin resistance mechanism MCR-1 in the human-animal interface has been mediated by IncI2 plasmids.

First isolation of a methicillin-resistant Staphylococcus aureus from bovine mastitis in Argentina.

This research communication describes the first isolation of a methicillin-resistant Staphylococcus aureus (MRSA) from cow's mastitic milk in Argentina. Bovine mastitis causes important economic losses in the dairy industry and the most commonly isolated bacteria from bovine mastitis are staphylococci. The mecA gene present in MRSA bacteria confers resistance to almost all ß-lactam antibiotics, the most frequent drugs used in bovine mastitis therapy.

Characterization of Shiga toxin-producing Escherichia coli isolated from ground beef collected in different socioeconomic strata markets in Buenos Aires, Argentina.

Consumption of raw/undercooked ground beef is the most common route of transmission of Shiga toxin-producing E. coli (STEC). The aim of the study was to determine the STEC contamination level of the ground beef samples collected in 36 markets of different socioeconomic strata in Buenos Aires, Argentina, and the characterization of the isolated strains. Ninety-one out of 252 (36.1%) samples were stx+. Fifty-seven STEC strains were recovered. Eleven STEC strains belonged to O157 serogroup, and 46 to non-O157 serogroups. Virulence markers of the 57 STEC were stx1, 5.3% (3/57); stx2, 86.0% (49/57); stx1/stx2, 8.8% (5/57); ehxA, 61.4% (35/57); eae, 26.3% (15/57); saa, 24.6% (14/57). Shiga toxin subtypes were stx2, 31.5% (17/54); stx2c-vhb, 24.1% (13/54); stx2c-vha, 20.4% (11/54); stx2/stx2c-vha, 14.8% (8/54); stx2/stx2c-vhb, 5.6% (3/54); stx2c-vha/vhb, 3.7% (2/54). Serotypes O178:H19 and O157:H7 were prevalent. Contamination rate of STEC in all strata was high, and the highest O157 contamination was observed at low strata at several sampling rounds. Persistence of STEC was not detected. Sixteen strains (28.1%) were resistant to ampicillin, streptomycin, amikacin, or tetracycline. The STEC contamination level of ground beef could vary according to the sociocultural characteristics of the population.

The icaA gene in staphylococci from bovine mastitis.

INTRODUCTION: Staphylococcus aureus and coagulase-negative staphylococci (CNS) are frequently isolated from cows with mastitis. A main virulence factor of CNS is the ability to adhere and form biofilms. The intercellular gene cluster adhesion (ica) operon is one factor involved in biofilm production although ica-independent factors are also involved. Previous reports based on the results of S. epidermidis and S. aureus suggested that ica is highly conserved between species, but this detection decreases in other CNS biofilm producers. In this study we evaluated the presence of the icaA gene in strains of Staphylococcus spp. isolated from the milk of bovines with mastitis. METHODOLOGY: Thirty-seven staphylococci strains were evaluated by detecting the icaA gene. A new set of PCR primers was designed by consensus region of eight staphylococci from GenBank. Species characterization was performed using the Kloos and Schleifer scheme. RESULTS: We identified the presence of the gene in S. aureus (n:4), S. chromogenes (n:4), and S. sciuri strains (n:2). We also, identified the presence of the gene in S. xylosus (n:5) for the first time. The icaA gene was not detected in S. capitis (n:1), S. epidermidis (n:2), S. hominis (n:2), S. saccharolyticus (n:1), S. simulans (n:4) and S. saprophyticus (n:3). The icaA gene was detected in 40.54% (15/37) of the CNS evaluated. CONCLUSIONS: Our results confirm the presence of the ica operon in various species of CNS pointing to polysaccharide intercellular adhesin (PIA) as the most important component for the formation of biofilms.

First isolation in Argentina of a highly virulent Shiga toxin-producing Escherichia coli O145:NM from a domestic cat.

INTRODUCTION: Hemolytic uremic syndrome (HUS) is distributed worldwide. In Argentina, more than 450 cases of HUS, mostly sporadic, are reported annually. The main serotype isolated is O157:H7, and among non-O157 STEC, O145:NM is the most frequent strain. We studied the relationship of companion animals living in contact with a child with sporadic HUS, as carriers of Shiga toxin-producing Escherichia coli (STEC) strains. METHODOLOGY: Duplicate rectal swab samples were taken weekly from the household cat and dog at the home of a patient with HUS. Samples were plated on MacConkey and sorbitol MacConkey-CT agar. Confluent growth from each plate was screened for the presence of stx1, stx2 and rfbO157 gene by PCR assays. Up to 300 individual colonies taken from positive plates at screening were retested by PCR. RESULTS: The strain from the cat belonged to the highly virulent serotype O145:NM. Although this strain differed antigenically from the strain isolated from a child with HUS living in the same house, both carried the stx2, eae and ehxA virulence genes. The strain isolated from the dog belonged to the serotype O178:H19. CONCLUSIONS: An asymptomatic household cat may harbour the high virulent STEC strain, such as O145:NM, the second most frequently STEC serotype associated with HUS in Argentina. Companion animals are probably exposed to the same sources as the humans. More studies are needed to establish dogs and cats as sources of infection in the epidemiological cycle of infections caused by STEC strains, and to develop effective control strategies for this pathogen.