Outbreak of Pseudomonas aeruginosa High-Risk Clone ST309 Serotype O11 Featuring blaPER-1 and qnrVC6.

Pseudomonas aeruginosa is a leading cause of hospital-acquired infections worldwide. Biofilm production, antibiotic resistance, and a wide range of virulence factors contribute to their persistence in nosocomial environments. We describe an outbreak caused by a multidrug-resistant P. aeruginosa strain in an ICU. Antibiotic susceptibility was determined and blaPER-1 and qnrVC were amplified via PCR. Clonality was determined using PFGE and biofilm formation was studied with a static model. A combination of antibiotics was assessed on both planktonic cells and biofilms. WGS was performed on five isolates. All isolates were clonally related, resistant to ceftazidime, cefepime, amikacin, and ceftolozane-tazobactam, and harbored blaPER-1; 11/19 possessed qnrVC. Meropenem and ciprofloxacin reduced the biofilm biomass; however, the response to antibiotic combinations with rifampicin was different between planktonic cells and biofilms. WGS revealed that the isolates belonged to ST309 and serotype O11. blaPER-1 and qnrVC6 were associated with a tandem of ISCR1 as part of a complex class one integron, with aac(6')-Il and ltrA as gene cassettes. The structure was associated upstream and downstream with Tn4662 and flanked by direct repeats, suggesting its horizontal mobilization capability as a composite transposon. ST309 is considered an emerging high-risk clone that should be monitored in the Americas.

Novel Resistance Regions Carrying TnaphA6, blaVIM-2, and blaPER-1, Embedded in an ISPa40-Derived Transposon from Two Multi-Resistant Pseudomonas aeruginosa Clinical Isolates.

Antibiotic resistance is an alarming problem throughout the world and carbapenem-resistant Pseudomonas aeruginosa has been cataloged as critical in the World Health Organization list of microorganisms in urgent need for the development of new antimicrobials. In this work, we describe two novel resistance regions responsible for conferring a multidrug resistance phenotype to two clinical isolates of P. aeruginosa (Pa873 and Pa6415) obtained from patients hospitalized in the ICU of University Hospital of Uruguay. Bacterial identification and antibiotic susceptibility tests were performed using MALDI-TOF and the Vitek 2 system, respectively. WGS was performed for both isolates using Oxford Nanopore Technologies and Illumina and processed by means of hybrid assembly. Both isolates were resistant to ceftazidime, cefepime, piperacillin-tazobactam, aztreonam, and imipenem. Strain Pa6415 also showed resistance to ciprofloxacin. Both strains displayed MICs below the susceptibility breakpoint for CAZ-AVI plus 4 mg/L of aztreonam as well as cefiderocol. Both resistance regions are flanked by the left and right inverted repeats of ISPa40 in two small regions spanning 39.3 and 35.6 kb, for Pa6415 and Pa873, respectively. The resistance region of Pa6415 includes TnaphA6, and the new Tn7516 consists of IRi, In899, qacEΔ1-sul1-ISCR1, qnrVC6-ISCR1-blaPER-1-qacEΔ1-sul1, araJ-like, IS481-like tnpA, ISPa17, and IRR. On the other hand, the resistance region of Pa873 includes Tnaph6 and the new Tn7517 (IRi, In899, qacEΔ1-sul1, ISCR1-blaPER-1-qacEΔ1-sul1, araJ-like, IS481-like tnpA, ISPa17, and IRR). It is necessary to monitor the emergence of genetic structures that threaten to invalidate the available therapeutic resources.

Imported One-Day-Old Chicks as Trojan Horses for Multidrug-Resistant Priority Pathogens Harboring mcr-9, rmtG, and Extended-Spectrum ß-Lactamase Genes.

Antimicrobial resistance is a critical issue that is no longer restricted to hospital settings but also represents a growing problem involving intensive animal production systems. In this study, we performed a microbiological and molecular investigation of priority pathogens carrying transferable resistance genes to critical antimicrobials in 1-day-old chickens imported from Brazil to Uruguay. Bacterial identification was performed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, and antibiotic susceptibility was determined by Sensititre. Antimicrobial resistance genes were sought by PCR, and clonality was assessed by pulsed-field gel electrophoresis (PFGE). Four multidrug-resistant (MDR) representative strains were sequenced by an Illumina and/or Oxford Nanopore Technologies device. Twenty-eight MDR isolates were identified as Escherichia coli (n = 14), Enterobacter cloacae (n = 11), or Klebsiella pneumoniae (n = 3). While resistance to oxyiminocephalosporins was due to blaCTX-M-2, blaCTX-M-8, blaCTX-M-15, blaCTX-M-55, and blaCMY-2, plasmid-mediated quinolone resistance was associated with the qnrB19, qnrE1, and qnrB2 genes. Finally, resistance to aminoglycosides and fosfomycin was due to the presence of 16S rRNA methyltransferase rmtG and fosA-type genes, respectively. Short- and long-read genome sequencing of E. cloacae strain ODC_Eclo3 revealed the presence of IncQ/rmtG (pUR-EC3.1; 7,400 bp), IncHI2A/mcr-9.1/blaCTX-M-2 (pUR-EC3.2, ST16 [pMLST; 408,436 bp), and IncN2/qnrB19/aacC3/aph(3″)-Ib (pUR-EC3.3) resistance plasmids. Strikingly, the blaCTX-M-2 gene was carried by a novel Tn1696-like composite transposon designated Tn7337. In summary, we report that imported 1-day-old chicks can act as Trojan horses for the hidden spread of WHO critical-priority MDR pathogens harboring mcr-9, rmtG, and extended-spectrum ß-lactamase genes in poultry farms, which is a critical issue from a One Health perspective. IMPORTANCE Antimicrobial resistance is considered a significant problem for global health, including within the concept of One Health; therefore, the food chain connects human health and animal health directly. In this work, we searched for microorganisms resistant to antibiotics considered critical for human health in intestinal microbiota of 1-day-old baby chicks imported to Uruguay from Brazil. We describe genes for resistance to antibiotics whose use the WHO has indicated to "watch" or "reserve" (AWaRe classification), such as rmtG and mcr9.1, which confer resistance to all the aminoglycosides and colistin, respectively, among other genes, and their presence in new mobile genetic elements that favor its dissemination. The sustained entry of these microorganisms evades the sanitary measures implemented by the countries and production establishments to reduce the selection of resistant microorganisms. These silently imported resistant microorganisms could explain a considerable part of the antimicrobial resistance problems found in the production stages of the system.

Transferable Resistance to Highest Priority Critically Important Antibiotics for Human Health in Escherichia coli Strains Obtained From Livestock Feces in Uruguay.

The aim of this work was to detect Escherichia coli isolates displaying resistance to oxyimino-cephalosporins, quinolones, and colistin in feces from livestock in Uruguay. During 2016-2019, fecal samples from 132 broiler and layer chicken flocks, 100 calves, and 50 pigs, were studied in Uruguay. Samples were cultured on MacConkey Agar plates supplemented with ciprofloxacin, ceftriaxone, or colistin. E. coli isolates were identified by mass spectrometry and antibiotic susceptibility testing was performed by disk diffusion agar method and colistin agar test. Antibiotic resistance genes were detected by polymerase chain reaction and sequencing. The most frequently detected resistance gene was qnrB19, recovered from 87 animals. Regarding plasmid-mediated quinolone resistance genes, qnrS1 was the second in prevalence (23 animals) followed by qnrE1, found in 6 chickens and two calves. Regarding resistance to oxyimino-cephalosporins, 8 different ß-lactamase genes were detected: bla CTX-M-8 and bla CMY-2 were found in 23 and 19 animals, respectively; next, bla CTX-M-2 and bla SHV-12 in 7 animals each, followed by bla CTX-M-14 in 5, bla CTX-M-15 and bla SHV2a in 2, and bla CTX-M-55 in a single animal. Finally, the mcr-1 gene was detected only in 8 pigs from a single farm, and in a chicken. Isolates carrying bla CMY-2 and bla SHV-12 were also found in these animals, including two isolates featuring the bla CMY-2/mcr-1 genotype. To the best of our knowledge, this is the first work in which the search for transferable resistance to highest priority critically important antibiotics for human health is carried out in chickens and pigs chains of production animals in Uruguay.

First three Escherichia coli isolates harbouring mcr-1 in Uruguay.

OBJECTIVE: This report described the first Escherichia coli (E. coli) isolates harbouring mcr-1 in Uruguay. METHODS: Three E. coli isolates were obtained from blood, urine and rectal swabs from different patients in two hospitals. Extended-spectrum ß-lactamases (ESBL), plasmid-encoded (pAmpC) ß-lactamases, plasmid-mediated quinolone resistance (PMQR) genes, class 1 integrons, and mcr-1, mcr-2 and mcr-3 were sought and characterised in three E. coli isolates. Transfer of resistance determinants was assessed by conjugation. Clonality was analysed by multilocus sequence typing. RESULTS: All isolates were categorised as being colistin-resistant and the mcr-1 gene was detected. Two isolates were also resistant to oxyimino cephalosporins: one on account of blaCMY-2 and the other due to blaCTX-M-15, the latter also harbouring transferable quinolone-resistance genes (aac(6')Ib-cr and qnrB). All mcr-1 genes were transferred by conjugation to recipient strains. The mcr-1-bearing isolates belonged to sequence types ST10, ST93 and ST5442. CONCLUSIONS: ST10 is considered as a high-risk clone worldwide. This type of mcr-1-harbouring clone is a major concern for human and animal health and must be under close surveillance. This study detected the presence of mcr-1 for the first time in Uruguay, albeit in an allodemic manner, associated with different antibiotic-resistance genes and from diverse clinical contexts. Considering that colistin is often the last therapeutic option available for multidrug-resistant Gram-negative bacilli infections, it is important to maximise precautions to avoid dissemination of isolates carrying mcr-1.

Draft Genome Sequences of Two Multidrug-Resistant Salmonella enterica Serovar Typhimurium Clinical Isolates from Uruguay.

Multidrug-resistant Salmonella enterica isolates are an increasing problem worldwide; nevertheless, the mechanisms responsible for such resistance are rarely well defined. Multidrug-resistant S. enterica serovar Typhimurium isolates ST3224 and ST827 were collected from two patients. The characteristics of both genomes and antimicrobial resistance genes were determined using next-generation sequencing.

Molecular Characterization of Carbapenem-Resistant Acinetobacter baumannii in the Intensive Care Unit of Uruguay's University Hospital Identifies the First rmtC Gene in the Species.

Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are an increasing concern in intensive care units (ICUs) worldwide. The combination of carbapenemases and 16S rRNA-methyltransferases (16S-RMTases) further reduces the therapeutic options. OXA-carbapenemase/A. baumannii clone tandems in Latin America have already been described; however, no information exists in this region regarding the occurrence of 16S-RMTases in this microorganism. In addition, the epidemiology of A. baumannii in ICUs and its associated resistance profiles are poorly understood. Our objectives were as follows: to study the clonal relationship and antibiotic resistance profiles of clinical and digestive colonizing A. baumannii isolates in an ICU, to characterize the circulating carbapenemases, and to detect 16S-RMTases. Patients admitted between August 2010 and July 2011 with a clinically predicted hospital stay > 48 hr were included. Pharyngeal and rectal swabs were obtained during the first fortnight after hospitalization. Resistance profiles were determined with MicroScan® and VITEK2 system. Carbapenemases and 16S-RMTases were identified by PCR and sequencing, and clonality was assessed by pulsed-field gel electrophoresis and multilocus sequence typing. Sixty-nine patients were studied and 63 were diagnosed with bacterial infections. Among these, 29 were CRAB isolates; 49 A. baumannii were isolated as digestive colonizers. These 78 isolates were clustered in 7 pulsetypes, mostly belonging to ST79. The only carbapenemase genes detected were blaOXA-51 (n = 78), blaOXA-23 (n = 62), and blaOXA-58 (n = 3). Interestingly, two clinical isolates harbored the rmtC 16S-RMTase gene. To the best of our knowledge, this is the first description of the presence of rmtC in A. baumannii.

CTX-M-15 in combination with aac(6')-Ib-cr is the most prevalent mechanism of resistance both in Escherichia coli and Klebsiella pneumoniae, including K. pneumoniae ST258, in an ICU in Uruguay.

The objectives of this study were (i) to determine the extended-spectrum ß-lactamase-producing Escherichia coli and Klebsiella pneumoniae (ESBL-EcKp) clones circulating in an intensive care unit (ICU) in Uruguay between August 2010 and July 2011, (ii) to characterise the ESBL and plasmid-mediated quinolone resistance (PMQR) genes of the studied isolates and (iii) to determine the virulotype of the clinical isolates. Clinical and gut-colonising ESBL-EcKp from ICU patients were studied. Bacterial identification and antibiotic susceptibility determination were performed using a VITEK(®)2 system. Detection of ESBL, KPC and PMQR genes was performed by PCR and sequencing. Clonality was assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). In total, 54 ESBL-EcKp isolates (40 K. pneumoniae and 14 E. coli), with or without PMQR genes, were recovered from 30 of 68 inpatients. Forty-seven isolates were CTX-M-15-producers (36 as a single ESBL and 11 together with CTX-M-14). In addition, four isolates produced CTX-M-14, two produced CTX-M-2 and one produced SHV-5. No carbapenemases were detected either in E. coli or K. pneumoniae isolates. Among the ESBL-producing isolates, 42 also harboured PMQR genes: 27 aac(6')-Ib-cr; 14 aac(6')-Ib-cr and qnrB; and a single isolate carrying only qnrB. K. pneumoniae ST258, ST48 and ST16 and E. coli ST10 and ST405 were detected in 46/54 isolates, including 9 clinical isolates. In conclusion, non-KPC-producing K. pneumoniae ST258 harbouring different ESBL and PMQR genes was the main clone disseminated in the ICU. Extensive surveillance measures must be implemented to prevent the emergence of acquired plasmid-encoded blaKPC by ST258 K. pneumoniae.

Analysis of plasmid-mediated quinolone and oxyimino-cephalosporin resistance mechanisms in Uruguayan Salmonella enterica isolates from 2011-2013.

This study characterised the mechanisms of fluoroquinolone and oxyimino-cephalosporin resistance in human Salmonella enterica isolates in Uruguay. Salmonella enterica isolates were collected from 2011-2013 and were selected based on non-susceptibility to ciprofloxacin and/or oxyimino-cephalosporins. The disk diffusion assay was performed for various antibiotics, and the ciprofloxacin minimum inhibitory concentration (MIC) was determined following CLSI guidelines. Genetic relatedness was determined following PulseNet protocols. Extended-spectrum ß-lactamases, ampC alleles and plasmid-mediated quinolone resistance were characterised by PCR and sequencing. Plasmid analyses were carried out by conjugation or transformation assays, and plasmid-encoded genes were identified by PCR. Mutations in the quinolone resistance-determining region of gyrases were sought by PCR and sequencing. Among 579 isolates, 105 (18.4%) ciprofloxacin-non-susceptible (CIP-NS) isolates, 9 (1.6%) oxyimino-cephalosporin-resistant isolates and 2 (0.3%) isolates resistant to both antibiotic families were detected. Thirteen isolates carried qnrB alleles (twelve qnrB19 and one qnrB2), four carried blaCTX-M-8, two blaCTX-M-14, two blaSHV-2 and three blaCMY-2-like genes. No correlation was found between mutations in gyrases and ciprofloxacin MICs. Several co-circulating clones of S. enterica ssp. enterica serovar Typhimurium were detected; conversely, S. enterica ssp. enterica serovar Enteritidis corresponded mainly to a single circulating clone. Nine (75%) of twelve of CIP-NS extraintestinal isolates shared the same pulsotype with intestinal isolates. During the study period, the frequency of CIP-NS isolates increased, albeit with ciprofloxacin MICs of 0.125-0.5mg/L. Detection of the same quinolone-resistant clones recovered both from intestinal and extraintestinal samples highlights the significance of epidemiological surveillance of antibiotic susceptibility for every human Salmonella isolate.

Extended-spectrum ß-lactamases, transferable quinolone resistance, and virulotyping in extra-intestinal E. coli in Uruguay.

INTRODUCTION: To characterize extended-spectrum ß-lactamases (ESBLs) and plasmid-mediated quinolone resistance (PMQR) genes in Escherichia coli isolates obtained from extra-intestinal samples in three Uruguayan hospitals. METHODOLOGY: Fifty-five ESBL-producing E. coli isolates were studied. Virulence genes, ESBLs, and PMQR genes were detected by polymerase chain reaction. ESBL-producing isolates were compared by pulsed-field gel electrophoresis. Multi-locus sequence typing was also performed on 13 selected isolates. RESULTS: Thirty-seven isolates harbored blaCTX-M-15 (67.3%), eight blaCTX-M-2 (14.6%), five blaCTX-M-14 (9.1%), three carried both blaCTX-M-2 and blaCTX-M-14, one blaCTX-M-9, and one blaCTX-M-8. Among the CTX-M-15 producers, 92% belonged to sequence types ST131 and ST405, and carried aac(6')Ib-cr as well. Isolates harboring blaCTX-M-2, blaCTX-M-14, blaCTX-M-9, or blaCTX-M-8 were found to be genetically unrelated. CONCLUSIONS: The successful dissemination of CTX-M-15-producing E.coli isolates seems to be linked to the spreading of high-risk clones and horizontal gene transfer. A trade-off between carrying more antibiotic resistance and less virulence-related genes could partially account for the evolutionary advantages featured by successful clones.

Synthesis of metallo-ß-lactamase VIM-2 is associated with a fitness reduction in Salmonella enterica Serovar Typhimurium.

Antibiotic resistance, especially due to ß-lactamases, has become one of the main obstacles in the correct treatment of Salmonella infections; furthermore, antibiotic resistance determines a gain of function that may encompass a biological cost, or fitness reduction, to the resistant bacteria. The aim of this work was to determine in vitro if the production of the class B ß-lactamase VIM-2 determined a fitness cost for Salmonella enterica serovar Typhimurium. To that end the gene blaVIM-2 was cloned into the virulent strain S. Typhimurium SL1344, using both the tightly regulated pBAD22 vector and the natural plasmid pST12, for inducible and constitutive expression, respectively. Fitness studies were performed by means of motility, growth rate, invasiveness in epithelial cells, and plasmid stability. The expression of blaVIM-2 was accompanied by alterations in micro- and macroscopic morphology and reduced growth rate and motility, as well as diminished invasiveness in epithelial cells. These results suggest that VIM-2 production entails a substantial fitness cost for S. Typhimurium, which in turn may account for the extremely low number of reports of metallo-ß-lactamase-producing Salmonella spp.

First report of a clinical isolate of Leclercia adecarboxylata harbouring multiple resistance genes in Uruguay and review of the literature.

Here we report the detection of a Leclercia adecarboxylata strain, isolated from a case of osteomyelitis, harbouring multiple antibiotic resistance genes encoded on a 450-kb IncHI1/HI2 conjugative plasmid (pLa12). The plasmid carried a complex class 1 integron with the genetic array intI1-aac(6')-Ib-cr-blaOXA-1-catB3-arr3-qacEΔ1-sul1-ISCR1; in addition, a blaDHA-1-like allele linked to ampR-qacEΔ1-sul1 as well as blaSHV-12, blaTEM-1 and qnrB4-like genes were found. To the best of our knowledge, this is the first report of L. adecarboxylata harbouring transferable resistance genes to quinolones, chloramphenicol and rifampicin as well as a plasmidic class C ß-lactamase.

Polyclonal endemicity of Acinetobacter baumannii in ventilated patients in an intensive care unit in Uruguay.

OBJECTIVES: To identify the mechanisms responsible for respiratory infections by Acinetobacter baumannii in intubated patients and risk factors for digestive colonization and infection by A. baumannii. METHODS: We conducted a prospective study in an intensive care unit (ICU) between May 2005 and November 2006, including 175 consecutive patients at the beginning of invasive ventilation (day 1). We performed pharyngeal and rectal swabs on days 1, 4, 7, 10, 13, and 16. Respiratory samples were taken on days 1 and 7, or on suspicion of ventilator-associated pneumonia (VAP). RESULTS: We detected 62 patients with A. baumannii digestive colonization and 20 cases of A. baumannii lower respiratory infection (14 VAP and six purulent tracheobronchitis (PTB)). Digestive colonization by A. baumannii was an independent risk factor for lower respiratory tract infections with that microorganism (p<0.0001; relative risk 8.71, 95% confidence interval 2.73-27.77). Respiratory and rectal A. baumannii isolates from the same patients were compared by enterobacterial repetitive intergenic consensus (ERIC)-PCR; in 9/11 cases (eight VAP and one PTB) results suggested events of exogenous pneumonia with previous colonization, whereas the remaining two cases (two PTB) were suggestive of exogenous infection without previous colonization. CONCLUSIONS: In our unit the pathogenesis of VAP by A. baumannii is mixed, most cases corresponding to exogenous pneumonia with previous colonization.

Identification of the first blaCMY-2 gene in Salmonella enterica serovar Typhimurium isolates obtained from cases of paediatric diarrhoea illness detected in South America.

The objectives of this study were to investigate clinical isolates of Salmonella enterica serovar Typhimurium resistant to ß-lactam antibiotics, to characterise their mechanisms of antibiotic resistance and to evaluate the possible biological cost of expressing resistance genes. Two oxyimino-cephalosporin-resistant Salmonella isolates obtained from children with diarrhoea were characterised. The occurrence of plasmid-encoded blaCMY-2 genes was confirmed by molecular methods and conjugation assays; transcription levels were determined by quantitative real-time PCR (qRT-PCR). The genomic context of the ß-lactamases, replicon type and addiction systems were analysed by PCR. Genomic relatedness of both isolates was studied by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) assays. Growth curves, motility and invasiveness assays in Caco-2 cells were performed to analyse the bacterial fitness of both isolates. Both isolates carried a blaCMY-2-like allele in an IncI plasmid and belonged to the same MLST sequence type (ST19); nevertheless, they showed extensive differences in their PFGE profiles and virulotypes. Isolate STM709 appeared to lack the Salmonella virulence plasmid and displayed less motility and invasiveness in cultured cells than isolate STM910. qRT-PCR showed that isolate STM709 had higher blaCMY-2 mRNA levels compared with STM910. Altogether, the results suggest that a plasmid carrying blaCMY-2 could be disseminating among different clones of S. Typhimurium. Different levels of blaCMY-2 mRNA could have an effect on the fitness of this micro-organism, resulting in lower invasiveness and motility.

First human isolate of Salmonella enterica serotype Enteritidis harboring blaCTX-M-14 in South America.

We studied a clinical isolate of Salmonella enterica serotype Enteritidis showing resistance to oxyiminocephalosporins. PCR analysis confirmed the presence of bla(CTX-M-14) linked to IS903 in a 95-kb IncI1 conjugative plasmid. Such a plasmid is maintained on account of the presence of a pndAC addiction system. Multilocus sequence typing (MLST) analysis indicated that the strain belongs to ST11. This is the first report of bla(CTX-M-14) in Salmonella Enteritidis of human origin in South America.

Extended-spectrum ß-lactamases and plasmid-mediated quinolone resistance in enterobacterial clinical isolates in the paediatric hospital of Uruguay.

OBJECTIVES: To analyse the prevalence of resistance to ß-lactams and plasmid-mediated quinolone resistance in Enterobacteriaceae in the paediatric hospital of Uruguay. METHODS: A total of 368 enterobacterial isolates collected between 1 May and 30 November 2009 were studied for the presence of extended-spectrum ß-lactamases (ESBLs), qnr alleles and aac(6')Ib by phenotypic and molecular methods. The genomic context and transferability of ß-lactamase and qnr genes were examined by PCR and conjugation, respectively. RESULTS: The proportion of inpatients having an infection caused by ESBL-producing enterobacteria was 0.23% (16/7073) in paediatrics wards, 0.64‰ (3/4696) in the neonatology department and 0.03‰ (1/32 557) in the emergency department. ESBL-carrying enterobacteria constituted a total of 21.6% (16/74), 13% (3/23) and 0.37% (1/271) when samples were obtained from paediatrics wards, the neonatology department and the emergency department, respectively. Overall, CTX-M-2 (n = 7), CTX-M-9 (n = 3), CTX-M-8 (n = 2), CTX-M-15 (n = 1), SHV-5 (n = 5) and SHV-2 (n = 2) ß-lactamases were detected. Thirteen out of 20 ESBL-producing isolates also carried the aac(6')Ib gene, and the cr variant was detected in one of them. qnr alleles were detected in four isolates comprising two qnrA1 genes, a qnrB8-like variant and a new qnrB gene showing 26 amino acid differences from QnrB1. CONCLUSIONS: The proportion of ESBL-producing enterobacteria in Uruguay's paediatric hospital during the study period was 2.3 per 1000 hospitalized patients. The number of different microorganisms detected, as well as the various EBSLs, suggests the occurrence of sporadic episodes instead of nosocomial outbreaks. Nevertheless, the presence of new resistance genes reinforces the necessity for permanent surveillance programmes.

Detection of class 1 and 2 integrons, extended-spectrum ß-lactamases and qnr alleles in enterobacterial isolates from the digestive tract of Intensive Care Unit inpatients.

In this study, we searched for extended-spectrum ß-lactamases (ESBLs), class 1 and 2 integrons, and qnrA, qnrB and qnrS genes in 56 oxyimino-cephalosporin and/or ciprofloxacin-resistant enterobacterial isolates obtained from the gastrointestinal tract of patients admitted in an Intensive Care Unit in Uruguay. ESBLs were detected in 11 isolates (6 CTX-M-2, 3 CTX-M-9, 1 CTX-M-15 and 1 PER-2). qnr genes and integrons were detected in 5 and 24 isolates, respectively. Eight different antibiotic resistance gene cassettes were found within six different genetic arrangements. Two types of complex class 1 integrons carrying insertion sequence ISCR1 were found, one showing bla(CTX-M-2)-orf3 and the other qnrA1-ampR. Ten of the thirteen isolates carrying class 2 integrons presented the element IS5 inserted between intI2 and dfrA1, whereas another class 2 integron lacked the internal stop codon usually present in intI2. This is the first report of the occurrence of qnrA, qnrB and bla(CTX-M-9) in Uruguay. Dissemination of the different groups of CTX-M enzymes (i.e. groups 1, 2 and 9) appears to be a recent phenomenon in South America.

Surveillance of antibiotic resistance evolution and detection of class 1 and 2 integrons in human isolates of multi-resistant Salmonella Typhimurium obtained in Uruguay between 1976 and 2000.

OBJECTIVES: To study the evolution of antibiotic resistance in isolates of Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella Typhimurium) obtained in Uruguay between the years 1976 and 2000, and to determine the incidence of class 1 and 2 integrons in the multi-resistant isolates. METHODS: We studied 258 strains of Salmonella Typhimurium from various sources, isolated between 1976 and 2000. We determined the evolution of antibiotic resistance and the distribution of class 1 and 2 integrons in all isolates by means of disk diffusion assays and PCR. RESULTS: During the period 1989-2000 resistance to streptomycin was 56.8%, tetracycline 13.6%, sulfonamides 11.2%, and ampicillin 7.2%. Resistance to gentamicin, kanamycin, chloramphenicol, and nalidixic acid were lower than 5%; no resistance was detected to fluoroquinolones, oxyiminocephalosporins, and amikacin. These results show a dramatic decrease with respect to values found in the period 1976-1988. In this period, resistance to streptomycin was 63.2%, tetracycline 36.8%, sulfonamides 32.3%, and ampicillin 27.8%. Throughout the two periods, 29 multi-resistant Salmonella Typhimurium strains were isolated harboring some class of integron: 15 strains had only intI2, 11 strains presented both intI1 and intI2, and three isolates only intI1. CONCLUSIONS: Our results show a marked decrease in resistance throughout these years, along with a correlation between resistance to different antibiotics and the presence of integrons.