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.

Great Plasticity in a Great Pathogen: Capsular Types, Virulence Factors and Biofilm Formation in ESBL-Producing Klebsiella pneumoniae from Pediatric Infections in Uruguay.

Klebsiella pneumoniae is widely recognized as an opportunistic hospital and community pathogen. It is one of the priority microorganisms included in the ESKAPE group, and its antibiotic resistance related to extended-spectrum ß-lactamases (ESBL) is a global public health concern. The multi-drug resistance (MDR) phenotype, in combination with pathogenicity factors, could enhance the ability of this pathogen to cause clinical infections. The aim of this study was to characterize pathogenicity factors and biofilm formation in ESBL-producing K. pneumoniae from pediatric clinical infections. Capsular types, virulence factors, and sequence types were characterized by PCR. Biofilm formation was determined by a semiquantitative microtiter technique. MDR phenotype and statistical analysis were performed. The K24 capsular type (27%), virulence factors related to iron uptake fyuA (35%) and kfuBC (27%), and sequence types ST14 (18%) and ST45 (18%) were the most frequently detected. Most of the strains were biofilm producers: weak (22%), moderate (22%), or strong (12%). In 62% of the strains, an MDR phenotype was detected. Strains with K24 capsular type showed an association with ST45 and the presence of fyuA; strains with kfuBC showed an association with moderate or strong biofilm production and belonging to ST14. Weak or no biofilm producers were associated with the absence of kfuBC. The MDR phenotype was associated with the main ESBL gene, blaCTX-M-15. The high plasticity of K. pneumoniae to acquire an MDR phenotype, in combination with the factors exposed in this report, could make it even more difficult to achieve a good clinical outcome with the available therapeutics.

Shiga Toxin-Producing Escherichia coli (STEC) Associated with Calf Mortality in Uruguay.

In Uruguay, the mortality of dairy calves due to infectious diseases is high. Escherichia coli is a natural inhabitant of the intestinal microbiota, but can cause several infections. The aim of the work was to characterize E. coli isolates from intestinal and extraintestinal origin of dead newborn calves. Using PCR, virulence gene characteristics of pathogenic E. coli were searched. The pathogenic E. coli were molecularly characterized and the phylogroup, serogroup and the Stx subtype were determined. Antibiotic susceptibility was determined using the Kirby-Bauer disk diffusion method and plasmid-mediated quinolone resistance (PMQR) genes with PCR. Finally, clonal relationships were inferred using PFGE. Gene characteristics of the Shiga toxin-producing E. coli (STEC), Enteropathogenic E. coli (EPEC) and Necrotoxigenic E. coli (NTEC) were identified. The prevalence of the iucD, afa8E, f17, papC, stx1, eae and ehxA genes was high and no f5, f41, saa, sfaDE, cdtIV, lt, sta or stx2 were detected. The prevalence of STEC gene stx1 in the dead calves stood out and was higher compared with previous studies conducted in live calves, and STEC LEE+ (Enterohemorrhagic E. coli (EHEC)) isolates with stx1/eae/ehxA genotypes were more frequently identified in the intestinal than in the extraintestinal environment. E. coli isolates were assigned to phylogroups A, B1, D and E, and some belonged to the O111 serogroup. stx1a and stx1c subtypes were determined in STEC. A high prevalence of multi-resistance among STEC and qnrB genes was determined. The PFGE showed a high diversity of pathogenic strains with similar genetic profiles. It can be speculated that EHEC (stx1/eae/ehxA) could play an important role in mortality. The afa8E, f17G1 and papC genes could also have a role in calf mortality. Multidrug resistance defies disease treatment and increases the risk of death, while the potential transmissibility of genes to other species constitutes a threat to public health.

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.

Antibiotic susceptibility and fosfomycin resistance characterization in a cohort of children older than 6 years of age with urinary tract infection.

Fosfomycin tromethamol (FT) was reintroduced as an option for the treatment of low urinary tract infection (UTI) in children. In this study, we described the antibiotic sensitivity and mechanisms of resistance to fosfomycin in isolates from children older than 6 years with UTI. Urine culture and antibiotic susceptibility study were performed. In fosfomycin resistant strains, PCR for fos, blaCTX-M was performed followed by classification by phylogenetic group and sequencetyping. Escherichia coli was the most frequent etiological agent (89.2%). The susceptibility percentages were: fosfomycin 97.9%; amoxicillin-clavulanate 92.7%; cefuroxime and ceftriaxone 99%; nitrofurantoin 94.4%. An E. coli strain (ST69, phylogenetic group D) was resistant to fosfomycin (MIC 256mg/l) and carried the blaCTX-M-14 and fosA3 genes in a 45kb IncN-type plasmid. This is the first report of E. coli ST69 with blaCTX-M-14/fosA3 of human origin.

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.

Characterization of the Different Stages of Biofilm Formation and Antibiotic Susceptibility in a Clinical Acinetobacter baumannii Strain.

Acinetobacter baumannii is a relevant opportunistic pathogen, and one of the main microorganisms responsible for outbreaks in nosocomial infections worldwide. Its pathogenicity is mainly due to its resistance to multiple antibiotics and to its ability to form biofilms on abiotic surfaces. The objective of this study was to characterize the biofilm formation cycle of A. baumannii isolated from a patient in a hospital and compare its antibiotic resistance with the planktonic cells. To study biofilm formation, the classical microtiter assay was used, with crystal violet staining and optical density reading to classify the type of biofilm. Also, the effect of gentamicin and colistin on bacterial biofilm was studied with an extra step of antibiotic addition. For the characterization of the different biofilm formation stages, the strain was grown on a coverslip, and the stain was made with a mixture of fluorophores markers to visualize the biofilm with a confocal laser microscope. It was possible to differentiate the A. baumannii biofilm formation stages. Through these observations, it was possible to estimate the time elapsed between each stage. As the strain was susceptible to colistin and gentamicin, both antibiotics were evaluated after the biofilm was formed. Neither antibiotics showed an effect on the eradication of A. baumannii biofilm.

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.

Detection of qnrVC6, within a new genetic context, in an NDM-1-producing Citrobacter freundii clinical isolate from Uruguay.

OBJECTIVES: The objective of this study was to characterise the mechanisms underlying quinolone and oxyimino-cephalosporin resistance in a Citrobacter freundii clinical isolate obtained from the ICU in a university hospital in Uruguay. METHODS: Citrobacter freundii strain CF638 was isolated from a urine culture. Identification was performed using a VITEK®2 system, and antimicrobial susceptibility was established by MIC determination and disk diffusion assay. Resistance genes and mobile genetic elements were identified by PCR and sequencing. Plasmid transfer was assessed by conjugation and the plasmid size was estimated by S1-PFGE. Plasmid incompatibility (Inc) group and toxin-antitoxin systems were sought by PCR. RESULTS: Strain CF638 showed a multidrug-resistant profile, including resistance to carbapenems and quinolones. Transconjugant TcCF638, harbouring an ca. 200-kb IncA/C plasmid, also showed resistance to all ß-lactams (except aztreonam) and diminished susceptibility to ciprofloxacin. PCR was positive for blaNDM-1 and qnrVC in CF638 and TcCF638. Two different class 1 integrons were detected (In127 and In907). In127 featured the genetic array aadA2-ltr2. Conversely, complex In907 featured two variable regions (VRs); VR-1 consisted of aadB-blaOXA-10-aadA1cc, whereas VR-2 featured a qnrVC6 gene 108bp downstream from ISCR1 and 45bp upstream from qacEΔ1. Expression of qnrVC6 was due to a putative promoter region, detected using the Neural Network Promoter Prediction program. CONCLUSION: To the best of our knowledge, this constitutes the first report of qnrVC within a complex class 1 integron, as well as the first report of the occurrence of such a gene in an NDM-1-producing enterobacterial clinical isolate.

Zoonotic Potential and Antibiotic Resistance of Escherichia coli in Neonatal Calves in Uruguay.

Escherichia coli is one of the main etiological agents of neonatal calf diarrhea (NCD). The objective of this study was to assess the presence of virulence genes, genetic diversity, and antibiotic resistance mechanisms in E. coli associated with NCD in Uruguay. PCR was used to assess the presence of intimin, Shiga-like toxin, and stable and labile enterotoxin genes. Resistance to fluoroquinolones and oxyimino-cephalosporins was estimated on Müller-Hinton agar plates. Further antibiotic disc-diffusion tests were performed to assess bacterial multi-resistance. The presence of PMQR, ESBL, MCR-1, and integron genes was evaluated. Isolates were typed using ERIC-PCR, and 20 were selected for MLST, adhesion to Hep-2 cells, in vitro biofilm formation, and eukaryotic cytotoxicity. The prevalence of ETEC genes was lower than 3% in each case (estA and elt). Six isolates were EPEC (eae+) and 2 were EHEC/STEC (eae+/stx1+). The results of a diversity analysis showed high genetic heterogenicity among isolates. Additionally, different sequence types, including ST10, ST21, and ST69, were assigned to selected isolates. Thirty-six percent (96/264) of the isolates were fluoroquinolone-resistant, with 61/96 (63.5%) being multidrug-resistant. Additionally, 6 were oxyimino-cephalosporin-resistant. The qnrB, qnrS1, and blaCTX-M-14 genes were detected, whereas no isolates carried the mcr-1 gene. Isolates had the ability to adhere to Hep-2 cells and form biofilms. Only 1 isolate expressed toxins in vitro. E. coli from NCD cases in Uruguay are very diverse, potentially virulent, and may interact with eukaryotic cells. Zoonotic potential, together with resistance traits and the presence of horizontal transfer mechanisms, may play a significant role in infections caused by these microorganisms.

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.

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.

Sepsis caused by New Delhi metallo-ß-lactamase (blaNDM-1) and qnrD-producing Morganella morganii, treated successfully with fosfomycin and meropenem: case report and literature review.

OBJECTIVES: The objective of this study was to describe the microbiological characteristics of an extensively drug-resistant (XDR) isolate of Morganella morganii obtained from a patient with sepsis of urinary origin and to describe the patient's clinical characteristics. We further aimed to perform a literature review of the situation in Latin America regarding Gram-negative bacillus (GNB) carriers of New Delhi metallo-ß-lactamase (NDM-1) and qnr genes and current reports on the treatment of infections caused by XDR enterobacteria, with particular attention to colistin-resistant isolates. METHODS: The patient's clinical data were obtained from his medical history. Microbiological identification and susceptibility testing were done using the VITEK 2 Compact System. Resistance genes were detected by PCR and sequencing. RESULTS: Blood and urine cultures grew an M. morganii isolate (Mm4232) harboring NDM-1 and qnrD1. The patient was treated successfully with fosfomycin and double doses of meropenem. There are no previous reports of the use of fosfomycin and meropenem to treat infections by XDR enterobacteria harboring NDM-1 carbapenemase. CONCLUSIONS: This is the first report of qnrD1 in South America. We consider that this report could be helpful to physicians implementing treatments for infections caused by XDR GNB, including colistin-carbapenem-resistant GNB.

[Treatment failure due to acquisition of antibiotic resistance: report of two clinical cases]. / Fallo terapéutico por resistencia antibacteriana intra-tratamiento, a propósito de dos casos clínicos.

OBJECTIVE: We describe two cases of treatment failure due to intra-treatment acquisition of antibiotic resistant microorganisms with the aim of highlighting the possible molecular mechanisms by which treatment failure occurred. PATIENTS AND METHODS: We analyzed the clinical histories and the isolates obtained from 2 patients, one with a urinary tract infection (UTI) by E. coli, initially treated with cefuroxim (to which the isolate was susceptible), and another with osteoarthritis (OA) treated initially with meropenem plus vancomycin, developing K. pneumoniae susceptible to meropenem. During treatment, in both patients, resistant microorganisms were isolated, and empirical therapy was modified, initially with ceftriaxone and afterwards meropenem in case 1, and adding amikacin in case 2. Both strains (per patient) were compared by PFGE and resistance genes were sought by PCR. RESULTS: Regarding the UTI, the initial strain acquired an IncFIB SHV-5-producing plasmid. In the OA case, the initial susceptible strain was substituted by a CTX-M-9 and AadB-AadA2-Aac(6')Ib-producing K. pneumoniae.

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.