Betsy Esperanza Castro

Cryptococcosis in Colombia: Results of the national surveillance program for the years 2006-2010

INTRODUCTION Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are found with increasing the frequency, both in healthy individuals in the community and in hospitalized patients. In Colombia and the Andean region, CA-MRSA isolates have a genetic background that is related to the pandemic USA300 clone. OBJECTIVE Two molecular methods are designed and standardized for the rapid differentiation of Colombian community-acquired and hospital-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA) isolates. MATERIALS AND METHODS Two molecular methods were standardized for the identification of CA-MRSA isolates. The first method was based on the differential digestion of the carbamate kinase (arcC)and guanylate kinase (gmk) genes in the sequences type 5 (ST5) in the HA-MRSA isolates and 8 (ST8) in the CA-MRSA isolates. The second method was based on the PCR amplification of 5 specific virulence factors found in CA-MRSA and HA-MRSA isolates. The specificity and precision of each method were evaluated using 237 clinical MRSA isolates. RESULTS The first method identified 100% and 93.2% of the CA-MRSA and HA-MRSA isolates, respectively. The second method also correctly identified the two isolates types (CA-MRSA and HA-MRSA). CONCLUSIONS These two methods are a convenient alternative for the rapid identification of the CA-MRSA isolates, compared with other techniques such as pulsed field gel electrophoresis and multilocus sequence typing, which are time-consuming and more expensive.

Emergencia de fenotipos resistentes a cefalosporinas de tercera generación en Enterobacteriaceae causantes de infección del tracto urinario de inicio comunitario en hospitales de Colombia

INTRODUCTION Urinary tract infection (UTI) is a common disease in the community, and a matter of concern due to the increasing resistance of microorganisms to first line antibiotics and the emergence of multiresistant strains producing extended spectrum beta lactamases (ESBL) in the community. METHODS An analytical case-control study was conducted over twelve months in 9 hospitals in Colombia. We collected isolates of E. coli, Klebsiella spp. and Proteus spp. from patients with community-onset UTI. The presence of ESBL, AmpC and KPC beta-lactamases were characterized by microbiological and molecular methods. The aim of this study was to determine factors related to the presence of these mechanisms of the resistance to third generation cephalosporins. RESULTS A total of 325 isolates (287 E. coli, 29 Klebsiella spp. and 9 Proteus spp.) were included. The most frequent comorbidities among the patients were hypertension (n=82; 25.2%) and diabetes mellitus (n=68; 20.9%). Previous use of antimicrobials was found in 23% of patients, and 29% had a previous UTI. Resistance to third and fourth generation cephalosporins varied between 3.4% and 6.3% in E. coli and between 6.9% and 17.8% in K. pneumoniae. Seven (2.4%) CTX-M-15 ESBL-producing E. coli isolates were detected; four of them belonged to ST 131 clone. In K. pneumoniae we detected three KPC-3 carbapenemases (10.3%). CONCLUSIONS This study confirms the emergence of resistance to third generation cephalosporins enterobacteriaceae as a cause of community-onset UTI. We emphasize the presence of ST 131 clone and KPC carbapenemases circulating in Colombia outside the hospital environment.

Detection of a New Community Genotype Methicillin-Resistant Staphylococcus aureus Clone That Is Unrelated to the USA300 Clone and That Causes Pediatric Infections in Colombia

ABSTRACT The dissemination of a clone of community genotype methicillin-resistant Staphylococcus aureus (CG-MRSA) that is related to USA300 has been reported in Latin America. We recently detected isolates of a new clone of CG-MRSA (spa type t1635 and ACME-negative) that was genetically unrelated to the USA300 clone and that causes infections in children in Colombia. This finding indicates the appearance of a new clone of CG-MRSA in our region.

USA300-related methicillin-resistant Staphylococcus aureus clone is the predominant cause of community and hospital MRSA infections in Colombian children

OBJECTIVE Community-genotype methicillin-resistant Staphylococcus aureus (CG-MRSA) isolates are known to be more virulent and clinically aggressive in children. The goal of the present study was characterize the molecular epidemiology of MRSA isolates causing infections in Colombian children. METHODS An observational and prospective study was conducted between April 2009 and June 2011 at 15 hospitals in Bogotá, Colombia. A detailed epidemiological profile was made of 162 children infected with MRSA. The isolates were subjected to antimicrobial susceptibility testing, molecular characterization including 21 virulence genes, SCCmec, spa and agr typing, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). RESULTS Among all isolates included in the study, 85.8% were obtained from patients whose infectious process was initiated in the community; of these, 69,8% occurred in patients without healthcare-associated risk factors. The molecular characterization of the isolates showed a high proportion (95.1%) containing a community-genotype profile with a high prevalence of SCCmec type IV, PVL-positives, and also related to CC8. Most CG-MRSA isolates (143, 92.9%) were genetically related to the pandemic clone USA300, differing by the presence of SCCmec IVc and the absence of the arginine catabolic mobile element (ACME). CONCLUSIONS An increase in the frequency of CG-MRSA infections has been reported worldwide. In this study we found that almost all MRSA infections in our pediatric population were caused by community-genotype isolates, supporting the success of the CG-MRSA clones.

Genomic Epidemiology of NDM-1-Encoding Plasmids in Latin American Clinical Isolates Reveals Insights into the Evolution of Multidrug Resistance

Abstract Bacteria that produce the broad-spectrum Carbapenem antibiotic New Delhi Metallo-β-lactamase (NDM) place a burden on health care systems worldwide, due to the limited treatment options for infections caused by them and the rapid global spread of this antibiotic resistance mechanism. Although it is believed that the associated resistance gene blaNDM-1 originated in Acinetobacter spp., the role of Enterobacteriaceae in its dissemination remains unclear. In this study, we used whole genome sequencing to investigate the dissemination dynamics of blaNDM-1-positive plasmids in a set of 21 clinical NDM-1-positive isolates from Colombia and Mexico (Providencia rettgeri, Klebsiella pneumoniae, and Acinetobacter baumannii) as well as six representative NDM-1-positive Escherichia coli transconjugants. Additionally, the plasmids from three representative P. rettgeri isolates were sequenced by PacBio sequencing and finished. Our results demonstrate the presence of previously reported plasmids from K. pneumoniae and A. baumannii in different genetic backgrounds and geographically distant locations in Colombia. Three new previously unclassified plasmids were also identified in P. rettgeri from Colombia and Mexico, plus an interesting genetic link between NDM-1-positive P. rettgeri from distant geographic locations (Canada, Mexico, Colombia, and Israel) without any reported epidemiological links was discovered. Finally, we detected a relationship between plasmids present in P. rettgeri and plasmids from A. baumannii and K. pneumoniae. Overall, our findings suggest a Russian doll model for the dissemination of blaNDM-1 in Latin America, with P. rettgeri playing a central role in this process, and reveal new insights into the evolution and dissemination of plasmids carrying such antibiotic resistance genes.

Participation of the arcRACME protein in self-activation of the arc operon located in the arginine catabolism mobile element in pandemic clone USA300

ABSTRACT Staphylococcus aureus pandemic clone USA300 has, in addition to its constitutive arginine catabolism (arc) gene cluster, an arginine catabolism mobile element (ACME) carrying another such cluster, which gives this clone advantages in colonisation and infection. Gene arcR, which encodes an oxygen-sensitive transcriptional regulator, is inside ACME and downstream of the constitutive arc gene cluster, and this situation may have an impact on its activation. Different relative expression behaviours are proven here for arcR ACME and the arc ACME operon compared to the constitutive ones. We also show that the artificially expressed recombinant ArcRACME protein binds to the promoter region of the arc ACME operon; this mechanism can be related to a positive feedback model, which may be responsible for increased anaerobic survival of the USA300 clone during infection-related processes.

Emergence and spread of a new community-genotype methicillin-resistant Staphylococcus aureus clone in Colombia

BackgroundCommunity-genotype methicillin-resistant Staphylococcus aureus (CG-MRSA) clones are a global concern due to their resistance and increased virulence and their ability to cause infections both hospitalized patients and healthy people in the community. Here, we characterize 32 isolates of a new CG-MRSA clone. These isolates were identified in four cities in Colombia, South America.MethodsThe isolates were recovered from four different epidemiological and prospective studies that were conducted in several regions of Colombia. Molecular characterizations included multilocus sequence typing; pulsed-field gel electrophoresis; SCCmec, agr and spa typing; and whole-genome sequencing.ResultsAll isolates belonged to ST923 (clonal complex 8), harbouring SCCmec IVa and a spa type t1635 and lacking an arginine catabolism mobile element. The isolates were classified as COL923, were resistant to at least one non-beta-lactam antibiotic, and exhibited high frequencies (>60%) of resistance to macrolides and tetracycline. Using whole-genome sequencing, we found that this new clone harbours novel prophage 3 and beta-island structures and a slightly different pathogenicity island 5. Moreover, isolates belonging to the COL923 clone are grouped in a different clade than USA300 and USA300-LV.ConclusionOur results show the emergence and spread of the COL923 clone in different cities in Colombia. This clone is resistant to several antibiotics and possesses new structures in its mobile genetic elements.