A comparison of methicillin-resistant and methicillin-susceptible Staphylococcus aureus reveals no clinical and epidemiological but molecular differences.

Most studies on Staphylococcus aureus have focused on the molecular epidemiology of methicillin-resistant S. aureus (MRSA) infections. In contrast, little information is available regarding the molecular epidemiology of currently circulating methicillin-susceptible S. aureus (MSSA) isolates in hospital settings, an epoch when the epidemiology of S. aureus has undergone significant changes. We conducted a cross-sectional study to compare the clinical, epidemiological, and genetic characteristics of MSSA and MRSA isolates at 3 tertiary-care hospitals in Medellín, Colombia, from February 2008 to June 2010. The infections were classified according to the Centers for Disease Control and Prevention (CDC) definitions. Genotypic analysis included spa typing, multilocus sequence typing (MLST) and staphylococcal cassette chromosome (mec) (SCCmec) typing. A total of 810 patients was enrolled. One hundred infections (12.3%) were classified as community-associated (31 CA-MSSA, 69 CA-MRSA), 379 (46.8%) as healthcare-associated community-onset (136 HACO-MSSA, 243 HACO-MRSA), and 331 (40.9%) as healthcare-associated hospital-onset (104 HAHO-MSSA, 227 HAHO-MRSA). Genotype analyses showed a higher diversity and a more varied spa type repertoire in MSSA than in MRSA strains. Most of the clinical-epidemiological characteristics and risk factors evaluated did not allow for discriminating MRSA- from MSSA-infected patients. The lack of equivalence among the genetic backgrounds of the major MSSA and MRSA clones would suggest that the MRSA clones are imported instead of arising from successful MSSA clones. This study emphasizes the importance of local surveillance to create public awareness on the changing S. aureus epidemiology.

Concern levels of beta-lactamase-producing Gram-negative bacilli in hospital wastewater: hotspot of antimicrobial resistance in Latin-America.

Hospital wastewater (HWW) discharges are among the main sources of antibiotic-resistant bacteria. This study detected a high frequency of beta-lactamase-producing Gram-negative Bacilli in HWW of different geographical regions of Colombia, even in the presence of the wastewater treatment plant, highlighting the importance of regulating these environments in developing countries.

Climatological and Epidemiological Conditions Are Important Factors Related to the Abundance of blaKPC and Other Antibiotic Resistance Genes (ARGs) in Wastewater Treatment Plants and Their Effluents, in an Endemic Country.

Several physicochemical and season factors have been related to the abundance of antibiotic resistance genes (ARGs) in wastewater treatment plants (WWTPs), considered hotspots of bacterial resistance. However, few studies on the subject have been carried out in tropical countries endemic for resistance mechanisms such as blaKPC. In this study, the occurrence of ARGs, particularly blaKPC, was determined throughout a WWTP, and the factors related to their abundance were explored. In 2017, wastewater samples were taken from a WWTP in Colombia every 15 days for 6 months, and a total of 44 samples were analyzed by quantitative real-time PCR. sul1, sul2, blaKPC, and ermB were found to be the most prevalent ARGs. A low average reduction of the absolute abundance ARGs in effluent with respect to influent was observed, as well as a greater absolute abundance of ARGs in the WWTP effluent in the rainy season. Factors such as temperature, pH, oxygen, total organic carbon (TOC), chemical oxygen demand (COD), and precipitation were significantly correlated with the absolute abundance of several of the ARGs evaluated. A generalized linear mixed-effects model analysis showed that dissolved oxygen and precipitation in the sampling day were important factors related to the absolute concentration of blaKPC over time. In conclusion, the abundance of ARGs in the WWTP could be influenced by endemic conditions and physicochemical and climatological parameters. Therefore, it is necessary to continuously monitor clinical relevant genes in WWTPs from different global regions, even more so in low-income countries where sewage treatment is limited.

Metagenomic analysis of urban wastewater resistome and mobilome: A support for antimicrobial resistance surveillance in an endemic country.

In developing countries, where high levels of antimicrobial resistance are observed in hospitals, the surveillance of this phenomenon in wastewater treatment plants (WWTPs) and the environment is very limited, especially using cutting-edge culture-independent methods. In this study, the composition of bacterial communities, the resistome and mobilome (the pool of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs), respectively) at a WWTP were determined using shotgun metagenomics and culture-based approaches. Wastewater samples were collected at four sampling points of a WWTP in Antioquia, Colombia. A total of 24 metagenomes were analyzed. Specifically, there were marked differences in bacterial community composition, resistome, and mobilome, according to the WWTP sampling points. Bacterial families of clinical importance such as Moraxellaceae, Aeromonadaceae, and Enterobacteriaceae were mainly detected in the WWTP influent and effluent samples. Genes encoding resistance to macrolide-lincosamide-streptogramin, ß-lactams, and those conferring multidrug resistance (e.g., acrB, adeG, and mexD) were the most abundant. Moreover, some clinically important ARGs such as blaKPC-2 and blaCTX-M, and others not reported locally, such as blaTEM-196, blaGES-23, blaOXA-10, mcr-3, and mcr-5 were frequently detected. Co-occurrence network analyses indicated a significant association of ARGs such as blaOXA-58 and blaKPC genes with Aeromonadaceae and Enterobacteriaceae. Among the markers of MGEs, intI1 and ISCR8 were the most frequently detected. Altogether, this work reveals the importance of shotgun metagenomics and culture-based approaches in antimicrobial resistance studies. The findings also support that WWTPs are hotspots for antimicrobial resistance, whose analysis constitutes a powerful tool to predict the impact of antimicrobial resistance in a population.

Differences in epidemiological and molecular characteristics of nasal colonization with Staphylococcus aureus (MSSA-MRSA) in children from a university hospital and day care centers.

BACKGROUND: Clinical significance of Staphylococcus aureus colonization has been demonstrated in hospital settings; however, studies in the community have shown contrasting results regarding the relevance of colonization in infection by community-associated MRSA (CA-MRSA). In Colombia there are few studies on S. aureus colonization. The aim of this study was to determine the molecular and epidemiological characteristics of nasal colonization by S. aureus (MSSA-MRSA) in children from a university hospital and day care centers (DCCs) of Medellin, Colombia. METHODS: An observational cross-sectional study was conducted in 400 children (200 in each setting), aged 0 months to 5 years, during 2011. Samples were collected from each nostril and epidemiological information was obtained from the parents. Genotypic analysis included spa typing, PFGE, MLST, SCCmec typing, detection of genes for virulence factors and agr groups. RESULTS: Frequency of S. aureus colonization was 39.8% (n = 159) (hospital 44.5% and DCCs 35.0%) and by MRSA, 5.3% (n = 21) (hospital 7.0% and DCCs 3.5%). Most S. aureus colonized children were older than two years (p = 0.005), the majority of them boys (59.1%), shared a bedroom with a large number of people (p = 0.028), with history of ß-Lactamase inhibitors usage (p = 0.020). MSSA strains presented the greatest genotypic diversity with 15 clonal complexes (CC). MRSA isolates presented 6 CC, most of them (47.6%) belonged to CC8-SCCmec IVc and were genetically related to previously reported infectious MRSA strains. CONCLUSION: Differences in epidemiological and molecular characteristics between populations may be useful for the understanding of S. aureus nasal colonization dynamics and for the design of strategies to prevent S. aureus infection and dissemination. The finding of colonizing MRSA with similar molecular characteristics of those causing infection demonstrates the dissemination capacity of S. aureus and the risk of infection among the child population.

CC8 MRSA strains harboring SCCmec type IVc are predominant in Colombian hospitals.

BACKGROUND: Recent reports highlight the incursion of community-associated MRSA within healthcare settings. However, knowledge of this phenomenon remains limited in Latin America. The aim of this study was to evaluate the molecular epidemiology of MRSA in three tertiary-care hospitals in Medellín, Colombia. METHODS: An observational cross-sectional study was conducted from 2008-2010. MRSA infections were classified as either community-associated (CA-MRSA) or healthcare-associated (HA-MRSA), with HA-MRSA further classified as hospital-onset (HAHO-MRSA) or community-onset (HACO-MRSA) according to standard epidemiological definitions established by the U.S. Centers for Disease Control and Prevention (CDC). Genotypic analysis included SCCmec typing, spa typing, PFGE and MLST. RESULTS: Out of 538 total MRSA isolates, 68 (12.6%) were defined as CA-MRSA, 243 (45.2%) as HACO-MRSA and 227 (42.2%) as HAHO-MRSA. The majority harbored SCCmec type IVc (306, 58.7%), followed by SCCmec type I (174, 33.4%). The prevalence of type IVc among CA-, HACO- and HAHO-MRSA isolates was 92.4%, 65.1% and 43.6%, respectively. From 2008 to 2010, the prevalence of type IVc-bearing strains increased significantly, from 50.0% to 68.2% (p = 0.004). Strains harboring SCCmec IVc were mainly associated with spa types t1610, t008 and t024 (MLST clonal complex 8), while PFGE confirmed that the t008 and t1610 strains were closely related to the USA300-0114 CA-MRSA clone. Notably, strains belonging to these three spa types exhibited high levels of tetracycline resistance (45.9%). CONCLUSION: CC8 MRSA strains harboring SCCmec type IVc are becoming predominant in Medellín hospitals, displacing previously reported CC5 HA-MRSA clones. Based on shared characteristics including SCCmec IVc, absence of the ACME element and tetracycline resistance, the USA300-related isolates in this study are most likely related to USA300-LV, the recently-described 'Latin American variant' of USA300.