Silvina Fernández

Methicillin-resistant Staphylococcus aureus ST30-SCCmec IVc clone as the major cause of community-acquired invasive infections in Argentina

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have become a major concern worldwide. We conducted a prospective multicenter study of invasive CA-MRSA to evaluate clinical features and genotype of strains causing invasive infections in Argentina. A total of 55 patients with invasive CA-MRSA infections were included. Most patients (60%) had bloodstream infections, 42% required admission to intensive care unit and 16% died. No CA-MRSA isolates were multiresistant (resistant ⩾3 classes of antibiotics). All isolates carried Panton-Valentine leukocidin (PVL) genes and staphylococcal cassette chromosome (SCCmec) type IV. The majority CA-MRSA strains belonged to ST30 and had identical pulsed-field gel electrophoresis (PFGE) patterns, qualifying as a clonal dissemination of a highly transmissible strain. The main clone recovered from patients with CA-MRSA invasive infections was genotyped as pulsed-field gel electrophoresis type C-ST30, SCCmec type IVc-spa type 019, PVL positive. It has become predominant and replaced the previously described CA-MRSA clone (PFGE type A, ST5, SCCmec type IV, spa type 311).

Prospective Multicenter Study of Community-Associated Skin and Skin Structure Infections due to Methicillin-Resistant Staphylococcus aureus in Buenos Aires, Argentina

Background Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is now the most common cause of skin and skin structure infections (SSSI) in several world regions. In Argentina prospective, multicenter clinical studies have only been conducted in pediatric populations. Objective Primary: describe the prevalence, clinical and demographic characteristics of adult patients with community acquired SSSI due to MRSA; secondary: molecular evaluation of CA-MRSA strains. Patients with MRSA were compared to those without MRSA. Materials and Methods Prospective, observational, multicenter, epidemiologic study, with molecular analysis, conducted at 19 sites in Argentina (18 in Buenos Aires) between March 2010 and October 2011. Patients were included if they were ≥14 years, were diagnosed with SSSI, a culture was obtained, and there had no significant healthcare contact identified. A logistic regression model was used to identify factors associated with CA-MRSA. Pulse field types, SCCmec, and PVL status were also determined. Results A total of 311 patients were included. CA-MRSA was isolated in 70% (218/311) of patients. Clinical variables independently associated with CA-MRSA were: presence of purulent lesion (OR 3.29; 95%CI 1.67, 6.49) and age <50 years (OR 2.39; 95%CI 1.22, 4.70). The vast majority of CA-MRSA strains causing SSSI carried PVL genes (95%) and were SCCmec type IV. The sequence type CA-MRSA ST30 spa t019 was the predominant clone. Conclusions CA-MRSA is now the most common cause of SSSI in our adult patients without healthcare contact. ST30, SCCmec IV, PVL+, spa t019 is the predominant clone in Buenos Aires, Argentina.

Community-acquired necrotizing pneumonia caused by methicillin-resistant Staphylococcus aureus ST30-SCCmecIVc-spat019-PVL positive in San Antonio de Areco, Argentina

Community-acquired methicillin-resistant Staphylococcus aureus is the first cause of skin and soft tissue infections, but can also produce severe diseases such as bacteremia, osteomyelitis and necrotizing pneumonia. Some S. aureus lineages have been described in cases of necrotizing pneumonia worldwide, usually in young, previously healthy patients. In this work, we describe a fatal case of necrotizing pneumonia due to community-acquired methicillin-resistant S. aureus clone ST30-SCCmecIVc-spat019-PVL positive in an immunocompetent adult patient.

Increase in IS256 transposition in invasive vancomycin heteroresistant Staphylococcus aureus isolate belonging to ST100 and its derived VISA mutants.

In Staphylococcus aureus, transposition of IS256 has been described to play an important role in biofilm formation and antibiotic resistance. This study describes the molecular characterization of two clinical heterogeneous vancomycin-intermediate S. aureus (hVISA) isolates recovered from the same patient (before and after antibiotic treatment) and two VISA derivatives obtained by serial passages in the presence of vancomycin. Our results showed that antibiotic treatment (in vivo and in vitro) could enhance IS256 transposition, being responsible for the eventual loss of agr function. As far as we know this is the first study that reports the increase of IS256 transposition in isogenic strains after antibiotic treatment in a clinical setting.

Capacitation and Acrosome Reaction Induction on Thawed Dama dama Deer Spermatozoa: Glycine Effect as Cryopreservation Diluent Supplement

The aim of this research was to evaluate two different diluents for sperm cryopreservation and to study functional parameters in relation to the response to heparin, lysophosphatidylcholine and progesterone, in frozen-thawed semen of fallow deer (Dama dama) during the reproductive season (brama). In this way, fallow deer can be used as a biological model of endangered cervids. Semen was obtained by electroejaculation. Heparin, progesterone and lysophosphatidylcholine were used as capacitation and acrosome reaction inducers, respectively. Capacitation and acrosome reaction were evaluated by chlorotetracycline epifluorescence technique (CTC), membrane integrity by Hypo-osmotic swelling test (HOS) and viability and acrosome integrity by trypan blue stain/DIC. Data was analyzed by ANOVA and Tukey Test (P < 0.05). Semen was cryopreserved in different diluents and Fructose-Tris-Glycine extender was selected. Capacitation with heparin at different incubation times determined that the highest capacitation percentage was obtained at 45 minutes incubation. Progesterone (1 ′M) and lysophosphatidylcholine in heparin capacitated sperm induced acrosome reaction (P < 0.05). This study contributes to improve cryopreservation methods and to increase the knowledge about capacitation and acrosome reaction in vitro in deer spermatozoa, allowing an advance in the development of reproductive biotechnologies.

High virulence of methicillin resistant Staphylococcus aureus ST30-SCCmecIVc-spat019, the dominant community-associated clone in Argentina

Community-acquired methicillin resistant Staphylococcus aureus emerged as a worldwide health problem in the last few years. In Argentina, it is found in 70% of skin and skin structure infections in previously healthy adult patients and causes severe invasive diseases. The ST30-SCCmecIVc-spat019 clone is predominant in adult infections and has displaced the previously prevalent ST5-SCCmecIVa-spat311 clone in community settings. In the present work we compared the virulence of both clones in order to explain the displacement, and found that ST30-IVc is associated with invasive infections in adult patients from Argentina and possesses a different virulence-associated genes profile compared to ST5-IVa. A representative strain of ST30 lineage has a more aggressive behavior in animal models of infection and expresses higher level of Fibronectin binding protein A coding gene, which could enhance the bacterial invasion capacity.

Progesterone causes metabolic changes involving aminotransferases and creatine kinase in cryopreserved bovine spermatozoa

Progesterone (P4) is capable of inducing acrosome reaction in many species. The objective of this study was to determine the activity of enzymes involved in metabolism that contribute to the redox state and supply energy for acrosome reaction in cryopreserved bull spermatozoa. To accomplish this aim, acrosome reaction was induced by P4 in capacitated and non-capacitated samples. Alanine and aspartate aminotransferases (ALT, AST) and creatine kinase (CK) activities were measured spectrophotometrically at 340 nm after acrosome reaction with P4. Oxygen consumption was measured polarographically. ALT and AST activities increased by the addition of P4 capacitated and non-capacitated samples. P4 addition provoked an increase in CK activity in non-capacitated spermatozoa compared to heparin capacitated spermatozoa with or without P4 addition. P4 increased oxygen consumption, the percentage of acrosome reacted spermatozoa as well as the absence of acrosome integrity in both capacitated and non-capacitated bovine spermatozoa, but oxygen consumption in P4 samples was significantly lower than in heparin capacitated spermatozoa (P<0.05). Acrosome reaction induction by P4 required different creatine kinase activity with the same oxygen consumption and transaminases level to maintain oxidative metabolism and redox state through reducing equivalents transfer between cytosolic and mitochondrial compartment. In conclusion, P4 induces a lower oxidative metabolism during acrosome reaction in bovine cryopreserved spermatozoa, compared to heparin induced capacitation process.

Estudio comparativo de clones de aislamientos de Staphylococcus Aureus resistentes a meticilina prevalentes en la Argentina

Fil: Gardella, Noella. Universidad de Buenos Aires. Facultad de Farmacia y Bioquimica; Argentina

Estandarización del análisis multi-locus de número variable de repeticiones en tándem para el estudio de Staphylococcus aureus resistentes a meticilina aislados de la comunidad en Paraguay

Staphylococcus aureus is a pathogen that can produce several infections with a wide range of severity and it has the hability to adapt to different tissues. The epidemiology is complex, by circulation of many differents clones worlwide, so the analysis for its identification requires reproducible and high discriminatory powder molecular methods. The aim of this study was to standardize the molecular technique multiple-locus variable number of tandem repeat analysis (MLVA) for the genetic variability analysis of S. aureus isolates, previously characterized by pulsed field gel electrophoresis (PFGE). The MLVA was made by PCR amplification of seven VNTR locus (clfA, clfB, sdrC, sdrD, sdrE, sspA y spA). A high level of reproducibility has reached in the study. The use of isolates previously typified by multi-locus secuencing typing (MLST), PFGE, locus spa and cassette SCCmec, allowed to validate the MLVA clusters comparatively. The isolates that were clustered by MLVA as the same isolate, showed the same results by other molecular techniques, and the MLVA can distinguish isolates with identical PFGE patterns. This technique have all criteria of a usefull molecular typification technique.