Beatriz Perazzi

Accuracy of Cefoxitin Disk Testing for Characterization of Oxacillin Resistance Mediated by Penicillin-Binding Protein 2a in Coagulase-Negative Staphylococci

ABSTRACT The Clinical and Laboratory Standards Institute (CLSI) proposed, beginning in 2004, the use of cefoxitin disks to predict resistance mediated by the mecA gene in all species of coagulase-negative staphylococci (CoNS). The aim of this work was to evaluate the efficiency of the cefoxitin disk and of oxacillin-salt agar screening (MHOX) to characterize the oxacillin resistance mediated by the mecA gene in CoNS. One hundred seven CoNS isolates from different clinical samples were studied. Detection of the mecA gene by PCR was considered the “gold standard.” The susceptibility to oxacillin and cefoxitin was detected by the disk diffusion and agar dilution tests, as described by the CLSI. MHOX was also performed with 6 μg/ml of oxacillin and 4% NaCl. The sensitivities of the oxacillin and cefoxitin disks for all CoNS species were 88% and 80%, respectively, whereas the specificities were 63% and 100%, respectively. The sensitivities of the agar dilution test for oxacillin and cefoxitin (for proposed breakpoints of ≥4 μg/ml for resistance and ≤2 μg/ml for susceptibility) were 90% and 85%, respectively, whereas the specificities were 76% and 98%, respectively. MHOX showed a sensitivity of 90% and a specificity of 95% for all CoNS species. Both the MHOX and the cefoxitin disk results indicate that these are appropriate methods for the evaluation of oxacillin resistance mediated by the mecA gene in all CoNS species.

Resistencia enzimática a betalactámicos en el género Proteus y evaluación de los fenotipos y genotipos de resistencia a cefalosporinas de tercera y cuarta generación en Proteus mirabilis

Introduccion. El objetivo de este trabajo fue evaluar la resistencia a betalactamicos en el genero Proteus y caracterizar las betalactamasas responsables de dicha resistencia. Metodos. Se analizaron 99 cepas (87 P. mirabilis; 10 P. vulgaris, y 2, P. penneri) aisladas de pacientes atendidos en un Hospital Universitario. Los ensayos de susceptibilidad a antibioticos se realizaron de acuerdo con las recomendaciones del National Committee for Clinical Laboratory Standards. La presencia de betalactamasas de espectro extendido (BLEE) fue inferida por el metodo de difusion de doble disco y por la concentracion inhibitoria minima (CIM) de cefalosporinas de tercera y cuarta generacion solas y en presencia de acido clavulanico. Se estimo el punto isoelectrico (pI) por isoelectroenfoque y la presencia de los genes codificantes se confirmo por reaccion en cadena de la polimerasa (PCR). Resultados. Una betalactamasa de amplio espectro fue detectada en aquellos aislamientos resistentes a penicilinas y cefalosporinas de primera generacion (28%), mientras que la enzima CTX-M-2 fue detectada en los aislamientos de P. mirabilis resistentes a cefalosporinas de tercera y cuarta generacion (18%). Uno de los P. vulgaris presento sensibilidad disminuida a cefotaxima debido a una enzima de pI 7,4, mientras que la resistencia a cefotaxima en un P. penneri fue relacionada con una enzima de pI 6,8. Ambas enzimas fueron activas sobre cefotaxima (1.000 mg/l) en el ensayo iodometrico. Conclusion. La betalactamasa de amplio espectro en el genero Proteus fue TEM-1 mientras que CTX-M-2 fue la BLEE responsable de la resistencia a cefalosporinas de tercera y cuarta generacion en P. mirabilis. En P. vulgaris y P. penneri esta resistencia se asocio a la hiperproduccion de la betalactamasa cromosomica.

Clinical, microbiological, and genetic characteristics of heteroresistant vancomycin-intermediate Staphylococcus aureus bacteremia in a teaching hospital.

The emergence of vancomycin intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) is of major concern worldwide. Our objective was to investigate the prevalence, phenotypic and molecular features of hVISA strains isolated from bacteremic patients and to determine the clinical significance of the hVISA phenotype in patients with bacteremia. A total of 104 S. aureus blood isolates were collected from a teaching hospital of Argentina between August 2009 and November 2010. No VISA isolate was recovered, and 3 out of 92 patients (3.3%) were infected with hVISA, 2 of them methicillin-resistant S. aureus (MRSA) (4.5% of MRSA). Macro Etest and prediffusion method detected 3/3 and 2/3 hVISA respectively. Considering the type of bacteremia, the three cases were distributed as follows: two patients had suffered multiple episodes of bacteremia (both hVISA strains recovered in the second episode), while only one patient had suffered a single episode of bacteremia with hVISA infection. MRSA bloodstream isolates exhibiting the hVISA phenotype were related to HA-MRSA Cordobes clone (ST5-SCCmec I-spa t149) and MRSA Argentinean pediatric clone (ST100-SCCmec IVNV-spa t002), but not to CA-MRSA-ST30-SCCmec IV-spa t019 clone that was one of the most frequent in our country. Although still relatively infrequent in our hospital, hVISA strains were significantly associated with multiple episodes of bacteremia (p=0.037) and genetically unrelated.

Three-dimensional digital colposcopy.

Traditional colposcopy has used a device with magnifying lens and a source of light to brighten and visualize the cervix. Technical improvements such as colpophotography were incorporated to obtain a permanent record of the colposcopy images. More recently, digital colposcopy integrated new and advanced tools to improve the possibilities of the colposcopic method (1 3). In conventional colposcopy, images are observed only in two dimensions (2D), i.e. width and height, without focal depth. The application of three-dimensional (3D) images to obtain more detailed images in order to visualize different aspects of the epithelial surfaces has improved the diagnostic efficiency of this technique. Such 3D images are currently employed in different fields of medicine such as ecography and computerized axial tomography. In this sense, they may also be employed in the colposcopic diagnosis of all lower genital tract lesions (4). The usual equipment employed for digital colposcopy to obtain 3D images is a colposcope with a videocamera connected to a computer. The captured images are visualized on the monitor screen of the computer. Afterwards, either the whole or selected areas of the image can be analyzed in 3D representation (width, height and depth) on the monitor screen. The computer must hold hardware with a microprocessor (CPU) of at least 1 GHz and a 1 GB RAM memory to create 3D images; moreover, it must include a 3D video adapter with an accelerated graphics port and should dispose of specialized software. The 3D colposcopic image presented in Figure 1 was obtained with the 3D Studio Max software (Autodesk† 3ds Max† software, San Rafael, California, USA). Other software may also be used (4). Details of the epithelial surfaces are

Caracterización y distribución de especies de Citrobacter en un hospital universitario

Objetivos a) Identificar a nivel de especie las cepas pertenecientes al genero Citrobacter, siguiendo el esquema de pruebas bioquimicas convencionales propuesto por Brenner et al; b) determinar la utilidad de la llave dicotomica de O`Hara comparandola con el esquema propuesto por Brenner et al, evaluando su sensibilidad y especificidad, y c) establecer la distribucion y frecuencia de las diferentes especies en los especimenes clinicos. Materiales y metodos Se estudiaron 122 cepas aisladas en forma consecutiva, unica e ininterrumpida en el periodo comprendido entre mayo de 1994 y agosto de 1997, que fueron identificadas como Citrobacter spp. Las mismas provenian de distintos materiales clinicos correspondientes a pacientes hospitalizados y ambulatorios atendidos en el Hospital de Clinicas. Los organismos fueron identificados segun el esquema propuesto por Brenner y la llave dicotomica de O`Hara. Resultado El esquema de Brenner identifico a nivel de especie 111 cepas de las 122 estudiadas. C. freundii fue la especie mas frecuente (59/111), seguida por C. koseri (18/111), C. werkmanii (15/111), C. braakii (9/111), C. youngae (6/111) y C. amalonaticus (4/111). La llave dicotomica de O`Hara identifico el 94% de las cepas estudiadas (104/111). Para C. freundii los sitios de infeccion o colonizacion mas frecuentes fueron el tracto urinario y el intestino, (p Fischer Conclusiones El esquema de O`Hara podria ser una alternativa valida para la identificacion de las citrobacterias en los laboratorios de microbiologia, teniendo en cuenta que estas son importantes patogenos oportunistas.

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.

Evaluación de la disfunción vaginal en mujeres embarazadas sintomáticas y asintomáticas mediante la utilización de los estados vaginales básicos (EVB) y su comparación con el estudio microbiológico convencional

Infections of the lower genital tract associated to maternal and perinatal complications frequently occur during pregnancy. The aim of this study was to evaluate vaginal dysfunction through the analysis of basic vaginal states (BVS) using the methodology of balance of the vaginal content (BAVACO) and to compare it with the microbiological study of candidiasis, trichomoniasis and bacterial vaginosis (BV). Pregnant patients (1238) were examined from 2010 to 2012. In asymptomatic (A) (n: 1046) and symptomatic pregnant women (S) (n: 192) BVS I was 59.5% and 26% of the patients, respectively. BVS II was observed in 19.7% of A and in 17.2% of S. BVS III was only detected in A in 0.4%. BVS IV was observed in 14.4% of A and in 38% of S. BVS V was detected in 6% of A and in 18.8% of S. Yeasts were associated to BVS I and II in 55.5% and 23.2% of A, respectively; and in 32.4% and 31% of S, respectively. Trichomonas were associated to BVS I in 50% of A, to IV in 44.4% of S and to V in 33.3% of S. BAVACO susceptibility to detect yeasts was 80.4% and 85.5% in A and S, respectively; 40% and 75% in A and S, respectively, to detect trichomonas and 100% in A and S to detect BV. BAVACO specificity was 100% for all pathogens in A and S. The study of BVS proved useful as a guide to evaluate vaginal dysfunction, regardless of symptomatology. Therefore, this study is recommended as prenatal control.

Etiología bacteriana de la neumonía nosocomial y resistencia a los antimicrobianos en pacientes con y sin tratamiento antimicrobiano previo

Resumen es: La neumonia nosocomial (NN) se asocia a una elevada morbimortalidad y es la segunda causa de infeccion intrahospitalaria despues de la infeccion urinaria...

Optimization of Trichomonas vaginalis Diagnosis during Pregnancy at a University Hospital, Argentina

The aim of this study was to evaluate different methods for Trichomonas vaginalis diagnosis during pregnancy in order to prevent maternal and perinatal complications. A total of 386 vaginal exudates from pregnant women were analyzed. T. vaginalis was investigated by 3 types of microscopic examinations direct wet mount with physiologic saline solution, prolonged May-Grunwald Giemsa (MGG) staining, and wet mount with sodium-acetate-formalin (SAF)/methylene blue method. PCR for 18S rRNA gene as well as culture in liquid medium were performed. The sensitivity and specificity of the microscopic examinations were evaluated considering the culture media positivity or the PCR techniques as gold standard. The frequency of T. vaginalis infection was 6.2% by culture and/or PCR, 5.2% by PCR, 4.7% by culture, 3.1% by SAF/methylene blue method and 2.8% by direct wet smear and prolonged MGG staining. The sensitivities were 83.3%, 75.0%, 50.0%, and 45.8% for PCR, culture, SAF/methylene blue method, and direct wet smear-prolonged MGG staining, respectively. The specificity was 100% for all the assessed methods. Microscopic examinations showed low sensitivity, mainly in asymptomatic pregnant patients. It is necessary to improve the detection of T. vaginalis using combined methods providing higher sensitivity, such as culture and PCR, mainly in asymptomatic pregnant patients, in order to prevent maternal and perinatal complications.

New Biochemical Parameters in the Differential Diagnosis of Ascitic Fluids

Background In the cases of ascitis, it is essential to determine their origin using the parameters obtained by the cytological and biochemical examinations. The aim of this study was to evaluate the usefulness of different biochemical markers and the number of cells in the differential diagnosis of ascitic fluid (AF). Methods One hundred ninety-one cases of AF were studied, who were admitted to the hospital from January 01, 2009 to December 31, 2014. One hundred fifty-two of them were included in the analysis, and the remaining 39 were excluded because they had more than one associated pathology, clotted or hemolyzed. Results The more frequent etiologies of AF were the cirrhosis (29%), the infections (22%) and the neoplasies (19%). Other pathologies reached 16%. Cutoff > 300 cells/mm3 detected the 78% of exudates. The AF/serum (S) of aspartate aminotransferase (AST) (> 0.5), lactate dehydrogenase (LDH) (> 0.6), proteins (PT) (> 0.5), cholesterol (COL) (> 0.4), and alanine aminotransferase (ALT) (> 0.5) correctly detected 80%, 78%, 72%, 70% and 70% of the exudates, respectively. Conclusion We proposed the utilization of a new cutoff of cellular counting, major of 300/mm3, since it would allow improving the detection of exudate ascites, without including the transudate ascites. AST AF/serum ratio (AF/S) showed the major usefulness in the differentiation and characterization of AF; LDH, proteins, cholesterol and ALT might be also acceptable in the above mentioned differentiation. The serum-ascites albumin gradient (SAAG) turned out to be a good marker of portal hypertension associated with cirrhotic processes. Creatine kinase (CK), alkaline phosphatase (ALP), amylase (AMI), total bilirubin (TB), triglycerides (TG) and glucose (GLU) did not allow differentiating exudates from transudates.