Martha von Specht

Community-associated methicillin-resistant Staphylococcus aureus, eastern Argentina

Sixty-nine community-associated methicillin-resistant Staphylococcus aureus recovered in 6 healthcare centers from northeastern and eastern Argentina were genotyped by pulsed-field gel electrophoresis. The predominant pulsotype was widely distributed harbored SCCmec type IV and Panton-Valentine leukocidin genes. Representative isolates were characterized by multilocus sequence typing and spa typing, demonstrating that this clone belonged to ST5 and spa type 311.

Meningitis neumocócica en niños menores de 15 años. Dieciséis años de vigilancia epidemiológica en Misiones, Argentina

We report the results of pneumococcal meningitis surveillance conducted at the Provincial Pediatric Hospital of Posadas, Misiones (Argentina), before the con...

Distribución de serotipos y perfiles de sensibilidad a los antimicrobianos de cepas de Streptococcus pneumoniae aisladas en niños en Misiones, Argentina

Antecedentes. El objetivo de este trabajo fue evaluar los patrones de resistencia antibiotica local y los serotipos de Streptococcus pneumoniae implicados en enfermedades invasivas en pacientes pediatricos del Hospital Provincial de Pediatria de Misiones, Argentina. Metodos. Se estudiaron 101 cepas aisladas de ninos a partir de muestras esteriles, entre junio de 1998 y junio de 2001. Las muestras se procesaron por el metodo habitual, y los patrones de resistencia antibiotica se determinaron segun pautas del National Committee for Clinical Laboratory Standards (NCCLS), por tecnicas de difusion y dilucion. La serotipificacion se efectuo mediante la reaccion de Quellung. Resultados. El 62% de las neumonias, el 70% de las neumonias con derrame y de las meningitis y 78% de las sepsis correspondieron a ninos menores de 2 anos de edad (74% del total de pacientes). Se identificaron 12 serotipos entre 71 cepas analizadas. Los tipos 14 (37,1%), 5 (21,4%), 1 (10%), 6A/6B (7,1%), 9N y 19A (5,7%) y 9V (4,3%) fueron los mas frecuentes. Se observo sensibilidad disminuida a penicilina en el 39% de los aislamientos, el 17,5% de los cuales presento resistencia intermedia y el 21,5% alto nivel de resistencia. Para ningun aislamiento la concentracion inhibitoria minima (CIM) fue superior a 4 µg/ml. La resistencia a penicilina quedo circunscrita a cinco serotipos, correspondiendo en el 84% de los casos al 14. Entre 71 aislamientos en que se efectuo la CIM a cefotaxima, 50 presentaron un valor menor o igual a 0,5 µg/ml; 18 una CIM de 1 µg/ml y tres de 2 µg/ml. No se detectaron cepas cuya CIM fuera superior a 2 µg/ml. El 22% de los aislamientos fue resistente a tetraciclina, el 48% a trimetoprima-sulfametoxazol, el 11% a cloranfenicol y el 6,8% a eritromicina. Ningun aislamiento fue resistente a vancomicina, ofloxacino ni rifampicina. Los patrones de resistencia combinada mas comunes, entre las cepas no sensibles a penicilina, fueron: penicilina-trimetoprima-sulfametoxazol (20%) seguido de penicilina-cefotaxima-trimetoprima-sulfametoxazol (7%; 3 aislamientos con CIM a cefotaxima = 2 µg/ml) y penicilina-trimetoprima-sulfametoxazol-cloranfenicol (5%). Conclusiones. Los patrones de resistencia y los tipos capsulares circulantes locales observados en este trabajo permiten adecuar esquemas terapeuticos a nuestra realidad y brindan informacion al equipo medico para evaluar el uso de vacunas como herramienta de prevencion y control de las infecciones invasivas por S. pneumoniae.

Susceptibilities to carbapenems and presence of cphA gene on food-borne Aeromonas

ABSTRACT The purpose of this study was to determine the susceptibilities of food-borne Aeromonas to carbapenems, as well as to investigate the presence of a metallo carbapenemase-encoding gene, named cphA. Minimum Inhibitory Concentration (MIC) was determined following NCCLS standards. All the tested microorganisms were susceptible to imipenem, meropenem and biapenem. However, a strong inoculum size effect on carbapenem MICs was observed for most of the strains. Six strains, out of seven, showed the presence of metallo--β−lactamases but cphA gene was detected in only two strains of A. veronii bv. sobria . Key words: metallocarbapenemase, cphA gene, food borne Aeromonas . * Author for correspondence INTRODUCTION Evolution of bacterial resistance to antibiotics in humans, animals and the environment is the result of the interaction between the exposure to antibiotics, selection of microorganisms carrying primordial genes of resistance, and transmission of resistance genes between bacteria. Selective effects occur in selective compartments, where particular antibiotic concentrations result in a differential growth rate of resistant bacterial variants (Baquero et al., 1998) This may happen even at very low antibiotic concentrations able to select low-level-resistant bacteria. Analysis of selective environment-related antibiotic-host-bacteria interactions is essential to understand the biology of antibiotic resistance. (Baquero et al., 1998) To anticipate emergence of resistance, it is necessary to better understand the genetics and biochemistry of resistance mechanisms and to develop methodologies to foresee their evolution at the individual or population level (Baquero et al., 1998). Most retrospective and prospective studies show that after the introduction of an antibiotic, the level of resistance increases both among pathogenic bacteria and in commensal bacteria (van den Bogaard and Stobberingh, 2000). Moreover, commensal bacteria constitute a reservoir of resistance genes for (potentially) pathogenic bacteria. Their level of resistance is considered to be a good indicator for selection pressure by antibiotic use and for resistance problems to be expected in pathogens. Aeromonas strains have been found to be able to produce up to three different β-lactamases

First time identification of Pandoraea sputorum from a patient with cystic fibrosis in Argentina: a case report

BackgroundPandoraea species are considered emerging pathogens in the context of cystic fibrosis (CF) and are difficult to identify by conventional biochemical methods. These multidrug resistant bacteria remain poorly understood particularly in terms of natural resistance, mechanisms of acquired resistance and impact on the prognosis of the disease and the lung function. Among them, Pandoraea sputorum has been previously described in few cases of CF patients from Spain, Australia, France and United States, underlining the need of more clinical data for a better knowledge of its pathogenicity. This is the first report relating to P. sputorum in a CF patient in Argentina.Case presentationPandoraea sputorum was identified in a nine-year-old cystic fibrosis patient from Argentina, after treatment failure during an exacerbation. The isolates were successfully identified by combining molecular techniques based on 16S rRNA sequencing and mass spectrometry (MS) methods, after reassessing previous misidentified isolates by conventional methods. After first isolation of P. sputorum, patient’s clinical condition worsened but later improved after a change in the treatment. Although isolates showed susceptibility to trimethoprim–sulfamethoxazole and imipenem, in our case, the antibiotic treatment failed in the eradication of P. sputorum.ConclusionsAll combined data showed a chronic colonization with P. sputorum associated to a deterioration of lung function. We noted that the presence of P. sputorum can be underestimated in CF patients and MALDI-TOF MS appears to be a promising means of accurate identification of Pandoraea species.

Tos convulsa: características clinicoepidemiológicas de 20 casos confirmados atendidos en el Hospital Pediátrico de la provincia de Misiones

Pertussis or whooping cough is a respiratory disease that has emerged in recent years in several countries including Argentina. The aim is to retrospectively describe clinical and epidemiological characteristics of 20 patients in the Pediatric Hospital of Misiones with confirmed diagnosis of whooping cough, according to criteria set by WHO and CDC, during the years 2005 and 2006. The median age was 4 months, 13 were male (65%). Fourteen patients (70%) were younger than 6 months and 9 (45%) younger than 3 months. All had cough (average duration of 7.6 days), 5 (25%) paroxysmal cough and 1 (5%) apnea and cyanosis. Two children died. Sixteen (80%) had not the three doses of vaccine quadruple, 7 children (35%) were younger than 3 months and had no dose. The disease remains a public health problem affecting not only children but also adults.

Resistance to β-lactams in enterococci

Enterococci are intrinsically resistant to several antimicrobial classes and show a great ability to acquire new mechanisms of resistance. Resistance to β-lactam antibiotics is a major concern because these drugs either alone or in combination are commonly used for the treatment of enterococcal infections. Ampicillin resistance, which is rare in Enterococcus faecalis, occurs in most of the hospital-associated Enterococcus faecium isolates. High-level resistance to ampicillin in E. faecium is mainly due to the enhanced production of PBP5 and/or by polymorphisms in the beta subunit of this protein. The dissemination of high-level ampicillin resistance can be the result of both clonal spread of strains with mutated pbp5 genes and horizontal gene transfer.