Beta-lactam antibiotics and viridans group streptococci / Antibióticos beta-lactámicos y estreptococos grupo viridans

Abstract The aim of this review is to present an update on the susceptibility of viridans groupstreptococci (VGS) to -lactam antimicrobials, with emphasis on the Argentinean scenario. VGSare a heterogeneous group including five groups of species, each one exhibiting peculiar sus-ceptibility patterns to penicillin (PEN). Species of the Streptococcus mitis group are frequentlynonsusceptible to PEN. PEN resistance is associated with changes in PEN-binding proteins. InArgentina, one to two thirds of VGS are nonsusceptible to PEN. Third generation cephalosporinsand carbapenems are currently more effective in vitro than PEN against VGS. Mortality was asso-ciated to nonsusceptibility to PEN in at least two studies involving patients with bacteremiacaused by VGS. Treatment of endocarditis due to VGS should be adjusted/to the PEN suscepti-bility of the isolates. Vancomycin may be an alternative choice for treating endocarditis causedby PEN-resistant isolates (MIC 4 g/ml).

Resumen El objetivo de esta revisión es presentar una actualización sobre la sensibilidad de los estreptococos del grupo viridans (EGV) a los antimicrobianos p-lactámicos, con énfasis en el escenario argentino. Los EGV son un grupo heterogéneo que incluye cinco grupos de especies, y cada una presenta su patrón especial de sensibilidad a la penicilina (PEN). Las especies del grupo Streptococcus mitis, con mayor frecuencia, no son sensibles a la PEN. La resistencia a la PEN se asocia con cambios de las proteínas ligadoras de PEN. En la Argentina, de uno a dos tercios de los EGV no son sensibles a la PEN. Las cefalosporinas de tercera generación y los carbapenemes son actualmente más eficaces in vitro que la PEN contra los EGV. La mortalidad se asoció con la no sensibilidad a la PEN en al menos dos estudios de pacientes con bacteriemia por EGV. El tratamiento de las endocarditis por EGV debe ajustarse según la sensibilidad a la PEN de los aislados. La vancomicina podría ser una elección alternativa para el tratamiento de las endocarditis por cepas resistentes a PEN (CIM >4 ^g/ml).

Beta-lactam antibiotics and viridans group streptococci.

The aim of this review is to present an update on the susceptibility of viridans group streptococci (VGS) to ß-lactam antimicrobials, with emphasis on the Argentinean scenario. VGS are a heterogeneous group including five groups of species, each one exhibiting peculiar susceptibility patterns to penicillin (PEN). Species of the Streptococcus mitis group are frequently nonsusceptible to PEN. PEN resistance is associated with changes in PEN-binding proteins. In Argentina, one to two thirds of VGS are nonsusceptible to PEN. Third generation cephalosporins and carbapenems are currently more effective in vitro than PEN against VGS. Mortality was associated to nonsusceptibility to PEN in at least two studies involving patients with bacteremia caused by VGS. Treatment of endocarditis due to VGS should be adjusted/to the PEN susceptibility of the isolates. Vancomycin may be an alternative choice for treating endocarditis caused by PEN-resistant isolates (MIC≥4µg/ml).

Resistance to ß-lactams in Streptococcus pneumoniae.

Streptococcus pneumoniae is an important causal agent of pneumonia, meningitis, sepsis, bacteremia, and otitis media. Penicillin resistance rates in S. pneumoniae have remained stable in Argentina in the last years. In the late '90s more isolates with MIC of penicillin ≥2µg/ml were observed; however, their frequency has decreased in recent years. The phenotypic expression of penicillin resistance is due to a modification in penicillin-binding proteins associated with a mosaic structure in the coding genes. The expansion of successful resistant clones varies among the different regions and is influenced by the use of antibiotics, vaccines, particularly conjugated ones, as well as population density. Parenteral treatment with high doses of penicillin G continues to be effective for the treatment of pneumonia and bacteremia, oral aminopenicillins for otitis media and sinusitis and third generation cephalosporins for meningitis.

[Development of a simple medium for the selective isolation of bacteria belonging to the Streptococcus anginosus group]. / Desarrollo de un medio simple para el aislamiento selectivo de bacterias del grupo Streptococcus anginosus.

Bacteria of the Streptococcus anginosus group (SAG) have recently been recognized as contributors of bronchopulmonary disease in cystic fibrosis (CF). Routine detection and quantification are limited by current CF microbiology protocols. The development of the CHROMagar™ StrepB chromogenic medium modified by the addition of plasma, nalidixic acid, colistin and sulfadiazine to make it selective for SAG bacteria is described. This medium could be used as a diagnostic tool to detect SAG in respiratory samples from patients suffering from chronic lung disease.

Resistencia a los β -lactámicos en enterococos / 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 faecium 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 resistance horizontal gene transfer.

Los enterococos son intrínsecamente resistentes a varias clases de antimicrobianos y presentan una gran capacidad para adquirir mecanismos de resistencia. La resistencia a los antibióticos p-lactámicos es preocupante porque estos fármacos solos o combinados se usan comúnmente para el tratamiento de las infecciones enterocócicas. La mayoría de los aislamientos hospitalarios de Enterococcus faecium presentan resistencia a la ampicilina, la cual es rara en Enterococcus faecalis. El alto nivel de resistencia a la ampicilina en E. faecium se debe principalmente a la hiperproducción de PBP5 y/o a polimorfismos en la subunidad beta de esta proteína. La propagación de esta resistencia puede deberse tanto a la diseminación clonal de cepas con genes pbp5 mutados como a la transferencia horizontal de genes.

Resistance to ß-lactams in enterococci.

Enterococci are intrinsically resistant to several antimicrobial classes and show a great ability to acquire new mechanisms of resistance. Resistance to ß-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.

Susceptibility to β-lactams in β-hemolytic streptococci / Sensibilidad a los β-lactámicos en estreptococos β-hemolíticos

Group A (GAS), B (GBS), c (GCS) and G (GGS) β-hemolytic streptococci are important human pathogens. They cause infections of different severity and frequency. Nowadays, after 70 years of use, penicillin is still universally active against GAS, GCS and GGS. However, therapeutic failures have been recorded in 2-28% of pharyngitis cases (median: 12%) attributable to different causes. By contrast, some GBS with reduced susceptibility to penicillin have been described, especially in Japan. In this group of bacteria, it is important to highlight that confirmation by reference methods is mandatory when decreased susceptibility to penicillin is suspected as well as checked for the detection of the mechanisms involved.

Los estreptococos β-hemolíticos de los grupos A (GAS), B (GBS), C (GCS) y G (GGS) son importantes patógenos humanos. Ellos producen infecciones de diversa gravedad y frecuencia. Aún después de más de 70 años de uso, la penicilina sigue siendo activa in vitro frente al 100% de los GAS, GCS y GGS. No obstante se han producido fallas terapéuticas entre el 2-28% de los casos de faringitis (media: 12%), atribuibles a diversas causas. En cambio se han descrito aislados de GBS con sensibilidad reducida a la penicilina, especialmente en Japón. Es importante que toda sospecha de sensibilidad disminuida a la penicilina en este grupo de bacterias sea confirmada por los métodos de referencia y comprobada mediante la detección de los mecanismos involucrados.

Susceptibility to ß-lactams in ß-hemolytic streptococci.

Group A (GAS), B (GBS), C (GCS) and G (GGS) ß-hemolytic streptococci are important human pathogens. They cause infections of different severity and frequency. Nowadays, after 70 years of use, penicillin is still universally active against GAS, GCS and GGS. However, therapeutic failures have been recorded in 2-28% of pharyngitis cases (median: 12%) attributable to different causes. By contrast, some GBS with reduced susceptibility to penicillin have been described, especially in Japan. In this group of bacteria, it is important to highlight that confirmation by reference methods is mandatory when decreased susceptibility to penicillin is suspected as well as checked for the detection of the mechanisms involved.

[Infections due to unusual bacteria and bacterial oncogenesis]. / Infecciones por bacterias poco comunes y oncogénesis bacteriana.

The recovery of an unusual organism in the clinical microbiology laboratory may be an indicator of an immunological abnormality in the patient. For instance, an important relationship between Clostridium septicum and colon carcinoma as well as between leukemia or lymphoma with species frequently considered contaminants (Bacillus spp., Corynebacterium spp.) or others rarely isolated from different contexts (Capnocytophaga spp.) were described. Some bacteria are almost exclusively isolated from AIDS patients (Rhodococcus equi). Campylobacter spp., Aeromonas spp., group G and mitis group streptococci were more frequently isolated in individuals suffering from any type of cancer than in other patients. Furthermore, some other bacteria can be considered markers of an undetected cancer that can be found mostly in neutropenic patients rather than in immunologically normal individuals. Possible mechanisms of bacterial oncogenesis include a modification of the inflammatory response, antigen-derived lymphoproliferation, and induction of hormones that increase epithelial cell proliferation. Typical examples of the above are: gastric adenocarcinoma induced by Helicobacter pylori, the association between group bovis bacteremia and colon carcinoma and the mucosa-associated lymphoid tissue (MALT) related to Helicobacter species (gastric MALT) and Chlamydophila spp. (ocular MALT). Isolation of any of these pathogens should require a thorough search for possible malignant diseases.

Infecciones por bacterias poco comunes y oncogénesis bacteriana. / [Infections due to unusual bacteria and bacterial oncogenesis].

The recovery of an unusual organism in the clinical microbiology laboratory may be an indicator of an immunological abnormality in the patient. For instance, an important relationship between Clostridium septicum and colon carcinoma as well as between leukemia or lymphoma with species frequently considered contaminants (Bacillus spp., Corynebacterium spp.) or others rarely isolated from different contexts (Capnocytophaga spp.) were described. Some bacteria are almost exclusively isolated from AIDS patients (Rhodococcus equi). Campylobacter spp., Aeromonas spp., group G and mitis group streptococci were more frequently isolated in individuals suffering from any type of cancer than in other patients. Furthermore, some other bacteria can be considered markers of an undetected cancer that can be found mostly in neutropenic patients rather than in immunologically normal individuals. Possible mechanisms of bacterial oncogenesis include a modification of the inflammatory response, antigen-derived lymphoproliferation, and induction of hormones that increase epithelial cell proliferation. Typical examples of the above are: gastric adenocarcinoma induced by Helicobacter pylori, the association between group bovis bacteremia and colon carcinoma and the mucosa-associated lymphoid tissue (MALT) related to Helicobacter species (gastric MALT) and Chlamydophila spp. (ocular MALT). Isolation of any of these pathogens should require a thorough search for possible malignant diseases.

Infecciones por bacterias poco comunes y oncogénesis bacteriana / [Infections due to unusual bacteria and bacterial oncogenesis].

The recovery of an unusual organism in the clinical microbiology laboratory may be an indicator of an immunological abnormality in the patient. For instance, an important relationship between Clostridium septicum and colon carcinoma as well as between leukemia or lymphoma with species frequently considered contaminants (Bacillus spp., Corynebacterium spp.) or others rarely isolated from different contexts (Capnocytophaga spp.) were described. Some bacteria are almost exclusively isolated from AIDS patients (Rhodococcus equi). Campylobacter spp., Aeromonas spp., group G and mitis group streptococci were more frequently isolated in individuals suffering from any type of cancer than in other patients. Furthermore, some other bacteria can be considered markers of an undetected cancer that can be found mostly in neutropenic patients rather than in immunologically normal individuals. Possible mechanisms of bacterial oncogenesis include a modification of the inflammatory response, antigen-derived lymphoproliferation, and induction of hormones that increase epithelial cell proliferation. Typical examples of the above are: gastric adenocarcinoma induced by Helicobacter pylori, the association between group bovis bacteremia and colon carcinoma and the mucosa-associated lymphoid tissue (MALT) related to Helicobacter species (gastric MALT) and Chlamydophila spp. (ocular MALT). Isolation of any of these pathogens should require a thorough search for possible malignant diseases.

Otitis media aguda: prevalencia de otopatógenos en pacientes de un hospital público / Acute otitis media: prevalence of ear pathogens in patients at a public hospital

Introducción y objetivo: La otitis media aguda (OMA) es una de las afecciones más frecuentes en la infancia y es la causa más común de prescripción de antibióticos en pediatría. El método indicado para identificar el germen responsable en OMA es la obtención de material del oído medio para cultivo mediante timpanocentesis. El objetivo de este estudio es describir la prevalencia de gérmenes causantes de OMA en pacientes eutróficos de 1 a 120 meses, que consultaron en un hospital público pediátrico. Método: Se incluyeron pacientes eutróficos con OMA con retención de contenido purulento en oído medio y OMA supurada con drenaje insuficiente de exudado que consultaron al Servicio de Otorrinolaringología de un hospital pediátrico desde mayo del 2009 hasta agosto del 2010. Resultados: Se incluyeron en el estudio 324 pacientes de los cuales 180 (55,6%) eran varones. Mediana de edad: 8 meses (rango intercuartílico: 4-15 meses). OMA bilateral se registró en 109/324 (33,6%) pacientes (se obtuvieron 433 muestras para cultivo).Al momento del diagnóstico 37% (120/324) de los niños recibían antibioticoterapia. De estos, el 59% (71/120) presentaron desarrollo bacteriano en los cultivos. La antibioticoterapia era adecuada en el 71,8% de los casos; en el 28,2% restante no se cubría el espectro del germen aislado. Conclusión: Los microorganismos más frecuentemente aislados fueron Streptococcus pneumoniae (39,5%), Haemophilus influenzae (37,4%), Moraxella catarrhalis (6,1%) y Streptococcus pyogenes (3,0%) (AU)

Background and objective: Acute otitis media (AOM) is one of the most common diseases in childhood and is the most common cause of antibiotic prescriptions in children. The gold standard for identifying the pathogens causing AOM is tympanocentesis. This is only possible in the stage of AOM when exudate is retained in the middle ear. The aim of this study was to describe the prevalence of organisms causing AOM in eutrophic patients at a public paediatric hospital. Material and methods: We included all patients with AOM diagnosed by otomicroscopy with purulent exudate retained in middle ear and suppurative AOM with inadequate drainage consulting at the Otorhinolaryngology Department in a paediatric tertiary care centre from 2 May 2009 to 31 August 2010. Results: There were 324 patients included in the study, with 180/324 (55.6%) being male. The median age was 8 months (interquartile range: 4 to 15 months). Bilateral AOM was recorded in 109/324 (33.6%) patients (433 samples for culture were obtained by tympanocentesis in 324 patients). At diagnosis, 37% (120/324) of the children had been receiving antimicrobial treatment. Of the patients who had received antibiotics, 71/120 (59.1%) had bacterial growth in middle ear fluid (MEF) cultures, with 51/71 (71.8%) being susceptible to the antibiotic they received; 20/71 (28.2%) patients were receiving an antibiotic that did not cover the spectrum of organisms isolated. Conclusion: The pathogens most frequently isolated are Streptococcus pneumoniae (39.5%), Haemophilus influenzae (37.4%), Moraxella catarrhalis (6.1%) and Streptococcus pyogenes (3.0%) (AU)

[Acute otitis media: prevalence of ear pathogens in patients at a public hospital]. / Otitis media aguda: prevalencia de otopatógenos en pacientes de un hospital público.

BACKGROUND AND OBJECTIVE: Acute otitis media (AOM) is one of the most common diseases in childhood and is the most common cause of antibiotic prescriptions in children. The gold standard for identifying the pathogens causing AOM is tympanocentesis. This is only possible in the stage of AOM when exudate is retained in the middle ear. The aim of this study was to describe the prevalence of organisms causing AOM in eutrophic patients at a public paediatric hospital. MATERIAL AND METHODS: We included all patients with AOM diagnosed by otomicroscopy with purulent exudate retained in middle ear and suppurative AOM with inadequate drainage consulting at the Otorhinolaryngology Department in a paediatric tertiary care centre from 2 May 2009 to 31 August 2010. RESULTS: There were 324 patients included in the study, with 180/324 (55.6%) being male. The median age was 8 months (interquartile range: 4 to 15 months). Bilateral AOM was recorded in 109/324 (33.6%) patients (433 samples for culture were obtained by tympanocentesis in 324 patients). At diagnosis, 37% (120/324) of the children had been receiving antimicrobial treatment. Of the patients who had received antibiotics, 71/120 (59.1%) had bacterial growth in middle ear fluid (MEF) cultures, with 51/71 (71.8%) being susceptible to the antibiotic they received; 20/71 (28.2%) patients were receiving an antibiotic that did not cover the spectrum of organisms isolated. CONCLUSION: The pathogens most frequently isolated are Streptococcus pneumoniae (39.5%), Haemophilus influenzae (37.4%), Moraxella catarrhalis (6.1%) and Streptococcus pyogenes (3.0%).

Tinea capitis. Experiencia de 2 años en un hospital de pediatría de Buenos Aires, Argentina / Tinea capitis: two years experience in a paediatric hospital of Buenos Aires, Argentina

La tiña de cabeza (tinea capitis) es una dermatofitosis causada por hongos pertenecientes a los géneros Microsporum y Trichophyton, y constituye un importante problema sanitario en Argentina. El objetivo fue conocer la incidencia y la respuesta terapéutica en los pacientes que asistieron a la consulta en un hospital pediátrico de alta complejidad durante un período de 2 años de estudio. Se diagnosticaron 98 casos de tinea capitis y 13 de querion de Celso. Microsporum canis se aisló en el 61,28% de los casos. El rango de los valores de concentración mínima inhibitoria para fluconazol, itraconazol, voriconazol, terbinafina, ketoconazol y griseofulvina fueron, respectivamente, > 32: 0,06–4; < 0,015–2; < 0,015–0,25; 0,13–8, y de 0,06–128mg/ml(AU)

Tinea capitis is an infection caused by dermatophytes of the genera Microsporum and Trichophyton, and constitutes a major health problem in Argentina. The aim of the present study was to find out the incidence of those etiological agents and the therapeutic response in patients attending a High-Complexity Paediatric Hospital within a two-year period. A total of 98 tinea capitis were diagnosed, 13 of which were Celsus kerion. Microsporum canis was isolated in 61.28%. The range of values for minimum inhibitory concentrations were >32, 0,06–4; <0,015–2; <0,015–0.25; 0.13–8; 0.06–128mg/mL for fluconazole itraconazole, voriconazole, terbinafine, ketoconazole and griseofulvin, respectively(AU)

[Tinea capitis: two years experience in a paediatric hospital of Buenos Aires, Argentina]. / Tinea capitis. Experiencia de 2 años en un hospital de pediatría de Buenos Aires, Argentina.

Tinea capitis is an infection caused by dermatophytes of the genera Microsporum and Trichophyton, and constitutes a major health problem in Argentina. The aim of the present study was to find out the incidence of those etiological agents and the therapeutic response in patients attending a High-Complexity Paediatric Hospital within a two-year period. A total of 98 tinea capitis were diagnosed, 13 of which were Celsus kerion. Microsporum canis was isolated in 61.28%. The range of values for minimum inhibitory concentrations were >32, 0.06-4; <0.015-2; <0.015-0.25; 0.13-8; 0.06-128 microg/mL for fluconazole itraconazole, voriconazole, terbinafine, ketoconazole and griseofulvin, respectively.