Comparison of two MALDI-TOF MS systems for theidentification of clinically relevant anaerobic bacteriain Argentina

Abstract The aim of this study was to compare the performance of two MALDI-TOF MS systems in the identification of clinically relevant strict anaerobic bacteria. The 16S rRNA gene sequencing was the gold standard method when discrepancies or inconsistencies were observed between platforms. A total of 333 isolates were recovered from clinical samples of different centers in Buenos Aires City between 2016 and 2021. The isolates were identified in duplicate using two MALDI-TOF MS systems, BD Bruker Biotyper (Bruker Daltonics, Bremen, Germany) and Vitek MS (bioMèrieux, Marcy-l'Etoile, France). Using the Vitek MS system, the identification of anaerobic isolates yielded the following percentages: 65.5% (n: 218) at the species or species-complex level, 71.2% (n: 237) at the genus level, 29.4% (n: 98) with no identification and 5.1% (n: 17) with misidentification. Using the Bruker Biotyper system, the identification rates were as follows: 85.3% (n: 284) at the species or species-complex level, 89.7% (n: 299) at the genus level, 14.1% (n: 47) with no identification and 0.6% (n: 2) with misidentification. Differences in the performance of both methods were statistically significant (p-values <0.0001). In conclusion, MALDI-TOF MS systems speed up microbial identification and are particularly effective for slow-growing microorganisms, such as anaerobic bacteria, which are difficult to identify by traditional methods. In this study, the Bruker system showed greater accuracy than the Vitek system. In order to be truly effective, it is essential to update the databases of both systems by increasing the number of each main spectrum profile within the platforms.

Resumen El objetivo de este estudio fue comparar el desempeño de dos sistemas MALDI-TOF MS en la identificación de bacterias anaerobias estrictas de interés clínico. La secuenciación del gen 16S ARNr fue el método de referencia utilizado cuando se observaron discrepancias o inconsistencias entre plataformas. Se recuperaron 333 aislados de muestras clínicas de diferentes centros de la Ciudad Autónoma de Buenos Aires entre 2016 y 2021. Los aislados se identificaron por duplicado mediante dos sistemas MALDI-TOF MS: el BD Bruker Biotyper (Bruker Daltonics, Bremen, Alemania) y el Vitek MS (bioMèrieux, Marcy-l'Etoile, Francia). A través del sistema Vitek MS, los mismos fueron identificados a nivel de especie o complejo de especies en un 65,5% (n: 218) y de género en un 71,2% (n: 237), mientras que no se identificaron en un 29,4% (n: 98) y fue incorrecta en el 5,1% (n: 17). Mediante el sistema Bruker Biotyper, dichos valores fueron del 85,3% (n: 284), del 89,7% (n: 299), del 14,1% (n: 47) y del 0,6% (n: 2), respectivamente. La diferencia entre ambos métodos fue estadísticamente significativa (p<0,0001). En conclusión, los sistemas MALDI-TOF MS aceleran la identificación microbiana. Son especialmente útiles para los microorganismos de crecimiento lento, como las bacterias anaerobias, que son difíciles de identificar con los métodos tradicionales. El sistema Bruker demostró ser más preciso que el Vitek MS. Para que estos métodos sean realmente efectivos es fundamental actualizar las bases de datos de ambos sistemas e incrementar el número de espectros de referencia dentro de las plataformas.

Comparison of two MALDI-TOF MS systems for the identification of clinically relevant anaerobic bacteria in Argentina.

The aim of this study was to compare the performance of two MALDI-TOF MS systems in the identification of clinically relevant strict anaerobic bacteria. The 16S rRNA gene sequencing was the gold standard method when discrepancies or inconsistencies were observed between platforms. A total of 333 isolates were recovered from clinical samples of different centers in Buenos Aires City between 2016 and 2021. The isolates were identified in duplicate using two MALDI-TOF MS systems, BD Bruker Biotyper (Bruker Daltonics, Bremen, Germany) and Vitek MS (bioMèrieux, Marcy-l'Etoile, France). Using the Vitek MS system, the identification of anaerobic isolates yielded the following percentages: 65.5% (n: 218) at the species or species-complex level, 71.2% (n: 237) at the genus level, 29.4% (n: 98) with no identification and 5.1% (n: 17) with misidentification. Using the Bruker Biotyper system, the identification rates were as follows: 85.3% (n: 284) at the species or species-complex level, 89.7% (n: 299) at the genus level, 14.1% (n: 47) with no identification and 0.6% (n: 2) with misidentification. Differences in the performance of both methods were statistically significant (p-values <0.0001). In conclusion, MALDI-TOF MS systems speed up microbial identification and are particularly effective for slow-growing microorganisms, such as anaerobic bacteria, which are difficult to identify by traditional methods. In this study, the Bruker system showed greater accuracy than the Vitek system. In order to be truly effective, it is essential to update the databases of both systems by increasing the number of each main spectrum profile within the platforms.

Diagnóstico microbiológico de infección por Clostridioides difficile en épocas de COVID-19 en un hospital pediátrico de alta complejidad / Microbiological diagnosis of Clostridioides difficile infection in times of COVID-19 in a high complexity pediatric hospital

Resumen La infección por Clostridioides difficile (ICD) puede variar desde diarrea hasta megacolon tóxico. Los objetivos del trabajo fueron mostrar la variación en el número de casos diagnosticados de ICD en este laboratorio entre 2020, cuando comenzó la pandemia de COVID-19 y 2019 y 2021 y detallar los casos precedidos por la infección de SARS-CoV-2. El presente es un estudio retrospectivo observacional en el que se registraron el número total de muestras procesadas con sospecha de ICD y el de positivas y los antecedentes clínicos de pacientes con ICD hasta dos meses después de su diagnóstico de COVID-19. Durante 2020 se procesaron menos muestras que en 2019 y 2021; sin embargo, el porcentaje de positividad fue de 13,1%, 7,2% y 7,8%, respectivamente. Esto pudo deberse a mejoras en el criterio clínico al momento de seleccionar las muestras con sospecha de ICD.

Abstract Clostridioides difficile infection (CDI) can cause anything from diarrhea to toxic megacolon. The objectives of this study were: to show the variation in the number of diagnosed cases of CDI in this center, comparing 2020, when the COVID-19 pandemic began, with 2019 and 2021 and to detail cases preceded by SARS-CoV-2 infection. This is an observational retrospective study in which the total number of samples processed with suspected CDI were recorded. The positive ones and the clinical history of patients with a diagnosis of CDI up to two months after their diagnosis of SARS-CoV-2 infection were recorded as well. During 2020 a smaller number of samples were processed. However, during this year the percentage of positivity was 13.1% vs. 7,2% and 7.8% during 2019 and 2021, respectively. It is believed that this may have been due to improvements in clinical suspicion and sample selection for CDI diagnosis.

Resumo A infecção por Clostridioides difficile (ICD) pode causar desde diarreia até megacólon tóxico. Os objetivos desta apresentação foram: mostrar a variação do número de casos diagnosticados de ICD neste laboratório, entre 2020 quando começou a pandemia de COVID-19 e 2019 e 2021 e, detalhar os casos precedidos pela infecção por SARS-CoV-2. Esse estudo foi retrospectivo observacional e foram registrados: o número total de amostras processadas com suspeita de ICD e de amostras positivas e os antecedentes clínicos daqueles pacientes com diagnóstico de ICD até dois meses após o diagnóstico de COVID 19. Durante 2020, foram processadas menos amostras do que em 2019 e 2021; no entanto, o percentual de positividade foi de 13,1%, 7,2% e 7,8%, respectivamente. Isso pode ter sido resultado de melhorias no critério clínico na hora de selecionar as amostras com suspeita de ICD.

The dilemma of identifying Peptoniphilus species by using two MALDI-TOF MS systems.

Two commercial MALDI-TOF MS systems were used to identify 18 isolates, belonging to the Peptoniphilus genus; also the 16S rRNA sequencing identity was compared against the MALDI-TOF MS system results. Bruker Biotyper system provided higher accuracy than Vitek MS system, however, adding spectra could allow a more reliable species level identification.

Detection of toxigenic Clostridioides --#1;Clostridium--#3; difficile: Usefulness of two commercially available enzyme immunoassays and a PCR assay on stool samples and stool isolates / Detección de Clostridioides --#1;Clostridium--#3; difficile toxigénico: utilidad de dos métodos de enzimoinmunoensayo comerciales y una PCR en las muestras de materia fecal y en los respectivos aislamientos

The best laboratory diagnostic approach to detect Clostridioides --#1;Clostridium--#3; difficile infection (CDI) is a subject of ongoing debate. With the aim of evaluating four laboratory diagnostic methods, 250 unformed stools from patients with suspected CDI submitted to nine medical center laboratories from November 2010 to December 2011, were studied using: (1) an immunochromatographic rapid assay test that combines the qualitative determination of glutamate dehydrogenase (GDH) plus toxins A and B (QAB), the CDIFF QUIK CHEK COMPLETE assay; (2) an enzyme immunoassay for qualitative determination of toxins A and B, the RIDASCREENTC. difficile Toxin A/B assay (RAB); (3) a PCR for the toxin B gene assay (PCR); and (4) the toxigenic culture (TC).C. difficile isolates from direct toxin negative stools by QAB, RAB and PCR were evaluated for toxigenicity by the same direct tests, in order to assess the contribution of the TC (QAB-TC, RAB-TC, PCR-TC). A combination of the cell culture cytotoxicity neutralization assay (CCCNA) in stools, and the same assay on isolates from direct negative samples (CCCNA-TC) was considered the reference method (CCCNA/CCCNA-TC). Of the 250 stools tested, 107 (42.8%) were positive by CCCNA/CCCNA-TC. The GDH and PCR/PCR-TC assays were the most sensitive, 91.59% and 87.62%, respectively. The QAB, RAB, QAB/QAB-TC and RAB/RAB-TC had the highest specificities, ca. 95%. A negative GDH result would rule out CDI, however, its low positive likelihood ratio (PLR) of 3.97 indicates that a positive result should always be complemented with the detection of toxins. If the RAB, QAB, and PCR assays do not detect toxins from direct feces, the toxigenic culture should be performed. In view of our results, the most accurate and reliable methods to be applied in a clinical microbiology laboratory were the QAB/QAB-TC, and RAB/RAB-TC, with PLRs >10 and negative likelihood ratios <0.30.

El mejor procedimiento para realizar el diagnóstico de laboratorio de la infección causada por Clostridioides --#1;Clostridium--#3; difficile (ICD) es aún objeto de debate. Con el fin de evaluar cuatro métodos diagnósticos de laboratorio, se estudiaron 250 muestras de heces diarreicas provenientes de pacientes con sospecha de ICD remitidas a los laboratorios de nueve centros médicos entre noviembre de 2010 y diciembre de 2011. Dichas muestras se analizaron mediante los siguientes métodos:1) un ensayo rápido inmunocromatográfico que combina la detección cualitativa de la glutamato deshidrogenasa (GDH) y de las toxinas Ay B (QAB), CDIFF QUIK CHEK COMPLETE;2) un enzimoinmunoanálisis para la determinación cualitativa de las toxinas A/B, RIDASCREENTC. difficile Toxin A/B (RAB);3) un método molecular basado en PCR para la detección del gen que codifica la toxina B (PCR) y 4) el cultivo toxigénico (TC). Como método de referencia se utilizó la combinación del ensayo de citotoxicidad sobre cultivo de células con la neutralización de toxina mediante anticuerpo específico en los filtrados de las heces (CCCNA) y el mismo método en sobrenadantes de aislamientos de C. difficile (CCCNA-TC). La toxigenicidad de las cepas aisladas de muestras directas negativas con QAB, RAB y PCR se evaluó con los mismos métodos, con el propósito de detectar la contribución del TC (QAB-TC, RAB-TC, PCR-TC). De las 250 muestras estudiadas, 107 (42,8%) fueron positivas por CCCNA/CCCNA-TC. Los métodos GDH y PCR/PCR-TC fueron los más sensibles: 91,59 y 87,62%, respectivamente. Los métodos QAB, RAB, QAB/QAB-TC y RAB/RAB-TC mostraron las mayores especificidades, del 95%, aproximadamente. Un resultado negativo para GDH excluiría la ICD, pero su baja razón de verosimilitud positiva (PLR), que fue 3,97, indica que un resultado positivo debe complementarse con la detección de toxinas. Cuando no se detectan toxinas directas por RAB, QAB ni PCR, debería realizarse el TC. De acuerdo con nuestros resultados, los métodos más precisos y confiables para ser aplicados en un laboratorio de microbiología clínica son QAB/QAB-TC y RAB/RAB-TC, con una PLR> 10 y una razón de verosimilitud negativa < 0,30.

Detection of toxigenic Clostridioides [Clostridium] difficile: Usefulness of two commercially available enzyme immunoassays and a PCR assay on stool samples and stool isolates.

The best laboratory diagnostic approach to detect Clostridioides [Clostridium] difficile infection (CDI) is a subject of ongoing debate. With the aim of evaluating four laboratory diagnostic methods, 250 unformed stools from patients with suspected CDI submitted to nine medical center laboratories from November 2010 to December 2011, were studied using: (1) an immunochromatographic rapid assay test that combines the qualitative determination of glutamate dehydrogenase (GDH) plus toxins A and B (QAB), the CDIFF QUIK CHEK COMPLETE assay; (2) an enzyme immunoassay for qualitative determination of toxins A and B, the RIDASCREEN™ C. difficile Toxin A/B assay (RAB); (3) a PCR for the toxin B gene assay (PCR); and (4) the toxigenic culture (TC). C. difficile isolates from direct toxin negative stools by QAB, RAB and PCR were evaluated for toxigenicity by the same direct tests, in order to assess the contribution of the TC (QAB-TC, RAB-TC, PCR-TC). A combination of the cell culture cytotoxicity neutralization assay (CCCNA) in stools, and the same assay on isolates from direct negative samples (CCCNA-TC) was considered the reference method (CCCNA/CCCNA-TC). Of the 250 stools tested, 107 (42.8%) were positive by CCCNA/CCCNA-TC. The GDH and PCR/PCR-TC assays were the most sensitive, 91.59% and 87.62%, respectively. The QAB, RAB, QAB/QAB-TC and RAB/RAB-TC had the highest specificities, ca. 95%. A negative GDH result would rule out CDI, however, its low positive likelihood ratio (PLR) of 3.97 indicates that a positive result should always be complemented with the detection of toxins. If the RAB, QAB, and PCR assays do not detect toxins from direct feces, the toxigenic culture should be performed. In view of our results, the most accurate and reliable methods to be applied in a clinical microbiology laboratory were the QAB/QAB-TC, and RAB/RAB-TC, with PLRs >10 and negative likelihood ratios <0.30.

Identification of CfiA coding genes in Bacteroides fragilis isolates recovered in Argentina. Inconsistencies in CfiA organization and nomenclature.

CfiA (CcrA) metallo-ß-lactamase is the main carbapenem resistance mechanism in B. fragilis. From cfiA positive isolates detected in a previous surveillance study, 3 displayed resistance to imipenem while the remaining were susceptible. The aim of this study was to identify the cfiA alleles and to analyze the presence of IS elements in their upstream regions. CfiA-1, CfiA-4, CfiA-13, CfiA-19 and CfiA-22 were detected. IS elements belonging to IS21 family and IS942 group were identified upstream to cfiA in the 3 imipenem resistant isolates. We present an exhaustive analysis of cfiA/CfiA registers in databases, illustrating the inconsistencies in both organization and nomenclature. According to this analysis CfiA family comprises nowadays 15 different CfiA variants coded by 24 cfiA sequences. Curation of CfiA database is mandatory, if not new cfiA admission at GenBank will contribute to make this classification more complex.

Absceso cerebral en niños: experiencia en diez años en un hospital pediátrico de alta complejidad / Brain abscess in children: ten years of experience in a third level pediatric hospital

El absceso cerebral es una infección focal, que se presenta con una frecuencia de 0,3-1,3 casos cada 100000 personas/año.¹ Se describe la epidemiología, clínica y microbiología de 38 niños con diagnóstico de absceso cerebral internados entre el 1/4/2005 y el 31/12/2015 en el Hospital de Pediatría "Prof. Dr. Juan P. Garrahan" de la Ciudad de Buenos Aires. Veinticuatro pacientes fueron varones. La mediana de edad fue de 132 meses. Se detectaron factores predisponentes en 25 niños. La mediana de evolución entre el inicio de los síntomas y la consulta fue de 7 días. Hubo 27 casos con lesiones únicas. Se realizó un drenaje quirúrgico en 34 pacientes. Las bacterias más frecuentes fueron anaerobios, Streptococcus viridans y Staphylococcus aureus. La mediana de tratamiento antibiótico fue de 56 días y la mediana de internación fue de 43 días. La letalidad fue del 3%.

Brain abscess is a focal infection that occurs with a frequency of 0.3-1.3 cases per 100,000 people/year. We describe the epidemiology, clinical and microbiology characteristics of 38 children diagnosed with brain abscess hospitalized between 4/1/2005 and 12/31/2015 at Hospital de Pediatría "Prof. Dr. Juan P. Garrahan" in Buenos Aires City. Twenty-four patients were male. The median age was 132 months. Predisposing factors were detected in 25 children. The median evolution from onset of symptoms to the visit was 7 days. There were 27 cases with single lesions. Surgical drainage was performed in 34 patients. The most frequent bacteria were anaerobes, Streptococcus viridans and Staphylococcus aureus. The median of antibiotic treatment was 56 days and the median of hospitalization was 43 days. The lethality was 3%.

[Brain abscess in children: ten years of experience in a third level pediatric hospital]. / Absceso cerebral en niños: experiencia en diez años en un hospital pediátrico de alta complejidad.

Brain abscess is a focal infection that occurs with a frequency of 0.3-1.3 cases per 100,000 people/year. We describe the epidemiology, clinical and microbiology characteristics of 38 children diagnosed with brain abscess hospitalized between 4/1/2005 and 12/31/2015 at Hospital de Pediatría "Prof. Dr. Juan P. Garrahan" in Buenos Aires City. Twenty-four patients were male. The median age was 132 months. Predisposing factors were detected in 25 children. The median evolution from onset of symptoms to the visit was 7 days. There were 27 cases with single lesions. Surgical drainage was performed in 34 patients. The most frequent bacteria were anaerobes, Streptococcus viridans and Staphylococcus aureus. The median of antibiotic treatment was 56 days and the median of hospitalization was 43 days. The lethality was 3%.

El absceso cerebral es una infección focal, que se presenta con una frecuencia de 0,3-1,3 casos cada 100 000 personas/año.1 Se describe la epidemiología, clínica y microbiología de 38 niños con diagnóstico de absceso cerebral internados entre el 1/4/2005 y el 31/12/2015 en el Hospital de Pediatría "Prof. Dr. Juan P. Garrahan" de la Ciudad de Buenos Aires. Veinticuatro pacientes fueron varones. La mediana de edad fue de 132 meses. Se detectaron factores predisponentes en 25 niños. La mediana de evolución entre el inicio de los síntomas y la consulta fue de 7 días. Hubo 27 casos con lesiones únicas. Se realizó un drenaje quirúrgico en 34 pacientes. Las bacterias más frecuentes fueron anaerobios, Streptococcus viridans y Staphylococcus aureus. La mediana de tratamiento antibiótico fue de 56 días y la mediana de internación fue de 43 días. La letalidad fue del 3%.

Actinomicosis torácica: presentación de un caso / Thoracic actinomycosis: report of a case

La actinomicosis es una enfermedad producida por bacterias del género Actinomyces. La forma torácica representa el 30% de los casos. La evolución es habitualmente crónica, con clínica variable. Se presenta una nina de 11 años de edad con tumefacción subescapular derecha de un mes de evolución, asociada a fiebre, hiporexia y pérdida de peso. Se diagnosticó actinomicosis torácica producida por Actinomyces meyeri. Recibió tratamiento antibiótico durante un año, con resolución completa. Aunque es poco frecuente, debe ser tenida en cuenta como diagnóstico diferencial en cuadros de tumoración torácica de larga evolución con compromiso del estado general. Debe informarse al microbiólogo la sospecha diagnóstica por lo difícil de su desarrollo en los medios de cultivo habitual.

Actinomycosis is a disease produced by bacteria of the genus Actinomyces. The thoracic form represents 30% of the cases. Signs and symptoms are generally unspecific. A previously healthy 11 year old girl was admitted with a chest mass of a month of evolution associated with fever, hyporexia and weight loss. Thoracic actinomycosis was diagnosed with the isolation of Actinomyces meyeri in the mass drainage. She received antibiotic treatment for a year with complete resolution. Although rare, it should be taken into account as a differential diagnosis in long evolution thoracic tumor affecting the general condition. The microbiologist must be warned about the suspected diagnosis because it is difficult to find it in routinely used culture media.

[Thoracic actinomycosis: report of a case]. / Actinomicosis torácica: presentación de un caso.

Actinomycosis is a disease produced by bacteria of the genus Actinomyces. The thoracic form represents 30% of the cases. Signs and symptoms are generally unspecific. A previously healthy 11 year old girl was admitted with a chest mass of a month of evolution associated with fever, hyporexia and weight loss. Thoracic actinomycosis was diagnosed with the isolation of Actinomyces meyeri in the mass drainage. She received antibiotic treatment for a year with complete resolution. Although rare, it should be taken into account as a differential diagnosis in long evolution thoracic tumor affecting the general condition. The microbiologist must be warned about the suspected diagnosis because it is difficult to find it in routinely used culture media.

Serotype distribution of pneumococci isolated from pediatric patients with acute otitis media and invasive infections, and potential coverage of pneumococcal conjugated vaccines.

A 16-month prospective, descriptive study was conducted on pneumococcal serotype distribution isolated from children with acute otitis media (AOM) and invasive infections (INV). Eighty-nine children with pneumococcal INV and 324 with a first episode of AOM were included. Bacterial pathogens (N = 326) were isolated from the middle-ear fluid of 250 patients. A total of 30 pneumococcal serotypes were identified. Prevalent serotypes were 14, 19A, 9V, 3, 19F, 6A, 23F, and 18C in AOM and 14, 1, 19A, 5, 12F, 6B, and 18C in INV. Potential coverage with PCV10 vaccine would be 46.5 % and 60.7 % for pneumococci involved in AOM and INV, respectively; it would be 71.7 % and 73 % with PCV13. PCV10, conjugated with a Haemophilus protein, would have an immunologic coverage of 39.9 % for AOM vs. 18.5 % with PCV13. However, differences in the prevention of INV were crucial for the decision to include the 13-valent vaccine in the national calendar for children less than two years old in Argentina.

Serotype distribution of pneumococci isolated from pediatric patients with acute otitis media and invasive infections, and potential coverage of pneumococcal conjugated vaccines / Distribución de serotipos de neumococos aislados de pacientes pediátricos con otitis media aguda e infecciones invasivas y su cobertura potencial a través de vacunas conjugadas

A 16-month prospective, descriptive study was conducted on pneumococcal serotype distribution isolated from children with acute otitis media (AÜM) and invasive infections (INV). Eighty-nine children with pneumococcal INV and 324 with a first episode of AOM were included. Bacterial pathogens (N = 326) were isolated from the middle-ear fluid of 250 patients. A total of 30 pneumococcal serotypes were identified. Prevalent serotypes were 14, 19A, 9V, 3, 19F, 6A, 23F, and 18C in AOM and 14, 1, 19A, 5, 12F, 6B, and 18C in INV. Potential coverage with PCV10 vaccine would be 46.5 % and 60.7 % for pneumococci involved in AOM and INV, respectively; it would be 71.7 % and 73 % with PCV13. PCV10, conjugated with a Haemophilus protein, would have an immunologic coverage of 39.9 % for AOM vs. 18.5 % with PCV13. However, differences in the prevention of INV were crucial for the decision to include the 13-valent vaccine in the national calendar for children less than two years old in Argentina.

Se realizó un estudio prospectivo descriptivo sobre la distribución de serotipos de neumococos aislados de niños con otitis media aguda (OMA) y con infecciones invasivas (INV) en un período de 16 meses. Se incluyeron 89 niños con INV neumocócicas y 324 con un primer episodio de OMA. Trescientos cuarenta y seis patógenos se aislaron de las secreciones de oído medio obtenidas de 250 pacientes. Se identificaron 30 serotipos y los más prevalentes fueron el 14, 19A, 9V, 3, 19F, 6A, 23F y 18C en OMA y el 14, 1, 19A, 5, 12F, 6B y 18C en INV. La cobertura potencial con la vacuna PCV10 sería de 46,5 % y 60,7 % para neumococos involucrados en OMA y en INV, respectivamente; con la PCV13, esta sería de 71,7 % y 73 %. La PCV10 conjugada con una proteína de Haemophilus tendría una cobertura inmunológica del 39,9 % para OMA, contra una cobertura del 18,5 % de la PCV13. Sin embargo, las diferencias en la prevención de INV fueron determinantes a la hora de considerar incorporarla al calendario nacional de vacunación para niños menores de 2 años en la Argentina.

Serotype distribution of pneumococci isolated from pediatric patients with acute otitis media and invasive infections, and potential coverage of pneumococcal conjugated vaccines / Distribución de serotipos de neumococos aislados de pacientes pediátricos con otitis media aguda e infecciones invasivas y su cobertura potencial a través de vacunas conjugadas

A 16-month prospective, descriptive study was conducted on pneumococcal serotype distribution isolated from children with acute otitis media (AÜM) and invasive infections (INV). Eighty-nine children with pneumococcal INV and 324 with a first episode of AOM were included. Bacterial pathogens (N = 326) were isolated from the middle-ear fluid of 250 patients. A total of 30 pneumococcal serotypes were identified. Prevalent serotypes were 14, 19A, 9V, 3, 19F, 6A, 23F, and 18C in AOM and 14, 1, 19A, 5, 12F, 6B, and 18C in INV. Potential coverage with PCV10 vaccine would be 46.5 % and 60.7 % for pneumococci involved in AOM and INV, respectively; it would be 71.7 % and 73 % with PCV13. PCV10, conjugated with a Haemophilus protein, would have an immunologic coverage of 39.9 % for AOM vs. 18.5 % with PCV13. However, differences in the prevention of INV were crucial for the decision to include the 13-valent vaccine in the national calendar for children less than two years old in Argentina.(AU)

Se realizó un estudio prospectivo descriptivo sobre la distribución de serotipos de neumococos aislados de niños con otitis media aguda (OMA) y con infecciones invasivas (INV) en un período de 16 meses. Se incluyeron 89 niños con INV neumocócicas y 324 con un primer episodio de OMA. Trescientos cuarenta y seis patógenos se aislaron de las secreciones de oído medio obtenidas de 250 pacientes. Se identificaron 30 serotipos y los más prevalentes fueron el 14, 19A, 9V, 3, 19F, 6A, 23F y 18C en OMA y el 14, 1, 19A, 5, 12F, 6B y 18C en INV. La cobertura potencial con la vacuna PCV10 sería de 46,5 % y 60,7 % para neumococos involucrados en OMA y en INV, respectivamente; con la PCV13, esta sería de 71,7 % y 73 %. La PCV10 conjugada con una proteína de Haemophilus tendría una cobertura inmunológica del 39,9 % para OMA, contra una cobertura del 18,5 % de la PCV13. Sin embargo, las diferencias en la prevención de INV fueron determinantes a la hora de considerar incorporarla al calendario nacional de vacunación para niños menores de 2 años en la Argentina.(AU)

Serotype distribution of pneumococci isolated from pediatric patients with acute otitis media and invasive infections, and potential coverage of pneumococcal conjugated vaccines. / Serotype distribution of pneumococci isolated from pediatric patients with acute otitis media and invasive infections, and potential coverage of pneumococcal conjugated vaccines.

A 16-month prospective, descriptive study was conducted on pneumococcal serotype distribution isolated from children with acute otitis media (AOM) and invasive infections (INV). Eighty-nine children with pneumococcal INV and 324 with a first episode of AOM were included. Bacterial pathogens (N = 326) were isolated from the middle-ear fluid of 250 patients. A total of 30 pneumococcal serotypes were identified. Prevalent serotypes were 14, 19A, 9V, 3, 19F, 6A, 23F, and 18C in AOM and 14, 1, 19A, 5, 12F, 6B, and 18C in INV. Potential coverage with PCV10 vaccine would be 46.5

and 60.7

for pneumococci involved in AOM and INV, respectively; it would be 71.7

and 73

with PCV13. PCV10, conjugated with a Haemophilus protein, would have an immunologic coverage of 39.9

for AOM vs. 18.5

with PCV13. However, differences in the prevention of INV were crucial for the decision to include the 13-valent vaccine in the national calendar for children less than two years old in Argentina.

Isolation of Serratia rubidaea from a mixed infection after a horse bite.

Horse bite infections are very rarely reported in the medical literature. Here we present a case of a severe facial infection in a 2-year-old boy after a horse bite, from which Serratia rubidaea and Enterobacter cloacae were isolated. Some pieces of grass were found inside the wound and were removed before performing a surgical toilet. The presence of these two gram-negative bacteria associated with a horse bite infection, as well as other organisms such as anaerobes, Pseudomonas, gram-positive cocci, Actinobacillus spp., previously described in other works, should be taken into account when selecting the antibiotics for prophylactic treatment of farm animal bites.

First national survey of antibiotic susceptibility of the Bacteroides fragilis group: emerging resistance to carbapenems in Argentina.

The antibiotic susceptibility rates of 363 clinical Bacteroides fragilis group isolates collected from 17 centers in Argentina during the period from 2006 to 2009 were as follows: piperacillin-tazobactam, 99%; ampicillin-sulbactam, 92%; cefoxitin, 72%; tigecycline, 100%; moxifloxacin, 91%; and clindamycin, 52%. No metronidazole resistance was detected in these isolates during this time period. Resistance to imipenem, doripenem, and ertapenem was observed in 1.1%, 1.6%, and 2.3% of B. fragilis group strains, respectively. B. fragilis species showed a resistance profile of 1.5% to imipenem, 1.9% to doripenem, and 2.4% to ertapenem. This is the first report of carbapenem resistance in Argentina. The cfiA gene was present in 8 out of 23 isolates, all of them belonging to the B. fragilis species and displaying reduced susceptibility or resistance to carbapenems (MICs ≥ 4 µg/ml). Three out of eight cfiA-positive isolates were fully resistant to carbapenems, while 5 out of 8 isolates showed low-level resistance (MICs, 4 to 8 µg/ml). The inhibition by EDTA was a good predictor of the presence of metallo-ß-lactamases in the fully resistant B. fragilis strains, but discrepant results were observed for low-level resistant isolates. B. fragilis was more susceptible to antimicrobial agents than other Bacteroides species. Bacteroides vulgatus species was the most resistant to ampicillin-sulbactam and piperacillin-tazobactam, and B. thetaiotaomicron/ovatus strains showed the highest level of resistance to carbapenems, with an unknown resistance mechanism. B. vulgatus and the uncommon non-Bacteroides fragilis species were the most resistant to moxifloxacin, showing an overall resistance rate of 15.1%.

[First Argentine consensus guidelines for in vitro antimicrobial susceptibility testing of clinically relevant anaerobic bacteria in humans/ Anaerobic Subcommittee of the Asociación Argentina de Microbiología]. / Primer consenso argentino para el estudio de la sensibilidad in vitro a los antimicrobianos de las bacterias anaerobias de importancia clínica en humanos.

Through time, anaerobic bacteria have shown good susceptibility to clinically useful antianaerobic agents. Nevertheless, the antimicrobial resistance profile of most of the anaerobic species related to severe infections in humans has been modified in the last years and different kinds of resistance to the most active agents have emerged, making their effectiveness less predictable. With the aim of finding an answer and for the purpose of facilitating the detection of anaerobic antimicrobial resistance, the Anaerobic Subcommittee of the Asociación Argentina de Microbiología developed the First Argentine consensus guidelines for in vitro antimicrobial susceptibility testing of clinically relevant anaerobic bacteria in humans. This document resulted from the compatibilization of the Clinical and Laboratory Standards Institute recommendations, the international literature and the work and experience of the Subcommittee. The Consensus document provides a brief taxonomy review, and exposes why and when anaerobic antimicrobial susceptibility tests should be conducted, and which antimicrobial agents can be used according to the species involved. The recommendations on how to perform, read and interpret in vitro anaerobic antimicrobial susceptibility tests with each method are exposed. Finally, the antibiotic susceptibility profile, the classification of antibiotics according to their in vitro activities, the natural and acquired mechanisms of resistance, the emerging resistance and the regional antibiotic resistance profile of clinically relevant anaerobic species are shown.

Otitis media crónica superada en niños / Chronic suppurative otitis media in children

La otitis media crónica supurada es una enfermedad del oído medio caracterizada por inflamación crónica de la mucosa del oído medio y mastoides, perforación de la membrana timpánica y otorrea. Para determinar las características clínicas de la OMC en niños se realizó un estudio prospectivo, longitudinal y descriptivo durante 3 meses en el Servicio de Otorrinolaringología del Hospital Nacional de Pediatría ¶Prof. Dr. J. P. Garrahan÷. Población, material y métodos. De los pacientes asistidos en el Servicio de ORL se seleccionaron los que cumplían con los criterios diagnósticos de otitis media crónica: otorrea (permanente o intermitente) de más de tres meses de evolución, a través de perforación timpánica documentada por otomicroscopia. Se excluyeron aquellos con sospecha de colesteatoma, enfermedades tumorales, inmunodeficiencias primarias y secundarias, anomalías craneofaciales, síndromes genéticos y los que no concurrieron a controles posteriores. A todos se les realizó otomicroscopia, toma de material para cultivo y tratamiento local inicial con alcohol 70 boricado a saturación. Resultados. De 115 niños con otitis media crónica se incluyeron 96 en el estudio (51 por ciento [n igual 49] masc menos 49 por ciento [n igual 47] fem). Edad media: 77 más o menos 43,78 meses. El tiempo medio de otorrea fue de 12 meses (rango 1 menos 175 m). Presentaban sinusopatía maxilar 48 (50 por ciento) pacientes. La otitis crónica era bilateral en 33,3 por ciento (32) y unilateral en 66,7 por ciento (64). Microbiología: se aislaron 153 gérmenes del material aspirado de oído medio, 50 por ciento (48) de los cultivos fueron polimicrobianos. Las bacterias más comunes fueron Pseudomonas aeruginosa (53/153) y Proteus (33/153). Desarrollaron gérmenes anaerobios 18/153 cultivos. El tratamiento inicial con alcohol 70 boricado a saturación resolvió la otorrea en el 77 por ciento de los casos(AU)