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.

Bacteremia and sepsis by Arcanobacterium haemolyticum in a young immunocompetent patient / Bacteriemia y sepsis por Arcanobacterium haemolyticum en un paciente joven inmunocompetente

Abstract We report the case of a twenty-year-old immunocompetent male patient presenting to the emergency room with pharyngitis and fever. Blood cultures were drawn and Arcanobacterium haemolyticum (rough biotype) was recovered. The presence of the arcanolysin gene was investigated at the molecular level and the upstream region was amplified and sequenced in order to correlate it with the smooth or rough biotype. Although the isolate was susceptible to penicillin, vancomycin and gentamicin, empirical treatments first with amoxicillin/clavulanic acid (1g/12h) and then with ceftriaxone (1g/12h) failed and the infection evolved to sepsis. Finally, treatment with vancomycin (1 g/12 h) plus piperacillin/tazobactam (4.5g/8h) was effective. Lemierre's syndrome was ruled out. To the best of our knowledge, this is the first case of bacteremia by A. haemolyticum reported in Argentina.

Resumen Se describe el caso de un paciente varón inmunocompetente de veinte anos de edad que se presentó en la sala de emergencias con faringitis y fiebre. Se extrajeron muestras para realizar hemocultivos y se recuperó Arcanobacterium haemolyticum (biotipo rugoso). Se investigó la presencia del gen de la arcanolisina por un método molecular, y se amplificó y Faringitis; secuenció la región upstream de dicho gen para determinar su correlación con los biotipos lisos Bacteriemia; o rugosos. Aunque el aislamiento fue sensible a la penicilina, la vancomicina y la gentamicina, Sepsis; los tratamientos empíricos primero con amoxicilina/ácido clavulánico (1 g/12 h) y luego con Síndrome de Lemierre ceftriaxona (1 g/12 h) no fueron efectivos, y la infección evolucionó a sepsis. Finalmente, el tratamiento con vancomicina (1 g/12 h) más piperacilina/tazobactam (4,5g/8h) fue efectivo. Se descartó la presencia del síndrome de Lemierre. Según nuestro conocimiento, este es el primer caso de bacteriemia por A. haemolyticum reportado en Argentina.

Bacteremia and sepsis by Arcanobacterium haemolyticum in a young immunocompetent patient.

We report the case of a twenty-year-old immunocompetent male patient presenting to the emergency room with pharyngitis and fever. Blood cultures were drawn and Arcanobacterium haemolyticum (rough biotype) was recovered. The presence of the arcanolysin gene was investigated at the molecular level and the upstream region was amplified and sequenced in order to correlate it with the smooth or rough biotype. Although the isolate was susceptible to penicillin, vancomycin and gentamicin, empirical treatments first with amoxicillin/clavulanic acid (1g/12h) and then with ceftriaxone (1g/12h) failed and the infection evolved to sepsis. Finally, treatment with vancomycin (1g/12h) plus piperacillin/tazobactam (4.5g/8h) was effective. Lemierre's syndrome was ruled out. To the best of our knowledge, this is the first case of bacteremia by A. haemolyticum reported in Argentina.