Minimum Bactericidal Concentration Techniques in Mycobacterium tuberculosis: A Systematic Review.

Minimum bactericidal concentration (MBC) assay is an accepted parameter for evaluating new antimicrobial agents, and it is frequently used as a research tool to provide a prediction of bacterial eradication. To the best of our knowledge, there is no standardization among researchers regarding the technique used to detect a drug's MBC in Mycobacterium tuberculosis. Thus, the aim of this systematic review is to discuss the available literature in determining a drug's MBC in M. tuberculosis, to find the most commonly used technique and standardize the process. A broad and rigorous literature search of three electronic databases (PubMed, Web of Knowledge, and LILACS) was performed according to the PRISMA statement. We considered studies that were published from January 1, 1990 to February 19, 2019. Google Scholar was also searched to increase the number of publications. We searched for articles using the MeSH terms "microbiological techniques," "Mycobacterium," "antibacterial agents." In addition, free terms were used in the search. The search yielded 6,674 publications. After filter application, 5,348 publications remained. Of these, we evaluated the full text of 187 publications. By applying the inclusion criteria, 69 studies were included in the present systematic review. In the literature analyzed, a great variety in the techniques used to determine a drug's MBC in M. tuberculosis was observed. The most common variability is related to the culture media used, culture incubation time, and the percentage of bacterial death for the drug to be considered as bactericidal. The most commonly used technique for drug's MBC determination was carried out using the drug's minimum inhibitory concentration (MIC) assay. Aliquots from prior MIC values were subcultured in Middlebrook agar and incubated for 4 weeks at 35°C for determining the colony forming unit (CFU) with relevance to detect 99.9% bacilli killed or reduction in 3 log10 viable bacilli.

Are the classic signs of infection in concordance with results from percutaneous aspiration to diagnose infection in pressure injuries?

AIM: To explore the concordance between the presence of classic signs of infection and the positive diagnosis identified by the microbiological culture of fluid collected by percutaneous aspiration. BACKGROUND: The classic signs of infection are commonly applied in some contexts to confirm infection in pressure injuries, but its accuracy has been questioned in chronic wounds. Little is known about the concordance of this method with others, such as the deep fluid culture from pressure injuries collected by percutaneous aspiration. DESIGN: Multicentre, cross-sectional observational study. METHODS: Pressure injuries of patients from four health centres were analysed. Three types of data were recorded between February 2011 and March 2012: i) socio-demographic and clinical data, ii) number and type of infection signs and iii) microbiological results of deep fluid culture from injuries. The concordance was calculated with the kappa index to find a possible concordance between both methods. RESULTS: On 40·2% (n = 47) of injuries, two or more classic signs of infection or purulent exudate as unique sign were present, while the total positive results in the microbiological cultures were 50·4% (n = 59). The disparity of positive results, depending on the location and the stage of the pressure injury and the method applied, suggested a poor concordance between methods. The -0·092 kappa index confirmed the non-concordance of the analysed methods. CONCLUSIONS: The tandem strategy is not useful to indicate an infection in pressure injuries. We advocate exploring other signs of infection and the adoption of other more reliable signs together with the classic signs of infection.

Avaliação de métodos de manutenção da esterilidade do órgão dental humano extraído para armazenamento em banco de dentes / Evaluation of methods for maintaining sterility of the extracted human dental organ during storage in a tooth bank

A importância de um banco de dentes humanos em uma instituição de se justifica e se mostra vantajosa, uma vez que permite a máxima aproximação da realidade ao se trabalhar com o órgão extraído. Este estudo teve o propósito de avaliar métodos de manutenção da esterilidade do órgão dental humano extraído armazenado. Foram utilizados 72 dentes incisivos humanos extraídos, obtidos em clínicas de graduação e de pós-graduação da Universidade Positivo, Curitiba, PR, Brasil. Os elementos dentários foram cedidos pelos pacientes, por meio de termo de doação devidamente assinado. Após os procedimentos de limpeza e de desinfecção, 36 dentes foram esterilizados em autoclave e 36 foram somente limpos. Os dentes foram, então, armazenados em recipientes contendo o método (autoclavagem ou limpeza) ou a solução de escolha, por um período de 15 e 120 dias. Testes microbiológicos foram realizados a fim de determinar qual método ou solução de armazenamento promove a manutenção da esterilidade no tempo determinado. Melhores desempenhos foram observados quando as amostras foram armazenadas em Incidin Extra N®, formol e álcool, mesmo para os dentes não autoclavados. As substâncias em análise nos períodos propostos se mostraram capazes de impedir o crescimento microbiano. Este experimento poderá auxiliar o desenvolvimento de um protocolo de processamento e de administração do órgão dental humano extraído em um banco de dentes (AU).

The importance of a human teeth bank in an institution is justified and it is advantageous, since it allows the maximum approximation of reality when working with the extracted organ. This study aimed to evaluate methods for maintaining the sterility of extracted human teeth during storage. A total of 72 human incisors extracted in the undergraduate and graduate clinics of Universidade Positivo (Curitiba, PR, Brazil) were used in this study. The teeth were provided by patients, who signed a donation form. After all teeth were subjected to cleaning and disinfection procedures, 36 teeth were autoclaved as well. Teeth were then stored in various solutions for periods of 15 and 120 days. Microbiological tests were conducted to determine which method or storage promoted maintenance of sterility. Better results were obtained for teeth - including autoclaved teeth - stored in Incidin Extra N®, formaldehyde, and alcohol. The solutions analyzed over the proposed time periods have been shown to prevent microbial growth. Results of this study will aid in developing a protocol of processing for extracted human dental teeth to be stored in a tooth bank (AU).

Comparison of three methods based on endoscopic gastric biopsies for diagnosis of Helicobacter pylori active infection in a clinical setting / Comparação de três métodos baseados em biopsias gástricas endoscópicas para o diagnóstico da infecção ativa pelo Helicobacter pylori em um ambiente clínico

CONTEXT: The correct diagnosis and effective treatment of Helicobacter pylori gastric infection are essential in controlling this infection. OBJECTIVE: To compare the diagnostic value of three tests based in endoscopic gastric biopsies histopathological evaluation with hematoxylin-eosin (H-E) staining, urease rapid test and microbiological culture for detecting Helicobacter pylori active infection, in order to make recommendations for daily clinical practice. METHODS: Gastric biopsies from 115 adult patients (85 female/30 male) were obtained by upper gastrointestinal endoscopy and studied by histopathological evaluation with H-E (antrum-corpus), urease test in 2 hours (antrum) and microbiological culture (antrum). RESULTS: Helicobacter pylori active infection was diagnosed in 67 percent of patients. Helicobacter pylori active infection was detected by histopathological evaluation with H-E, urease test and microbiological culture in 87 percent, 79 percent and 70 percent of the positive cases, respectively. There were significant differences when histopathological evaluation with H-E and urease test rapid test when compared with microbiological test (P<0.01). There was no significant difference between histopathological evaluation with H-E and urease test (P = 0.7). The kappa index of agreement for histopathological evaluation with H-E/urease test was 0.56, histopathological evaluation with H-E/microbiological culture 0.6, and urease test/microbiological culture 0.64. CONCLUSIONS: In a hospital setting like the one studied, histopathological evaluation with H-E and urease test are the most recommended tests for diagnosis of Helicobacter pylori active infection based in endoscopic biopsies. If pathological information of gastric lesions will be required, histopathological evaluation with H-E is essential. Urease test is mandatory if a prompt diagnosis is necessary. Microbiological culture can be used in cases of persistent or complicated infection, which may require studies on Helicobacter virulence or antimicrobial susceptibility. Selected cases might demand a combination of several tests. The three tests exhibit a good concordance level for Helicobacter pylori active infection diagnosis.

CONTEXTO: O diagnóstico correto e o tratamento eficaz da infecção pelo Helicobacter pylori são essenciais no controle desta infecção. OBJETIVO: Comparar o valor de três testes de diagnóstico baseado em biopsias gástricas endoscópicas: avaliação histopatológica com hematoxilina-eosina (H-E), teste da urease e cultura microbiológica para a detecção da infecção ativa pelo H. pylori, com a finalidade de recomendações para a clínica diária prática. MÉTODOS: Biopsias gástricas de 115 pacientes (85 mulheres e 30 homens) foram obtidas por endoscopia digestiva alta e estudadas por avaliação histopatológica com H-E (antro-corpo), teste de urease em 2 horas (antro) e cultura microbiológica (antro). RESULTADOS: Infecção ativa pelo H. pylori foi diagnosticada em 67 por cento dos pacientes e detectada pela avaliação histopatológica com H-E, pelo teste de urease e pela cultura microbiológica em 87 por cento, 79 por cento e 70 por cento dos casos positivos, respectivamente. Houve diferenças significativas quando a avaliação histopatológica com H-E e o teste rápido de urease quando comparadas com a cultura microbiológica (P<0,01). Não houve diferença significativa entre a avaliação histopatológica com H-E e o teste de urease (P = 0,7). O índice kappa para avaliação histopatológica com H-E/teste de urease foi de 0,56, avaliação histopatológica com H-E/cultura microbiológica 0,6, e teste de urease/cultura microbiológica 0,64. CONCLUSÕES: Em condições similares ao estudado, avaliação histopatológica com H-E e teste de urease são os testes mais recomendados para o diagnóstico de infecção ativa pelo H. pylori com base em biopsias endoscópicas. A avaliação histopatológica com H-E é essencial quando exigido o estudo de lesões gástricas. O teste de urease é obrigatório no caso de diagnóstico precoce rápido. A cultura microbiológica pode ser usada em casos de infecção persistente ou complicada, que podem exigir estudos sobre a virulência ou susceptibilidade do Helicobacter aos antimicrobianos. Os casos selecionados podem exigir a combinação de vários testes. Os três testes apresentam bom nível de concordância para o diagnóstico da infecção ativa pelo H. pylori.

Evaluation of an Automated Instrument, PREVI Isola(R) for Inoculation of Body Fluids and Urine Samples onto Agar Plates

BACKGROUND: In most clinical microbiology laboratories, inoculation of specimens on plates is performed manually and is a time-consuming process. The efficiency of this process can be improved by using an automated instrument. Currently, several automated instruments have been introduced for inoculation of samples. In this study, we have evaluated an automated instrument, PREVI Isola(R) (Biomerieux, France), used for inoculation of body fluids and urine specimens. METHODS: Both manual and automated instrument methods were used to inoculate 74 body fluid and 204 urine samples. Precision was evaluated by testing 3 types of urine samples (A, 6x10(3) colony-forming units (CFU)/mL; B, 3x10(4) CFU/mL; and C, >10(6) CFU/mL) in replicates of 20. Results of the 2 methods were compared by counting the isolated colonies on agar plates after incubation. The time required for both methods was also compared. RESULTS: The coefficient of variation (CV) of samples A, B, and C examined using the automated instrument method was 176.1%, 18.1%, and 12.6%, respectively. The sensitivity and specificity of testing body fluid samples were 77% and 100%, respectively, and those of urine samples were 87% each. The time required for testing 15 body fluid specimens and that for inoculation of each specimen was 9.7 min shorter using PREVI Isola(R) than using the manual method. CONCLUSIONS: The results of body fluid and urine culture by inoculation using the automated instrument, PREVI Isola(R), showed relative good agreement with those obtained using the manual method. The use of PREVI Isola(R) would be expected to reduce the time and labor involved in inoculating various kinds of specimens.