[Use of different PCR-based techniques integrated into a non-tuberculous identification algorithm]. / Utilización de diferentes técnicas de biología molecular integradas en un algoritmo de identificación de micobacterias no tuberculosas.

INTRODUCTION: The aim of the present work was to demonstrate the utility of a non-tuberculous mycobacteria (NTM) identification algorithm, which integrates different PCR-based techniques and basic phenotypic features. Moreover, the algorithm for pattern restriction analysis of hsp65 (hsp65 PRA) interpretation has been updated. METHODS: The workflow chosen consisted of the identification by a DNA hybridization probe method, followed by PCR-restriction enzyme analysis of hsp65 (hsp65 PRA) in those isolates that cannot be identified by hybridization probes. If necessary, 16S rRNA gene and hsp65 gene sequencing were used for speciation. RESULTS: A total of 236 NTM were collected, in which 102 (43.2%) isolates were identified by DNA specific probes and 76 (32.2%) isolates were identified with hsp65 PRA. Partial sequencing of the 16S rRNA gene was used for species identification of the remaining 58 (24.5%) isolates. Fifty-three (22.4%) were identified using this method. Five isolates (2.1%) were submitted for partial sequencing of hsp65 gene and one isolate was identified with this method. Four strains (1.7%) could not be identified at species level. Three new PRA patterns were found. Seven isolates tested positive with the AccuProbe Mycobacterium avium complex identification test but did not test positive with the M. avium or Mycobacterium intracellulare specific probes. Five and two of these isolates were identified as M. intracellulare and Mycobacterium colombiense, respectively. CONCLUSION: This approach allowed us to identify almost all NTM isolates found in this study, including some recently described species.

Impaired fitness of Mycobacterium tuberculosis resistant isolates in a cell culture model of murine macrophages.

OBJECTIVES: We analysed the ability of Mycobacterium tuberculosis clinical isolates to penetrate and grow inside murine macrophages as a surrogate of fitness. METHODS: Thirty-five drug-resistant and 10 drug-susceptible M. tuberculosis isolates were studied in a murine macrophage model from the J774.2 cell line in a 6 day protocol, performing semi-quantitative counts in Middlebrook 7H11 medium. The mycobacterial penetration index (MPI) after infection and the mycobacterial growth ratio (MGR) inside the macrophages were determined to evaluate the fitness of isolates. RESULTS: Isolates with the katG S315T mutation and multidrug-resistant (MDR) isolates had a significantly lower MGR compared with drug-susceptible isolates. The MPI of the isolates with the katG S315T mutation showed a significant decrease compared with the MPI of those without this mutation. A trend to significantly lower values was also observed on comparing the MPI of the MDR isolates with that of the drug-susceptible isolates and the isolates resistant to isoniazid. CONCLUSIONS: The isoniazid-resistant and MDR isolates with mutations in the katG gene showed decreased multiplication inside murine macrophages, suggesting a lower fitness of M. tuberculosis with these resistance patterns.

Characterization of mutations in streptomycin-resistant Mycobacterium tuberculosis clinical isolates in the area of Barcelona.

OBJECTIVES: To determine the proportion and type of mutations in Mycobacterium tuberculosis isolates resistant to streptomycin, and their relationship with the level of resistance and with the epidemiological molecular pattern of the isolates. METHODS: Sixty-nine streptomycin-resistant isolates from a M. tuberculosis strain collection (1995-2005) from Barcelona were studied. The MIC of streptomycin for each isolate was determined using the proportions method with Middlebrook 7H11 medium. The entire rpsL gene and two specific fragments of the rrs gene (the 530 loop and the 912 region) were sequenced. IS6110-restriction fragment length polymorphism and spoligotyping were performed in each isolate. RESULTS: Twenty-six (26/69, 37.7%) streptomycin-resistant isolates presented a mutation in either the rpsL gene and/or the rrs530 loop, with no mutation in the rrs912 region. Seventeen (24.6%) isolates showed rpsL mutations (codons 43 and 88) associated with high MIC levels. Nine (13.0%) isolates had alterations in the rrs gene (A513T, A513C and C516T). Nineteen isolates (19/64, 29.7%) were classified into seven clusters (containing 2-5 isolates per cluster). Nineteen different spoligotype patterns were found. All the LAM3 spoligotype isolates (10/67, 14.9%) were associated with a C491T change in the rrs gene, being also observed in all LAM3 streptomycin-susceptible isolates. CONCLUSIONS: Mutations in the rpsL and rrs genes were detected in 37.7% of streptomycin-resistant M. tuberculosis isolates. High-level resistance was associated with mutations in the rpsL gene, whereas wild-type isolates showed low MIC levels. The presence of the C491T substitution in the rrs gene in streptomycin-susceptible and -resistant isolates demonstrates that this change is an epidemiological marker associated with LAM3 sublineage.

Microbial indicators and pathogens: removal, relationships and predictive capabilities in water reclamation facilities.

Four water reclamation facilities in north-eastern Spain were monitored over 2 years to determine the occurrence and concentrations of a set of microbial indicators (total coliforms, Escherichia coli, enterococci, spores of sulphite reducing clostridia, somatic coliphages, F-specific RNA phages, phages infecting Bacteroides fragilis strain RYC2056 and phages infecting Bacteroides tethaiotaomicron strain GA-17), and two selected pathogens (cytopathogenic enteroviruses and viable Cryptosporidium oocysts). The indicator (survival) and index (presence) functions of the various indicators tested were evaluated through the wastewater treatments. The inactivation pattern of all groups of bacteriophages tested was closer to the inactivation of enteroviruses than to the inactivation of the conventional bacterial indicators tested. The inactivation of sulfite reducing clostridia spores and bacteriophages more closely approximates the reduction of viable Cryptosporidium than do the conventional bacterial indicators. We observed neither index functions nor a predictive relationship between any of microbial indicators and viable Cryptosporidium oocysts. In contrast, several regression models (r>0.6) and discriminant functions (67-88% well classified samples) based mostly on numbers of bacteriophages were able to predict both the presence and concentrations of enteroviruses. A combination of both bacterial and bacteriophage indicators seem to be the best choice for ensuring the microbial quality of reclaimed water.

Predominant virulent IbA10G2 subtype of Cryptosporidium hominis in human isolates in Barcelona: a five-year study.

BACKGROUND: Cryptosporidium infection is a worldwide cause of diarrheal disease. To gain insight into the epidemiology of the infection in a certain geographic area, molecular methods are needed to determine the species/genotypes and subtypes. METHODOLOGY/PRINCIPAL FINDINGS: From 2004 to 2009, 161 cryptosporidiosis cases were detected in two hospitals in Barcelona. Diagnosis was performed by microscopic observation of oocysts in stool specimens following modified Ziehl-Neelsen staining. Most cases (82%) occurred in children. The number of cases increased in summer and autumn. Molecular characterization of Cryptosporidium was performed in 69 specimens, and C. hominis and C. parvum were identified in 88.4% and 10.1% of the cases, respectively. C. meleagridis was detected in one specimen. Subtyping based on the gp60 polymorphism showed six subtypes, four C. hominis and two C. parvum. Subtype IbA10G2 was the most prevalent subtype corresponding to 90% of all C. hominis isolates. This is the first report on the distribution of specific Cryptosporidium subtypes from humans in Spain. CONCLUSIONS/SIGNIFICANCE: In our geographic area, the anthroponotic behavior of C. hominis, the lower infective dose, and the higher virulence of certain subtypes may contribute to the high incidence of human cryptosporidiosis caused by the IbA10G2 subtype. Further studies should include populations with asymptomatic shedding of the parasite.

Diagnostic accuracy of a 16S ribosomal DNA gene-based molecular technique (RT-PCR, microarray, and sequencing) for bacterial meningitis, early-onset neonatal sepsis, and spontaneous bacterial peritonitis.

The diagnostic accuracy of a 16S ribosomal DNA (rDNA) gene-based molecular technique for bacterial meningitis (BM), early-onset neonatal sepsis (EONS), and spontaneous bacterial peritonitis (SBP) is evaluated. The molecular approach gave better results for BM diagnosis: sensitivity (S) was 90.6% compared to 78.1% for the bacterial culture. Percentages of cases correctly diagnosed (CCD) were 91.7% and 80.6%, respectively. For EONS diagnosis, S was 60.0% for the molecular approach and 70.0% for the bacterial culture; and CCD was 95.2% and 96.4%, respectively. For SPB diagnosis, the molecular approach gave notably poorer results than the bacterial cultures. S and CCD were 48.4% and 56.4% for the molecular approach and 80.6% and 89.1% for bacterial cultures. Nevertheless, bacterial DNA was detected in 53.3% of culture-negative samples. Accuracy of the 16S rDNA PCR approach differs depending on the sample, the microorganisms involved, the expected bacterial load, and the presence of bacterial DNA other than that from the pathogen implied in the infectious disease.

Comparative study between two laser scanning cytometers and epifluorescence microscopy for the detection of Cryptosporidium oocysts in water.

BACKGROUND: Cryptosporidium detection in water and environmental samples has increased during the last years, largely due to an increase in the number of reported waterborne outbreaks of cryptosporidiosis and the implementation of new regulations about Cryptosporidium monitoring in water supplies. The aim of this study was to validate and compare the capacity of two laser scanning cytometers commercially available (LSC and ChemScanRDI), against manual microscopic enumeration of Cryptosporidium oocysts in surface water and reference material samples. METHODS: Reference material and surface water samples were analysed by two laser scanning cytometers methodologies and by manual epifluorescence microscopy. Two mAbs from commercial suppliers were used to evaluate background reduction. RESULTS: Highly significant correlations were obtain between both cytometers (R(2) = 0.99) and with manual microscopy (R(2) = 0.98), showing that oocysts counts made by cytometers were equivalent to those obtained with conventional methods. We observed a variability in oocysts counts when different antibodies where used with laser scanning cytometers and manual microscopy. CONCLUSIONS: This study showed the efficacy of the laser scanning technology (LSC and ChemScanRDI), as an automated and a more standardized alternative to manual epifluorescence microscopy examination, for Cryptosporidium detection in water samples. High quality antibodies are needed for automated enumeration as well as for manual microscope observations.