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1.  Molecular Investigation of Tularemia Outbreaks, Spain, 1997–2008 
Emerging Infectious Diseases  2014;20(5):754-761.
This disease has reemerged because of persistence of local reservoirs of infection.
Tularemia outbreaks occurred in northwestern Spain in 1997–1998 and 2007–2008 and affected >1,000 persons. We assessed isolates involved in these outbreaks by using pulsed-field gel electrophoresis with 2 restriction enzymes and multilocus variable number tandem repeat analysis of 16 genomic loci of Francisella tularensis, the cause of this disease. Isolates were divided into 3 pulsotypes by pulsed-field gel electrophoresis and 8 allelic profiles by multilocus variable number tandem repeat analysis. Isolates obtained from the second tularemia outbreak had the same genotypes as isolates obtained from the first outbreak. Both outbreaks were caused by genotypes of genetic subclade B.Br:FTNF002–00, which is widely distributed in countries in central and western Europe. Thus, reemergence of tularemia in Spain was not caused by the reintroduction of exotic strains, but probably by persistence of local reservoirs of infection.
PMCID: PMC4012790  PMID: 24750848
tularemia; Francisella tularensis subsp. holarctica; bacteria; pulsed-field gel electrophoresis; variable number tandem repeat loci; outbreaks; genotyping; molecular investigation; phylogenetics; zoonoses; Spain
2.  Molecular Characterization of Mycoplasma agalactiae Reveals the Presence of an Endemic Clone in Spain 
Journal of Clinical Microbiology  2013;51(2):656-660.
Mycoplasma agalactiae isolates from Spain were genetically characterized to investigate their genomic diversity and to better understand their relationship to isolates from other countries. Molecular typing revealed a high genomic homogeneity in Spanish M. agalactiae isolates, which clearly shows the circulation of one endemic clonal population.
PMCID: PMC3553876  PMID: 23224102
3.  A survey of Mycoplasma agalactiae in dairy sheep farms in Spain 
Contagious Agalactia (CA) is one of the major animal health problems in small ruminants because of its economic significance. Currently, four Mycoplasma spp. have been associated with this syndrome: M. agalactiae, M. mycoides subsp. capri, M. capricolum subsp. capricolum and M. putrefaciens. Their presence has been evaluated in several studies conducted in CA-endemic countries. However, previous Spanish studies have been focused on caprine CA, and there is a knowledge gap regarding which Mycoplasma species are present in sheep flocks from Spain, which has the second highest number of sheep amongst the 27 European Union member states. Consequently, we investigated the presence and geographic distribution of the four CA-causing mycoplasmas in Spanish dairy sheep farms. This is the first time such an investigation has been performed.
Three hundred thirty nine out of 922 sheep flocks were positive for M. agalactiae by real time PCR (36.8%) and 85 by microbiological identification (9.2%). Interestingly, all 597 milk samples assessed for the presence of M. mycoides subsp. capri, M. capricolum subsp. capricolum and M. putrefaciens tested negative. To evaluate the intermittent excretion of the pathogen in milk, we sampled 391 additional farms from 2 to 5 times, resulting that in 26.3% of the cases a previously positive farm tested negative in a later sampling.
M. agalactiae was the only Mycoplasma species detected in the study area showing a high frequency of presence and wide distribution. Therefore, the establishment of a permanent surveillance network is advantageous, as well as the implementation of control and prevention measures to hinder the dissemination of M. agalactiae and to prevent the entrance of other Mycoplasma species.
PMCID: PMC3514350  PMID: 23006445
Mycoplasma agalactiae; Contagious agalactia; Real time PCR; Sheep; Dairy; Spain
4.  Hepatitis E Virus in Pork Production Chain in Czech Republic, Italy, and Spain, 2010 
Emerging Infectious Diseases  2012;18(8):1282-1289.
Processing does not substantially abate endogenous virus.
We evaluated the prevalence of hepatitis E virus (HEV) in the pork production chain in Czech Republic, Italy, and Spain during 2010. A total of 337 fecal, liver, and meat samples from animals at slaughterhouses were tested for HEV by real-time quantitative PCR. Overall, HEV was higher in Italy (53%) and Spain (39%) than in Czech Republic (7.5%). HEV was detected most frequently in feces in Italy (41%) and Spain (39%) and in liver (5%) and meat (2.5%) in Czech Republic. Of 313 sausages sampled at processing and point of sale, HEV was detected only in Spain (6%). HEV sequencing confirmed only g3 HEV strains. Indicator virus (porcine adenovirus) was ubiquitous in fecal samples and absent in liver samples and was detected in 1 slaughterhouse meat sample. At point of sale, we found porcine adenovirus in sausages (1%–2%). The possible dissemination of HEV and other fecal viruses through pork production demands containment measures.
PMCID: PMC3414029  PMID: 22840221
Hepatitis E virus; swine; pork food chain; molecular detection; reverse transcriptase polymerase chain reaction; zoonoses; food safety; viruses; Czech Republic; Italy; Spain
5.  Design and Application of Nucleic Acid Standards for Quantitative Detection of Enteric Viruses by Real-Time PCR 
Synthetic multiple-target RNA and DNA oligonucleotides were constructed for use as quantification standards for nucleic acid amplification assays for human norovirus genogroup I and II, hepatitis E virus, murine norovirus, human adenovirus, porcine adenovirus and bovine polyomavirus. This approach overcomes the problems related to the difficulty of obtaining practical quantities of viral RNA and DNA from these viruses. The quantification capacity of assays using the standards was excellent in each case (R2 > 0.998 and PCR efficiency > 0.89). The copy numbers of the standards were equivalent to the genome equivalents of representative viruses (murine norovirus and human adenovirus), ensuring an accurate determination of virus presence. The availability of these standards should facilitate the implementation of nucleic acid amplification-based methods for quantitative virus detection.
PMCID: PMC3107435  PMID: 21765877
Foodborne virus; Quantification; Nucleic acid standard; RT real-time PCR
6.  Mycoplasma agalactiae p40 Gene, a Novel Marker for Diagnosis of Contagious Agalactia in Sheep by Real-Time PCR: Assessment of Analytical Performance and In-House Validation Using Naturally Contaminated Milk Samples▿ † 
Journal of Clinical Microbiology  2008;47(2):445-450.
We evaluated the capacity of the Mycoplasma agalactiae p40 gene as a diagnostic marker for contagious agalactia in sheep by quantitative real-time PCR. The p40 gene encodes an immunodominant adhesin that plays a key role in cytoadhesion of M. agalactiae. The assay was 100% specific, with an analytical sensitivity of 1 genome equivalent (GE), a quantification that is highly linear (R2 > 0.992) and efficient (PCR efficiency, >0.992) over a 6-log dynamic range, down to 10 GE. We evaluated the capacity of the assay to detect Mycoplasma agalactiae in 797 milk samples (373 raw sheep milk samples from refrigerated tanks of different farms and 424 milk samples from individual sheep of a flock positive for M. agalactiae). In parallel, we also tested the samples by using microbiological isolation coupled with microscopy identification and by a PCR method recommended by the World Organization for Animal Health. While our assay was able to detect 57 (15.28%) positive samples of the 373 milk samples from different farms, identification by microbiological isolation coupled with microscopy detected only 36 (9.65%) samples, and the conventional PCR detected 31 (8.31%) samples. These findings showed that our assay based on the p40 gene is more specific and sensitive for the detection of M. agalactiae in actual natural samples and, thus, can be a promising alternative tool for diagnosis and epidemiological studies of M. agalactiae infection.
PMCID: PMC2643663  PMID: 19020058
7.  Quantitative Detection of Clostridium tyrobutyricum in Milk by Real-Time PCR▿ †  
Applied and Environmental Microbiology  2007;73(11):3747-3751.
We developed a real-time PCR assay for the quantitative detection of Clostridium tyrobutyricum, which has been identified as the major causal agent of late blowing in cheese. The assay was 100% specific, with an analytical sensitivity of 1 genome equivalent in 40% of the reactions. The quantification was linear (R2 > 0.9995) over a 5-log dynamic range, down to 10 genome equivalents, with a PCR efficiency of >0.946. With optimized detergent treatment and enzymatic pretreatment of the sample before centrifugation and nucleic acid extraction, the assay counted down to 300 C. tyrobutyricum spores, with a relative accuracy of 82.98 to 107.68, and detected as few as 25 spores in 25 ml of artificially contaminated raw or ultrahigh-temperature-treated whole milk.
PMCID: PMC1932699  PMID: 17449705
8.  Internally Controlled Real-Time PCR Method for Quantitative Species-Specific Detection and vapA Genotyping of Rhodococcus equi†  
We developed a novel quantitative real-time PCR (Q-PCR) method for the soil actinomycete Rhodococcus equi, an important horse pathogen and emerging human pathogen. Species-specific quantification was achieved by targeting the chromosomal monocopy gene choE, universally conserved in R. equi. The choE Q-PCR included an internal amplification control (IAC) for identification of false negatives. A second Q-PCR targeted the virulence plasmid gene vapA, carried by most horse isolates but infrequently found in isolates from other sources. The choE-IAC and vapA assays were 100% sensitive and specific as determined using 178 R. equi isolates, 77 nontarget bacteria, and a panel of 60 R. equi isolates with known vapA+ and vapA-negative (including vapB+) plasmid genotypes. The vapA+ frequency among isolate types was as follows: horse, 85%; human, 20%; bovine and pig, 0%; others, 27%. The choE-IAC Q-PCR could detect up to one genome equivalent using R. equi DNA or 100 bacteria/ml using DNA extracted from artificially contaminated horse bronchoalveolar lavage (BAL) fluid. Quantification was linear over a 6-log dynamic range down to ≈10 target molecules (or 1,000 CFU/ml BAL fluid) with PCR efficiency E of >0.94. The vapA assay had similar performance but appeared unsuitable for accurate (vapA+) R. equi quantification due to variability in target gene or plasmid copy number (1 to 9). The dual-reaction Q-PCR system here reported offers a useful tool to both medical and veterinary diagnostic laboratories for the quantitative detection of R. equi and (optional) vapA+ “horse-pathogenic” genotype determination.
PMCID: PMC1489618  PMID: 16751540
9.  A Novel Real-Time PCR for Listeria monocytogenes That Monitors Analytical Performance via an Internal Amplification Control 
Applied and Environmental Microbiology  2005;71(12):9008-9012.
We describe a novel quantitative real-time (Q)-PCR assay for Listeria monocytogenes based on the coamplification of a target hly gene fragment and an internal amplification control (IAC). The IAC is a chimeric double-stranded DNA containing a fragment of the rapeseed BnACCg8 gene flanked by the hly-specific target sequences. This IAC is detected using a second TaqMan probe labeled with a different fluorophore, enabling the simultaneous monitoring of the hly and IAC signals. The hly-IAC assay had a specificity and sensitivity of 100%, as assessed using 49 L. monocytogenes isolates of different serotypes and 96 strains of nontarget bacteria, including 51 Listeria isolates. The detection and quantification limits were 8 and 30 genome equivalents, and the coefficients for PCR linearity (R2) and efficiency (E) were 0.997 and 0.80, respectively. We tested the performance of the hly-IAC Q-PCR assay using various broth media and food matrices. Fraser and half-Fraser media, raw pork, and raw or cold-smoked salmon were strongly PCR-inhibitory. This Q-PCR assay for L. monocytogenes, the first incorporating an IAC to be described for quantitative detection of a food-borne pathogen, is a simple and robust tool facilitating the identification of false negatives or underestimations of contamination loads due to PCR failure.
PMCID: PMC1317324  PMID: 16332910
11.  Construction Strategy for an Internal Amplification Control for Real-Time Diagnostic Assays Using Nucleic Acid Sequence-Based Amplification: Development and Clinical Application 
Journal of Clinical Microbiology  2004;42(12):5832-5836.
An important analytical control in molecular amplification-based methods is an internal amplification control (IAC), which should be included in each reaction mixture. An IAC is a nontarget nucleic acid sequence which is coamplified simultaneously with the target sequence. With negative results for the target nucleic acid, the absence of an IAC signal indicates that amplification has failed. A general strategy for the construction of an IAC for inclusion in molecular beacon-based real-time nucleic acid sequence-based amplification (NASBA) assays is presented. Construction proceeds in two phases. In the first phase, a double-stranded DNA molecule that contains nontarget sequences flanked by target sequences complementary to the NASBA primers is produced. At the 5′ end of this DNA molecule is a T7 RNA polymerase binding sequence. In the second phase of construction, RNA transcripts are produced from the DNA by T7 RNA polymerase. This RNA is the IAC; it is amplified by the target NASBA primers and is detected by a molecular beacon probe complementary to the internal nontarget sequences. As a practical example, an IAC for use in an assay for the detection of Mycobacterium avium subsp. paratuberculosis is described, its incorporation and optimization within the assay are detailed, and its application to spiked and natural clinical samples is shown to illustrate the correct interpretation of the diagnostic results.
PMCID: PMC535304  PMID: 15583319
12.  Rapid Quantitative Detection of Listeria monocytogenes in Meat Products by Real-Time PCR 
Applied and Environmental Microbiology  2004;70(10):6299-6301.
We describe a quick and simple method for the quantitative detection of Listeria monocytogenes in meat products. This method is based on filtration, Chelex-100-based DNA purification, and real-time PCR. It can detect as few as 100 CFU/g and quantify as few as 1,000 CFU/g, with excellent accuracy compared to that of the plate count method. Therefore, it is a promising alternative for the detection of L. monocytogenes in meat products.
PMCID: PMC522080  PMID: 15466579
13.  Quantitative Detection of Listeria monocytogenes and Listeria innocua by Real-Time PCR: Assessment of hly, iap, and lin02483 Targets and AmpliFluor Technology 
We developed and assessed real-time PCR (RTi-PCR) assays for the detection and quantification of the food-borne pathogen Listeria monocytogenes and the closely related nonpathogenic species L. innocua. The target genes were hly and iap for L. monocytogenes and lin02483 for L. innocua. The assays were 100% specific, as determined with 100 Listeria strains and 45 non-Listeria strains, and highly sensitive, with detection limits of one target molecule in 11 to 56% of the reactions with purified DNA and 3 CFU in 56 to 89% of the reactions with bacterial suspensions. Quantification was possible over a 5-log dynamic range, with a limit of 15 target molecules and R2 values of >0.996. There was an excellent correspondence between the predicted and the actual numbers of CFU in the samples (deviations of <23%). The hly-based assay accurately quantified L. monocytogenes in all of the samples tested. The iap-based assay, in contrast, was unsuitable for quantification purposes, underestimating the bacterial counts by 3 to 4 log units in a significant proportion of the samples due to serovar-related target sequence variability. The combination of the two assays enabled us to classify L. monocytogenes isolates into one of the two major phylogenetic divisions of the species, I and II. We also assessed the new AmpliFluor technology for the quantitative detection of L. monocytogenes by RTi-PCR. The performance of this system was similar to that of the TaqMan system, although the former system was slightly less sensitive (detection limit of 15 molecules in 45% of the reactions) and had a higher quantification limit (60 molecules).
PMCID: PMC368366  PMID: 15006755

Results 1-13 (13)