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Biomedical subjects

David Velasco

Publications and source records attributed to David Velasco.

9 recordsLinked to original sources
PubMed2005

Evaluation of different methods for detecting methicillin (oxacillin) resistance in Staphylococcus aureus.

OBJECTIVES: To evaluate the performance of oxacillin, cefazolin, cefoxitin, cefotaxime and imipenem discs; Etest for oxacillin; microdilution; agar screening plates with 2 and 6 mg/L of oxacillin; and PBP2' agglutination for detection of methicillin-resistant Staphylococcus aureus (MRSA). METHODS: A total of 102 clinical S. aureus isolates, including 51 MRSA isolates, tested by PCR for the presence or absence of the mecA gene (gold standard method), isolated from different patients and at different times, were tested with: oxacillin (1 microg), cefazolin, cefoxitin, cefotaxime and imipenem (all 30 microg) discs; Etest for oxacillin; microdilution with oxacillin; agar screening tests (ORSAB medium) with 2 mg/L or 6 mg/L of oxacillin; and PBP2' agglutination with two different kits for detection of MRSA strains. RESULTS: The cefoxitin disc, ORSAB medium and PBP2' detection all showed 100% sensitivity. The cefoxitin, cefazolin and imipenem discs, Etest for oxacillin, microdilution and agar screening method with 6 mg/L at 24 h showed the highest specificity (100%), although variable degrees of sensitivity. The cefoxitin disc, which showed negative and positive predictive values of 100% and 98%, respectively was the best method for detecting MRSA isolates. CONCLUSIONS: In the absence of availability of molecular biology techniques, the cefoxitin disc was the best predictor of methicillin resistance in S. aureus from among the techniques tested.

Bacterial Proteins↗
PubMed2005

[Prevalence of antiretroviral drug resistance among previously untreated Spanish patients infected with HIV].

INTRODUCTION: Genotypic resistance was tested to investigate changes in the rates of resistance to antiretroviral drugs in non-treated patients in Spain. MATERIAL AND METHOD: A total of 209 HIV-infected patients from different autonomous communities in Spain without prior antiretroviral (AR) drug treatment were studied from 1997 to 2001. Regions of the HIV pol gene coding for protease (PR) and retrotranscriptase (RT) were sequenced in plasma samples by RT PCR amplification and automated PCR sequencing. RESULTS: At least one primary RT or PR mutation was detected in 14 patients (6.7%); 11 of them were associated with resistance to RT inhibitors (5.3%) and 3 to PR inhibitors (1.4%). The changes in the resistance rate between March 1997-February 1999 and March 1999-February 2001 were as follows: resistance mutations were detected in 3 of the 111 patients studied in the first period, and in 10 of 98 patients in the second period (2.7% versus 10.2%, P = 0.025). The infection time was less than three months in 1.5% of cases, less than 1 year in 13.4%, more than 1 year in 45.9% and unknown in 39.2%. CONCLUSION: The rate of primary resistance in naive patients is low in Spain, although there may be a trend toward an increase. The rising prevalence of resistance is a cause for concern.

Adolescent↗
PubMed2005

Cloning and functional analysis of the gene encoding the 33- to 36-kilodalton outer membrane protein associated with carbapenem resistance in Acinetobacter baumannii.

We investigated a multiresistant strain of Acinetobacter baumannii isolated in our hospital. Analysis of the N-terminal peptide sequence of the outer membrane proteins (OMPs) purified from the strain allowed us to clone and sequence the nucleotides of the gene encoding the 33- to 36-kDa OMP associated with carbapenem resistance in A. baumannii.

Acinetobacter↗
PubMed2004

Lack of correlation between phenotypic techniques and PCR-based genotypic methods for identification of Enterococcus spp.

A total of 123 genetically-unrelated strains of Enterococcus spp. strains (51 Enterococcus faecalis, 57 Enterococcus faecium, 10 Enterococcus gallinarum, and 5 Enterococcus casseliflavus) were phenotypically identified by biochemical profiles and by using an automated method. The strains were also analyzed by a PCR assay to assess the accuracy of the phenotypically-based methods for identification of Enterococcus spp. With this aim, a PCR assay using different cell targets, which allows simultaneous detection of glycopeptide-resistant genotypes as well as identification to the species level by means of different gene targets, was used as the gold standard method. All 51 strains of E. faecalis were correctly identified, whereas 48 of 57 strains (84.2%) of E. faecium, were correctly identified. All of the strains of E. gallinarum and 3 out of 5 strains of E. casseliflavus were also correctly identified. The overall results showed that it is possible to identify Enterococcus spp. at the molecular level in less than 30 hours, compared with the 48-96 hours required for the phenotypically-based methods. The excellent accuracy of the PCR assay in identifying these species, particularly E. faecium, must also be emphasized. These findings may have implications for the routine clinical identification of enterococci species.

Bacterial Typing Techniques↗
PubMed2004

Risk factors for colonization and infection in a hospital outbreak caused by a strain of Klebsiella pneumoniae with reduced susceptibility to expanded-spectrum cephalosporins.

Between February 2001 and January 2002, an increase in the number of Klebsiella pneumoniae isolates with reduced susceptibility to expanded-spectrum cephalosporins (RSKp) was detected in the neonatal unit of the Juan Canalejo Hospital, and 21 patients were either colonized or infected by the bacterial isolates. The current "gold standard" method for typing K. pneumoniae isolates is pulsed-field gel electrophoresis. However, this technique is expensive and time-consuming. In a search for faster and accurate alternatives to this method, we investigated PCR-based fingerprinting techniques (enterobacterial repetitive intergenic consensus sequence PCR [ERIC-PCR], repetitive extragenic palindromic sequence-based PCR [REP-PCR], and RAPD [randomly amplified polymorphic DNA]) for their ability to characterize K. pneumoniae isolates. The causal agent of the nosocomial outbreak was characterized by these techniques and was found to be a single epidemic strain (RSKp). A multiple regression logistic model was developed to identify potential independent factors associated with colonization and/or infection by RSKp. Logistic regression analysis was applied to all significant variables (P < 0.05) in the univariate analysis, and it was revealed that intubation (odds ratio [OR], 27.0; 95% confidence interval [95%CI], 5.39 to 135.14) and prematurity (OR, 4.4; 95%CI, 0.89 to 21.89) were such independent factors. Moreover, oxime cephalosporins did not appear to be statistically significant. Overall, the results showed that PCR-based techniques are expeditious and useful methods for typing K. pneumoniae isolates. Of the techniques studied, ERIC-PCR showed the highest discriminatory index (D = 0.828), followed by RAPD (D = 0.826) and REP-PCR (D = 0.773)

Cephalosporins↗
PubMed2003

[Antifungal susceptibility of Candida spp. isolates from blood cultures in a five-year period (1997-2001)].

INTRODUCTION: This retrospective study investigates the incidence of candidemia and antifungal susceptibility of Candida spp. isolates from blood cultures performed in the period from January 1997 to December 2001. METHODS: Amphotericin B, fluconazole, itraconazole and flucytosine minimal inhibitory concentrations (MICs) were determined using the Sensititre YeastOne broth microdilution assay for the 53 isolates detected in the study period: C. parapsilosis (22), C. albicans (19), C. glabrata (5), C. krusei (3), C. tropicalis (2) and C. guilliermondii (2). RESULTS: The incidence of candidemia was 0.25 episodes per 1000 admissions in the period studied. C. parapsilosis was present in 41.5% of cases, followed by C. albicans (35.8%), C. glabrata (9.4%), C. krusei (5.5%), C. tropicalis (3.7%) and C. guilliermondii (3.7%). Isolation of C. parapsilosis was significantly associated with the neonatal and pediatric ICU. None of the isolates presented an amphotericin B MIC > 1 micro g/ml. All the C. krusei isolates were resistant to fluconazole. Itraconazole resistance and dose-dependent fluconazole susceptibility was found in 80% of C. glabrata isolates. Only one C. parapsilosis isolate was resistant to flucytosine. CONCLUSIONS: The incidence of candidemia in our hospital was low. C. parapsilosis was the most common species and was associated with neonatal and pediatric ICUs. Fluconazole and itraconazole resistance was only found among C. krusei and C. glabrata isolates, which accounted for 15% of the total Candida spp. isolated from blood cultures in our hospital.

Adult↗
PubMed2002

[Efficacy of two semiautomatic methods for bacteriuria detection].

BACKGROUND: A quick and reliable method for detecting bacteriuria would allow to exclude the presence of microorganisms in the urine on the same day the sample is obtained.Objectives. Two semiautomatic methods have been evaluated for bacteriuria screening, taking the semiquantitative culture as reference method. MATERIAL AND METHOD: A prospective study of urine samples from patients suspected of having a urinary infection was designed. One method is based on bioluminescence that detects the presence of ATP liberated by the bacterial cell (Utiscreen-Coral Biomedical). The other semiautomatic method uses a nephelometry technique (Uro-quick). The results of each semiautomatic method were compared with the semiquantitative culture. Samples presenting counts > 104 UFC/ml of one or two microorganisms were considered as having urinary-tract infection (equivalent to significative bacteriuria). Cultures with counts < 5,000 UFC/ml or containing three or more microorganisms were classified as non-representative of significant bacteriuria. The nephelometric system allows to obtain results at two different times. Samples were divided into two groups to compare both situations. RESULTS: 1,090 urine samples, received consecutively, were considered. In the case of the bioluminescence system, the study was prolonged to 1,565 samples. The values obtained were: a) bioluminescence: general data, sensibilitiy (S) 5 94.4%; especificity (E) 5 72.8%; positive predictive value (PPV) 5 46.2% and negative predictive value (NPV) 5 98.2%; hospitalized patients only, S 5 97.5%; E 5 77.3%; PPV 5 61.2% and NPV 5 98.8%; and b) nephelometry: 195 min, S 5 96.7%; E 5 88.8%; PPV 5 67.9% and NPV 5 99.1%; 235 min, S 5 95.5%; E 5 81.0%; PPV 5 58.7% and NPV 5 98.4%. CONCLUSION: A negative predictive value from both methods under these conditions would allow them to be used in medical centers for the exclusion of bacteriuria.

Adenosine Triphosphate↗