Biomedical subjects

Joseph Silva

Publications and source records attributed to Joseph Silva.

11 recordsLinked to original sources

PubMed2006

Prevalence of enterotoxigenic Bacteroides fragilis in hospital-acquired diarrhea.

Stool specimens from 152 hospitalized patients with diarrhea were analyzed for the presence of enterotoxigenic Bacteroides fragilis (ETBF) by a nested polymerase chain reaction (PCR) assay. ETBF gene sequences were directly detected in 14/152 (9.21%) stools of patients. The prevalence of ETBF in hospital-acquired diarrhea was statistically significant when compared to a prevalence of 2.3% in control subjects (P = 0.04). B. fragilis was cultured from 19.7% (30/152) patients with diarrhea; 4 of these isolates were enterotoxigenic. To determine whether colonization with B. fragilis is heterogeneous in nature, multiple colonies from 17 individual patients were analyzed for enterotoxin gene sequences and genotyped by arbitrarily primed PCR. Of these 17 patients, 13 harbored multiple strain types suggesting heterogeneity of colonization with both enterotoxigenic and non-enterotoxigenic strains. Identification of ETBF in the stools of 10 patients in the absence of a positive culture is likely due to the noted heterogeneity and suggests that detection of enterotoxin by PCR should be performed directly in the stool. These preliminary data indicate that ETBF may play a role in hospital-acquired diarrhea of unknown origin and suggest the need for further studies.

Bacteroides Infections↗

PubMed2005

Clostridium difficile in emergency room.

Clostridium difficile strains are known as etiological agents of pseudomembranous colitis (PMC), antibiotic-associated diarrhea (AAC) and colitis (AAC) and hospital-acquired infections. The aim of this study was to determine the frequency of C. difficile infection among patients in the emergency room and to compare isolated strains by phenotypic and genotypic characteristics. During a period of 11 months, 56 stool samples taken from diarrheic patients hospitalized in the emergency room of the Medical Center UC Davis and 14 environmental samples were cultured for isolation of C. difficile strains. Eighteen C. difficile strains were isolated from stool samples cultured on selective TCCCA plates and 5 strains from environmental samples using Rodac plates. Eleven toxigenic (TcdA+/TcdB+), 6 non-toxigenic (TcdA-/TcdB-) and unique toxin A-negative/toxin B-positive (TcdA-/TcdB+) C. difficile strains were detected among patients' isolates and 3 toxigenic and 2 non-toxigenic strains-among environmental samples. The majority of C. difficile-positive patients were treated previously by antibiotics. Four strains isolated from patients' fecal samples and one strain isolated from the environment demonstrated high-level resistance to erythromycin and clindamycin (MIC >256mug/mL). The results obtained by AP-PCR and PCR-ribotyping revealed genetic heterogeneity among the strains isolated from patients' fecal samples. However, similarity was observed among environmental strains and strains isolated from patients' fecal samples. Considering the importance of emergency room patients as a potential source of C. difficile strains, it appears to be important examine these patients for C. difficile before transfer to the other hospital units.

Journal Article↗

PubMed2005

Prevalence of the ermB gene in Clostridium difficile strains isolated at a university teaching hospital from 1987 through 1998.

We analyzed 226 strains of Clostridium difficile for the presence of erythromycin ribosomal methylase B (ermB) genes. Forty-four strains (19.4%) carried ermB genes and were resistant to erythromycin. Toxin A and toxin B gene sequences were identified in 81.9% of these 44 strains. Strains of C. difficile that carry ermB genes are common etiologic agents of C. difficile-associated diarrhea.

Anti-Bacterial Agents↗

PubMed2005

Analysis of Clostridium difficile-associated diarrhea among patients hospitalized in tertiary care academic hospital.

The frequency of Clostridium difficile strains in stool samples of patients with diarrhea hospitalized in the hematology/oncology, surgery, orthopedics, transplantology ward, and emergency room of Davis Medical Center was analyzed. A total of 786 stool samples collected from patients with diarrhea and 180 samples taken from the hospital environment were cultured for C. difficile by routine methods. There were 119 strains of C. difficile isolated: 97 (12.3%) strains from patients' stools (no enteropathogen other than C. difficile was detected in these stool samples) and 22 (12.2%) strains from the hospital environment. It was confirmed that hospital environment plays an important role in transmission of C. difficile by AP-PCR and PCR ribotyping. Among 97 C. difficile strains isolated from patient' stools 25 were nontoxigenic (A-/B-), 67 were toxigenic (A+/B+), and 5 strains were toxin B-positive/toxin A-negative. Analysis of concomitant symptoms among hospitalized patients with diarrhea demonstrated significantly longer duration of diarrhea caused by nontoxigenic strains than in cases of diarrhea caused by toxigenic strains. On the other hand, among patients infected by toxigenic strains, significantly higher leukocytosis and longer duration of fever were observed. The resistance of isolated C. difficile strains to erythromycin and clindamycin indicated the possibility of transmission in the hospital strains with macrolide-lincosamide-streptogramin B resistance type.

Bacterial Proteins↗

PubMed2005

Co-infection of hamsters with toxin A or toxin B-deficient Clostridium difficile strains.

Male Syrian hamsters (Mesocricetus auratus) were used to study interactions between different toxin deficient strains of C. difficile. After sensitization with clindamycin, hamsters were intragastrically co-infected with the appropriate dilutions corresponding to 100, 1000 and 10,000 cells of four (toxin A or B-deficient) C. difficile strains (8864, P-829, W-38 and W-74). In addition, a group of hamsters was infected with C. difficile VPI 10463, a reference toxigenic strain. Colonization and mortality was observed within 48 hours in the group of hamsters infected with the reference toxigenic strain. No clinical disease was observed in the groups of hamsters co-infected with the toxin A or B-deficient strains. Re-infection of these hamsters (co-infected with toxin deficient isolates) with C. difficile VPI 10463 resulted in clinical disease and death suggesting that these strains do not confer protection against infection with a toxigenic strain. Macroscopic and microscopic observations of the cecum of re-infected hamsters demonstrated uniformly multiple large hemorrhagic areas without pseudomembranes. Hamsters infected with as few as 100-500 cells of the toxigenic strain--VPI 10463 alone demonstrated pseudomembranes and multiple hemorrhages. These results suggest that even though the toxin deficient strains did not prevent re-infection with a toxigenic strain of C. difficile, they may play a role in the histopathologic changes after re-infections in the hamster model. Further studies with a larger number of hamsters and C. difficile strains of various molecular profiles are required to better understand the interaction between these strains.

Animals↗

PubMed2004

Marked migration of sternotomy wires: a case report.

This case report of sternal dehiscence, complicated by pronounced migration of fractured sternotomy wires, demonstrates the utility of computerized tomography (CT) in the precise localization of the wire fragments. Although CT is not typically used to evaluate sternal wire abnormalities, selected cases of sternal dehiscence can benefit from this detailed survey. A review of the literature regarding complications was also performed.

Bone Wires↗

PubMed2004

Isolation of non-toxigenic strains of Clostridium difficile from cases of diarrhea among patients hospitalized in hematology/oncology ward.

Clostridium difficile has become the most common cause of hospital acquired diarrhea after antibiotic treatment. The aim of this study was to determine the frequency of C. difficile associated diarrhea among hematology/oncology ward patients and to characterize isolated strains. Twenty three toxigenic and thirteen non-toxigenic strains were detected among fecal isolates. Antibiotic susceptibility testing to erythromycin and clindamycin demonstrated a high degree of resistance (MIC > 256 ug/ml) to both antibiotics in 9 out of 13 nontoxigenic C. difficle strains. Out of 7 patients with maximal frequency of diarrhea (10 empties/day) in 4 cases non-toxigenic strains of C. difficile were isolated. In these cases duration of diarrhea was longer in time than in cases of diarrhea caused by toxigenic strains. Further investigation with a larger patient population is necessary to better understand the role that non-toxigenic C. difficile strains play in disease development.

Clostridioides difficile↗

PubMed2003

Prevalence and association of macrolide-lincosamide-streptogramin B (MLS(B)) resistance with resistance to moxifloxacin in Clostridium difficile.

Clostridium difficile remains the leading cause of nosocomially acquired diarrhoea. C. difficile usually exhibits resistance against beta-lactam antibiotics, whereas susceptibility to other drugs may vary. This study investigated the antimicrobial susceptibility of C. difficile to different antibiotics over a period of time and characterizes molecular mechanisms for resistance. One hundred and seventy-three toxigenic and 19 non-toxigenic C. difficile strains, recovered from patients in two university hospitals in Germany between 1986 and 2001, were investigated for their susceptibility to erythromycin, clindamycin, moxifloxacin, vancomycin and metronidazole employing the Etest. The genetic background for resistance was analysed using PCR and DNA sequencing. All strains were susceptible to vancomycin and metronidazole. Resistance to erythromycin, clindamycin and moxifloxacin was found in 27%, 36% and 12% of the tested strains, respectively. High-level resistance (MIC > 128 mg/L) against erythromycin and clindamycin was detected in 25% of the strains tested. Thirty-four of the macrolide-lincosamide-streptogramin B (MLS(B))-resistant strains carried the erythromycin resistance methylase gene. The results indicate an increase in the prevalence of resistance to MLS(B) and fluoroquinolone antibiotics in C. difficile. Fluoroquinolone resistance is associated with resistance to MLS(B) antimicrobials.

Anti-Bacterial Agents↗

PubMed2003

Molecular analysis of Clostridium difficile strains isolated from 18 cases of recurrent clostridium difficile-associated diarrhea.

Recurrence of Clostridium difficile-associated diarrhea (CDAD) occurs in 15 to 20% of patients after discontinuation of treatment. Arbitrarily primed PCR was used to investigate the epidemiology of recurrent CDAD in 18 patients. Reinfection with a new strain occurred in 6 of 18 patients (33.3%), while 12 patients relapsed with the original strain shortly after discontinuation of treatment. These data suggest that reinfection with exogenous C. difficile is a common problem and that not all recurrences are due to relapse.

Bacterial Typing Techniques↗

PubMed2002

Clindamycin resistant strains of Clostridium difficile isolated from cases of C. difficile associated diarrhea (CDAD) in a hospital in Sweden.

Fifty three strains of C. difficile recovered from the stools of 13 patients with clinical C. difficile associated diarrhea (CDAD) were analyzed for the presence of the ermB gene, for toxigenicity and fingerprinting profile by PCR based assays. Forty five percent of the isolates were resistant to clindamycin and positive for the ermB gene. All clindamycin resistant isolates were ermB positive and belonged to the same fingerprinting group, suggesting clonal spread. These preliminary results suggest that clindamycin resistant isolates may be common etiologic agents of CDAD in Sweden.

Adult↗

PubMed2002

Vaccines, viruses, and voodoo.

Vaccinations are invaluable in protection from a wide variety of diseases that can cause substantial morbidity and mortality. Although a rare complication of vaccination, autoimmune disorders represent one of these morbidities. Recently, widespread public concern has arisen from case reports suggesting that--similar to what has been observed after natural viral infections--there might be an association between specific immunizations and autoimmune diseases. Herein we address the biological plausibility of such a connection, focusing particularly on the examples of hepatitis B, rubella, and measles-mumps-rubella (MMR) vaccinations, and the autoimmune diseases they are potentially associated with. Our review of the available data suggests that, for the general population, the risk: benefit ratio is overwhelmingly in favor of vaccinations. However, the possibility cannot be ruled out that, in genetically susceptible individuals, vaccination can result in the unmasking of an autoimmune disease triggered by the immunization. We also critically examine the existing data suggesting a link between immunization against MMR and autism, and briefly discuss the controversial evidence pointing to a possible relationship between mercury exposure from vaccines and autistic disorders. There is a continued urgent need for rigorously designed and executed studies addressing these potential associations, although the use of vaccinations remains a critical public health tool for protection against infectious disease.

Adolescent↗