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Biomedical subjects

J W Sanders

Publications and source records attributed to J W Sanders.

At least 19 recordsLinked to original sources
PubMed2006

Epidemiology and genetic characterization of Shigella flexneri strains isolated from three paediatric populations in Egypt (2000-2004).

Ninety-seven isolates of Shigella flexneri from children seeking medical care from three sites in Egypt were characterized. Overall, 46.4% of children (median age 17 months) were febrile or reported blood in their stools, 25.8% were dehydrated and 16.5% were admitted to hospital. Serotypes 2a (37.1%), 1b (18.6%), 1c (17.5%), and 6 (15.5%) comprised over 88.7% of the total isolates. We observed marked resistance to ampicillin (87.6%), tetracycline (84.5%) and trimethoprim-sulfamethoxazole (63.9%). Pulsed-field electrophoresis grouped the majority of isolates within a serotype together, separately from isolates of an alternative serotype. The set gene was present in all serogroup 2a isolates, however, the sen gene was detected in every isolate. Our results show S. flexneri 1c has emerged as a dominant S. flexneri serotype in Egypt. Development and application of a Shigella vaccine should consider the diversity of Shigella serotypes within a geographical region prior to administration.

Anti-Bacterial Agents↗
PubMed2002

An observational clinic-based study of diarrheal illness in deployed United States military personnel in Thailand: presentation and outcome of Campylobacter infection.

Campylobacter is a leading cause of traveler's diarrhea in Thailand. Since resistance to quinolones is high among Campylobacter isolates, empiric therapy with quinolones for traveler's diarrhea may be ineffective in this region. We conducted an observational study among 169 U.S. military personnel with acute diarrhea and compared their microbiologic findings to those of 77 asymptomatic personnel deployed to Thailand in May 1998. Of 146 pathogenic bacterial isolates, the most common were nontyphoidal Salmonella (n = 31), enterotoxigenic Escherichia coli (n = 24), and C. jejuni/coli (n = 23). Campylobacter was strongly associated with disease (odds ratio = 5.9; 95% confidence interval = 1.3-37.3), with a more severe clinical presentation, and with a reduced functional ability at presentation (P = 0.02). In vitro resistance to ciprofloxacin was observed in 96% of the Campylobacter isolates. Sub-optimal treatment response to ciprofloxacin was observed in 17% of the cases of Campylobacter infection versus 6% due to other causes. These results highlight the importance of Campylobacter as a cause of severe traveler's diarrhea in Thailand and illustrates the ongoing problem with antibiotic-resistant strains and associated treatment problems.

Adult↗
PubMed2001

Diarrhea in the returned traveler.

Diarrhea in the returned traveler is a common problem that can be caused by a number of different pathogens. A history of the patient's travel and exposures, the duration of illness, the response to prior treatment, and the clinical syndrome can help to establish a good etiologic differential diagnosis on which further therapy can be based. Many of these patients can be treated empirically with antibiotics, either a fluoroquinolone or azithromycin, without further microbiologic evaluation. Those patients with severe or persistent disease or comorbid illnesses, or those who have failed empiric therapy, should undergo further microbiologic evaluation with directed stool cultures and ova and parasite screening. For those patients with negative evaluations, further empiric therapy may be warranted if syndromes are suggestive of specific agents of infection, such as by Giardia or Cyclospora species. Other patients may require endoscopic evaluation to exclude diagnoses such as tropical sprue or inflammatory bowel disease.

Diarrhea↗
PubMed2000

Methylobacterium mesophilicum infection: case report and literature review of an unusual opportunistic pathogen.

Methylobacterium mesophilicum is a methylotrophic, pink pigmented, gram-negative rod that was initially isolated from environmental sources that is being increasingly reported as a cause of opportunistic infections in immunocompromised hosts. We present the case of an immunocompromised woman who developed a central catheter infection with M. mesophilicum and review the other 29 cases reported in the literature, noting that it is frequently resistant to beta-lactam agents but is generally susceptible to aminoglycosides and quinolones.

Adult↗
PubMed2000

Heterologous coproduction of enterocin A and pediocin PA-1 by Lactococcus lactis: detection by specific peptide-directed antibodies.

Antibodies against enterocin A were obtained by immunization of rabbits with synthetic peptides PH4 and PH5 designed, respectively, on the N- and C-terminal amino acid sequences of enterocin A and conjugated to the carrier protein KLH. Anti-PH4-KLH antibodies not only recognized enterocin A but also pediocin PA-1, enterocin P, and sakacin A, three bacteriocins which share the N-terminal class IIa consensus motif (YGNGVXC) that is contained in the sequence of the peptide PH4. In contrast, anti-PH5-KLH antibodies only reacted with enterocin A because the amino acid sequences of the C-terminal parts of class IIa bacteriocins are highly variable. Enterocin A and/or pediocin PA-1 structural and immunity genes were introduced in Lactococcus lactis IL1403 to achieve (co)production of the bacteriocins. The level of production of the two bacteriocins was significantly lower than that obtained by the wild-type producers, a fact that suggests a low efficiency of transport and/or maturation of these bacteriocins by the chromosomally encoded bacteriocin translocation machinery of IL1403. Despite the low production levels, both bacteriocins could be specifically detected and quantified with the anti-PH5-KLH (anti-enterocin A) antibodies isolated in this study and the anti-PH2-KLH (anti-pediocin PA-1) antibodies previously generated (J. M. Martínez, M. I. Martínez, A. M. Suárez, C. Herranz, P. Casaus, L. M. Cintas, J. M. Rodríguez, and P. E. Hernández, Appl. Environ. Microbiol. 64:4536-4545, 1998). In this work, the availability of antibodies for the specific detection and quantification of enterocin A and pediocin PA-1 was crucial to demonstrate coproduction of both bacteriocins by L. lactis IL1403(pJM04), because indicator strains that are selectively inhibited by each bacteriocin are not available.

Animals↗
PubMed1998

Identification of a sodium chloride-regulated promoter in Lactococcus lactis by single-copy chromosomal fusion with a reporter gene.

An integration vector, pORI13, was developed to screen in Lactococcus lactis for expression signals induced by changes in the environment and to assay transcriptional activity of genes in single copy. The plasmid carries a promoterless Escherichia coli lacZ gene preceded by a start codon, a lactococcal ribosome binding site, and a multiple cloning site. Chromosomal Sau3AI fragments of L. lactis MG1363 DNA were cloned in pORI13 using a RepA+ E. coli as host. The resulting bank of plasmids was used for Campbell-type integration into the chromosome of L. lactis MG1363. The relatively large size of the chromosomal fragments used increases the chance of retaining complete genes in the targeted region. Screening of integrants in the presence of 0.3 M NaCl resulted in the isolation of a clone (NS3) in which expression of lacZ was dependent on the concentration of chloride ions.

Amino Acid Sequence↗
PubMed1998

A chloride-inducible acid resistance mechanism in Lactococcus lactis and its regulation.

Previously, a promoter was identified in Lactococcus lactis that is specifically induced by chloride. Here, we describe the nucleotide sequence and functional analysis of two genes transcribed from this promoter, gadC and gadB. GadC is homologous to putative glutamate-gamma-aminobutyrate antiporters of Escherichia coli and Shigella flexneri and contains 12 putative membrane-spanning domains. GadB shows similarity to glutamate decarboxylases. A L. lactis gadB mutant and a strain that is unable to express both gadB and gadC was more sensitive to low pH than the wild type when NaCl and glutamate were present. Expression of gadCB in L. lactis in the presence of chloride was increased when the culture pH was allowed to decrease to low levels by omitting buffer from the medium, while glutamate also stimulated gadCB expression. Apparently, these genes encode a glutamate-dependent acid resistance mechanism of L. lactis that is optimally active under conditions in which it is needed to maintain viability. Immediately upstream of the chloride-dependent gadCB promoter Pgad, a third gene encodes a protein (GadR) that is homologous to the activator Rgg from Streptococcus gordonii. gadR expression is chloride and glutamate independent. A gadR mutant did not produce the 3kb gadCB mRNA that is found in wild-type cells in the presence of NaCl, indicating that GadR is an activator of the gadCB operon.

Amino Acid Sequence↗
PubMed1997

A chloride-inducible gene expression cassette and its use in induced lysis of Lactococcus lactis.

A chloride-inducible promoter previously isolated from the chromosome of Lactococcus lactis (J. W. Sanders, G. Venema, J. Kok, and K. Leenhouts, Mol. Gen. Genet., in press) was exploited for the inducible expression of homologous and heterologous genes. An expression cassette consisting of the positive-regulator gene gadR, the chloride-inducible promoter Pgad, and the translation initiation signals of gadC was amplified by PCR. The cassette was cloned upstream of Escherichia coli lacZ, the holin-lysin cassette (lytPR) of the lactococcal bacteriophage r1t, and the autolysin gene of L. lactis, acmA. Basal activity of Pgad resulted in a low level of expression of all three proteins. Growth in the presence of 0.5 M NaCl of a strain containing the gadC::lacZ fusion resulted in a 1,500-fold increase of beta-galactosidase activity. The background activity levels of LytPR and AcmA had no deleterious effects on cell growth, but induction of lysin expression by addition of 0.5 M NaCl resulted in inhibition of growth. Lysis was monitored by following the release of the cytoplasmic marker enzyme PepX. Released PepX activity was maximal at 1 day after induction of lytPR expression with 0.1 M NaCl. Induction of acmA expression resulted in slower release of PepX from the cells. The presence of the inducing agent NaCl resulted in the stabilization of osmotically fragile cells.

Artificial Gene Fusion↗
PubMed1995

Disseminated Mycobacterium scrofulaceum infection: a potentially treatable complication of AIDS.

Disseminated Mycobacterium scrofulaceum infection has rarely been reported (only 8 cases to date), and no case of infection associated with AIDS has been reported in detail. We report a case of disseminated M. scrofulaceum infection in an AIDS patient that presented as chronic ulcerative and nodular skin lesions with probable cavitary lung involvement. We discuss reported cases of dissminated M. scrofulaceum infection and features of human immunodeficiency virus (HIV)-associated disease due to mycobacteria other than tuberculosis. Although our patient died before susceptibility testing could be completed, the M. scrofulaceum isolate was found to be susceptible to clarithromycin, ethambutol, and clofazimine. Physicians who evaluate skin lesions in HIV-infected persons should perform appropriate mycobacterial studies and search for disseminated disease. Drug susceptibility testing for mycobacteria other than tuberculosis is not yet standardized, but the broth dilution method, currently being studied in clinical trials of treatment for Mycobacterium avium complex, may be superior to older methods. After the possibility of Mycobacterium tuberculosis infection has been excluded, physicians should consider administering initial empirical therapy with two or more drugs, including a newer macrolide, to AIDS patients with disseminated mycobacterial disease.

AIDS-Related Opportunistic Infections↗
PubMed1995

Stress response in Lactococcus lactis: cloning, expression analysis, and mutation of the lactococcal superoxide dismutase gene.

In an analysis of the stress response of Lactococcus lactis, three proteins that were induced under low pH culture conditions were detected. One of these was identified as the lactococcal superoxide dismutase (SodA) by N-terminal amino acid sequence analysis. The gene encoding this protein, designated sodA, was cloned by the complementation of a sodA sodB Escherichia coli strain. The deduced amino acid sequence of L. lactis SodA showed the highest degree of similarity to the manganese-containing Sod (MnSod) of Bacillus stearothermophilus. A promoter upstream of the sodA gene was identified by primer extension analysis, and an inverted repeat surrounding the -35 hexanucleotide of this promoter is possibly involved in the regulation of the expression of sodA. The expression of sodA was analyzed by transcriptional fusions with a promoterless lacZ gene. The induction of beta-galactosidase activity occurred in aerated cultures. Deletion experiments revealed that a DNA fragment of more than 130 bp surrounding the promoter was needed for the induction of lacZ expression by aeration. The growth rate of an insertion mutant of sodA did not differ from that of the wild type in standing cultures but was decreased in aerated cultures.

Aerobiosis↗
PubMed1994

Evaluation of an enzyme immunoassay for detection of Chlamydia trachomatis in urine of asymptomatic men.

In a study of 1,486 men attending two sexually transmitted disease clinics, of whom 891 had no symptoms of urethritis, we compared an enzyme immunoassay (EIA) (Baxter-Bartels, formerly Northumbria AntigEnz) of urine sediment to urethral culture for the detection of Chlamydia trachomatis. C. trachomatis prevalence by culture alone was 7.7% in asymptomatic men and 10.9% in symptomatic men. Discrepant results between EIA of urine and urethral culture were evaluated by direct fluorescent-antibody staining (DFA) for elementary bodies in urine sediment or in culture transport media. When chlamydial infection was defined as either a positive urethral culture or positive EIA confirmed by DFA, chlamydia prevalence increased to 8.9% in asymptomatic men and 11.6% in symptomatic men. The urine EIA sensitivity, specificity, and positive and negative predictive values for chlamydia detection in asymptomatic men were 84.8, 99.3, 91.8, and 98.5%, respectively, with nearly identical results for symptomatic men. The sensitivities of urethral culture alone compared with the combination of urethral culture and urine EIA (with DFA confirmation) were 87.3 and 94.3% for asymptomatic and symptomatic men, respectively. The present EIA of urine sediment is both highly sensitive and specific for the detection of C. trachomatis in asymptomatic men, thus providing a noninvasive screening method for chlamydia infection in asymptomatic men attending sexually transmitted disease clinics.

Adolescent↗
PubMed1991

Ceftazidime monotherapy for empiric treatment of febrile neutropenic patients: a meta-analysis.

Whether ceftazidime monotherapy is equal in efficacy to combination regimens (Comb) for empiric treatment of febrile neutropenic patients was tested using meta-analysis. Published studies and abstracts of ceftazidime trials were identified, their quality assessed, the efficacy data abstracted and pooled, and effects of patient and study characteristics examined. The pooled odds ratio (OR) of failure of ceftazidime for febrile episodes was 1.27 (95% confidence interval [CI]: 0.79-2.03; n = 1077) and for bacteremic episodes was 0.72 (CI, 0.33-1.58; n = 248; OR less than 1.0 favors ceftazidime). Results were not significantly affected by type of antibiotic in Comb, age, neutropenia (less than 500/mm3), study quality, or combining abstracts. Results indicate that Comb does not offer a significant advantage over ceftazidime. A subgroup of profoundly neutropenic (less than 100/mm3) patients could not be assessed, raising the possibility that in this important subgroup monotherapy and Comb may not be equivalent. Use of ceftazidime empirically may require modification based on microbiologic results and clinical course.

Adolescent↗
PubMed1983

Auditory brain stem response measurement in the assessment of pseudohypoacusis.

In the evaluation of patients with pseudohypoacusis, a test that gives at least a suggestion of the patient's true auditory sensitivity is of great value. This report is an evaluation of the application and contribution of auditory brain stem response (ABR) measurement in pseudohypoacusis through a case study approach. Four patients suspected of having pseudohypoacusis on the basis of their histories and initial audiometric results were tested with the ABR procedure. In all cases the auditory sensitivity suggested by ABR was considerably better than the voluntary thresholds obtained on the initial audiograms. Following ABR measurement, all four patients showed marked improvement in voluntary threshold responses, and two gave responses that were within normal limits. Although auditory brain stem response measurement is not a test of hearing, it can be a powerful tool in the identification and quantification of nonorganic hearing loss.

Adolescent↗
PubMed1981

The acoustic reflex test in cochlear and eighth nerve pathology ears.

The clinical interpretation of acoustic reflex test results in ears with sensorineural impairment should be based on a consideration of three characteristics of the response: the reflex threshold hearing level, the reflex threshold sensation level, and the decay of the reflex. Examination of results in 152 ears with cochlear pathology and in 152 ears with acoustic tumor indicated that in some cases the combination of characteristics may be contradictory as to site of lesion. Regarding a contradictory response pattern as questionable -- neither confirming nor denying a specific site of lesion -- improves the predictive accuracy of the test through a reduction in the number of false identifications.

Adolescent↗
PubMed1981

Special auditory testing: review and update.

This report reviews the development of special auditory testing and the contribution of these procedures in neurotologic diagnosis. An evaluation of the tests comprising the traditional special auditory test battery indicates that most of them are no longer adequate to the task in that they are not sufficiently sensitive to minimal pathology of the eighth nerve. Several different auditory test methods are reviewed and recommended.

Audiometry, Evoked Response↗
PubMed1978

The successful hearing aid user.

Improvements and modifications in design, construction, evaluation, and application procedures with the wearable hearing aid have brought the benefits of successful hearing aid use to an ever increasing proportion of the hearing impaired population. Many of today's successful hearing aid users would have been regarded at one time as extremely poor risks for hearing aid use. As a consequence, many of the prognostic principles developed as guidelines in advising for or against hearing aid trial are no longer true and should be discarded. Every person who experiences difficulties related to a permanent hearing impairment, no matter how slight or severe hearing loss, should have access to aural rehabilitation, including the use of wearable amplication.

Deafness↗