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B Batchelor

Publications and source records attributed to B Batchelor.

15 recordsLinked to original sources
PubMed2006

Overview of waste stabilization with cement.

Cement can treat a variety of wastes by improving physical characteristics (solidification) and reducing the toxicity and mobility of contaminants (stabilization). Potentially adverse waste-binder interactions are an important consideration because they can limit solidification. Stabilization occurs when a contaminant is converted from the dissolved (mobile) phase to a solid (immobile) phase by reactions, such as precipitation, sorption, or substitution. These reactions are often strongly affected by pH, so the presence of components of the waste that control pH are critical to stabilization reactions. Evaluating environmental impacts can be accomplished in a tiered strategy in which simplest approach would be to measure the maximum amount of contaminant that could be released. Alternatively, the sequence of release can be determined, either by microcosm tests that attempt to simulate conditions in the disposal zone or by mechanistic models that attempt to predict behavior using fundamental characteristics of the treated waste.

Construction Materials↗
PubMed2001

Reductive dechlorination of tetrachloroethylene in soils by Fe(II)-based degradative solidification/stabilization.

Fe(II)-based degradative solidification/stabilization (DS/S) is a modification of conventional solidification/stabilization (S/S) that uses Fe(II) as a reducing agent for chlorinated organics while immobilizing inorganic contaminants. Feasibility of the Fe(II)-based DS/S technology in treating soils contaminated with tetrachloroethylene (PCE) was tested in this study. The results of the PCE degradation experiments conducted in the presence of a humic acid suggest that natural organic matter would not significantly interfere with the degradative reaction by the Fe(II)-containing reactive species in DS/S systems. Solid-phase degradation experiments showed that the DS/S technology could effectively treat PCE in soils without substantial production of chlorinated intermediates. A pseudo-first-order rate law reasonably described degradation kinetics. The half-lives of PCE ranged from 13 to 335 days, which are within time spans allowable for typical in-situ DS/S application. Trichloroethylene (TCE) was the only chlorinated product observed in the solid-phase experiments, and its presence was generally transitory with the amount being less than 7% of the initial amount of PCE on a molar basis. A surface reaction appears to control observed PCE degradation kinetics rather than mass transfer to the reactive surface.

Environmental Pollutants↗
PubMed2000

Speech and language screening for audiologists.

Speech and language screening by audiologists is not new, although few audiologists screen speech and language, which should be an integral component of the audiological evaluation. This article considers ASHA's views about speech and language screening by audiologists, screening tests available to audiologists, and the training of audiologists to screen speech and language.

Audiology↗
PubMed1996

Bacteriuria in a cohort of predominantly HIV-1 seropositive female commercial sex workers in Nairobi, Kenya.

Although significant bacteriuria and urinary tract infection are more common in immunocompetent women than men, studies linking HIV immunosuppression with an increased risk of developing urinary infection have so far only been carried out in men. We therefore examined the relationship between bacteriuria and HIV status and CD4+cell count in a relatively homogeneous cohort of female commercial sex workers (CSW) attending a community clinic in Nairobi. Two hundred and twenty-two women were enrolled, and grouped according to HIV status and CD4 count. Group 1 were HIV seronegative (n = 52); Group 2 were HIV seropositive with CD4 + counts above 500 x 10(6)/l (n = 51); Group 3 were HIV seropositive with CD4 + counts between 201 and 500 x 10(6)/l (n = 67); Group 4 were HIV seropositive with CD4+counts below 200 x 10(6)/l (n = 52). Clinical signs and symptoms were noted and mid-stream specimens of urine obtained for culture and sensitivity. Overall 23% (50/222) had significant bacteriuria. The rates in each group respectively were 25%, 29%, 19% and 23% and there was no significant association between bacteriuria and HIV status; or between bacteriuria and level of immuno-suppression as indicated by CD4 + count. Overall 19% (30/222) of women had symptoms (frequency; dysuria; loin pain; smelly urine) or signs (fever; loin tenderness) compatible with urinary tract infection. However there was no significant association between symptoms or signs of infection and bacteriuria or HIV status. A typical range of pathogens, predominantly Enterobacteriaceae, were isolated and there were high rates of resistance to commonly used antimicrobials as well as 10% resistance to ciprofloxacin. Although high rates of significant bacteriuria can occur in highly sexually-active women, this appears unrelated to HIV infection or the level of HIV-related immunosuppression and is generally asymptomatic or clinically indistinct.

Adolescent↗
PubMed1995

Disseminated Mycobacterium avium infection among HIV-infected patients in Kenya.

Previous studies from Africa have been unable to identify disseminated Mycobacterium avium complex (MAC) infection in patients with advanced human immunodeficiency virus (HIV) infection. We performed mycobacterial blood cultures and CD4 counts on 48 symptomatic adults with advanced HIV infection admitted to the hospital in Nairobi, Kenya over 4 weeks in 1992. Fourteen patients had mycobacteremia; these patients had significantly lower CD4 counts than the patients with negative cultures (14/mm3 vs. 85/mm3; p < 0.01). Three patients (6%) were bacteremic with M. avium (mean CD4 count, 10/mm3) and 11 (23%) were bacteremic with Mycobacterium tuberculosis complex (MTB) (mean CD4 count, 15/mm3). Thus, M. avium bacteremia was detected significantly less frequently in the study population than MTB bacteremia (p = 0.04). The minimum rate for HIV-associated disseminated M. avium infection in patients admitted to the hospital in Nairobi was estimated to be approximately 1%. Patients with mycobacteremia died or were discharged home sick before the diagnosis was made. Disseminated M. avium does occur in adults with advanced HIV infection in sub-Saharan Africa, but is less common than disseminated MTB.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Nasopharyngeal carriage of Staphylococcus aureus and carriage of tetracycline-resistant strains associated with HIV-seropositivity.

The aim of this prospective study was to investigate the relationship between carriage of antibiotic-resistant Staphylococcus aureus and infection with the human immunodeficiency virus (HIV). A total of 554 pernasal swabs was taken during a six-month period from 554 adult patients attending three outpatient clinics and from inpatients from a hospital in Nairobi, Kenya. Overall, 121 swabs (22%) yielded Staphylococcus aureus, there being significantly higher carriage in HIV-positive patients (71/264, 27%) than in HIV-negative patients (50/290, 17%); p = 0.008. Antimicrobial resistance rates were determined for 110 isolates and were high for penicillin (91%) and tetracycline (72%) and low for erythromycin (8%), methicillin (3%), gentamicin (5%) and chloramphenicol (0%). Genetic analysis showed plasmids in the range of 24-42 MDa to be associated with beta-lactamase production and plasmids in the range of 3-5 MDa to be associated with resistance to tetracycline, erythromycin and trimethoprim. All nine erythromycin-resistant strains were from HIV-positive patients (p = 0.02). There was a significant association of tetracycline resistance with HIV seropositivity (p = 0.002). The association of HIV seropositivity with Staphylococcus aureus carriage and carriage of antibiotic-resistant strains against the background of the HIV epidemic are of relevance in individual patient care and raise concern for public health.

Adult↗
PubMed1994

Hepatitis C virus infection detected by antibody tests and the polymerase chain reaction as a cause of liver dysfunction in renal transplant recipients.

Hepatitis C infection (HCV) is more prevalent in patients who have received kidney transplants than in the general population but the morbidity and mortality associated with infection in this group is unclear. Sera taken from 36 renal transplant recipients with chronic liver dysfunction and from 42 with normal liver function were tested for HCV infection by second generation ELISA (Abbott Laboratories) and second generation recombinant immunoblot assay (Chiron Corporation) (RIBA-2). Evidence of HCV replication was sought by reverse transcription polymerase chain reaction (RT PCR) using primers from the 5' nontranslated region (5'NTR). Infection was detected in 20/36 (54%) and in 2/42 (4.8%) controls (P < 0.01). Twelve liver dysfunction patients were positive by all three tests, six were positive by ELISA and RT PCR but had indeterminate RIBA-2, one was positive by ELISA and RIBA but negative by RT PCR, and one was positive only by RT PCR. Of two infected control patients, one was positive by all three tests and one who was later found to have been in the early stage of infection was positive only by RT PCR. Follow-up of infected patients showed persistence of viraemia in 14/15 (93%). Evidence of infection with different types of HCV was shown by the lack of amplification by RT PCR by primers with mismatching bases with HCV types 2 and 3. It is concluded that in our renal transplant patients, chronic HCV infection is usually associated with liver dysfunction and persistent infection is common.

Adult↗
PubMed1994

Recurrence of HIV-related tuberculosis in an endemic area may be due to relapse or reinfection.

SETTING: Two Research Clinics within Nairobi, Kenya, one in the Infectious Diseases Hospital, the national referral centre for tuberculosis, and one in a community based project in Pumwani district, and the Bacterial Molecular Genetics Unit at the London School of Hygiene and Tropical Medicine. OBJECTIVE: To determine whether recurrence of tuberculosis after 'adequate' treatment was due to reinfection with a different isolate of Mycobacterium tuberculosis or to relapse of the original infection. DESIGN: A retrospective comparison by DNA fingerprinting of sets of isolates of M. tuberculosis from patients with recurrence of tuberculosis and in whom isolates from the original episode had been stored was made. Five patients with recurrence of tuberculosis two to nineteen months after adequate treatment and documented clearance of disease were studied. RESULTS: In one patient, fingerprints of the isolates of M. tuberculosis from the recurrence were quite different to those from the original episode; in the other four, the fingerprints were identical. CONCLUSION: Reinfection rather than relapse was the cause of recurrence in at least one patient. The high 'relapse' rates seen in HIV-related tuberculosis in Africa may in part be due to increased susceptibility to reinfection and not to treatment failure.

AIDS-Related Opportunistic Infections↗
PubMed1994

Antimicrobial susceptibility and presence of extrachromosomal deoxyribonucleic acid in Salmonella and Shigella isolates from patients with AIDS.

The development of multi-drug resistance by enteric bacteria is an increasing problem in the developing countries. There is need to monitor antimicrobial susceptibility of these organisms in order to ensure appropriate treatment and control of infections. Antimicrobial susceptibility patterns, plasmid DNA content and restriction enzyme digests of plasmid deoxyribonucleic acid (DNA) were used to study 175 Salmonella and Shigella species isolated from predominantly HIV-seropositive adult patients in Nairobi, Kenya. All the isolates were sensitive to ciprofloxacin. A significantly higher proportion of Shigella species were resistant to chloramphenicol, cotrimoxazole, streptomycin and tetracycline compared to Salmonella species (p-value < 0.001). Multi-resistant Salmonella typhimurium isolates had 60, 40 and 5 MDa plasmids, the 5 MDa plasmid was absent in gentamicin sensitive isolates. In addition to 2-10 MDa range of plasmids, multi-resistant Shigella species had a heavy 100-105 MDa plasmid. Restriction enzyme digests were similar for the 60 and 40 MDa plasmid DNA bands from Salmonella typhimurium isolates but did not show any consistency among Shigella spp. Plasmid-encoded multi-drug resistance plays a major role in the spread of resistance among enteric bacteria. It is vital to use drugs rationally in order to control the emergence and spread of multi-drug resistance.

AIDS-Related Opportunistic Infections↗
PubMed1993

Increased recurrence of tuberculosis in HIV-1-infected patients in Kenya.

There is evidence that in human immunodeficiency virus 1 (HIV-1) infected patients with tuberculosis the rate of recurrence of tuberculosis is increased in those patients treated with a standard thiacetazone-containing regimen. To assess the impact of HIV-1 on tuberculosis in Kenya, patients with tuberculosis were studied prospectively. After treatment with either a standard thiacetazone plus isoniazid regimen or a short-course thiacetazone-containing regimen, overall recurrence rate of tuberculosis was 34 times greater in 58 HIV-1-positive patients than in 138 HIV-1-negative patients (adjusted rate ratio 33.8, 95% CI 4.3-264). Recurrence in the HIV-1-positive group was strongly associated with a cutaneous hypersensitivity reaction due to thiacetazone during initial treatment (rate ratio 13.2, 95% CI 3.1-56.2). In all patients with a cutaneous hypersensitivity reaction ethambutol was substituted for thiacetazone. No significant association was found between recurrence among HIV-1-positive patients and initial resistance, initial treatment regimen, a diagnosis of AIDS (WHO definition), or poor compliance. DNA fingerprinting suggested that both relapse and new infection may have produced recurrence of tuberculosis. In patients who had a cutaneous hypersensitivity reaction, increased recurrence rate may have been related to interruption of treatment, subsequent poor compliance, or more advanced immunosuppression. Alternatively, a change to the combination of ethambutol and isoniazid in the continuation phase for 11 months only may not be adequate.

AIDS-Related Opportunistic Infections↗
PubMed1976

Adipose tissue cellularity in human obesity.

All human obesity is characterised by adipocyte hypertrophy and when body weight exceeds 170 per cent of ideal, a maximum cell size of roughly twice normal is achieved. With greater severity, hyperplasia becomes increasingly manifest and when body weight exceeds 170 per cent of ideal, the degree of hyperplasia is well correlated with severity. Although severity and hypercellularity are often found in those with early onset of obesity, individuals can be found who are hypercellular but have had a later onset of obesity. Until the details of cellular development in man are more fully understood, the precise timing of 'critical' periods for cellular development must remain speculative.

Adipose Tissue↗
PubMedDate not supplied

Serological responses to brucellosis in HIV-seropositive patients.

Serial sera from 2 patients infected with the human immunodeficiency virus (HIV) type 1 attending a clinic in Nairobi, Kenya, and with blood cultures yielding Brucella melitensis, were tested by enzyme-linked immunosorbent assay for their serological response (Brucella-specific immunoglobulin (Ig) M and IgG) to Brucella infection. Antibody responses were comparable to those of immunocompetent individuals, one patient showing serology typical of acute brucellosis, the other of chronic brucellosis. Sera from 100 other patients, 65 of whom were HIV-positive, attending the same clinic but whose routine microbiological cultures were negative for Brucella, were tested retrospectively for Brucella-specific antibody. Eight had Brucella-specific IgM and IgG, 6 had IgM only and 21 had IgG only, suggesting relatively high levels of exposure to Brucella in the study cohort. There was no association between Brucella antibody status and HIV status. Brucellosis is probably underdiagnosed in Kenya. Brucella serology may be helpful in the diagnosis of patients with non-specific symptoms in East Africa, regardless of HIV status.

Antibodies, Bacterial↗