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F Mhalu

Publications and source records attributed to F Mhalu.

At least 37 records · Page 2Linked to original sources
PubMed1997

Evaluation of T cell subsets by an immunocytochemical method compared to flow cytometry in four countries.

The authors tested an alternative method for CD4 and CD8 T lymphocytes enumeration, the immunoalkaline phosphatase method (IA), in three African countries and in Denmark. The IA determinations from 136 HIV antibody positive and 105 HIV antibody negative individuals were compared to the corresponding results obtained by flow cytometry (FC) performed in the respective countries. The authors found good correspondence between the two methods for measurements of CD4 and CD8 T lymphocytes independent of serological status and geographical site. However, the CD4 and CD8 T lymphocytes values obtained by the two methods are not interchangeable as IA compared to FC consistently gives higher percentage of CD4 T lymphocytes, and lower percentage of CD8 T lymphocytes. Mean differences between the two methods did not differ between the three African countries indicating that the IA method provides systematic results. Replicate measurements suggested good correspondence between results obtained by IA. By using an IA level of < 300 CD4 T lymphocytes/microliter, the sensitivity was 81% and specificity 96% for detecting an FC level of < 200 CD4 T lymphocytes/microliter. Using an IA level of < 20% CD4 T lymphocytes, the sensitivity was 89% and specificity 95% for detecting an FC level of < 14% CD4 T lymphocytes. The FC and IA methods had the same internal correspondence between low absolute CD4 T cell count and low CD4 percentages; the sensitivity and specificity for detecting a low absolute CD4 T cell counts with a low CD4 percentage was 92% and 68% for FC and 91% and 73% for IA, respectively. The IA method is 10-fold cheaper than FC, is independent of advanced laboratory facilities, and does not need immediate processing of samples as blood smears can be stored for long periods. The IA method is therefore suitable for use in areas with limited resources and laboratory facilities where there is a need for immunological surveillance in hospital or community studies.

Alkaline Phosphatase↗
PubMed1997

Late postnatal transmission of human immunodeficiency virus type 1 infection from mothers to infants in Dar es Salaam, Tanzania.

OBJECTIVE: To study late postnatal transmission of human immunodeficiency virus type 1 in a cohort of children born to HIV-1-seropositive mothers who delivered at Muhimbili Medical Centre in Dar es Salaam, Tanzania. MATERIALS AND METHODS: Since 1991 a prospective cohort study of mother-to-child transmission of HIV-1 has been conducted at Muhimbili Medical Centre in Dar es Salaam. HIV-1-seropositive mothers and age-matched seronegative controls were recruited into the cohort at delivery together with their newborns. Diagnosis of HIV-1 infection in children was based on polymerase chain reaction, HIV-1 p24 antigen tests and HIV antibody tests. Late postnatal transmission was defined as HIV-1 infection occurring after 6 months of age in a child who was uninfected at 6 months of age and who had an HIV-1-seropositive mother. Children born to HIV-seronegative mothers were used as controls. Breast-feeding was universal in this cohort. CD4 and CD8 T lymphocytes were assayed by flow cytometry in the mothers. RESULTS: Among 139 children born to HIV-1-seropositive mothers and known to be HIV-uninfected at 6 months of age, 8 children became HIV-1-infected at the end of their first year of life or later. No conversions were observed in children younger than 11 months. The 8 conversions were observed during a follow-up covering 1555 child months between 6 and 27 months of age corresponding to a conversion rate of 6.2 per 100 child years. Among 260 children with HIV-seronegative mothers no child became HIV-infected during the follow-up. The percentage of CD4 T lymphocytes was similar in mothers with early and late transmission but was significantly lower in transmitting than in nontransmitting mothers. CONCLUSION: Because no HIV-1 infection occurred in children with HIV-seronegative mothers, we conclude that the observed infections at the end of the first year of life or later among children born to HIV-seropositive women were caused by late transmission from mother to child, most likely through breast-feeding.

AIDS Serodiagnosis↗
PubMed1997

Comparison of in-house and commercial sample preparation and PCR amplification systems for detection of human immunodeficiency virus type 1 DNA in blood samples from Tanzanian adults.

This study compared the performance of several in-house nested PCR systems and the Amplicor human immunodeficiency virus type 1 (HIV-1) PCR kit in the detection of HIV-1 DNA in Tanzanian samples prepared by two different methods. All six of the in-house primer sets evaluated had a higher sensitivity for HIV DNA detection in samples prepared by the Amplicor PCR sample preparation method than in those prepared by the Ficoll-Isopaque (FIP) density gradient centrifugation method. A sensitivity of 100% was achieved by combining two in-house primer sets. The sensitivity of the standard Amplicor HIV-1 PCR kit was only 59%, whereas a modified Amplicor HIV-1 PCR test had a sensitivity of 98%. Our data show that Tanzanian samples prepared by the Amplicor preparation method are more suitable for HIV-1 PCR testing than samples prepared by the FIP method. The modified, but not the standard, Amplicor HIV-1 PCR kit provides an alternative to the nested in-house PCR technique for the diagnosis of HIV infection.

Adult↗
PubMed1997

Recent trends on bacterial resistance to antibiotics.

Antimicrobial resistance has become a major medical and public health problem. The main factor responsible for development and spread of bacterial resistance is injudicious use of antimicrobial agents which has resulted in most gram positive and gram negative bacteria continuously developing resistance to the antimicrobials in regular use at different time periods. In East Africa, among E. coli in urinary tract infections, more than 80% are currently resistant to ampicillin, cotrimoxazole and tetracycline while more than 80% of the isolates are still susceptible to nitrofurantoin, gentamicin and third generation cephalosporins. Penicillin G resistant strains of pneumococci were first reported in 1967 but had gradually increased to about 20% in 1991. Among group A streptococci, all natural strains are still sensitive to penicillin G while resistance to tetracycline has reached alarming proportions. In Tanzania, more than 65% of N. gonorrhoeae isolates are beta-lactamase producers, however, spectinomycin, second and third generation cephalosporins and ciprofloxacin are effective against most strains. Vibrio cholerae 01 strains resistant to multiple antibiotics are widely spread globally, however, there are recent reports indicating that withdrawal of the drugs can lead to loss of the antibiotic resistance factors. Despite varied susceptibility of N. meningitidis strains world wide, isolates in Tanzania are still susceptible to commonly available drugs including penicillin G and chloramphenicol. Available methods for control of spread of bacterial resistance include rational use of antimicrobial agents including control in animal husbandry, change to newer antimicrobials, rotational use of drugs and constant surveillance for emerging bacterial resistance.

Africa↗
PubMed1996

Performance of a modified HIV-1 p24 antigen assay for early diagnosis of HIV-1 infection in infants and prediction of mother-to-infant transmission of HIV-1 in Dar es Salaam, Tanzania.

The aim of this study was to determine the utility of an amplified human immunodeficiency virus type 1 (HIV-1) p24 antigen (ag) assay using heated plasma or serum samples for the early diagnosis of HIV-1 infection in infants and for the prediction of the risk of mother-to-infant (MTI) transmission of HIV-1 in Dar es Salaam, Tanzania. The study included 125 samples from 76 infants positive for HIV-1 DNA by the polymerase chain reaction (PCR), 106 samples from 101 PCR-negative infants and 116 and 160 samples from seropositive and seronegative mothers, respectively. Samples were boiled to dissociate immune complexes and tested for HIV-1 p24 ag using a p24 ag amplification assay. Reactive samples were confirmed by a neutralization assay. Altogether, 123 of 125 samples from 76 PCR-positive infants were positive for p24 ag (sensitivity = 98.7%). HIV-1 p24 ag was found in all 18 samples collected at 1-8 weeks, in 35 of 36 samples collected at 9-26 weeks, in all 40 samples collected at 27-52 weeks, and in 30 of 31 samples collected > 52 weeks after birth. Detection of HIV-1 p24 ag was significantly more common in transmitting mothers (12 of 29, 41.4%) than in nontransmitting mothers (nine of 87, 10.3%) (p < 0.001). Among mothers with p24 antigenemia, the vertical transmission rate was significantly higher (12 of 21, 57%) than in mothers without p24 antigenemia (17 of 95, 18%) (p < 0.001). All samples from 101 PCR-negative children and 160 seronegative mothers were negative for p24 ag (specificity = 100%). We conclude that using heated plasma or serum increases the sensitivity of the p24 ag assay significantly. This modified simple test may be sufficient for the early diagnosis of HIV-1 infection in infants in settings with limited laboratory facilities. It is also useful for prediction of the risk of MTI transmission of HIV-1.

Biomarkers↗
PubMed1996

Nested PCR assays with novel primers yield greater sensitivity to Tanzanian HIV-1 samples than a commercial PCR detection kit.

To investigate the efficacy of the SK431/SK145 primer pair and two nested primer assays in amplifying African HIV-1 samples, a total of 35 Tanzanian PBMC samples were examined. These were assayed by two HIV-1 specific nested in-house PCR assays and a commercial HIV-1 PCR kit (GeneAmp) using SK431/SK145 as the primer pair. One of the nested PCR assays has been evaluated previously (old assay), whereas the modified assay was constructed from the HIV-1 sequence alignment released in August 1993. The modified nested primer assay showed increased sensitivity in the gag and env regions compared to the old nested primer assay. However, both the old and the modified nested primer assays displayed higher sensitivity for the detection of Tanzanian HIV-1 proviruses than the GeneAmp assay. When two regions were used (gag and env) as targets for the amplification, the modified nested primer assay detected 97.1% (34/35) of the proteinase K lysed samples, compared to 68.6% (24/35) using the SK431/SK145 primer pair (P < 0.01**). The results indicate that the SK431/SK145 primer pair may be less suitable when HIV-1 samples from Africa are analysed. The results also show that continuous modification of primer sequences can improve and maintain high sensitivity for the detection of highly divergent HIV-1 strains.

DNA Primers↗
PubMed1995

Early diagnosis of HIV-1 infection in infants in Dar es Salaam, Tanzania.

OBJECTIVES: To evaluate two simple methods, an immune complex dissociation (ICD) p24 antigen assay and an HIV-1-specific IgA antibody assay, for the early demonstration of HIV-1 infection in infants, using the polymerase chain reaction (PCR) as the reference method. DESIGN AND SETTING: Group A: 143 HIV-1-seropositive and 134 -seronegative mothers and their infants were recruited at delivery at the main hospital in Dar es Salaam, Tanzania. Group B: 26 HIV-PCR-positive hospitalized children in Dar es Salaam, 3-15 months old and suspected of having an HIV-related illness. METHODS: Blood samples were taken from mothers and infants in group A at intervals during the children's first 24 months and once from each of the children in group B. Peripheral blood mononuclear cells were tested by nested PCR for viral DNA. Plasma samples were tested by the Coulter p24 antigen (ag) enzyme-linked immunosorbent assay (ELISA) after acid dissociation of p24 antigen-antibody complexes. All p24-ag-positive reactions were confirmed by neutralization. Viral specific IgA antibodies were demonstrated in plasma by a modified ELISA. RESULTS: One hundred and sixty-three of 174 samples from seropositive mothers were PCR-positive (sensitivity 93.7%) and 612 of 614 samples from seronegative mothers and children of seronegative mothers were PCR-negative (specificity 99.7%). Twenty-nine of 145 (20.0%) children born to seropositive mothers were positive by PCR when tested during the first year of life. By use of both the p24 ag ELISA and the IgA antibody ELISA in combination, HIV-1 infection was detected in 9 of 17 (53%) PCR-positive children 1-8 weeks old, in 15 of 18 (83%) PCR-positive children 9-26 weeks old and in 23 of 24 (96%) PCR-positive children 27-52 weeks old. The specificities of the p24 ag ELISA and the IgA ELISA were 100%. CONCLUSIONS: The p24 ag assay and the IgA antibody ELISA, when used in combination, had a high sensitivity and specificity for detection of HIV-1 infection in infants, especially in those above the age of 6 months.

Journal Article↗
PubMed1994

Evaluation of the WHO human immunodeficiency virus (HIV) antibody testing strategy for the diagnosis of HIV infection.

OBJECTIVE: To evaluate a WHO testing strategy based on the use of two consecutive enzyme-linked immunosorbent assays (ELISA) as an alternative to ELISA followed by Western blotting (WB) for the serologic diagnosis of HIV infection. STUDY DESIGN: The study was of 2069 consecutive serum specimens from patients suspected of HIV infection received for HIV diagnostic testing at the HIV laboratory, Muhimbili Medical Centre, Dar es Salaam. The strategy involved testing all sera with Behring indirect anti-HIV 1 + 2 peptide ELISA, followed by Wellcozyme anti-HIV-1 recombinant competitive ELISA on those sera reactive by the first ELISA. WB was done on a sample of the sera reactive on both ELISAs and on all those giving discordant results on the two ELISAs. Of the 2069 sera tested, 837 (40.5%) were negative on the first ELISA, 1172 (56.6%) were reactive on both ELISAs and 60 (2.9%) were initially reactive on the first test but not on the second assay. RESULTS: Of the 1172 sera reactive on both ELISAs, 329 (28.1%) were tested by WB. The diagnostic accuracy of the WHO alternative testing strategy using WB confirmation as the 'gold' standard was as follows: sensitivity 99.4% (326/328), specificity 99.7%, (893/896), positive predictive value 99.1% (328/331) and negative predictive value 99.8% (893/895). Repeated testing by ELISA of the sera which initially gave discordant results on the two ELISAs increased the sensitivity to 100%. Three sera giving false positive reactions on both ELISAs became negative on both ELISAs after retesting. In order to achieve a specificity and a positive predictive value of 100%, it would have been necessary to subject all sera reacting on both ELISAs to retesting on one ELISA. CONCLUSIONS: A second ELISA based on different antigens and a different test principle compared with the first ELISA could be used as an alternative to the WB assay for confirmation of HIV antibodies. However, some modifications of the WHO strategy for diagnostic HIV antibody testing were required in order to maximize the diagnostic accuracy.

Journal Article↗
PubMed1992

High HIV seroprevalence and increased HIV-associated mortality among hospitalized patients with deep bacterial infections in Dar es Salaam, Tanzania.

OBJECTIVES: To correlate deep bacterial infections with HIV infection and evaluate the influence of HIV on clinical picture and outcome in patients with meningitis, pneumonia or pyomyositis. DESIGN: Case-control comparison of HIV seroprevalence between patients and an age- and sex-matched control group in a prospective cross-sectional study of hospitalized patients. PARTICIPANTS: One hundred and sixty-five patients admitted to hospital with either purulent meningitis, pneumonia or pyomyositis and 165 age- and sex-matched controls from orthopaedic/trauma wards. SETTING: University Hospital, Dar es Salaam, Tanzania. OUTCOME MEASURES: Differences in HIV seroprevalence and mortality. RESULTS: Of 78 patients with purulent meningitis, 19 (24%) were HIV-seropositive, compared with 13 (17%) in the control group (P = 0.345). Of 36 patients with meningitis seen before a meningococcal epidemic affected Dar es Salaam, there was a statistically significant association with HIV infection (P = 0.013). Ten out of 19 (53%) HIV-seropositives died, compared with nine out of 59 (15%) seronegatives (P = 0.028). Of patients with pneumococcal meningitis, five out of six (83%) seropositives died, compared with two out of 12 (17%) seronegatives (P = 0.013). Fifteen out of 45 (33%) patients with pneumonia were HIV-seropositive, compared with four (9%) in the control group (P = 0.001). There was no difference in mortality between seropositive and seronegative patients with pneumonia. HIV seroprevalence was 62% among 42 patients with pyomyositis and 12% among 42 controls (P less than 0.0001). Eighteen out of 25 (72%) seropositive patients with pyomyositis fulfilled the World Health Organization (WHO) clinical case definition for AIDS. Response to recommended antibiotic treatment was satisfactory among patients with pneumonia and pyomyositis. CONCLUSIONS: These results show a strong association between pyomyositis, pneumonia and HIV infection. They also indicate an increased mortality associated with HIV infection in patients with pyogenic meningitis, especially pneumococcal meningitis. Pyomyositis should be considered an indicator of stage III HIV disease in the proposed WHO clinical staging system.

AIDS-Related Opportunistic Infections↗
PubMed1992

Rotavirus infection in Tanzania: a virological, epidemiological and clinical study among young children.

Rotavirus infection in the Dar es Salaam area of Tanzania was studied in 99 hospitalized children with acute diarrhoea and 99 hospitalized non-diarrhoea referents matched for sex and age. Of the diarrhoea cases 43.4% had rotavirus in the stools as opposed to 15.2% of the referents. The high carrier rate among the referents represents a serious risk of nosocomial transmission. More referents than cases had serum IgG antibodies to rotavirus, 52.5% and 35.4%, respectively (P < 0.02), while there was no correlation with serum IgM and IgA or faecal IgA antibodies. The latex agglutination test had a sensitivity comparable to that of electron microscopy (100%) and a specificity of 93.8%. The Slidex test appeared to be superior to the Rotalex test in that it gives very few false-positive reactions. The SDS-PAGE patterns of 11 RNA segments were compatible with the presence of group A strains with considerable heterogeneity among the strains. Symptoms and signs and some environmental data were recorded. None of them was clearly associated with rotavirus infection among the diarrhoea cases. It is concluded that rotavirus is a major cause of acute infectious diarrhoea in Tanzania.

Antibodies, Viral↗
PubMed1992

The AIDS epidemic in Tanzania: rate of spread of HIV in blood donors and pregnant women in Dar es Salaam.

The prevalence of antibodies to HIV in population groups in Dar es Salaam, Tanzania has been monitored from late 1984 through 1991. In the pregnant women and blood donors the doubling time was about 2 years. If, however, the doubling time is calculated from reported cases of AIDS of the whole country, an average doubling time of 10 months is obtained. We point out factors that may bias calculations of the rate of spread of the virus and thus give rise to erroneous projections for the nearest years, especially the so-called transient effect. It is recommended that serosurveys of representative population groups are carried out at regular intervals.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Selection of primers of optimal sensitivity for the detection of HIV-1 from Africa and Europe by polymerase chain reaction.

In order to facilitate the detection of integrated HIV-1 proviral DNA from African as well as European patients, four new primer pairs for use in the polymerase chain reaction (PCR), localised in the gag, pol, vif and env genes of HIV-1, were constructed. The primer pairs were compared to all accessible HIV-1 sequences from African and European isolates and to some of the earlier published and most commonly used primer pairs. HIV-1 DNA was detected in blood drawn from 13 out of 13 individuals infected in Africa, in three out of three Tanzanian HIV-1 isolates and in three out of three asymptomatic Swedes infected in Europe. The new selection of primer pairs can be used as an alternative to enhance the detection of HIV-1 of different origins.

Acquired Immunodeficiency Syndrome↗
PubMed1991

A cross-sectional study of a program for HIV infection control among public house workers.

We report results of a cross-sectional study of a program for human immunodeficiency virus (HIV) infection control among public house workers in Dar es Salaam. Forty percent of the 605 workers sampled had been part of this program, which included behavioral counseling and provision of condoms, for 1 year. The remaining 60% were new recruits. Program participation was associated with both enhanced condom use (p less than 0.001) and behavioral modification (p less than 0.001). Females, and specifically barmaids, were more likely to be condom users but were less likely to have changed their behavior in other respects. Seropositivity to both HIV and Treponema pallidum tended to be higher among females, especially the barmaids. Since barmaids and waitresses in public houses in Dar es Salaam often engage in prostitution, it is felt that to effect a reduction of numbers of their sexual partners, there is a need to address the social and economic factors underlying high-risk sexual behavior.

Adult↗
PubMed1990

Prevalence of HIV-1 infection in the Kagera region of Tanzania: a population-based study.

A population-based survey was carried out in the Kagera region of the United Republic of Tanzania in 1987 to determine the magnitude of HIV-1 infection and to study associated risk factors. The region was divided into one urban and three rural zones. A multistage cluster sampling technique was adopted. Antibodies to HIV-1 were determined by enzyme-linked immunosorbent assay and confirmed by Western blot analysis. A total of 2,475 adults (aged 15-54 years) and 1,961 children (aged 0-14 years) was studied. The overall prevalence of HIV-1 infection among adults was 9.6%, with a higher prevalence in the urban zone (24.2%) than in the three rural zones (10.0, 4.5 and 0.4%, respectively). The corresponding figures for children were 1.3% overall: 3.9% in the urban area and for the rural areas 1.2, 0.8 and 0.0%, respectively. The age-specific seroprevalence for adults was highest in the age group 25-34 years. The age-standardized sex-specific prevalence was higher among women than men in the urban zone, while it was the same in the rural zones. Change of sexual partners among adults was associated with an increased risk of HIV-1 seropositivity. Travelling outside the region but within the country was also found to be associated with increased risk of HIV-1 infection but only in the rural population.

Adolescent↗
PubMed1988

Evaluation of commercial enzyme immunoassays for anti-HIV-1 using East African sera.

Sera from 622 blood donors collected in 1986 and 1987 in Tanzania were screened for antibodies to HIV-1 by seven different commercial enzyme-linked immunosorbent assay (ELISA) kits. All ELISA-positive sera were tested by Western blot analysis and many of them also by radioimmunoprecipitation assay (RIPA). Sixty-seven sera were confirmed positive. Eight sera, which were repeatedly positive on only one or two of the ELISA kits and showed weak, doubtful reactions on Western blot and RIPA, were considered indeterminate and were not included in the calculations of sensitivity and specificity of the various ELISA kits. The sensitivity of the ELISAs was as follows: Organon Vironostika: low cut-off 74.6%; Organon Vironostika: high cut-off 62.7%; Du Pont: 85.1%; Pasteur: 78.7%; Abbott: 80.8%; Abbott recombinant: 94.0%; Wellcozyme: 82.1%; Wellcozyme monoclonal: 98.5%. The specificity was as follows: Organon Vironostika: low and high cut-off 100%; Du Pont: 94.7%; Pasteur: 99.3%; Abbott: 100%; Abbott recombinant 98.7%; Wellcozyme: 99.8%; Wellcozyme monoclonal: 98.5%. In conclusion, the two new generation kits tested, Wellcozyme monoclonal and Abbott recombinant, had the highest sensitivity whereas the sensitivity of the first-generation tests was unexpectedly low.

AIDS Serodiagnosis↗