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Biomedical subjects

P R Mason

Publications and source records attributed to P R Mason.

At least 19 recordsLinked to original sources
PubMed1995

Pneumocystis carinii pneumonia in Zimbabwe.

Pneumocystis carinii pneumonia (PCP) is said to be rare in Africa, with reported rates of 0-22% in human-immunodeficiency-virus (HIV) infected individuals with respiratory symptoms. Over one year in a central hospital in southern Africa, 64 HIV-infected patients with acute diffuse pneumonia unresponsive to penicillin and sputum smear-negative for acid-fast bacilli underwent fibreoptic bronchoscopy. Bronchoalveolar lavage fluid was assessed for bacteria, fungi, Pneumocystis carinii, and mycobacteria. 21 patients (33%) had PCP and 24 (39%) had tuberculosis; 6 of these had both infections. 5 patients had Kaposi's sarcoma (KS) associated with PCP, tuberculosis, or another infection, in 1 patient KS was the only finding, and in 21 no pathogen was identified. A logistic regression model was used to assess clinical, radiographic, and arterial blood gas predictors of PCP and tuberculosis. Fine reticulonodular shadowing on the chest radiograph (nodular component < 1 mm) was the strongest independent predictor of PCP (odds ratio 8.5 [95% CI 6.1-10.9]). A respiratory rate of more than 40/min was the best clinical predictor of PCP (odds ratio 11.2 [95% CI 8.8-13.6]). Median CD4+ T cell count for all cases of PCP was 134/microL (range 5-355) and for tuberculosis without PCP 206/microL (range 61-787). In resource-limited countries, a regionally appropriate management algorithm is required.

AIDS-Related Opportunistic Infections↗
PubMed1992

Pathogens in dog bite wounds in dogs in Harare, Zimbabwe.

Over a year swabs were taken from 87 untreated bite wounds in dogs seen by veterinary practitioners in Harare, Zimbabwe. Swabs were also taken from normal skin adjacent to the wound site, and gingival swabs were collected from normal dogs coming to the same clinics. The swabs were cultured aerobically for pathogens, particularly Staphylococcus intermedius, and the antibiotic sensitivities of the pathogens were determined by disc diffusion assay. The most common pathogens isolated from the wounds were S intermedius (23 per cent), Escherichia coli (18 per cent) and non-lactose-fermenting coliforms (14 per cent). S intermedius was common on the normal skin of the dogs with infected wounds, and was associated with wounds on the abdomen, hindlimbs and tail and wounds that were more than three days old. This organism was, however, isolated only infrequently from the gums and there was little correlation in general between the prevalence of pathogens in the mouth and their prevalence in wounds. Of the S intermedius isolates from wounds, 30 per cent were resistant to penicillin and multiple antibiotic resistance was common among the enterobacterial isolates. The majority of the pathogens were sensitive to cotrimoxazole.

Animals↗
PubMed1992

Lysis of erythrocytes by Trichomonas vaginalis.

The in vitro hemolytic activity of 4 isolates of Trichomonas vaginalis was investigated. Repetitive hemolysis assays of any one isolate showed cyclical fluctuations in hemolytic activity, varying over 24 hr of continuous culture. Maximal hemolytic activity was detected using trichomonads in the lag phase of the growth cycle. Investigations showed that hemolysis was a contact-dependent phenomenon and microscopic investigation of samples showed a significant correlation between hemolysis and attachment of erythrocytes to the trichomonad surface. Quantitative data from cytoadherence assays using [51Cr]-labeled erythrocytes were consistent with these observations. It is suggested that hemolytic activity is dependent upon adherence of red blood cells to the surface of T. vaginalis.

Animals↗
PubMed1992

Experimental infection of dogs with a Zimbabwean strain of Rickettsia conorii.

Seroconversion was demonstrated in dogs artificially infected with a Zimbabwean strain of Rickettsia conorii. No haematological or biochemical abnormalities were found and the only clinical signs observed were pain, erythema and oedema at the inoculation site and regional lymphadenopathy. Intermittent rickettsaemia was detected using the centrifugation shell vial technique up to 10 days post inoculation.

Animals↗
PubMed1991

Tick-bite fever in Zimbabwe. Survey of antibodies to Rickettsia conorii in man and dogs, and of rickettsia-like organisms in dog ticks.

As part of a study of tick-bite fever in Zimbabwe, the prevalence of antibodies to Rickettsia conorii in dogs and humans was examined. Blood samples were obtained from 184 dogs in different parts of the country and tested by indirect immunofluorescence. In all, 150 (82%) were positive at a titre of 1/40 or higher. Dogs from the south and east of the country showed very high seroprevalence compared with dogs from the main urban centre, Harare. Human serum was obtained from blood donors, from people attending clinics with non-febrile illness and from agricultural workers. Antibodies to R. conorii were found in a high proportion of samples from the south and east, with 100% of blood donor samples in one area being positive. As with the dogs, a much lower proportion of samples from Harare were positive. The exact role of dogs and their ticks (Rhipicephalus sanguineus, R. simus and Haemaphysalis leachi) in the epidemiology of human tick-bite fever remains unclear, since dog ticks were seldom found to harbour rickettsia-like organisms and man is not one of their preferred hosts. While dogs may be of little importance in disease transmission, their value as sentinels of spotted-fever group rickettsias in the environment was confirmed.

Animals↗
PubMed1991

Transient infections of goats with a novel spotted fever group rickettsia from Zimbabwe.

A novel spotted fever group rickettsia has recently been isolated from Amblyomma hebraeum ticks in Zimbabwe. In a survey of 172 goat sera collected throughout Zimbabwe the highest prevalence of antibodies reactive with this rickettsia was in the south of the country, the area where A hebraeum is most commonly found. Nine goats were infected using male and female A hebraeum taken from a tick line shown to be infected with the novel rickettsia. By week 3 after infection, seroconversion occurred in all nine goats but no clinical signs of disease could be detected. A leucocytosis due to a mature neutrophilia one to two weeks after infection was the only abnormality. Rickettsaemia was detected only on day 3 after exposure to infected ticks. Immunosuppression failed to induce recrudescence of the rickettsaemia.

Animals↗
PubMed1991

Transmission of a spotted fever group rickettsia by Amblyomma hebraeum (Acari: Ixodidae).

Amblyomma hebraeum, a cattle tick common in southern Africa, was demonstrated to be capable of maintaining an infection with an unclassified spotted fever group rickettsia both transtadially and transovarially. All feeding stages of the tick transmitted the infection to rabbits. The rickettsia was isolated and found to be serotypically distinct from three strains of Rickettsia conorii by microimmunofluorescence. Rabbit serum titers were found to be higher with indirect fluorescent antibody (IFA) tests using the Amblyomma isolate than with those using a commercially available IFA test for R. conorii.

Animals↗
PubMed1991

Role of cattle in the epidemiology of tick-bite fever in Zimbabwe.

Almost 100% of 52 cattle tested from the southern areas of Zimbabwe were found to have antibodies reactive with Rickettsia conorii compared with less than 30% of 120 cattle from the north. Steers artificially infected with R. conorii isolated from Amblyomma hebraeum were found to show no hematological or biochemical signs of disease but did seroconvert. Clinical signs of infection were restricted to regional lymphadenopathy and dermal erythema, edema, and tenderness at the inoculation site. Rickettsemia was detectable for at least 32 days postinfection. Our findings indicate that cattle could be involved in the transmission of rickettsias by A. hebraeum and may serve as a reservoir of human tick-bite fever in southern Africa.

Animals↗
PubMed1991

Ocular cysticercosis: a case report and literature review.

We have described a case of cysticercosis in the vitreous chamber of the left eye of a 16-year-old female student. The patient had presented with marked loss of visual acuity of about two months duration, but there were no other clinical signs and no evidence of intestinal taeniasis. The initial response to chemotherapy with praziquantel was good, but the patient defaulted treatment and when seen again, there was an indication of increased inflammatory responses in the eye. A vitrectomy was carried out to remove the cysticercus and associated fibrous strands. When last seen, the patient was well with improvement of vision.

Adolescent↗
PubMed1991

Long-term effects of single-dose metrifonate on the control of urinary schistosomiasis in an endemic area.

During 1989 a survey for urinary schistosomiasis was carried out in children attending Kanhukamwe primary school where, 5 years previously, infected children had been treated with a single dose of metrifonate. The treatment programme had been supplemented by improvements in water supply and sanitation, but no mollusciciding or other vector control measures had been used. The majority of children examined had not taken part in the treatment programme but had grown up in the community where transmission was reduced. While the prevalence of infection in the children in the current study was similar to that seen 5 years previously, the intensity of infection was markedly lower. In a nearby village where improved water and sanitation had been provided but no treatments had been given, the intensity of infection in school-children of similar age remained high. About 20% of the children originally with negative urines and so untreated had now started excreting S. haematobium ova, compared with 45% of children who had been cured following treatment. Children who had been treated in 1983 but who had continued to excrete ova were retreated in this study. It was noted that children who responded well to the previous treatment (greater than 90% reduction in egg excretion) generally responded well when retreated, while poor responders (less than 90% reduction in egg excretion on original treatment) showed only a small reduction in egg excretion on retreatment.

Adolescent↗
PubMed1991

Seroepidemiology of spotted fever group rickettsial infections in humans in Zimbabwe.

In sera collected throughout Zimbabwe the prevalence of antibodies reactive with Rickettsia conorii (Kenya) and a Zimbabwean spotted fever group rickettsia (ZSFR) was investigated using an indirect immunofluorescence assay (IFA). A random sample of these sera was also tested using a commercial IFA test. There was close agreement between IFA titres using the African rickettsial antigens and the commercial antigen slides. When differences in titre were detected, these were rarely greater than a twofold serum dilution. In Western blot immunoassays, IFA positive human sera detected immunogens of ZSFR and R. conorii (Kenya) that could also be demonstrated with homologous mouse antisera. The overall seroprevalence was 52% to R. conorii (Kenya) and 55% to ZSFR. For both antigens the highest seroprevalence was recorded from the south of the country, where the highest incidence of clinical tick-bite fever was reported in a questionnaire survey to medical practitioners. No difference was found between the seroprevalence in males and females, but high titres of antibody were common in samples from young people.

Adolescent↗
PubMed1991

Community acquired staphylococcal skin infections in rural areas of Zimbabwe.

Swabs from superficial skin or wound infection in 254 outpatients at rural clinics and hospitals in the Eastern Districts of Zimbabwe were examined for microorganisms. The most common site of infection was on the limbs, with infected wounds or abscesses being the most common complaint. Staphylococcus aureus was by far the most common pathogen being isolated from almost half the specimens. Coliforms were obtained from 36pc and streptococci from 18pc of swabs. Over two-thirds of the staphylococcal isolates showed in-vitro resistance to penicillin and there was an indication that penicillin resistant strains occurred more frequently in specimens from the Mozambique border areas. Resistance to other antibiotics occurred only rarely in these isolates, and in particular we found only three strains showing methicillin resistance, with one of these also showing resistance to gentamicin. The value of penicillinase sensitive penicillins in treating superficial wound infections is questioned.

Ambulatory Care Facilities↗
PubMed1990

Reduced lymphocyte responses to mitogens in natural and experimental trichomoniasis.

Proliferative responses to mitogens were determined by using peripheral blood mononuclear cells from women with active trichomoniasis, with serological evidence of past infection with Trichomonas vaginalis, and with no evidence of current or past infection. Even after the human immunodeficiency virus antibody status of the patients was taken into account, cells from women with active trichomoniasis showed reduced responses to phytohemagglutinin, concanavalin A, pokeweed mitogen, and bacterial lipopolysaccharide. Similar findings were obtained by using spleen cells from mice inoculated subcutaneously with live trichomonads. Reduction in proliferative responses by these cells could be detected 3 days after inoculation. There was some evidence to suggest that more-pathogenic strains of the parasite induced a greater degree of immunosuppression. The responses of spleen cells from mice inoculated with trichomonad-free culture supernatants were within normal limits, indicating that live trichomonads were needed to induce suppression. Support for this was gained from studies with cells from women who were treated successfully. Cells from these women rapidly regained normal lymphoproliferative function. Interleukin-2 (IL-2) production by spleen cells from infected mice was determined from measurements of mitochondrial activity in an IL-2-dependent T-cell line following incubation with stimulated spleen cell culture supernatants. These tests demonstrated lower IL-2 activity in supernatants from cell cultures from infected mice than in those from uninfected mice. The reduction in IL-2 activity did not, however, appear to correlate with the degree of reduction of mitogen-induced lymphoproliferation. Suppression of T-cell-mediated immunity may be one of the mechanisms by which T. vaginalis is able to evade host responses to infection.

Animals↗
PubMed1990

Serological typing of spotted fever group Rickettsia isolates from Zimbabwe.

Eight rickettsialike organisms were isolated in tissue culture from ticks of dogs and cattle from various areas of Zimbabwe. These isolates and a reference strain, Rickettsia conorii Simko, were tested by microimmunofluorescence against homologous and heterologous antisera raised in mice. From the titers obtained by this method, specificity differences (SPDs) were calculated between each of the rickettsiae. Only small serological differences were detected among the isolates from ticks obtained from dogs (mean SPD, 0.5) and also among the isolates from ticks obtained from cattle (mean SPD, 0.3). However, when isolates from ticks obtained from dogs and cattle were compared, the serological differences were greater (mean SPD, 1.3). The isolates from ticks obtained from dogs were found to be very similar serologically to the Simko strain of R. conorii (mean SPD, 0.8), while three of four isolates from ticks obtained from cattle were different enough (SPD, greater than or equal to 3) to be identified as separate serotypes. These findings indicate that there is a high degree of antigenic heterogeneity among the tick-transmitted spotted fever group rickettsiae in Zimbabwe.

Animals↗
PubMed1990

Genital infections in women attending a genito-urinary clinic in Harare, Zimbabwe.

One hundred women attending a sexually transmitted diseases clinic in Harare were examined for presenting features and genital infections. The most common presenting symptoms were of discharge, lower abdominal pain and dysuria, and on examination signs of discharge, inflammation, haemorrhage or ulcers/erosions were noticeable in all women. Fourteen women had genital warts. Pathogens were detected in 95% of patients. Gonococcal infection occurred in 19 women, with 60% of the strains isolated being penicillinase producing. Yeasts were detected in specimens from 25 women while chlamydial infection appeared to be rare, evidence of infection being detected in only eight women. Sera from 44 women were positive by the RPR test and sera from 33 women were positive by TPHA. Gardnerella vaginalis was isolated from 48 women, Group B streptococci from 37 women, and Trichomonas vaginalis from 32 women.

Adolescent↗
PubMed1990

Neonatal septicaemia in Harare Hospital: aetiology and risk factors. The Puerperal Sepsis Study Group.

During February to June 1987, one hundred and sixty one babies admitted to Harare Neonatal Unit had positive blood cultures, giving a sepsis rate of 21/100 live births at Harare Hospital. The case records of these 161 babies were reviewed and compared with records of 50 babies admitted from the same catchment area and during the same time period but who had negative blood cultures. Babies with early (less than 48 hr) onset or late onset sepsis tended to have lower birth weights and shorter gestational ages than controls. Significant risk factors in maternal history were poor antenatal care and prolonged rupture of membranes. Hypothermia, respiratory distress, jaundice and hypoglycaemia were all common findings in babies with sepsis. Staph. aureus and Group B streptococci (GBS) were the most common isolates in both early and late onset sepsis, with Esch. coli and Klebsiella sp. being more common in early than in late onset disease. Cultures from the genital tract were obtained from 28 of the mothers whose babies developed sepsis. Only rarely, however, was an organism with similar identity and antibiogram to that isolated from the blood culture of the baby obtained from the mother. Nevertheless mothers of blood culture positive babies showed high carriage rates of GBS, B. melaninogenicus and Klebsiella. The overall mortality in sepsis cases was 28.5 pc, but mortality was discouragingly high where coliforms or Staph.epidermidis were isolated.

Female↗
PubMed1989

Microbial flora of the lower genital tract of women in labour at Harare Maternity Hospital. The Puerperal Sepsis Study Group.

The vaginal flora of 214 women who had been referred, in labour, to Harare Maternity Hospital was investigated by examination of vaginal washings and of cervical and urethral swabs taken before and/or after delivery. Four groups of patients were studied: women who had a normal vaginal delivery (NVD), women who were referred because of meconium stained liquor (MSL), women with a history of prolonged rupture of membranes (PROM), and women who were delivered by cesarean section (CS). The first three groups had received no antibiotics during the 7 days preceding specimen collection, while specimens were collected from CS patients only after at least 48 hr of i.v. penicillin and chloramphenicol. T. vaginalis was identified in 19 percent of women, but was not associated with any specific patient group. Chlamydial antigen was detected in 13 percent of patients, but in only one patient (2 percent) in the MSL group. N. gonorrhoeae were isolated from 7 percent of women overall and 25 percent of the strains were penicillinase-producing. Gonococci were recovered significantly more frequently from the PROM patients than from NVD patients as were Group B streptococci and pigment-producing Bacteroides species. Lactobacilli were isolated from only 20 percent of women, despite the use of specific transport and isolation media for these organisms. Specimens from CS patients were taken after these had received parenteral penicillin and chloramphenicol and it was therefore not surprising to find major differences in their vaginal flora with a virtual absence of Gram-positive bacteria, and a high-rate of carriage of multi-resistant coliforms.(ABSTRACT TRUNCATED AT 250 WORDS)

Carrier State↗