Bacteria isolated from bloodstream infections at a tertiary hospital in Dar es Salaam, Tanzania--antimicrobial resistance of isolates.

OBJECTIVE: A bloodstream infection (BSI) is a life-threatening condition. We studied the causative agents of BSIs and antimicrobial susceptibility patterns of bacterial isolates at Muhimbili National Hospital (MNH) in Dar es Salaam, Tanzania. METHODS: A retrospective analysis of blood culture results obtained at MNH from January 2005 to December 2009 was done. Blood culture isolates judged to be clinically significant and antimicrobial susceptibility results of the bacteria were included. The frequencies and proportions of bacteria isolated and antimicrobial susceptibility results were analysed and compared using Pearson's chi-square test and Fisher's exact test where applicable, or the Mann-Whitney U-test. RESULTS: A total of 13 833 blood cultures were performed. Bacterial pathogens were detected in 1 855 (13.4%), Gram-positive bacteria (1 523; 82.1%) being significantly more prevalent than Gram-negative bacteria (332; 17.9%) (p=0.008). The most common bacterial pathogens isolated were coagulase-negative staphylococci (CoNS) (1 250; 67.4%), S. aureus (245; 13.2%), Escherichia coli (131; 7%) and Klebsiella spp. (130; 7.0%). All bacteria isolated showed high resistance to penicillin G (70.6%), tetracycline (63.8%), cefotaxime (62.5%) and ampicillin (62.3%). Moderate to high resistance was seen against chloramphenicol (45.2%), erythromycin (35.0%), ciprofloxacin (29.3%), co-trimoxazole (25.0%) and gentamicin (23.5%). Of S. aureus isolates, 23.3% were resistant to methicillin. CONCLUSIONS: CoNS accounted for two-thirds of the bacterial pathogens isolated. High-level resistance was seen to first-line and inexpensive antimicrobial agents. Routine screening for extended-spectrum beta-lactamase production and methicillin resistance among Gram-negative rods and S. aureus from blood cultures should be instituted to monitor spread of multidrug-resistant isolates.

Humoral response to Mycobacterium tuberculosis-specific antigens in African tuberculosis patients with high prevalence of human immunodeficiency virus infection.

SETTING: The applicability of serodiagnosis of tuberculosis using Mycobacterium tuberculosis-complex-specific antigens in a Tanzanian population with high prevalence of HIV. OBJECTIVE: This study was performed to evaluate the usefulness, sensitivity and specificity of serology using M. tuberculosis-specific antigens in the diagnosis of tuberculosis in patients with and without HIV co-infection. DESIGN: Patients with proven pulmonary and extrapulmonary tuberculosis at a major referral centre in Tanzania were enrolled in the study. The control group consisted of patients without a history of previous tuberculosis admitted to the trauma ward and of healthy volunteers. Sera were analysed by an enzyme linked immunoassay (ELISA) using two M. tuberculosis specific proteins as antigen: the 38 kDa protein [3T] and a 17 kDa protein. In addition was recorded presence or absence of BCG scar and tuberculin sensitivity and the sera were tested for HIV and analysed for beta-2-microglobulin content. RESULT: Sensitivity and specificity were markedly reduced in tuberculosis patients with HIV co-infection compared to patients without this disease (73% and 70% versus 52% and 50% respectively). CONCLUSION: Serology for diagnosis of tuberculosis is not feasible in an HIV endemic region.

Serum immunoglobulin profiles in asymptomatic HIV-1 seropositive adults and in patients with AIDS in Dar es Salaam, Tanzania.

Serum levels of immunoglobulin classes and IgG subclasses were determined in healthy seronegative (n = 50) and in HIV-1 seropositive adults (n = 50) from Tanzania, a region with heterosexual HIV-1 transmission pattern. The mean levels of total IgG, IgG1, IgG3, IgA, IgM, and IgD obtained were found to be significantly higher in HIV-1 seropositive sera than in control sera. The mean IgA, IgM, IgD and IgG3 levels showed an increasing trend with progression from asymptomatic phase to AIDS phase. The mean levels for total IgG, IgG1 and IgG2 remained constant while that for IgG4 decreased with progression to AIDS phase. From the findings, it is concluded that polyisotypic hypergammaglobulinaemia and serum IgG subclass changes occur in HIV-1 seropositive individuals in Tanzania. The characteristic changes observed for IgD, IgG3 and IgG4 levels with evolution from asymptomatic to AIDS phases could be of value in monitoring disease progression.

Diagnosis of tuberculous lymphadenitis in an area of HIV infection and limited diagnostic facilities.

In order to evaluate procedures leading to the diagnosis of tuberculous lymphadenitis, a prospective clinical study was carried out of patients with lymphadenopathy admitted to the medical wards of a referral hospital in Tanzania. The yield of diagnostic procedures (direct auramine/Ziehl-Neelsen (ZN) stained smears, Löwenstein-Jensen (LJ) cultures, cytology and histological examinations of fine needle aspirations (FNA) and biopsy material of lymph nodes, respectively, was compared. We also tried to identify clinical diagnostic markers. One hundred and twenty-eight (99 HIV-seropositive) patients were included. In 89 (67 HIV-positive) patients TB lymphadenitis could be proven. Histology and LJ culture of a lymph node biopsy had the highest diagnostic yield, 85% and 88% respectively, followed by detection of acid-fast bacilli (AFB) in biopsy smear (53%) and in fine-needle aspirations (35%). The diagnostic yield of the several procedures was not affected by associated HIV infection. Macroscopic caseation was 100% predictive for TB with a sensitivity of 69%. Firm and matted lymph nodes, ESR > 100 mm/hr, a positive PPD skin test and pleural opacity on a chest x-ray proved to be independent predictors for TB. Retrospective testing of a stepwise diagnostic approach based on direct smears of FNA, macroscopic visible caseation and direct smear of biopsy tissue, suggests that in 93% of the patients a definite diagnosis of TB lymphadenitis could have been made. Our data suggest that in HIV/TB epidemic areas most of the cases of TB lymphadenitis can be diagnosed correctly by simple and cheap methods which are generally available at district hospitals. Our findings need further prospective validation, however.

PIP: In order to evaluate procedures leading to the diagnosis of tuberculous lymphadenitis, a prospective clinical study was carried out on patients with lymphadenopathy admitted to four medical wards of the Muhibili Medical Center, Dar es Salaam, Tanzania, from January to August 1991. The yield of diagnostic procedures (direct auramine/Ziehl-Neelsen stained smears, Lowenstein-Jensen [LJ] cultures, cytology and histological examinations of fine needle aspirations [FNA], and biopsy material of lymph nodes) was compared. Clinical diagnostic markers were also identified. 128 (99 HIV-seropositive) patients with a mean age of 30 years were included. 41% were male. In 89 (67 HIV-positive) patients, TB lymphadenitis could be demonstrated. 46 (30 HIV-positive) had TB lymphadenitis only and 43 (37 HIV-positive) had disseminated TB. In 10 patients TB was found in specimens other than the lymph node, making the total of TB patients 99. Histology and LJ culture of lymph node biopsy had the highest diagnostic yield, 85% and 88%, respectively, followed by detection of acid-fast bacilli in biopsy smears (53%) and in FNAs (35%). The diagnostic yield of the procedures was not affected by associated HIV infection. Macroscopic caseation was 100% predictive of TB with a sensitivity of 69%. Multivariate logistic regression analysis demonstrated four independent predictors of TB: 1) firm and matted lymph nodes (odds ratio [OR] 11.8); 2) erythrocyte sedimentation rate (ESR) 100 mm/hr (OR 4.6); 3) a positive purified protein derivative (PPD) skin test (OR 10.2); and 4) pleural opacity on a chest X-ray (OR 9.5). Retrospective testing of a stepwise diagnostic approach based on direct smears of FNA, macroscopic visible caseation, and direct smears of biopsy tissue suggests that in 93% of the patients a definite diagnosis of TB lymphadenitis could have been made. These data suggest that in HIV/TB epidemic areas most of the cases of TB lymphadenitis can be diagnosed correctly by simple and cheap methods which are generally available at district hospitals.

Diagnosis of tuberculosis in patients with pleural effusion in an area of HIV infection and limited diagnostic facilities.

In a prospective study of 118 patients with pleural effusion, tuberculosis (TB) was diagnosed in 112. In 84 patients the diagnosis of TB was made by detection of acid-fast bacilli by stain (auramine, Ziehl-Neelsen) or by culture of mycobacteria (Löwenstein-Jensen medium) in pleural fluid or pleural tissue (obtained by closed biopsy) or by the presence of caseating granulomas in histological sections. In 28 patients the diagnosis of TB was considered probable, based on good response to anti-tuberculous therapy. The highest diagnostic yield was obtained by histology (85%), followed by culture of pleural biopsy (37%) and pleural fluid culture (36%). Pulmonary tuberculosis was found in 8 patients and dissemination of TB to other sites in 25 patients of whom 20 were HIV positive. By logistic regression analysis we identified 2 independent diagnostic markers for TB pleuritis: pleural fluid protein > 50 g/l (Odds ratio 12.1, 95% confidence interval (CI): 1.1-128.3) and adenosine deaminase of > 10 U/l (Odds ratio 11.08, 95% CI: 1.3-96.4). We conclude that conventional facilities of a referral hospital are sufficient to diagnose tuberculous pleuritis as well as disseminated tuberculosis irrespective of HIV infection. However, for regions with overstretched health services and high prevalences of tuberculous pleurisy in patients with pleural effusion we suggest a simplified diagnostic approach based on exclusion of other causes of pleural effusion by simple means and use of these diagnostic markers.

PIP: In a prospective study of 118 patients with pleural effusion admitted to four medical wards in Muhimbili Medical Center between January and August 1991, Dar es Salaam, Tanzania, tuberculosis (TB) was diagnosed in 112. In 84 patients the diagnosis of TB was made by detection of acid-fast bacilli by stain (auramine, Ziehl-Neelsen) or by culture of mycobacteria (Lowenstein-Jensen medium) in pleural fluid or pleural tissue obtained by closed biopsy or by the presence of caseating granulomas in histological sections. In 28 patients the diagnosis of TB was considered probable, based on good response to anti-tuberculous therapy. In the remaining 6 non-TB patients adenocarcinoma (1), bacterial infection (2), and aspecific inflammation (3) were diagnosed. 58% of the TB and 3 of the non-TB patients were infected with HIV. The diagnostic procedures were evaluated in 75 patients. The highest diagnostic yield was obtained by histology (85%), followed by culture of pleural biopsy (37%), and pleural fluid culture (36%). Pulmonary tuberculosis was found in 8 (4 HIV-positive) patients and dissemination of TB to other sites in 25 patients, of whom 20 were HIV-positive. By logistic regression analysis, two independent diagnostic markers for TB pleuritis were identified: pleural fluid protein 50 g/l (odds ratio [OR] 12.1) and pleural fluid adenosine deaminase level of 10 U/l (OR 11.08). The sensitivity of these two diagnostic tests was 82% and 97.3%, and the specificity was 83.6% and 50%, respectively. TB was the underlying cause in nearly all patients who presented with pleural effusion (94.9%). TB was confirmed in 75% of these using the referral hospital. Conventional facilities of a referral hospital are sufficient to diagnose tuberculous pleuritis as well as disseminated tuberculosis irrespective of HIV infection. However, in regions with overburdened health facilities and high prevalence of tuberculous pleurisy in patients with pleural effusion, a simplified diagnostic approach is suggested based on exclusion of other causes of pleural effusion by simple use of these diagnostic markers.

Mutans streptococci in caries-active and caries-free infants in Tanzania.

The occurrence of mutans streptococci species was investigated in Tanzanian infants aged between 1.0 and 3.5 years with rampant caries and without caries using biochemical and immunological techniques. These infants came from Turiani and Singida, where the caries prevalence for this age group was 12.8% and 1.6% respectively. Streptococcus mutans was found to be the only mutans streptococcal species. The other species, including the previously reported Streptococcus rattus, were not found. Consequently, the differences in caries experience observed between and within the two populations could not be explained by differences in mutans streptococcal species.

Fermentation of carbohydrates in different flours by Streptococcus mutans.

The ability of Streptococcus mutans to ferment carbohydrates and to produce acid was investigated in different flours in vitro. The amounts of acid produced suggest a possible ecological role of the tested flours in the occurrence of Strep. mutans in dental plaque.

The influence of dietary sugars and starch on the establishment of Streptococcus mutans and Actinomyces viscosus in dental plaque of specific pathogen-free rats.

The establishment of S. mutans together with A. viscosus was investigated in dental plaque of specific pathogen-free (SPF) rats fed different carbohydrate diets. Two Tanzanian S.mutans strains MM3 and MM24 and one Tanzanian A. viscosus strain MM13 were used for this purpose. The basic diet consisting of 32% skim-milk, 7% yeast extract and 1% soy bean oil was supplemented with either 10% lactose and 50% corn flour, or 10% glucose and 50% corn flour, or 60% amylum or 60% wheat flour. S. mutans and A. viscosus were enumerated twenty days after inoculation. S. mutans counts were high irrespective of the dietary regime. A. viscosus counts in the glucose, lactose and amylum groups were of the same magnitude and significantly higher than those of the wheat flour group. The hypothesis that the establishment of S. mutans in sucrose free diets could be facilitated by the extracellular polysaccharides produced by A. viscosus was not supported by the present data. The finding that S. mutans can establish in high number in dental plaque of SPF rats in the absence of sucrose corroborates previous reports indicating high S. mutans counts in African populations with a low sucrose intake.

Mutans streptococci and lactobacilli in breast-fed children with rampant caries.

This study aimed to investigate the prevalence of selected components of the oral microflora in breast-fed children who developed rampant caries (resembling nursing caries) under hitherto unexplained circumstances. Dental plaque and saliva samples were collected from breast-fed children, aged between 1 and 2.5 years, with and without rampant caries. Mutans streptococci and lactobacilli were isolated from dental plaque of all children with rampant caries and from most caries-free children. None of the colonies of mutans streptococci resembled those of Streptococcus sobrinus. The mean counts of the mutans streptococci and lactobacilli were 100-fold higher in plaque samples from children with rampant caries as compared with caries-free children. No difference could be found between the numbers of mutans streptococci in plaque overlaying cavities and that from adjacent sound enamel. In contrast, the counts of lactobacilli in plaque were approximately 100-fold higher from cavities than from sound surfaces. The levels of mutans streptococci in saliva were directly related to the presence of rampant caries. The results show that caries-free and caries-active breast-fed children, aged 1 to 2.5 years, harbour mutans streptococci and lactobacilli on their teeth. Rampant caries in these children can occur in the absence of nursing bottles or any other feeding abuse during weaning and in the presence of an aciduric plaque microflora, as has been reported for children with nursing bottle caries.

Enzyme-linked immunosorbent assay using monoclonal antibodies for identification of mycobacteria from early cultures.

A simple enzyme-linked immunosorbent assay (ELISA) for the identification of cultured mycobacteria belonging to the Mycobacterium tuberculosis complex, the Mycobacterium avium complex, and Mycobacterium kansasii has been developed (R. Schöningh, C. P. H. J. Verstijnen, S. Kuijper, and A. H. J. Kolk. J. Clin. Microbiol. 28:708-713, 1990). The test for the routine identification of cultured mycobacteria was introduced in five clinical laboratories located in Tanzania, Thailand, Vietnam, and The Netherlands. The ELISA can be conducted without an ELISA reader since the test can be read visually. The results of identification of 255 strains of the M. tuberculosis complex by microbiological means and by ELISA were compared; the specificity and the sensitivity were 100%. For the M. avium complex, the specificity was 100% and the sensitivity was 64%. All 26 M. kansasii strains tested could be identified as M. kansasii. The ELISA described here proved to be useful in both well- and modestly equipped laboratories and may replace the microbiological method of identification of M. tuberculosis and M. kansasii.

Neonatal tetanus despite protective serum antitoxin concentration.

Using the ELISA technique to estimate serum antibodies against tetanus toxin, seven neonates with clinical tetanus were found to have antibody levels 4-13 times higher than the presumed minimum protective level of 0.01 IU/ml. All but one of their mothers had been vaccinated with tetanus toxoid in pregnancy. In two other neonates, whose mothers had received multiple booster doses of toxoid during pregnancy, the anti-toxin concentrations were 100- and 400-times the presumed protective level. Therefore the toxin dose may overwhelm the pre-existing anti-toxin level and produce disease. Furthermore, multiple booster injections of tetanus toxoid may not only enhance serum anti-toxin titres, but could also lead to an ineffective immune response.

Prevalence of antibodies to human T-lymphotropic virus type 1 (HTLV-1) in an HIV-endemic region of Africa.

Serum samples from 267 healthy subjects and patients either infected or not infected with HIV-1 in Dar es Salaam, Tanzania, were examined by enzyme-linked immunosorbent assay and western blot techniques for evidence of HTLV-1 infection. Specific antibodies were detected in only 1% of the sera. Positive sera were likely to be from individuals infected with HIV-1. Tanzania and probably the other East African countries are non-endemic for HTLV-1. Prevalences are too low to provide justification for screening of blood donations. However, screening of donor blood for HIV-1 will limit transmission of HTLV-1 by this route as well.