Line-probe assay and molecular typing reveal a potential drug resistant clone of Mycobacterium tuberculosis in Ethiopia

Background

Antimicrobial resistance is a global concern of increasing significance. Multidrug resistant tuberculosis (MDR-TB) is spreading worldwide. It is important to monitor trends of antimycobacterial resistance. This is particularly true for high TB burden countries such as Ethiopia where disproportionally less drug sensitivity data are reported from.

Methods

The prevalence of drug resistance was assessed with the line probe assay GenoType MTBDRplus in a set of 161 M. tuberculosis strains that were selected from four common lineages and sub-lineages previously identified in Ethiopia. Most of the tested M. tuberculosis isolates had been genotyped by established Spoligotyping and MIRU-VNTR typing methods.

Results

The proportion of MDR-TB among the isolates was 3.1%. Mono-resistance was 1.2% to rifampicin and 4.3% to isoniazid, and resistance to either of the two first line drugs was 8.7%. Strains of Lineage 4 had the highest resistance rate (13.6%) followed by Lineage 3 (4.9%). None of the isolates representing Lineages 1 and Lineage 7 were drug resistant. Multidrug resistance among pulmonary TB and TB lymphadenitis clinical isolates was 2.8 and 3.7%, respectively. Drug resistance of strains carrying the most prevalent spoligotype in Ethiopia - SIT149 - was further explored. Stratification by MIRU-VNTR identified one genotype with a high rate of drug resistance against Rifampicin and Isoniazid and circulation of a potential MDR-TB clone is proposed.

Conclusion

Although the strain selection was not fully randomized, the overall M. tuberculosis drug resistance rate in this strain set was 8.7% while the rate of MDR was 3.1%. In parallel, we identified a sub-lineage that showed a high rate of resistance to both rifampicin and isoniazid. These resistant strains may belong to a clone of M. tuberculosis that is circulating in the highlands of Ethiopia.

Electronic supplementary material

The online version of this article (10.1186/s40794-018-0075-3) contains supplementary material, which is available to authorized users.

Whole genome sequencing reveals within-host genetic changes in paired meningococcal carriage isolates from Ethiopia

Background

Meningococcal colonization is a prerequisite for transmission and disease, but the bacterium only very infrequently causes disease while asymptomatic carriage is common. Carriage is highly dynamic, showing a great variety across time and space within and across populations, but also within individuals. The understanding of genetic changes in the meningococcus during carriage, when the bacteria resides in its natural niche, is important for understanding not only the carriage state, but the dynamics of the entire meningococcal population.

Results

Paired meningococcal isolates, obtained from 50 asymptomatic carriers about 2 months apart were analyzed with whole genome sequencing (WGS). Phylogenetic analysis revealed that most paired isolates from the same individual were closely related, and the average and median number of allelic differences between paired isolates defined as the same strain was 35. About twice as many differences were seen between isolates from different individuals within the same sequence type (ST). In 8%, different strains were detected at different time points. A difference in ST was observed in 6%, including an individual who was found to carry three different STs over the course of 9 weeks. One individual carried different strains from the same ST.

In total, 566 of 1605 cgMLST genes had undergone within-host genetic changes in one or more pairs. The most frequently changed cgMLST gene was relA that was changed in 47% of pairs. Across the whole genome, pilE, differed mostly, in 85% of the pairs. The most frequent mechanisms of genetic difference between paired isolates were phase variation and recombination, including gene conversion. Different STs showed variation with regard to which genes that were most frequently changed, mostly due to absence/presence of phase variation.

Conclusions

This study revealed within-host genetic differences in meningococcal isolates during short-term asymptomatic carriage. The most frequently changed genes were genes belonging to the pilin family, the restriction/modification system, opacity proteins and genes involved in glycosylation. Higher resolution genome-wide sequence typing is necessary to resolve the diversity of isolates and reveals genetic differences not discovered by traditional typing schemes, and would be the preferred choice of technology.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3806-3) contains supplementary material, which is available to authorized users.

Prevalence and epidemiology of meningococcal carriage in Southern Ethiopia prior to implementation of MenAfriVac, a conjugate vaccine

Background

Neisseria meningitidis colonizes humans and transmits mainly by asymptomatic carriage. We sought to determine the prevalence and epidemiology of meningococcal carriage in Ethiopia prior to the introduction of MenAfriVac, a serogroup A meningococcal conjugate vaccine.

Methods

A cross-sectional meningococcal carriage study was conducted in Arba Minch, southern Ethiopia. A total of 7479 oropharyngeal samples were collected from 1 to 29 year old volunteers, between March and October, 2014. The swabs were cultured for N. meningitidis and Neisseria lactamica in Ethiopia. N. meningitidis isolates were confirmed and characterized by their serogroup, sequence type (ST) and PorA:FetA profile in Norway.

Results

Overall carriage prevalence was 6.6 %. There was no significant difference in overall carriage between male (6.7 %) and female (6.4 %) participants. Highest carriage prevalence (10.9 %) for females was found in the 15–19 years of age, while prevalence among males was highest (11.3 %) in the 20–24 age group. Non-groupable isolates dominated (76.4 %), followed by serogroups X (14.0 %) and W (5.9 %) isolates. No serogroup A was found. Most non-groupable isolates were ST-192. Serogroup W isolates were assigned to the ST-11 clonal complex, and serogroup X isolates to the ST-181 and ST-41/44 clonal complexes. Overall carriage prevalence of N. lactamica was 28.1 %. Carriage of N. meningitidis and N. lactamica varied depending on age and geographic area, but there was no association between carriage of the two species.

Conclusions

Epidemic strains of serogroups W and X were circulating in this area of Ethiopia. As no serogroup A was found among the carriage isolates the immediate impact of mass-vaccination with MenAfriVac on transmission of N. meningitidis in this population is expected to be marginal.

The socioeconomic impact of multidrug resistant tuberculosis on patients: results from Ethiopia, Indonesia and Kazakhstan

BACKGROUND

One of the main goals of the post-2015 global tuberculosis (TB) strategy is that no families affected by TB face catastrophic costs. We revised an existing TB patient cost measurement tool to specifically also measure multi-drug resistant (MDR) TB patients' costs and applied it in Ethiopia, Indonesia and Kazakhstan.

METHODS

Through structured interviews with TB and MDR-TB patients in different stages of treatment, we collected data on the direct (out of pocket) and indirect (loss of income) costs of patients and their families related to the diagnosis and treatment of TB and MDR-TB. Direct costs included costs for hospitalization, follow-up tests, transport costs for health care visits, and food supplements. Calculation of indirect costs was based on time needed for diagnosis and treatment. Costs were extrapolated over the patient's total treatment phase.

RESULTS

In total 406 MDR-TB patients and 197 other TB patients were included in the survey: 169 MDR-TB patients and 25 other TB patients in Ethiopia; 143 MDR-TB patients and 118 TB patients in Indonesia; and 94 MDR-TB patients and 54 other TB patients in Kazakhstan. Total costs for diagnosis and current treatment episode for TB patients were estimated to be USD 260 in Ethiopia, USD 169 in Indonesia, and USD 929 in Kazakhstan, compared to USD 1838, USD 2342, and USD 3125 for MDR-TB patients, respectively. These costs represented 0.82-4.6 months of pre-treatment household income for TB patients and 9.3-24.9 months for MDR-TB patients. Importantly, 38-92 % reported income loss and 26-76 % of TB patients lost their jobs due to (MDR) TB illness, further aggravating the financial burden.

CONCLUSIONS

The financial burden of MDR-TB is alarming, although all TB patients experienced substantial socioeconomic impact of the disease. If the patient is the breadwinner of the family, the combination of lost income and extra costs is generally catastrophic. Therefore, it should be a priority of the government to relieve the financial burden based on the cost mitigation options identified.

Performance of general health workers in leprosy control activities at public health facilities in Amhara and Oromia States, Ethiopia

BACKGROUND

Leprosy is a chronic infectious disease of public health importance and one of the leading causes of permanent physical disability. Nevertheless, the drop in prevalence following multidrug therapy has resulted in the neglect of leprosy. The annual incidence of leprosy has remained the same in Ethiopia since decades with more than 76% of the reported new cases coming from Oromia and Amhara Regional States. This study was aimed to assess the knowledge, attitude and skill of general health workers in leprosy control activities at public health facilities in Oromia and Amhara Regional States.

METHODS

A cross-sectional study was conducted from September 2011 to February 2012 at different public health facilities in selected eight zones in Oromia and Amhara Regional States. A multistage sampling method was used to obtain representative samples. High and low endemic zones for leprosy were included in the study in both regional states. Data were collected from general health workers through a structured self-administered questionnaire and at on-site assessment of their performance. Baseline socio-demographic data, health workers' attitude towards leprosy and their knowledge and skill in the management of leprosy were assessed. Bloom's cut off point was used to describe the knowledge and practical skills of the respondents while Likert's scale was used for attitude assessment.

RESULT

A total of 601 general health workers responsible for leprosy control activities at public health facilities were included in knowledge and attitude assessment and 83 of them were subjected to practical evaluation, with on-site observation of how they handle leprosy patients. These included medical doctors (4%), health officers and nurses with Bachelor degree in Science (27%), clinical nurses with diploma (66%) and health assistants (2.8%). The median age of the respondents was 26.0 years and females made up of 45%. Generally the knowledge and skills of the respondents were found to be poor while attitude towards leprosy was positive for the majority of the respondents. The result showed that 519 (86.3%) had poor knowledge. Overall 155 (25.8%) of the respondents had positive attitude towards leprosy while 205 (34.1%) had intermediate (mixed) attitude and 241 (40.1%) had negative attitude to the disease. Among 83 respondents assessed for diagnosis of leprosy only 15(18.0%) diagnosed leprosy correctly. Variation in knowledge and attitude indicated a significant difference (p < 0.05) among different health institutions, professions, gender, in-service training and years of experience.

CONCLUSION

The current finding underlines that although leprosy control activities are integrated to the general health services in the country, the knowledge and skills of leprosy diagnosis, treatment and management by health workers was unsatisfactory. Hence, attention should be given to develop training strategies that can improve health worker knowledge and promote better leprosy management at public health facilities. This could be achieved through pre-service and in-service training and giving adequate emphasis to leprosy related practical work and continuous follow- up.

A Randomized, Placebo-Controlled Trial Evaluating Safety and Immunogenicity of the Killed, Bivalent, Whole-Cell Oral Cholera Vaccine in Ethiopia

Killed whole-cell oral cholera vaccine (OCV) has been a key component of a comprehensive package including water and sanitation measures for recent cholera epidemics. The vaccine, given in a two-dose regimen, has been evaluated in a large number of human volunteers in India, Vietnam, and Bangladesh, where it has demonstrated safety, immunogenicity, and clinical efficacy. We conducted a double-blind randomized placebo-controlled trial in Ethiopia, where we evaluated the safety and immunogenicity of the vaccine in 216 healthy adults and children. OCV was found to be safe and elicited a robust immunological response against Vibrio cholerae O1, with 81% adults and 77% children demonstrating seroconversion 14 days after the second dose of vaccine. This is the first study to evaluate safety and immunogenicity of the vaccine in a population outside Asia using a placebo-controlled, double-blind, randomized study design.

Identification and Characterization of Mycobacterium Tuberculosis Isolates from Cattle Owners in North Western and North Eastern Parts of Rural Ethiopia

Tuberculosis (TB) is a major global public health problem resulting in a considerable morbidity and mortality worldwide. Ethiopia ranks 8^th among the 22 high TB burden countries. Establishing an appropriate and improved intervention strategy to prevent and control tuberculosis requires the presence of evidence based data on the genetic diversity of its causative agent. The current research work, therefore, was to differentiate strains of Mycobacterium tuberculosis isolated from pulmonary tuberculosis patients who own cattle in North Eastern and North Western parts of Ethiopia using molecular techniques. Sputum samples were collected from Acid Fast Bacilli (AFB) positive pulmonary tuberculosis patients and cultured on Lowenstein-Jensen (LJ) medium containing glycerol and sodium pyruvate. Deoxyribonucleic acid (DNA) was extracted from each positive culture, spoligotyping and single nucleotide polymorphisms were performed to further differentiate strains of M. tuberculosis, after deletion typing PCR confirmed that all the isolates were Mycobacterium tuberculosis. The mean age of study participants was 35.7 years (18-63 years) + 13.24. The majority (55.7%) were from North Gondar zone. Spoligotyping revealed that (47/50) 94% had interpretable patterns and 3 lineages namely; East-Africa-Indian (57.4%), Euro-American-African (EAA lineage-Lineage 4) 38.3% and Ethiopian (lineage-7) 2/50 (4.3%). Lineage 7 was registered in North Wollo zone only. In this study 8 clusters (with cluster size ranging from 2-8), 8 unique and 10 new patters were recorded. Spoligotype International Types (SIT) (21, 25, 26, 35, 53, 109, 149 and 289), were found as clusters and of these SIT 25 (7) and SIT 289 (8) were the predominant ones. Our study proved that 3 Mycobacterium tuberculosis lineages, namely; the ancient, intermediate between the modern lineages as well as modern were identified. Besides, considerable clustering was seen, which indicates the presence of current TB transmission in the study areas.

Immunocytochemical detection of Mycobacterium Tuberculosis complex specific antigen, MPT64, improves diagnosis of tuberculous lymphadenitis and tuberculous pleuritis

BACKGROUND

A rapid, sensitive and accurate laboratory diagnosis is of prime importance in suspected extrapulmonary tuberculosis (EPTB) cases. However, traditional techniques for the detection of acid-fast bacilli have limitations. The aim of the study was to evaluate the diagnostic value of immunocytochemical staining for detection of Mycobacterium tuberculosis complex specific antigen, MPT64, in aspirates from pleural effusions and lymph nodes, the most common presentations of EPTB.

METHOD

A cross-sectional study was conducted by including patients at Tikur Anbessa Specialized Hospital and the United Vision Medical Services from December 2011 to June 2012. Lymph node aspirates and pleural fluid samples were collected and analyzed from a total of 51 cases (26 tuberculous (TB) pleuritis and 25 TB lymphadenitis) and 67 non-TB controls. Each specimen was subjected to Ziehl-Neelsen (ZN) staining, culture on Lowenstein- Jensen (LJ) medium, cytological examination, Polymerase Chain Reaction (PCR) using IS1081gene sequence as a primer and immunocytochemistry (ICC) with polyclonal anti-MPT64 antibody. All patients were screened for HIV.

RESULT

ICC was positive in 38 of 51 cases and in the 7 of 67 controls giving an overall sensitivity and specificity of 74.5% and 89.5%, respectively. Using IS1081-PCR as a reference method, the sensitivity and specificity, positive and negative predictive value of ICC was 88.1%, 89.5%, 82.2% and 93.2%, respectively. The case detection rate increased from 13.7% by ZN stain to 19.6% by LJ culture, to 66.7% by cytology and 74.5% by ICC.

CONCLUSION

Immunocytochemistry with anti-MPT64 antigen improved detection of TB in pleural effusion and lymph node aspirates. Further studies using monoclonal antibodies on samples from other sites of EPTB is recommended to validate this relatively simple diagnostic method for EPTB.

Hydatidosis: prevalence and its economic importance in ruminants slaughtered at Adama municipal abattoir, Central Oromia, Ethiopia

A cross-sectional study was conducted from November 2007 to April 2008 to estimate the prevalence of hydatidosis in ruminants slaughtered at Adama municipal abattoir. An attempt was also made to estimate the annual economic loss due to condemnation of organs during meat inspection. A retrospective analysis of data spanning a 10-year period (1997-2007) was also undertaken to determine the presence of the parasite during this period. A total of 1152 ruminants (852 cattle, 92 sheep and 208 goats) were inspected following slaughter. Hydatidosis was prevalent in 46.8% cattle, 29.3% sheep, and 6.7% goats. In cattle, 326 (55.2%) of the lung, 219 (37.1%) of the liver, 21 (3.6%) of the spleen, 15 (2.5%) of the heart and 10 (1.7%) of the kidney were found to be infected with hydatid cysts. In sheep, hydatid cysts were recovered from 22 (55.0%) of the lung, 16 (40.0%) of the liver and 2 (5.0%) of the spleen while none of the heart and kidney were recorded positive. In goats, the degree of infection was 6 (33.3%) of lung, 10 (55.6%) of liver, 1 (5.6%) of spleen and kidney each. According to the retrospective data, a total of 107,333 cattle were slaughtered and during this period 13,519 of the liver, 18,304 of the lung, 1142 of the kidneys, 537 of the hearts and 150 of the spleens were found to be infected with hydatidosis. The total annual economic loss incurred due to hydatidosis in ruminants slaughtered at Adama municipal abattoir was estimated to be to 52,828 ETB (5869.8 USD). The current results suggest that a thorough investigation that leads to a disease control strategy is required to reduce the economic and public health consequences of hydatidosis.

Serodiagnosis of tuberculous lymphadenitis using a combination of antigens

Background: The diagnosis of extra-pulmonary tuberculosis (EPTB) by conventional methods such as culture and microscopy has low sensitivity and requires an invasive procedure. A simple rapid serological test would be of great value. Methodology: Six antigens (ESAT-6, Ag85A, TB10.4, Rv3881c, lipoarabinomannan (LAM) and Ara6-BSA) were tested in an ELISA to detect antigen-specific IgG and IgM antibodies in sera from 54 culture- and histology-confirmed tuberculous lymphadenitis (TBLN) patients as follows: four were HIV seropositive; sera from 25 was smear positive for pulmonary tuberculosis (PTB); 15 were culture- and histology-negative lymphadenitis (non-TBLN) patients; and 22 werehealthy controls (HCs). Results: The sensitivities of the antigens for the detection of IgG in sera of TBLN patients ranged from 4% to 30%. Specificities ranged from 73% to 100% with sera from non-TBLN patients and 91% to 100% with sera from HCs. Sensitivities of the antigens for detection of IgM ranged from 0% to 15% and specificities ranged from 80% to 100% with sera from non-TBLN patients and 91% to 100% with sera from HCs. LAM was the most potent antigen for detection of IgG. When LAM and ESAT-6 were combined, sensitivity increased up to 43% and specificity with non-TBLN was 80% with HC 96%. Conclusions: The study suggests that the combined use of LAM and ESAT-6 for IgG antibody detection in sera from TBLN patients could be a supplement to microscopy of fine-needle aspirate (FNA) to diagnose TBLN among patients suspected of TBLN.

Identification and genotyping of the etiological agent of tuberculous lymphadenitis in Ethiopia

BACKGROUND

In Ethiopia, little has been done to assess how Mycobacterium bovis has contributed to human tuberculosis, though the population routinely consumes unpasteurized milk and raw meat. The aim of this study was to determine the proportion of M. tuberculosis and M. bovis as etiological agents of tuberculous lymphadenitis (TBLN).

METHODS

Patients with lymphadenopathy (n = 171) were included in a cross-sectional study at Butajira Hospital, Southern Ethiopia. Lymph node biopsies were cultured. Patients' HIV status was identified. DNA from positive cultures was tested by PCR to identify M. bovis and M. tuberculosis. Isolates were genotyped by multiplex ligation-dependent probe amplification (MLPA) assay.

RESULTS

Among 171 patients, 156 had culture results. Of these, 107 (69%) were positive for M. tuberculosis complex (MTC). Six of the 10 HIV-positive patients were culture positive. M. tuberculosis specific sequences were identified in the DNA of each of 100 samples as assessed by RD10 targeted PCR, and each of the 95 isolates exhibited the M. tuberculosis specific TbD1 deletion by MLPA analysis. No M. bovis was identified. These results indicate that all the isolates were modern M. tuberculosis strains. Furthermore, MLPA studies confirmed that 42% of the isolates showed the Haarlem genotype and 12% displayed sequences compatible with INH resistance. No mutations conferring resistance to ethambutol or rifampicin were detected.

CONCLUSIONS

Our data showed that M. tuberculosis strains had common characteristics with strains causing pulmonary TB, which appears to be the main etiological agent of TBLN.

Diagnosis of tuberculous lymphadenitis in Ethiopia: correlation with culture, histology and HIV status

SETTING

Butajira, Southern Ethiopia.

OBJECTIVE

To compare the diagnostic capacity of the clinical criteria for tuberculous lymphadenitis (TBLN) with histological and/or culture results and to assess the association of human immunodeficiency virus (HIV) with tuberculosis (TB) lymphadenitis.

DESIGN

Patients (n=171) were included in the study from October 2005 until July 2006 at Butajira Hospital. Laboratory tests were performed to confirm TBLN. HIV status was identified in TBLN patients and retrospectively in 1608 healthy individuals.

RESULT

A total of 136/161 (84.5%) patients were diagnosed with TBLN by histology. TBLN was culture-confirmed in 107/156 (68.6%) patients. The sensitivity, specificity, positive and negative predictive values of histology were respectively 92.5%, 49%, 79.8% and 75% when compared to culture as gold standard. Patients positive for TBLN by cytology and Ziehl-Neelsen (ZN) were also positive by histology and culture. Among the 143 confirmed TBLN patients, nine (6.3%) were HIV-positive. Of the 1608 healthy individuals, 77 (4.8%) were HIV-positive. Younger age (P=0.0001), female sex (P=0.016), not being married (P=0.0001) and illiteracy (P=0.016) showed a strong association with HIV in healthy individuals.

CONCLUSION

Clinical criteria alone over-diagnosed TBLN by 15.4% compared to histological and/or bacteriological results. The HIV prevalence in TBLN patients and healthy individuals was the same.

Nasal carriage of Mycobacterium leprae DNA in healthy individuals in Lega Robi village, Ethiopia

The number of registered leprosy patients world-wide has decreased dramatically after extensive application of WHO recommended Multiple Drug Therapy (MDT). The annual number of new cases has, however, been almost unchanged in several populations, indicating that the infection is still present at community level. Nasal carriage of Mycobacterium leprae DNA was studied in Lega Robi village in Ethiopia. MDT had been applied for more than ten years, and 718 residents over 5 years old were eligible for the study. During the first survey nasal swab samples were collected from 664 (92.5%) individuals. The results of a Peptide Nucleic Acid-ELISA test for M. leprae DNA interpreted by stringent statistical criteria were available for 589 (88.7%) subjects. Thirty-five (5.9%) individuals without clinical signs of leprosy were positive for M. leprae DNA. Seven PCR positive individuals lived in a household where one or two other members were also positive for M. leprae DNA. During a second survey 8 (46%) of 175 interpretable PNA-ELISA tests were positive. Of 137 individuals tested twice, only two were positive on both occasions whereas 10 were PCR positive only once. The study confirms the widespread distribution of M. leprae DNA in healthy individuals. The feasibility of curbing possible transmission of subclinical infection needs further consideration.

Diversity of rhizobia associated with Amorpha fruticosa isolated from Chinese soils and description of Mesorhizobium amorphae sp. nov

Fifty-five Chinese isolates from nodules of Amorpha fruticosa were characterized and compared with the type strains of the species and genera of bacteria which form nitrogen-fixing symbioses with leguminous host plants. A polyphasic approach, which included RFLP of PCR-amplified 16S rRNA genes, multilocus enzyme electrophoresis (MLEE), DNA-DNA hybridization, 16S rRNA gene sequencing, electrophoretic plasmid profiles, cross-nodulation and a phenotypic study, was used in the comparative analysis. The isolates originated from several different sites in China and they varied in their phenotypic and genetic characteristics. The majority of the isolates had moderate to slow growth rates, produced acid on YMA and harboured a 930 kb symbiotic plasmid (pSym). Five different RFLP patterns were identified among the 16S rRNA genes of all the isolates. Isolates grouped by PCR-RFLP of the 16S rRNA genes were also separated into groups by variation in MLEE profiles and by DNA-DNA hybridization. A representative isolate from each of these DNA homology groups had a separate position in a phylogenetic tree as determined from sequencing analysis of the 16S rRNA genes. A new species, Mesorhizobium amorphae, is proposed for the majority of the isolates, which belonged to a moderately slow- to slow-growing, acid-producing group based upon their distinct phylogenetic position, their unique electrophoretic type, their low DNA homology with reference strains representing the species within the genus Mesorhizobium and their distinct phenotypic features. Strain ACCC 19665 was chosen as the type strain for M. amorphae sp. nov.

Rhizobium huautlense sp. nov., a symbiont of Sesbania herbacea that has a close phylogenetic relationship with Rhizobium galegae

The nitrogen-fixing rhizobial symbionts of Sesbania herbacea growing in the nature reserve at the Sierra de Huautla, Mexico, were isolated and characterized. All 104 isolates together with the type strain for Rhizobium galegae, HAMBI 540T, had similar 16S rRNA genes as revealed by PCR-RFLP analysis. Similarity in the sequences of the 16S rRNA genes placed the isolates on a phylogenetic branch shared with R. galegae. Among 66 randomly selected isolates, three closely related electrophoretic alloenzyme types (ETs) were identified, which were distinct from 10 ETs distinguished among 23 strains of R. galegae. A new species Rhizobium huautlense, represented by the Sesbania isolate SO2T, is proposed based upon low estimates of DNA relatedness between our chosen type strain and the type strains for the other species, the dissimilarity of the nucleotide sequence of the 16S rRNA genes, and their distinct ETs compared with R. galegae. The description of R. huautlense is significant because in the reconstruction of the phylogeny at R. huautlense there was a shift in the node of the branch of Agrobacterium vitis relative to that of R. galegae. The revised phylogenetic tree would tend to indicate common ancestry between R. galegae and Rhizobium leguminosarum.

Rhizobium mongolense sp. nov. is one of three rhizobial genotypes identified which nodulate and form nitrogen-fixing symbioses with Medicago ruthenica [(L.) Ledebour]

Medicago ruthenica [(L.) Ledebour] is native to inner Mongolia where rhizosphere samples were collected for the isolation of 106 rhizobial cultures. Besides nodulating the original trap host, the isolates formed nitrogen-fixing symbioses with Phaseolus vulgaris. Only half of the isolates nodulated alfalfa (Medicago sativa), but these did not form nitrogen-fixing symbioses. Rhizobium tropici also formed nitrogen-fixing symbioses with Medicago ruthenica. A total of 56 distinctive multilocus electrophoretic types (ETs) were identified among 94 of the 106 isolates which were analysed for variation in electrophoretic mobility of 12 enzyme loci. One isolate (USDA 1920) possessed a unique ET, while the ETs of the other isolates formed two weakly divergent subgroups approximately equal in size. It was concluded from small subunit rRNA gene sequences of eight isolates of Medicago ruthenica that they belonged to the genus Rhizobium and not to the genus Sinorhizobium which is more commonly associated with Medicago. Genomic similarity, determined from DNA hybridization analysis, between USDA 1920 and the strain representing the remaining isolates (USDA 1844) was lower than 20%. Based upon these observations it was concluded that at least three genomic species of rhizobia form nitrogen-fixing symbioses with Medicago ruthenica. One of these genomic species is R. tropici, another is represented by the single isolate USDA 1920 and the name Rhizobium mongolense is proposed for the third genomic species represented by USDA 1844.

Identification and characterization of human B-cell epitopes in recombinant antigens of Leishmania aethiopica

Recombinant DNA fragments from Leishmania aethiopica that code for epitopes which react with human antibodies have been characterized by cross-hybridization studies and DNA sequence analysis. Twenty clones could be grouped into seven different groups (I-VII), probably representing seven different L. aethiopica antigens. The DNA sequences of representative clones from the seven groups have been obtained and the amino acid sequence of the respective recombinant antigens established. The recombinant antigens have been analysed by epitope scanning with patient sera, and octapeptides that contain potential B-cell epitopes have been identified in all seven recombinant antigens. These octapeptides have further been tested with additional patient sera and control sera, and three octapeptides (HAFCHEEG, YHSSVVHD and SYAPCSLK) were found to contain major epitopes recognizing specific antibodies in nine, seven and four, respectively, of the twenty sera tested. Fifteen of the twenty sera reacted with one or more of these three octapeptides.

Phylogenetic relationships among Rhizobium species nodulating the common bean (Phaseolus vulgaris L.)

The phylogenetic relationships among Rhizobium species that nodulate Phaseolus vulgaris (common bean) were determined by directly sequencing the amplified 16S ribosomal DNA genes of these organisms. The bean strains formed four separate clusters. One cluster was composed of Rhizobium leguminosarum bv. trifolii, R. leguminosarum bv. viciae, and R. leguminosarum bv. phaseoli. Two other clusters comprised Rhizobium etli and Rhizobium tropici, and the fourth cluster contained a single bean-nodulating strain. Data for species identification were obtained from DNA-DNA reassociation experiments. The levels of DNA relatedness among strains belonging to the three biovars of R. leguminosarum ranged from 58 to 67%. The levels of DNA relatedness between R. leguminosarum bv. phaseoli and R. etli and R. tropici ranged from 43 to 45% and 13 to 16%, respectively. The levels of DNA relatedness between the strain belonging to the fourth cluster and strains of the other three Rhizobium species that nodulate beans were less than 10%.

Variability among Rhizobium Strains Originating from Nodules of Vicia faba

Rhizobium strains from nodules of Vicia faba were diverse in plasmid content and serology. Results of multilocus gel electrophoresis and restriction fragment length polymorphism indicated several deep chromosomal lineages among the strains. Linkage disequilibrium among the chromosomal types was detected and may have reflected variation of Rhizobium strains in the different geographical locations from which the strains originated. An investigation of pea strains with antibodies prepared against fava bean strains and restriction fragment length polymorphism analyses, targeting DNA regions coding for rRNA and nodulation, indicated that Rhizobium strains from V. faba nodules were distinguishable from those from Pisum sativum, V. villosa, and Trifolium spp.

Isolation and characterization of recombinant antigens from Leishmania aethiopica that react with human antibodies

A genomic expression library of Leishmania aethiopica was constructed in lambda gt11 and screened with patient sera and sera from healthy people living in an area of endemicity. Forty-five recombinant clones were isolated and partly characterized. Clone-specific antibodies were prepared and used with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western immunoblot analysis to estimate the molecular masses of the parasite-derived antigens containing the reactive epitope(s). Antigens with apparent molecular masses of 90, 85, 63, 50, 41, 25 and 24 kDa as well as several antigens with lower molecular masses were detected. The clone-specific antibodies from patients with diffuse cutaneous leishmaniasis reacted with high-molecular-weight antigens (30,000 less than Mr less than 90,000), whereas antibodies from patients with localized cutaneous leishmaniasis recognized low-molecular-weight antigens (Mr less than 25,000). Nine different purified recombinant antigens were obtained from lysogens in Escherichia coli Y1089 by immunoaffinity chromatography on anti-beta-galactosidase columns and were subsequently tested with patient sera. It is suggested that some of these recombinant antigens might be used for immunodiagnostic purposes.