Genetic diversity of ‘Candidatus Liberibacter africanus’ in South Africa based on microsatellite markers

Citrus Greening disease (CG) in South Africa (SA) is associated with the fastidious bacterium ‘Candidatus Liberibacter africanus’ (Laf). It has been observed that Laf isolates obtained from different geographic localities in SA differed in the rate of transmission during grafting experiments leading to the hypothesis that genetic variation of Laf may exist in this country. To determine this, 167 Laf isolates obtained from Limpopo, North West, Mpumalanga and the Western Cape were subjected to microsatellite analyses, using four polymorphic markers. From UPGMA and STRUCTURE analysis, it was shown that most sources belong to one of two major genetic groups of Laf and these comprise 25 distinct haplotypes. Four samples included within this study did not group with these two major groups, suggesting a potential third and fourth genetic group of Laf being present, which can be validated by further sampling. Results further indicate that Laf populations in SA are formed by geographic locality. The high genetic diversity observed for Laf within this study is consistent with the hypothesis that Laf originated on the African continent, warranting further genetic analysis of Laf populations from Africa. This is the first study to unveil the genetic diversity of Laf.

Advances in Epidemiological Studies of Herpes Zoster

Mycoplasma genitalium (Mg) commonly causes nongonococcal urethritis and cervicitis. Mg is a fastidious bacterium that poses difficulty in time-consuming isolation and culture. Lack of specificity for serological tests also hampers clinical research of Mg. With development of molecular biology, polymerase chain reaction tests, which exhibit high sensitivities and specificities, became primary tools for foundational and clinical studies of Mg.

Similarities and Differences in Physiological Responses to ‘Candidatus Liberibacter solanacearum’ Infection Among Different Potato Cultivars

Zebra chip disease (ZC), putatively caused by the fastidious bacterium ‘Candidatus Liberibacter solanacearum’, is a threat to potato growers worldwide. However, little is known about biochemical shifts in different potato genotypes in response to ‘Ca. L. solanacearum’ infection. To address this, ‘Red La Soda’, ‘Russet Norkotah’, and ‘FL 1867’ potato were infected with ‘Ca. L. solanacearum’ 4, 3, 2, and 1 weeks before harvest to observe variability in cultivar responses to ‘Ca. L. solanacearum’ infection. ZC symptoms, ‘Ca. L. solanacearum’ titers, and tuber biochemistry were assessed. Red La Soda tubers exhibited greater symptoms when infected for 4 weeks than Russet Norkotah or FL 1867 tubers. ‘Ca. L. solanacearum’ titers did not vary among cultivars. Tuber levels of amino acids, carbohydrates, and phenolics varied among cultivars but no consistent trends were observed. Individual amino acids and phenolics were greater in FL 1867 than Red La Soda, whereas others were greater in Red La Soda or Russet Norkotah than FL 1867. Most amino acids, carbohydrates, and phenolics were positively associated with infection duration and symptoms regardless of cultivar. Associations between most of the evaluated compounds and ‘Ca. L. solanacearum’ titer were positive in Red La Soda. However, no associations between ‘Ca. L. solanacearum’ quantity and compounds were observed in FL 1867 and Russet Norkotah.

Assessment of Persistence of Bartonella henselae in Ctenocephalides felis

ABSTRACTBartonella henselae(Rhizobiales:Bartonellaceae) is a Gram-negative fastidious bacterium of veterinary and zoonotic importance. The cat fleaCtenocephalides felis(Siphonaptera: Pulicidae) is the main recognized vector ofB. henselae, and transmission among cats and humans occurs mainly through infected flea feces. The present study documents the use of a quantitative molecular approach to follow the daily kinetics ofB. henselaewithin the cat flea and its excreted feces after exposure to infected blood for 48 h in an artificial membrane system.B. henselaeDNA was detected in both fleas and feces for the entire life span of the fleas (i.e., 12 days) starting from 24 h after initiation of the blood meal.

Differentiation of Strains of Xylella fastidiosa Infecting Grape, Almonds, and Oleander Using a Multiprimer PCR Assay

Xylella fastidiosa is a xylem-limited, nutritionally fastidious bacterium that causes several plant diseases including Pierce's disease (PD) in grape and leaf scorch in almond (ALS) and oleander (OLS). OLS strains belong to X. fastidiosa subsp. sandyi, PD strains belong to X. fastidiosa subsp. fastidiosa, and strains from almond designated as ALS strains are of two general types belonging either to X. fastidiosa subsp. multiplex or X. fastidiosa subsp. fastidiosa. The ALS strains assigned to X. fastidiosa subsp. multiplex belong to two different genotypes (ALSI and ALSII) below the subspecies level. The OLS strains do not infect grape or almond. PD strains produce diseases in grape, alfalfa, almond, and some weeds, but they do not infect oleander, oak, peach, or citrus. ALS strains that belong to X. fastidiosa subsp. multiplex do not produce disease on grape. In this study, a relatively simple polymerase chain reaction (PCR) based method was developed to distinguish among PD, OLS, and ALS strains. PCR performed with primers XF1968-L and XF1968-R amplified a 638-bp fragment from OLS strains but not from PD strains or ALS strains that belong to X. fastidiosa subsp. fastidiosa. PCR with primers XF2542-L and XF2542-R amplified a 412-bp fragment from PD strains, but not from OLS strains. PCR with primers ALM1 and ALM2 produced a fragment of 521 bp from strains isolated from almond that belong to X. fastidiosa subsp. multiplex. The combination of the three primer sets allowed the distinction of the two ALS genotypes of X. fastidiosa subsp. multiplex. These results are in agreement with those obtained from analysis of sequences of 16S-23S rDNA intergenic spacer regions sequence analysis and with previous results based on randomly amplified polymorphic DNA analysis.

Haemophilus Ducreyi

Genital ulcer disease as a risk factor for HIV transmission has become apparent in the fight against AIDS. In poor communities in developing countries with people living under low hygienic conditions chancroid is often reported to be the most common form of genital ulcer. It is caused by Haemophilus ducreyi; a fastidious bacterium, notoriously difficult to grow in the laboratory. Apart from a few small micro-epidemics from time to time the disease, which has interesting immunological aspects, is now rare and almost forgotten in most industrialized countries. This may be part of the reason why there is no simple and inexpensive diagnostic test available yet that would be useful in the low-resource settings where chancroid is prevalent. The present review focuses on the diagnosis and pathogenesis of chancroid.