Molecular characterization of the penile microbiome of Dorper rams (Ovis aries)

Courchay, Auberi Marie Madeleine (2017-03)

Thesis (MScAgric)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: Characterizing the bacterial community inhabiting the penile environment of Dorper rams may provide insight into the aetiology of ulcerative balanoposthitis (UB), a venereal disease of unknown aetiology, which occurs predominantly in this breed, and that is of great economic importance to the mutton industry in South Africa. Profiling of the bacteria present in the penile environment of healthy and diseased rams was carried out previously using culture-based methods. These culture-based studies identified Mycoplasma mycoides mycoides large colony (MMMLC) and Trueperella pyogenes as potentially contributing to the incidence of UB. Although cultured-based methods have been described as the gold standard for identification of bacteria, many bacteria are uncultivable or grow slowly and poorly in-vitro. The advent of high throughput next generation sequencing (HT-NGS), a culture-independent bacterial identification approach, has offered high coverage and depths in determining the bacterial penile community. Thus, this study aimed to characterize and compare the penile bacterial microbiome of Dorper rams that were healthy and diseased by means of 16S amplicon sequencing, a method of HT-NGS. Swab samples of the preputial and penile mucosa were collected from 113 rams, of which 40 Dorper ram samples (20 infected, 20 healthy) were chosen for further analysis in this study. Genomic DNA was extracted and amplified based on the V3V4 hypervariable region of the 16S rRNA bacterial gene. Bioinformatics analysis was performed using UPARSE and the ecological and statistical analyses such as Principal Coordinate Analysis (PCoA) was performed in QIIME and XLSTAT. Additional analyses comparing the predicted bacterial microbiota in healthy and diseased populations was carried out using LEfSe. A total of 789 OTUs from 9 964 842 sequences of high quality were obtained from the healthy and diseased communities indicating a high bacterial diversity in the penile environment, higher than previously reported and isolated using culture-based bacterial identification methods. The genus Corynebacterium was the most dominant genus identified (20.9%), irrespective of health status. A high inter-sample variation in microbiota was revealed. There were no significant differences in bacterial diversity or community composition between the healthy and diseased ram groups. The microbiota population was thus similar, with a few OTUs of high biological relevance belonging to genera Fusobacterium and Porphyromonas, as well as uncharacterized genera within Aerococaceae and Bacteroidales that were enriched in the diseased community. MMMLC and Trueperella pyogenes were not associated with UB in this study, which is contradictory to previous reports. However, a new Mycoplasma species, Mycoplasma hyopharyngis, not previously isolated in sheep and in cases of UB in Dorper rams, was identified and although not significantly different, had a higher abundance in the diseased population. The prevalence and predominance of Corynebacterium across all samples suggests this genus forms part of the core microbiome of the penile environment. High inter-sample variation in microbiota may depict true biological representation, however, future studies using homogenous ram populations (i.e. same type, same age) under the same environmental factors (i.e. management, feeding regime, etc.) should be conducted to validate these findings. Ulcerative balanoposthitis is not caused as a result of a change in bacterial diversity or community composition but OTUs enriched in the diseased ram population may be disease-specific/disease-associated and their role in UB warrants further investigation. No definitive aetiological agent was thus identified but the OTUs enriched in diseased rams can help direct future studies towards the identification of an aetiological agent of UB.

AFRIKAANSE OPSOMMING: Die karakterisering van die bakteriële gemeenskap wat die penis skede omgewing van Dorper ramme kan insig oor die etiologie van ulseratiewe balanoposthitis (UB), 'n geslagsiekte van onbekende etiologie wat hoofsaaklik in dié ras voorkom, verskaf. Die siekte is van groot ekonomiese belang vir die skaapvleis bedryf in Suid-Afrika. Vorige studies oor die karakterisering van die bakterieë in die penis skede omgewing van gesonde en siek ramme was gebaseer op kultuur-gebaseerde metodes. Hierdie kultuur-gebaseerde studies het Mycoplasma mycoides mycoides Large Colony (MMMLC) en Trueperella pyogenes as organismes geïdentifiseer wat moontlik bydra tot die voorkoms van UB. Hoewel kultuur-gebaseerde metodes beskryf word as die goue standaard vir die identifisering van bakterieë, kan baie bakterieë nie in vitro gekweek word nie of swak groei word in vitro waargeneem. Die bekendstelling van 'n hoë deurset volgende generasie volgorde bepalingstegniek (HT-NGS), 'n kultuur-onafhanklike benadering, bied ʼn wye dekking asook besonderse diepte waarmee die bakteriële gemeenskap in die penis skede omgewing bepaal kan word. Dié studie was daarop gemik om die bakteriële mikrobioom van die skede omgewing van siek en gesonde Dorper ramme met behulp van 16S amplikon volgordebepaling, ‘n HT-NGS metode, te karakteriseer en te vergelyk. Depper monsters van die voorvel en penis mukosa omgewing is van 113 ramme versamel, waarvan 40 Dorper ram monsters (20 besmet, 20 gesonde) vir verdere analise in hierdie studie gekies is. Die genomiese DNS is geëkstraheer en versterk gebaseer op die V3V4 hiper-variërende streek van die 16S rRNS bakteriële geen. Bio-informatiese analise is met behulp van UPARSE uitgevoer en die ekologiese en statistiese ontledings soos Hoof Koördinaat Ontleding (PCoA) is uitgevoer in QIIME en XLSTAT. Bykomende ontledings wat die voorspelde bakteriële mikrobiota in gesonde en siek bevolkings vergelyk het, is uitgevoer met behulp van LEfSe. 'n Totaal van 789 operasionele taksonomiese eenhede (OTE’e) van 9 964 842 sekwense van 'n hoë gehalte is verkry uit die gesonde en siek gemeenskappe, wat dui op 'n hoë bakteriële diversiteit in die penis omgewing, hoër as wat voorheen berig en geïsoleer was deur kultuur-gebaseerde bakteriële identifikasie metodes. Die genus Corynebacterium was die mees dominante genus geïdentifiseer (20.9%), ongeag die gesondheidstatus van ʼn ram. 'n Hoë inter-monster variasie in mikrobiota is gevind. Daar was geen betekenisvolle verskille in bakteriële diversiteit of gemeenskapsamestelling tussen die gesonde en siek ram groepe nie. Die mikrobiota bevolking was soortgelyk tussen siek en gesonde ramme, met 'n paar OTE’e van 'n hoë biologiese relevansie (d.i. genera Fusobacterium en Porphyromonas, asook nie-gekarakteriseerde genera binne Aerococaceae en Bacteroidales) wat meer volop in die siek was. Die bakterieë MMMLC en Trueperella pyogenes kon nie in dié studie in verband gebring word met die voorkoms van UB nie, wat teenstrydig is met die vorige verslae. ʼn Nuwe mikoplasma spesie, Mycoplasma hyopharyngis, wat nog nie voorheen in skape en gevalle van UB in Dorper ramme geïsoleer is nie, is geïdentifiseer en alhoewel nie betekenisvol nie, het in hoër getalle in die siek ramme voorgekom. Die voorkoms en oorheersing van Corynebacterium in beide die siek en gesonde ramme dui aan dat dié genus deel vorm van die kern mikrobioom van die penis omgewing. Hoë inter-monster variasie in mikrobiota kan normaal wees, maar daar word aanbeveel dat toekomstige studies waar moontlik homogene ram bevolkings (d.w.s. dieselfde ras, ouderdom, ens.) onder dieselfde omgewingsfaktore (bv. bestuur, voeding, ens.) gedoen moet word om hierdie bevindinge te bevestig. Ulseratiewe balanoposthitis word dus nie veroorsaak deur 'n verandering in bakteriële diversiteit of gemeenskap samestelling nie, maar die OTE’s wat meer volop in die siek ramme voorgekom het mag siekte-spesifiek wees of verband hou met UB. Derhalwe moet hierdie organismes se rol in die voorkoms van UB verder ondersoek word. Geen definitiewe etiologiese agent is dus geïdentifiseer nie, maar die OTE’s geïdentifiseer in hierdie studie kan leiding verskaf oor die ontwerp van toekomstige studies vir die identifisering van 'n etiologiese agent van UB.

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