Mostafa Al Yassiry Bench C 12/10/2017 
Higher order taxa
Bacteria – Bacteroidetes – Bacteroidetes – Bacteroidales – Prevotellaceae – Prevotella
Description and significance
The Prevotella species are commonly found and cultured from the rumen and hindgut of cattle and sheep. In humans, they make for opportunistic pathogens and are known for causing periodontal and tooth problems (1). In addition, they have also been found to thrive in the vaginal area, and are sometimes also recovered from the anaerobic infections of the respiratory tract including sinusitis, lung abscess, chronic otitis media, aspiration pneumonia and pulmonary empyema. Studying these bacteria would help scientists and researchers understand better the modes of their spread, their activity and the factors that could hamper their growth, which in turn, could possibly help pave the way for research and development of new drugs and medications to deal with the infections it causes.
Prevotella Oris has not been completely sequenced (1). The only two strains from the Prevotella family that have been completely sequenced are Prevotella intermedia 17 and Prevotella ruminicola 23 (2). The genome of Prevotella intermedia 1, had a De novo assembly of 127,972 reads averaging a length of 6,598 bp using the Hierarchical Genome Assembly Process (HGAP). This resulted in two closed circular chromosomes of 606,227-bp and 2,131,046-bp in size with average coverages of 194.0× and 214.6×, respectively and had a GC content of 43.5%. 2,510 coding sequences, as well as 61 RNA sequences were identified (14).
Cell structure and metabolism
Prevotella Oris is a gram negative, anaerobic bacterium which has been found to be associated with some major oral and systemic infections. It is a non pigmented bacterium which has been identified through bacterial cultures and lab tests, which are often not usually regarded as a reliable method of detection (1). This is why, a study conducted in 2007 attempted to develop a PCR assay for the direct detection of the organism (3). Previous studies have found that P. Oris is able to produce immunoglobulin A protease, hyaluronidase and b-lactamase which possibly point out to the pathogenic nature of the organism. Studies have found that Prevotella makes use of steroid hormones as growth factors, which is why, their occurrence is significantly higher in pregnant women, and is also isolated from women suffering from bacterial vaginosis. It has also been found and isolated from dental infections occurring in individuals suffering from Down’s Syndrome, a chromosome disorder.
Prevotella bacteria are gram negative, rod shaped and singular cells that are generally found thriving in anaerobic conditions (5). Prevotella Oris has been found and isolated from lesions of several oral infections, dentoalveolar abscess (4), endodontic infections and sometimes even from lesions of systemic infections such as meningitis, empyema and cervical spinal epidural abscess. The Prevotella species, particularly Prevotella Oris, requires hemim for their growth and multiplication. They are also found to use two survival mechanisms to thrive. First, they colonize by binding or attaching themselves to other bacteria, which in turn, creates a larger area of infection than the previously infected area. Secondly, it also possesses natural antibiotic resistant genes, which help it survive and colonize. However, an investigation did reveal how the use of hyaluronic acid as a medium could have bacteriostatic effects on the Prevotella species, specifically Prevotella Oris and high molecular weight hyaluronic acid had the maximum impact. An earlier study also attempted to decode the acid tolerance and acid neutralizing activity of this bacteria in oral infections. It was found that Prevotella in general, thrives more under acidic conditions, and during growth, it tends to increase the pH. Studies on acid neutralization also revealed that the Prevotella cells produced succinic and isolvaleric acids which clearly suggests the deamination of amino acids, which in turn, clearly explains how Prevotella survives in both sub gingival and supragingival plaque. Infact, this colonization may also help create an environment in these areas, paving way for Porphyromonas gingivalis, another bacteria, to thrive. Prevotella has also been found to run down in families, not genetically, but through intrafamilial carriage. While it does display signs of antibiotic resistance, it has been found susceptible to clindamycin.
Prevotella Oris has been found to be a cause of some major infections including endodontic infection, periodontal disease (7), bacteremia, dentoalveolar abscess, and in some cases, is also found to be largely response for the spread of odontogenic infection. In addition, its presence has also been identified in lesions of systemic infections such as cervical spinal epidural abscess (6), meningitis as well as empyema. The DNA of Prevotella Oris has also been identified and detected in some pus samples taken from individuals suffering from odontogenic infections. Apart from thriving in the oral and vaginal areas, Prevotella has also been recovered from some respiratory tract infections including pneumonia, sinusitis, chronic otitis media, pulmonary empyema and lung abscess (8). Sometimes, they may also be found in the abscesses and burns near the mouth and in bites, brain abscesses, urinary tract infections and in cases of osteomyelitis. A study focusing on the gut bacteria of children in different regions also revealed that Prevotella was found to make up of 53% of the total gut bacteria present in the children in Africa (13). It is believed that consumption of a diet rich in carbohydrates and fiber may be linked to increased occurrence of these bacteria. In fact, the gut environment was found to change detectably on the consumption of different types of food in this study, but Prevotella came up more significantly in individuals who consumed a diet rich in carbohydrates. In addition, Prevotella was also found to intensify and exacerbate colitis in mice as per some new study findings (10). In another study, it was found that Prevotella overgrowth caused a reduction in the growth of lactobacillus in mice, which further led to the onset and development of osteomyelitis in the subjects. Conversely, when the growth of Prevotella'Italic text was reduced and the growth of lactobacillus was increased, the latter offered protection against osteomyelitis. This study proved to be a clear example of how dietary modifications tend to have a huge impact on the body and gut microflora, which further explains how it could either trigger or suppress certain chronic health conditions, and in this case, osteomyelitis. Another finding also revealed how this bacteria was involved in the progression of carothid atherosclerosis, which further strengthens the studies that have linked poor oral health and the occurrence of dental caries to heart conditions, some of which can be potentially life threatening.
Application to biotechnology
Prevotella Oris has not yet been a part of any major groundbreaking studies or researches revolving around the production of compounds and enzymes. Little is known about its genetic sequence-however, new studies are now highlighting different characteristics associated with it. However, new and new studies are now being carried out to understand and decode its various applications in different fields (12). A recent study on the Prevotella species derived from humans also compared the gene repertoires of its species derived from different other body sites in humans. This reported an open pan genome which clearly demonstrated a vast diversity of gene pool.
Since there is not a lot known about Prevotella Oris, new and new studies and research findings are highlighting more and more characteristics of this bacterium which could hopefully prove to be helpful in many ways.A recent study published in the Journal of Oral Biosciences attempted to understand and decode the hemolytic activity of Prevotella Oris. The study revealed important facts about how P. Oris displayed an acceleration in hemolytic activity during its growth phase, and then a decrease in the activity was noted during the stationary phase (11). These findings could possibly help researchers understand its pathogenic potential in different oral and systemic infections. Another study focused on the development of a PCR assay for the easy detection of Prevotella Oris in clinical samples. This PCR assay would in turn, help provide a specific and reliable detection method for the bacteria. A different research attempted understand the trend of antibiotic resistance in the Prevotella species, including Prevotella Oris. Different strains of Prevotella bacteria were taken into consideration and their resistance to different antibiotics including penicillin, metrodinazole, tetracycline, clindamycin and b-lactamase was tested (10). These findings would prove to be extremely helpful for medical practitioners and would help them understand and determine the right antibiotic to be used for a particular strain, which could in turn, improve patient outcomes. Another study also focused on understanding antibiotic resistance in different strains of Prevotella bacteria, and the percentage of susceptibility was also calculated. Published in the Dental Research Journal, another finding identified Prevotella species as one of the many bacteria responsible for dental abscesses. This study pointed out that such abscesses respond well to surgical treatments, and antimicrobials can be used to limit the spread of infection. However, it also pointed out that there is a need of good quality clinical trials to be conducted to find out the right treatment. It also highlighted how dental abscesses are poorly discussed in medical history, and if left untreated, they have the potential to progress and transform into major health issues including cavernous sinus thrombosis, septicemia, brain abscess, shock and in some cases may even lead to death. Another recent study found a strong link between Prevotella species thriving in the body, specifically Prevotella Corpi, and an increased risk of the onset of rheumatoid arthritis, an autoimmune disorder that affects millions of people around the globe (9) . It was found that when Prevotella thrives in the gut, it tends to decrease the occurrence of Bacteroides which in turn, leads to a loss in the concentration of healthy and beneficial gut microbes. This in turn, supports the systemic immune response associated with joint inflammation, thereby leading to the onset of rheumatoid arthritis. These findings can turn out to be a huge help for individuals affected by the disease, because the current measures taken to deal with it focus solely on reducing the intensity of symptoms and providing relief from pain. If steps are taken to assess and limit the multiplication of the Prevotella species and a healthy gut environment is maintained, rheumatoid arthritis could be stopped right in its tracks. The antibiotic resistance of Prevotella has proved to be a major setback, and hopefully, further studies will pave the way for development of new targeted drugs to help treat infections occurring due to these bacteria.
1. [Youseﬁmashouf R, Duerden BI, Eley A, Rawlinson A, Goodwin L. Incidence and distribution of nonpigmented Prevotella species in periodontal pockets before and after periodontal therapy. Microb Ecol Health Dis 1993; 6:35–42]
2. [Riggio MP, Lennon A. Development of a novel PCR assay for detection of Prevotella oris in clinical specimens. FEMS Microbiology Letters 2007; 123-128]
3. [Brito LCN, Teles FR, Teles RP, Franca EC, Ribeiro-Sobrinho AP, Haffajee AD, Socransky SS. Use of multiple-displacement ampliﬁcation and checkerboard DNA–DNA hybridization to examine the microbiota of endodontic infections. J Clin Microbiol 2007; 45:3039–49]
4. [Dymock D, Weightman AJ, Scully C, Wade WG. Molecular analysis of microﬂora associated with dentoalveolar abscesses. J Clin Microbiol 1996;34:537–42.]
5. [Civen R, Jousimiessomer H, Marina M, Borenstein L, Shah H, Finegold SM. A retrospective review of cases of anaerobic empyema and update of bacteriology. Clin Infect Dis 1995;20:S224–9]
6. [Frat JP, Godet C, Grollier G, Blanc JL, Robert R. Cervical spinal epidural abscess and meningitis due to Prevotella oris and Peptostreptococcus micros after retropharyngeal surgery. Intensive Care Med 2004;30:1695]
7. [Holdman VL, Moore CEW, Churn JP, Johnson LJ. Bacteroides oris and Bacteroides buccae, new species from human periodontitis and other human infections. Int J Syst Bacteriol 1982;32:125–31]
8. [Holdman VL, Johnson LJ. Description of Bacteroides loesheii sp. nov. and emendation of the descriptions of Bacteroides melaninogenicus (Oliver and Wherry) Roy and Kelly 1939 and Bacteroides denticola Shah and Collins 1981.Int J Syst Bacteriol 1982;32:399–409]
9. [Johnson LJ, Holdman VL. Bacteroides intermedius comb. nov. and descriptions of Bacteroides corporis sp. nov. and Bacteroides levii sp. nov. Int J Syst Bacteriol 1983;33:15–25]
10. [Martinez JL, Delgado-Iribarren A, Baquero F. Mechanisms of iron acquisition and bacterial virulence. FEMS Microbiol Rev 1990;6:45–56]
11. [Sato, Toshiya & Kamaguchi, Arihide & Nakazawa, Futoshi. (2012). Purification and characterization of hemolysin from Prevotella oris. Journal of Oral Biosciences. 54. 113–118. 10.1016/j.job.2012.03.002]
12. [Tanaka S, Yoshida M, Murakami Y, et al. (2008). "The relationship of Prevotella intermedia, Prevotella nigrescens and Prevotella melaninogenica in the supragingival plaque of children, caries and oral malodor". J Clin Pediatr Dent. 32 (3): 195–200. PMID 18524268. doi:10.17796/jcpd.32.3.vp657177815618l1]
13. [De Filippo, C.; Cavalieri, D.; Di Paola, M.; Ramazzotti, M.; Poullet, J. B.; Massart, S.; Collini, S.; Pieraccini, G.; Lionetti, P. (2010). "Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and rural Africa". Proceedings of the National Academy of Sciences. 107 (33): 14691–6. PMC 2930426 Freely accessible. PMID 20679230. doi:10.1073/pnas.1005963107]
14. [Nambu, T.; Yamane, K.; Maruyama, H.; Mashimo, C.; Yamanaka, T. (2015). “Complete Genome Sequence of Prevotella intermedia Strain 17-2”. Genome Announcements. 3(4): e00951-15.Published online 2015 Aug 20. doi: 10.1128/genomeA.00951-15]
This page is written by Mostafa Al Yassiry for the MICR3004 course, Semester 2, 2017