Case report: vertebral osteomyelitis secondary to a dental abscess.

BACKGROUND: Vertebral osteomyelitis can be attributed to many factors including immunosuppression, diabetes, malignancy, collagen disease, periodontal disease, open fractures, and endoscopic procedures. Anaerobic bacteria, such as Veillonella species, are found in the oral cavity and are rarely implicated in the infection. This report describes vertebral osteomyelitis secondary to a dental abscess with positive Veillonella cultures. CASE DESCRIPTION: A 76-year-old man presented to the hospital due to back pain with a four-day history of fever and chills. CT scans revealed several abscesses in the lumbar region as well as indications of vertebral osteomyelitis. After a psoas drain, the patient began antibiotics with a combination of ampicillin-sulbactam, metronidazole, and levofloxacin, but due to the patient's penicillin allergy, he was initially desensitized to this antibiotic for a significant period of time. Laminectomies, foraminotomies, and facetectomies were performed, but the infection spread to vertebral levels. The patient was then switched to a combination of vancomycin, metronidazole, and levofloxacin which eliminated the infection. Final laminectomy was performed with posterior segmental instrumentation and arthrodesis. Post-operatively, there were no signs of infection. The patient recovered well and regained mobility. Deeper examination of the patient's medical history revealed a severe tooth abscess immediately before the onset of bacteremia. CONCLUSION: We believe that a delay in the onset of antibiotic treatment is what led to the initial bacteremia that ultimately took root in the lower lumbar vertebrae. To the best of our ability, we could identify only one other case that linked vertebral osteomyelitis to the oral cavity.

Odontogenic orbital abscess with intracranial and pulmonary involvement.

A 58-year-old woman presented to the emergency department with left ptosis and complete ophthalmoplegia. Imaging demonstrated a left orbital abscess. Her past medical history included cavitatory lung disease and "aseptic" meningitis 2 months previously. An anaerobic organism and commensal of the oral flora, Peptostreptococcus sp., was cultured from the orbital abscess. The patient was found to have a carious upper molar with chronic buccal abscess, which was extracted. This case presents an uncommon pathogen arising from an odontogenic infection as the etiology for orbital abscess, cavitatory lung disease, and meningitis in one patient.

Acute periodontal lesions.

This review provides updates on acute conditions affecting the periodontal tissues, including abscesses in the periodontium, necrotizing periodontal diseases and other acute conditions that cause gingival lesions with acute presentation, such as infectious processes not associated with oral bacterial biofilms, mucocutaneous disorders and traumatic and allergic lesions. A periodontal abscess is clinically important because it is a relatively frequent dental emergency, it can compromise the periodontal prognosis of the affected tooth and bacteria within the abscess can spread and cause infections in other body sites. Different types of abscesses have been identified, mainly classified by their etiology, and there are clear differences between those affecting a pre-existing periodontal pocket and those affecting healthy sites. Therapy for this acute condition consists of drainage and tissue debridement, while an evaluation of the need for systemic antimicrobial therapy will be made for each case, based on local and systemic factors. The definitive treatment of the pre-existing condition should be accomplished after the acute phase is controlled. Necrotizing periodontal diseases present three typical clinical features: papilla necrosis, gingival bleeding and pain. Although the prevalence of these diseases is not high, their importance is clear because they represent the most severe conditions associated with the dental biofilm, with very rapid tissue destruction. In addition to bacteria, the etiology of necrotizing periodontal disease includes numerous factors that alter the host response and predispose to these diseases, namely HIV infection, malnutrition, stress or tobacco smoking. The treatment consists of superficial debridement, careful mechanical oral hygiene, rinsing with chlorhexidine and daily re-evaluation. Systemic antimicrobials may be used adjunctively in severe cases or in nonresponding conditions, being the first option metronidazole. Once the acute disease is under control, definitive treatment should be provided, including appropriate therapy for the pre-existing gingivitis or periodontitis. Among other acute conditions affecting the periodontal tissues, but not caused by the microorganisms present in oral biofilms, infectious diseases, mucocutaneous diseases and traumatic or allergic lesions can be listed. In most cases, the gingival involvement is not severe; however, these conditions are common and may prompt an emergency dental visit. These conditions may have the appearance of an erythematous lesion, which is sometimes erosive. Erosive lesions may be the direct result of trauma or a consequence of the breaking of vesicles and bullae. A proper differential diagnosis is important for adequate management of the case.

Radiography-based score indicative for the pathogenicity of bacteria in odontogenic infections.

OBJECTIVE: To develop a new radiography-based score to assess the potential of bacteria to cause odontogenic infections derived from the occurrence of bacteria at small or large radiographical lesions. MATERIALS AND METHODS: The patients analyzed were a sub-population from a large randomized clinical trial comparing moxifloxacin and clindamycin in the treatment of inflammatory infiltrates and odontogenic abscesses. Routine radiographs were used to analyze the area of the periapical radiolucent lesions. Lesions were stratified by their radiographically measured area as large (>9 mm(2)) or small (≤9 mm(2)). A risk ratio was calculated for each species from the frequency of their occurrence in large vs in small lesions. RESULTS: Fifty-one patients, 19 with abscesses and 32 with infiltrates, were evaluated. Overall, the radiographical lesion areas ranged from 0.4-46.2 mm(2) (median = 9 mm(2)). An increased risk (risk ratio >1) to occur at large abscess lesions was observed for Prevotella (P.) oralis, P. buccae, P. oris, P. intermedia, Fusobacterium nucleatum and Streptococcus (Strep.) anginosus group. An increased risk to occur at large infiltrate lesions was found for Strep. salivarius, Strep. parasanguis, Strep. anginosus group, Capnocytophaga spp., Neisseria (N.) sicca, Neisseria spp., Staphylococcus (Staph.) aureus, P. intermedia, P. buccae, Prevotella spp. and P. melaninogenica. CONCLUSIONS: The radiography-based score suggests that certain Prevotella spp., F. nucleatum and Strep. anginosus groups play a crucial role in the pathogenesis of odontogenic abscesses, and that various streptococci, Neisseria spp., Capnocytophaga spp., Staph. aureus and Prevotella spp. are involved in the pathogenesis of odontogenic infiltrates.

Microbiological analysis of a prospective, randomized, double-blind trial comparing moxifloxacin and clindamycin in the treatment of odontogenic infiltrates and abscesses.

The objective of this study was to identify the oral pathogens found in odontogenic infections, to determine their susceptibilities to amoxicillin-clavulanic acid (AMC), clindamycin (CLI), doxycycline (DOX), levofloxacin (LVX), moxifloxacin (MXF), and penicillin (PEN), and to search for associations between specific pathogens and types of infection. Swabs from patients enrolled in a randomized, double-blind phase II trial comparing MXF with CLI for the treatment of odontogenic abscesses or inflammatory infiltrates were cultured on media for aerobes and anaerobes. All bacterial isolates were identified at the species level. Overall, 205 isolates were cultured from 71 patients: 77 viridans group streptococci, 56 Prevotella spp., 19 Neisseria spp., 17 Streptococcus anginosus group isolates and hemolytic streptococci, 15 other anaerobes, and 21 other bacteria. Ninety-eight percent of pathogens were susceptible to MXF, 96% to AMC, 85% to LVX, 67% to PEN, 60% to CLI, and 50% to DOX. S. anginosus group and hemolytic streptococci were found significantly more frequently (P = 0.04) in patients with abscesses (12/95) than in patients with infiltrates (5/110). In four patients with infiltrates who failed to respond to CLI therapy, three isolates of the Streptococcus mitis group and four Neisseria spp. resistant to CLI were found. In this study, S. anginosus group and hemolytic streptococci were clearly associated with odontogenic abscesses. Our analysis suggests that viridans group streptococci and Neisseria spp. play a decisive role in the etiology of odontogenic infiltrates. The high in vitro activity of MXF against odontogenic bacteria corresponds well to its clinical results in the treatment of odontogenic abscesses and infiltrates.

Streptococcal lung abscesses from a dental focus following tocilizumab: a case report.

Patients suffering from dental infections and concurrently using immunosuppressive medication are at increased risk of developing systemic streptococcal infections. Tocilizumab is a novel therapeutic agent targeting interleukin-6. We describe a case of streptococcal lung abscesses from a dental focus after use of tocilizumab for treatment of Takayasu arteritis.

[Dentogenic infections-part I: the significance of bacterial isolation of dentogenic infections under routineous conditions]. / Odontogene Infektionen - Teil I : Zur Wertigkeit der Erregerbestimmung bei odontogenen Infektionen in der klinischen Routine.

The microflora of odontogenic infections is typically polymicrobial with increased resistance rates against various antibiotics. The purpose of the present study was to analyze bacterial spectra and resistance in odontogenic infections under routineous conditions.Microbiological samples were collected and transported under routineous conditions in a prospective study of 19 patients. All Bacterial spectra and resistance rates were compared with the results of a former prospective evaluation.There were 11 men, 5 woman and 3 children (age range of 2-86 years). A total of only 38 bacterial strains were analyzed. The ratio between aerobes and anaerobes was nearly 1:1. The resistance rates were nearly the same for Penicillin G, but a 2-fold increased resistance for clindamycin against aerobes and a more than 10-fold increased resistance against anaerobes was noted.Prospective studies under standardized conditions are necessary to isolate strict anaerobes and to detect changes in antibiotic efficiency.

Chronic periodontitis with multiple risk factor syndrome: a case report.

OBJECTIVE: Multiple risk factor syndrome is a clustering of cardiovascular risk factors, such as diabetes, dyslipidemia, hypertension, and obesity associated epidemiologically with insulin resistance. This report describes the clinical course of a patient suffering from severe periodontitis with multiple risk factor syndrome, and discusses the association between periodontal infection and systemic health. METHODS: The patient had a history of type 2 diabetes, dyslipidemia, and hypertension for over 10 years. At baseline, her hemoglobin A1 c was 8.1%. However, she had no diabetic complications except periodontitis. The IgG antibody titers against Porphyromonas gingivalis FDC 381 and SU63 were elevated above the mean of healthy subjects +2 standard deviations. Intensive periodontal treatment, including periodontal surgery, was performed to reduce periodontal infection and bacteremia. Her systemic and periodontal conditions were evaluated longitudinally for 10 years. RESULTS: Following periodontal treatment, antibody titers against Porphyromonas gingivalis and hemoglobin A1c values were significantly improved. The other clinical data and medication for her systemic condition also remained stable during supportive periodontal therapy. However, she developed myocardial infarction, and showed continuous deterioration of hemoglobin A1 c level and periodontitis. CONCLUSION: The long-term clustering of risk factors, such as diabetes, dyslipidemia, hypertension, and periodontitis, are associated with the development of myocardial infarction. Treatment of systemic conditions in combination with comprehensive periodontal treatment is important in management of patients with multiple risk factor syndrome.

Fusobacterium nucleatum causing a pyogenic liver abscess: a rare complication of periodontal disease that occurred during the COVID-19 pandemic.

Fusobacterium nucleatum is a periodontal commensal and pathogen. In rare cases, these anaerobic gram-negative bacilli have been reported to cause pyogenic liver abscesses (PLAs). We describe a patient who developed a periodontal abscess during the COVID-19 pandemic and was unable to access the restricted General Dental Services at this time. She subsequently developed a F. nucleatum bacteraemia and liver abscess. The non-specific signs and symptoms experienced meant the patient self-isolated due to suspected COVID-19 infection and presentation to hospital was delayed. We also include the results of a literature search of other cases of PLAs attributed to F. nucleatum PLAs often develop insidiously. They require percutaneous drainage and prolonged antimicrobial therapy. Clinicians should be aware of this rare complication of a dentoalveolar infection in a patient who is systemically unwell.

Spread of odontogenic infections in Port Harcourt, Nigeria.

PURPOSE: Odontogenic infections constitute a substantial portion of diseases encountered by oral and maxillofacial surgeons. Infections start from dental tissues and sometimes rapidly spread to contiguous spaces. The consequence is a fulminant disease with significant morbidity and mortality. The study was aimed at studying the pattern of spread, approach to management, and outcome of these infections at a Nigerian teaching hospital. PATIENTS AND METHODS: A retrospective study of all patients with orofacial infections who presented to our center over an 18-month period was carried out. The medical records were reviewed to retrieve the following: age, gender, source of infection, anatomic fascial spaces involved, associated medical conditions, various treatment modalities, types of antibiotics administered, causative micro-organisms, length of stay in the hospital, and any complications encountered. Infections were classified into 2 categories: those that are confined to the dentoalveolar tissues belong to category I, and those that have spread into the local/regional soft tissue spaces and beyond belong to category II. RESULTS: Odontogenic infections constituted 11.3% of the total oral and maxillofacial surgery cases. A total of 261 patients were treated for odontogenic infections. There were 146 female patients (59.8%) and 98 male patients (40.2%) in the first category, whereas the second category comprised 10 male patients (58.8%) and 7 female patients (41.2%). The fascial spaces involved, in descending order, were submasseteric in 10 (22.7%), submandibular in 9 (20.5%), and sublingual in 6 (13.6%). The causative micro-organisms commonly found were Klebsiella and Streptococcus spp. Incision and drainage were performed in the 17 cases with spreading infection. Amoxicillin, amoxicillin/clavulanate, and metronidazole were the most routinely administered antibiotics. CONCLUSIONS: Our experience shows that delay in presentation, self-medication, aging, male gender, and unusual causative agents are some of the factors associated with spread. Therefore efforts must be made to further improve public dental awareness.

Pregnancy complicated by Ludwig's angina requiring delivery.

At 33 weeks of gestation, a 24-year-old developed Ludwig's angina that worsened despite aggressive therapy. This is the first reported case of Ludwig's Angina in pregnancy that required an emergent cesarean section for fetal indications. Delivery may have contributed to improvement in the mother's health status.

Penicillin compared with other advanced broad spectrum antibiotics regarding antibacterial activity against oral pathogens isolated from odontogenic abscesses.

OBJECTIVES: We examined the spectrum of oral pathogens found in odontogenic abscesses and their susceptibility to penicillin as well as to amoxicillin with clavulanic acid, doxycycline, clindamycin and moxifloxacin. The in vitro results were compared with clinical observations. PATIENTS AND METHODS: One hundred and eighty eight swabs were obtained from 94 patients with odontogenic abscesses. Bacterial strains were isolated for susceptibility tests. The same patients were investigated for their clinical outcome after standard therapy. RESULTS: A total of 517 bacterial strains were isolated from 94 patients. Ninety eight per cent of abscesses were polymicrobial. The most prevalent bacteria were Viridans streptococci representing 54% of the aerobic/facultative anaerobic bacteria. Prevotella spp. comprised 53% of the anaerobes. No multiresistant strains were detected. Susceptibility testing revealed a sensitivity of over 99% of aerobes/facultative aerobes and 96% of anaerobes sensitivity for moxifloxacin. The corresponding values for penicillin were lowest at 61% and 79%, respectively. In the clinical collective, patients with minor abscesses and no risk of further progression received surgical treatment without antibiotics (36%). Penicillin was administered additionally in 30%. Amoxicillin with clavulanic acid was given in 18% and clindamycin in 15%. Ninety two of the 94 patients showed significant recovery with the described treatment. Only in two cases was a change to the latest broader spectrum antibiotics necessary. CONCLUSION: In contrast to the moderate in vitro results, penicillin successfully treated the pathogens derived from odontogenic abscess sufficiently when adequate surgical treatment was provided. One third of the patients was treated successfully with incision and drainage only. We suggest that one good reason for its clinical efficacy is the susceptibility of the dominant aerobe/facultative aerobe and anaerobe strains to penicillin.

Severe versus local odontogenic bacterial infections: comparison of microbial isolates.

AIM: It was the aim of this study to evaluate the clinical and microbiological differences between severe and local odontogenic abscesses. METHODS: Thirty patients were prospectively enrolled. Sixteen of 30 patients suffered from a severe life-threatening abscess of the head and neck, whereas 14/30 patients presented with a localized submucous abscess. Anaerobic bacteria were identified and susceptibility testing was performed using E test strips for penicillin, amoxicillin + clavulanic acid, imipenem + cilastatin, clindamycin and metronidazole. RESULTS: The mean duration until removal of all drains was 14.1 and 3.5 days, respectively. Anaerobic bacteria were found in all episodes of local abscesses, whereas 19% of the severe episodes were culture negative, and in 13%, only aerobes were identified. A total of 60 anaerobes were isolated from 27 patients (2.2 isolates/positive sample). The dominating species were Prevotella sp. (n = 17), Peptostreptococcus sp. (n = 15) and Propionibacterium sp. (n = 5). Eighty-seven percent of the isolates were susceptible to penicillin. Ninety-seven percent of the anaerobes were susceptible to amoxicillin + clavulanic acid, imipenem + cilastatin, and clindamycin. Eighty-three percent were susceptible to metronidazol. There was a tendency for a higher rate of episodes with penicillin-resistant bacteria in the patients with severe abscesses (14 vs. 31%). No difference in susceptibility regarding amoxicillin + clavulanic acid and clindamycin (7%) was observed.

Assessment of the endodontic microbiota of abscessed primary teeth using microarray technology.

CONTEXT: Knowledge of the microbial composition of abscessed primary tooth is limited. AIM: The aim was to investigate the presence of 10 oral bacterial species in samples from abscessed primary tooth root canals using microarray technology and to determine their association with clinical findings. SUBJECTS AND METHODS: The samples were collected from root canals of 20 primary molars with acute primer infection. The bacterial composition of the samples was semi-quantitatively defined using a microarray system (ParoCheck®). Clinical parameters included the presence of spontaneous pain, mobility, percussion sensitivity and swelling. STATISTICAL ANALYSIS: Data were statistically analyzed by Student' t-test, Fisher's exact Chi-square test, Freeman-Halton-Fisher's exact test, and Spearman's rho correlation analysis. RESULTS: All the tested species were detected in the samples. Fusobacterium nucleatum was the most frequent bacterium (100%), followed by Parvimonas micra (65%), Provetella intermedia (45%), and Treponema denticola (45%). According to paired bacterial combinations, F. nucleatum was significantly positively correlated with P. intermedia and P. micra (P < 0.05). T. denticola was significantly positively correlated with Porphyromonas gingivalis, Tannerella forsythia, Campylobacter rectus, and P. micra, while it was negatively correlated with Eikenella corrodens (P < 0.05). No statistically significant relationships were found between the presence of any bacteria and clinical findings. CONCLUSION: Microarray technology used in this study has demonstrated the presence of various bacteria with varying proportions in the root canals of abscessed primary teeth. The results regarding the high rate of certain bacterial combinations suggest the enhanced pathogenicity due to additive or synergistic effects of these microbial combinations.

Genotype variation and capsular serotypes of Porphyromonas gingivalis from chronic periodontitis and periodontal abscesses.

Porphyromonas gingivalis is considered an important pathogen in periodontal disease. While this organism expresses a number of virulence factors, no study combining different virulence polymorphisms has, so far, been conducted. The occurrence of combined virulence (Cv) genotypes in 62 isolates of P. gingivalis was investigated from subjects displaying either chronic periodontitis or periodontal abscess. The Cv genotypes, based on gene variation of fimbriae (fimA), Lys-specific cystein proteinase (kgp) and Arg-specific cystein proteinase (prpR1/rgpA), were evaluated by PCR. The isolates were also subjected to capsular polysaccharide K-serotyping. A total of 18 Cv genotype variants based on fimA: kgp: rgpA were identified, of which II:I:A and II:II:A Cv genotypes (53.3%) were the two most frequently detected combinations. Moreover, 36% of the isolates were K-typeable, with the K6 serotype being the most prevalent (23%). Two isolates had the same genotype as the virulent strain W83. The results indicate that chronic periodontitis is not associated with a particularly virulent clonal type. A highly virulent genotype (e.g. strain W83) of P. gingivalis can be found in certain periodontitis patients.

Microbiology of acute sinusitis of odontogenic origin presenting with periorbital cellulitis in children.

OBJECTIVES: This study was undertaken to evaluate the aerobic and anaerobic microbiology of acute maxillary sinusitis of odontogenic origin presenting with periodontal infection in children. METHODS: Aspirates of 18 acutely infected maxillary sinuses that were associated with odontogenic infection in children who presented with periorbital cellulitis were processed for aerobic and anaerobic bacteria. RESULTS: A total of 54 isolates were recovered (3.0 per specimen): 13 aerobic and facultative (0.7 per specimen) and 41 anaerobic (2.3 per specimen). The number of isolates per specimen varied from 1 to 4. Aerobic and facultative organisms alone were recovered in 2 specimens (11%), anaerobes only in 7 (39%), and mixed aerobic and anaerobic bacteria in 9 (50%). The predominant aerobic and facultative organisms were alpha-hemolytic streptococci (4), microaerophilic streptococci (3), and Streptococcus pyogenes and Staphylococcus aureus (2 each). The predominant anaerobic bacteria were anaerobic gram-negative bacilli (17), Peptostreptococcus spp (11), Fusobacterium spp (8), and Propionibacterium acnes (2). Twelve beta-lactamase-producing bacteria were recovered from 9 specimens (50%). CONCLUSIONS: This study demonstrates the unique aerobic and anaerobic microbiological features of acute maxillary sinusitis of odontogenic origin presenting with periorbital cellulitis in children.

Management of odontogenic infection of pulpal and periodontal origin.

The dental biofilm is a complex bacterial ecosystem that undergoes evolution, maturing and development, and thus leads to odontogenic infection. The infection is normally located in the tissues of the dental organ itself, and follows a chronic course of evolution. However, bacterial pathogens express virulence factors in the biofilm, and this together with changes in host immunity, may cause clinical exacerbations and spread of infection to other areas of the body. Odontogenic infection management should take into consideration the fact that therapeutic success lies in the control of the infectious aetiologic agent, using mechanical-surgical debridement and/or antimicrobial therapy. Debridement techniques have a fundamentally quantitative effect (by reducing the size of the inoculum) and therefore if these techniques are used alone to control infection, despite an initial clinical improvement that is sometimes prematurely considered as therapeutic success, odontopathogens may persist and the process may recur or become chronic. Microbiological examination may be helpful in defining therapeutic success in a more reliable way, it could define the prognosis of recurrence more precisely, and could enable the most appropriate antibiotic to be selected, thus increasing therapeutic efficacy. Antimicrobial therapy brings about a quantitative and qualitative change in the bacterial composition of the biofilm, in addition to being able to act on sites that are inaccessible through mechanical debridement. However, incorrect antimicrobial use can lead to a selection of resistant bacterial species in the biofilm, in addition to side effects and ecological alterations in the host. In order to minimise this risk, and obtain maximum antimicrobial effect, we need to know in which clinical situations their use is indicated, and the efficacy of different antibiotics with regard to bacteria isolated in odontogenic infection.

Bacterial isolates and antimicrobial susceptibilities from odontogenic abscesses in rabbits: 48 cases.

The medical record database of a veterinary teaching hospital was searched from 2000 through 2014 for records of client-owned rabbits with positive cultures from odontogenic abscesses. Data reviewed included sex, age, abscess location, sampling technique, previous antimicrobial treatments, microorganisms identified and antibiotic susceptibility of aerobic bacteria. Forty-eight client owned rabbits with one or more odontogenic abscesses and culture results were evaluated. One hundred and eighty-five isolates (52 aerobic, 133 anaerobic) were identified from 61 positive cultures from odontogenic abscesses. The most common aerobic bacterial isolates were Pseudomonas aeruginosa (14/52), Pasteurella species (10/52), Streptococcus species (8/52) and Staphylococcus species (7/52). The most common anaerobic bacterial isolates were Fusobacterium species (36/133), Peptostreptococcus species (27/133) and Bacteroides species (27/133). Mixed aerobic and anaerobic isolates were detected in 73.3 per cent of cultures and 50.8 per cent of the samples had greater than three isolates. P aeruginosa was susceptible to amikacin and gentamicin, had variable resistance to enrofloxacin, and resistance to chloramphenicol. Pasteurella species, Streptococcus species and Staphylococcus species isolates were susceptible to most antibiotics tested. The bacterial isolates from rabbit odontogenic abscesses are a mixture of aerobic and anaerobic Gram-positive and Gram-negative organisms and without culture and susceptibility testing, it is difficult to predict appropriate antimicrobial treatment.

Genes Contributing to Porphyromonas gingivalis Fitness in Abscess and Epithelial Cell Colonization Environments.

Porphyromonas gingivalis is an important cause of serious periodontal diseases, and is emerging as a pathogen in several systemic conditions including some forms of cancer. Initial colonization by P. gingivalis involves interaction with gingival epithelial cells, and the organism can also access host tissues and spread haematogenously. To better understand the mechanisms underlying these properties, we utilized a highly saturated transposon insertion library of P. gingivalis, and assessed the fitness of mutants during epithelial cell colonization and survival in a murine abscess model by high-throughput sequencing (Tn-Seq). Transposon insertions in many genes previously suspected as contributing to virulence showed significant fitness defects in both screening assays. In addition, a number of genes not previously associated with P. gingivalis virulence were identified as important for fitness. We further examined fitness defects of four such genes by generating defined mutations. Genes encoding a carbamoyl phosphate synthetase, a replication-associated recombination protein, a nitrosative stress responsive HcpR transcription regulator, and RNase Z, a zinc phosphodiesterase, showed a fitness phenotype in epithelial cell colonization and in a competitive abscess infection. This study verifies the importance of several well-characterized putative virulence factors of P. gingivalis and identifies novel fitness determinants of the organism.