Eikenella corrodens infections in human: Reports of six cases and review of literatures.

PURPOSE: To investigate clinical characteristics of six cases of Eikenella corrodens infection in Ningbo First Hospital in China in recent 2 years. METHODS: We retrospectively analyze medical records of six cases of E. corrodens infection in Ningbo First Hospital from 2020 to 2021. And we describe the gender, age, clinical manifestations, antimicrobial administration, and treatment of the six patients. RESULTS: Five of the patients had deep infection and they were treated with surgical drainage or abscess resection plus antimicrobial administration. After treatment, five patients were discharged and recovered well, and another patient was transferred to another hospital for further treatment. All the six cases were in line with the reports on the clinical characteristics of patients infected with E. corrodens at home and abroad before 2021. CONCLUSION: Eikenella corrodens is a part of the normal flora of human oropharynx, but it can migrate to other parts of the human body to cause severe invasive disease in humans. Although it is susceptible to most antimicrobials, it needs debridement in the treatment of deep infection.

Lung abscess secondary to lung cancer with a coinfection of Granulicatellaadiacens and other bacteria: a case report.

BACKGROUND: Granulicatella adiacens is facultative anaerobic Gram-positive bacteria, which mainly involve bacterial endocarditis and bacteremia, but there are few reports of local suppurative infection. A case of lung abscess with a coinfection of Granulicatella adiacens and other bacteria in a lung cancer patient will be reported in this paper. To our knowledge, this is the first case report describing lung abscess due to G.adiacens. CASE PRESENTATION: A 52-year-old Chinese woman was admitted to the hospital, She complained of coughing and expectoration for 1 month, shortness of breath for half a month, and dyspnea for 1 day. After a series of examinations, she was diagnosed with lung abscess, pleural effusion, and bronchogenic carcinoma. Draining pus culture demonstrated Granulicatella adiacens. After more than 5 weeks of antibiotic therapies in total, she gradually recovered to fight against lung cancer. CONCLUSION: This is the first reported lung abscess caused by G.adiacens. In immunosuppressed hosts, G.adiacens is a virulent pathogen associated with a spectrum of intrathoracic suppurative. Earlier diagnosis and proper drainage surgery with effective antibiotics treatment are very important, and antimicrobial treatment should be more than 5 weeks. When complex pulmonary infection interferes with the CT diagnosis, clinical suspicion of lung cancer should be increased if G.adiacens or Eikenella corrodens is detected from a pulmonary infection.

Lung abscess secondary to lung cancer with Eikenella corrodens and Streptococcus anginosus: a case report.

BACKGROUND: Eikenella corrodens and Streptococcus anginosus, which are primary colonization bacteria of the normal flora of the oropharynx, are infrequent bacteria, especially the former. Here, we report a case of lung abscess with a coinfection of Eikenella corrodens and Streptococcus anginosus in a lung cancer patient. CASE PRESENTATION: A 66-year-old Chinese man with lung cancer was admitted to the hospital, complaining of a cough and expectoration for five months and fever for two months. After a series of inspections to differentiate a cancer-related fever from an infectious fever, he was diagnosed with lung abscess. Draining pus culture demonstrated Eikenella corrodens and Streptococcus anginosus. After more than 1 month of antibiotic therapy and draining in total, he gradually recovered to fight against lung cancer. CONCLUSION: This report highlights the increased pathogenicity of Eikenella corrodens and Streptococcus anginosus in an immunocompromised cancer patient, especially after a few invasive operations. Additionally, even though a patient has been diagnosed with cancerous fever, strong vigilance is needed in case an infection arises.

Pediatric acute dacryocystitis due to Eikenella corrodens: A case report.

Eikenella corrodens is a facultatively anaerobic gram-negative rod bacterium in the oropharynx and respiratory tract. It is a member of HACEK (Haemophilus spp., Aggregatibacter spp., Cardiobacterium hominis, E. corrodens, and Kingella kingae) group commonly associated with endocarditis and craniofacial infections. It is usually susceptible to penicillin, second and third-generation cephalosporins, and carbapenem, but has variable susceptibility to first-generation cephalosporin. We herein provide a description of the first case of pediatric acute dacryocystitis caused by E. corrodens. The patient did not respond to oral cephalexin and required surgical drainage followed by intravenous cefotaxime. Also provided is a brief review of the current literature.

Severe purulent pericarditis caused by invasive Eikenella corrodens: case report and literature review.

BACKGROUND: Eikenella corrodens is a slowly growing gram-negative bacillus that can cause severe invasive disease in human. Although E. corrodens infections in various sites of human body have been well described, pericarditis caused by invasive E. corrodens has rarely been reported. CASE PRESENTATION: Here we report the case of a 63-year old male with a complaint of left shoulder pain. The patient was diagnosed as purulent pericarditis by chest computed tomography scan and ultrasound-guided pericardiocentesis, and the pathogen of E. corrodens was identified in the pericardial fluid culture. The clinical condition of the patient deteriorated quickly, and he died right after the drainage surgery even though the pathogen was sensitive to antibiotics treatment. CONCLUSION: E. corrodens is a rare pericarditis associated pathogen. Purulent pericarditis caused by E. corrodens presents atypical manifestations and rapid progression of infection in immunosuppressed individuals such as neutropenic patients. Earlier diagnosis and proper drainage surgery with effective antibiotics treatment may improve the prognosis.

Comparative In Vitro Activity of Omadacycline against Dog and Cat Bite Wound Isolates.

Omadacycline was tested against 125 isolates recovered from infected cat and dog bites in humans. Its activity was similar to that of other compounds in the tetracycline class, and it was active against strains exhibiting tetracycline resistance. Against anaerobic isolates, resistance to tetracyclines was more prominent and omadacycline was the most active of the group. All isolates had omadacycline MICs of <1 µg/ml, with the exception of Eikenella corrodens, which showed reduced susceptibility to the entire tetracycline group.

Eikenella corrodens endocarditis and liver abscess in a previously healthy male, a case report.

BACKGROUND: Eikenella corrodens is one of the HACEK bacteria constituting part of the normal flora of the oropharynx, however, still an uncommon pathogen. We report a case of a large Eikenella corrodens liver abscess with simultaneously endocarditis in a previously healthy male. CASE PRESENTATION: A 49-year-old Danish man was admitted because of one-month malaise, fever, cough and unintentional weight loss. On admission there was elevated white blood cell count and C-reactive protein, as well as affected liver function tests. Initially pneumonia was suspected, but due to lack of improvement on pneumonia treatment, a PET-CT scan was performed, which showed a large multiloculated abscess in the liver. The abscess was drained using ultrasound guidance. Culture demonstrated Eikenella corrodens. Transesophageal echocardiography revealed aortic endocarditis. The patient was treated with antibiotics and abscess drainage, on which he slowly improved. He was discharged after 1.5 months of hospitalisation. On follow-up 2 months later, the patient was asymptomatic with normalized biochemistry and ultrasound showed complete regression of the abscess. CONCLUSIONS: This is the first case of documented Eikenella corrodens concurrent liver abscess and endocarditis. The case report highlights that Eikenella corrodens should be considered as a cause of liver abscess. Empirical treatment of pyogenic liver abscess will most often cover Eikenella corrodens, but the recommended treatment is a third generation cephalosporin or a fluoroquinolon. A multiloculated liver abscess may require drainage several times during treatment. The finding of Eikenella corrodens should elicit an echocardiography to diagnose endocarditis even in patients without clinical signs of endocarditis.

Purpura fulminans with Lemierre's syndrome caused by Gemella bergeri and Eikenella corrodens: a case report.

BACKGROUND: Gemella bergeri is one of the nine species of the genus Gemella and is relatively difficult to identify. We herein describe the first case of septic shock due to a Gemella bergeri coinfection with Eikenella corrodens. CASE PRESENTATION: A 44-year-old Asian man with a medical history of IgG4-related ophthalmic disease who was prescribed corticosteroids (prednisolone) presented to our hospital with dyspnea. On arrival, he was in shock, and a purpuric eruption was noted on both legs. Contrast enhanced computed tomography showed fluid retention at the right maxillary sinus, left lung ground glass opacity, and bilateral lung irregular opacities without cavitation. Owing to suspected septic shock, fluid resuscitation and a high dose of vasopressors were started. In addition, meropenem, clindamycin, and vancomycin were administered. Repeat computed tomography confirmed left internal jugular and vertebral vein thrombosis. Following this, the patient was diagnosed with Lemierre's syndrome. Furthermore, he went into shock again on day 6 of hospitalization. Additional soft tissue infections were suspected; therefore, bilateral below the knee amputations were performed for source control. Cultures of the exudates from skin lesions and histopathological samples did not identify any pathogens, and histopathological findings showed arterial thrombosis; therefore it was concluded that the second time shock was associated with purpura fulminans. Following this, his general status improved. He was transferred to another hospital for rehabilitation. The blood culture isolates were identified as Gemella bergeri and Eikenella corrodens. Gemella bergeri was identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry and confirmed by 16S rRNA gene sequencing later. The primary focus of the infection was thought to be in the right maxillary sinus, because the resolution of the fluid retention was confirmed by repeat computed tomography. CONCLUSIONS: Gemella bergeri can be the causative pathogen of septic shock. If this pathogen cannot be identified manually or through commercial phenotypic methods, 16S rRNA gene sequencing should be considered.

Purification and characterization of hemolysin from periodontopathogenic bacterium Eikenella corrodens strain 1073.

Eikenella corrodens 1073 was found to show hemolytic activity when grown on sheep blood agar. A high and dose-dependent hemolytic activity was detected in the cell envelope fraction, which was further purified by ion-exchange and gel-filtration chromatography. Consequently, a 65-kDa protein with hemolytic activity was obtained, suggesting that this protein might be a hemolysin. Its N-terminal amino acid sequence was nearly identical to that of X-prolyl aminopeptidase from E. corrodens ATCC 23834. To confirm that X-prolyl aminopeptidase functions as a hemolytic factor, we expressed the hlyA gene, encoding X-prolyl aminopeptidase, in Escherichia coli. After induction with isopropyl ß-D-1-thiogalactopyranoside, a protein of about 65 kDa was purified on a Ni column, and its hemolytic activity was confirmed. Meanwhile, a strain with a disrupted hlyA gene, which was constructed by homologous recombination, did not show any hemolytic activity. These results suggested that X-prolyl aminopeptidase might function as a hemolysin in E. corrodens.

Eikenella corrodens endocarditis of the tricuspid valve in an intravenous drug user.

Infective endocarditis of the tricuspid valve (TVE) occurs predominantly in selected groups of patients including intravenous drug users (IVDUs). The most often cultured pathogen in IVDUs is Staphylococcus aureus. Eikenella corrodens, normally existing as a commensal in the mouth and the upper respiratory tract, is identified as an etiologic pathogen of endocarditis very rarely. The authors describe a case of a 27-year-old male with a past history of staphylococcal TVE readmitted to hospital after 5 months due to progression of right-sided heart failure. Bacteriological work-up revealed typical features and growth of E. corrodens. In echocardiography large vegetations on the damaged tricuspid valve and massive tricuspid regurgitation were seen. The prognosis of the disease, despite introduction of appropriate antibiotic therapy, was poor as he refused to undergo cardiac surgery.

Accuracy of commercial kits and published primer pairs for the detection of periodontopathogens.

OBJECTIVES: Despite the input of microbiome research, a group of 20 bacteria continues to be the focus of periodontal diagnostics and therapy. The aim of this study was to compare three commercial kits and laboratory-developed primer pairs for effectiveness in detecting such periodontopathogens. MATERIALS AND METHODS: Fourteen bacterial mock communities, consisting of 16 randomly assembled bacterial strains, were used as reference standard for testing kits and primers. Extracted DNA from mock communities was analyzed by PCR in-house with specific primers and forwarded for analysis to the manufacturer's laboratory of each of the following kits: ParoCheck®Kit 20, micro-IDent®plus11, and Carpegen® Perio Diagnostik. RESULTS: The kits accurately detected Fusobacterium nucleatum, Prevotella intermedia/Prevotella nigrescens, Parvimonas micra, Aggregatibacter actinomycetemcomitans, Campylobacter rectus/showae, Streptococcus mitis, Streptococcus mutans, and Veillonella parvula. The in-house primers for F.nucleatum were highly specific to subtypes of the respective periopathogen. Other primers repeatedly detected oral pathogens not present in the mock communities, indicating reduced specificity. CONCLUSIONS: The commercial kits used in this study are reliable tools to support periodontal diagnostics. Whereas the detection profile of the kits is fixed at a general specificity level, the design of primers can be adjusted to differentiate between highly specific strains. In-house primers are more error-prone. Bacterial mock communities can be established as a reference standard for any similar testing. CLINICAL RELEVANCE: The tested kits render good results with selected bacterial species. Primers appear to be less useful for routine clinical diagnostics and of limited applicability in research. Basic information about the periodontopathogens identified in this study supports clinical decision-making.

Case-based update: primary intraventricular brain abscess in a 10-year-old child.

BACKGROUND: Intraventricular abscesses are very rare and usually result from secondary rupture of a brain abscess. In the few published cases, clinical presentation was subacute and different pathogens were found. The diagnosis might be mistaken as an intraventricular tumor. CASE REPORT: This is a case of a 10-year-old girl suffering from cyanotic heart disease that was presented with subacute onset of headache, vomiting, and some signs of inflammation. Symptoms lead to early brain imaging (CT/MRI) demonstrating left ventricular horn lesion affecting adjacent brain structures. Neuroradiologists suspected an intraventricular tumor, but cardiac history and signs of inflammation led to lumbar puncture and evidence of CNS infection, and intraventricular abscess was suspected. Navigated aspiration was performed, and multi-sensitive Eikenella corrodens was cultivated. Broad antibiotic treatment and dexamethasone were initiated, and symptoms disappeared. Follow-up imaging demonstrated gradual regression of the intraventricular abscess. The girl underwent regular professional teeth cleaning which was discussed as possible cause of infection. CONCLUSIONS: Although an isolated intraventricular abscess is a very rare event, typical predisposing cardiac history together with central nervous symptoms and an intracranial contrasting mass should always lead to the differential diagnosis of a brain abscess and be biopsied first. E. corrodens is a typical organism of the mouth flora, but a rare cause for a brain abscess. Harmless teeth cleaning procedures may cause hematogenic spread and lead to CNS infections, e.g., in patients with predisposing diseases. To our knowledge, there are only six previous reports of primary intraventricular brain abscess.

From Pansinusitis to Cerebritis Due to Eikenella corrodens.

Meningitis is a rare but possible complication of sinusitis. We present a case of a 21-year-old woman with a history of fever, headache and nasal obstruction who presented at the emergency department with psychomotor agitation. Orotracheal intubation and invasive mechanical ventilation were given to protect airway. Blood analysis showed leukocytosis and elevated C-reactive protein. Cerebral and maxillofacial computed tomography (CT) demonstrated pansinusitis with gas foci more prominent in the left frontal sinus with an area of ​​bone rarefaction on the posterior wall with possible communication with the cranial cavity. Lumbar puncture was performed. Empirical antibiotic and corticosteroid therapy were started. Neurosurgery (NC) and Ear Nose and Throat (ENT) surgeons declined indication for urgent surgery and she was admitted at General ICU. On the fourth day of hospitalization, a brain magnetic resonance imaging (CE-MRI) was performed, revealing subdural empyema and cerebritis adjacent to the frontal sinus. She was transferred to the reference neurosurgical center for surgical interventions and was admitted post-operatively at the Neurocritical Care Unit (NCCU). Reevaluation MRI showed residual anterior frontal empyema and absence of focus control in peri-nasal sinusitis, requiring a new ENT surgery. A Streptococcus spp was isolated from the blood, Eikenella corrodens from the pus collected from the sinuses, and the CSF was sterile. The patient completed 21 days of antibiotic therapy. She was extubated on the 19th day, with Broca's aphasia and right hemiparesis, and on the 23rd day transferred to the ENT Service and later to the Rehabilitation Service. We present a case of atypical central nervous system (CNS) infection by a rare agent, highlighting the importance of vigilance, focus control, and neurocritical care. In a severe and complex manifestation like this, the management typically involves medical and surgical interventions. Subdural empyema should be treated as a neurosurgical emergency due to the potential rapid deterioration in patient's neurological condition, attributed to secondary damage. In this case, brain multimodal monitoring, was very helpful in acute phase management. Neurocritical care teams should be involved early in patients with this presentation of CNS infection to provide optimal management, reducing complications and secondary brain lesions therefore improving patient outcomes.

Haemophilus aphrophilus and Eikenella corrodens Coinfection of Brain: An Unusual Case from China.

Background: The HACEK group comprises Haemophilus spp., Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae, are Gram-negative bacteria that are slow-growing and fastidious. These organisms are common causes of culture-negative endocarditis. However, brain abscesses caused by Haemophilus aphrophilus and E. corrodens have been rarely reported. The case we describe, which was promptly identified and successfully treated, will be meaningful for the diagnosis and treatment of such infectious diseases. Case Presentation: Herein, we report a case of brain abscess in a young man who was infected with Haemophilus aphrophilus and E. corrodens. The patient was admitted to the hospital with sudden onset of vomiting, coma, and fever. Magnetic resonance imaging (MRI) of the brain and cerebrospinal fluid cell counts suggested cerebral abscess, he underwent drainage of the abscess and empirical antimicrobial therapy of meropenem (2 g every 8 hours) and linezolid (0.6 g every 12 hours) for more than 10 days without significant improvement. Metagenomic next-generation sequencing (mNGS) of drainage fluid and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) detection for isolated bacteria from samples suggested the presence of H. aphrophilus and E. corrodens. After 7 weeks of ceftriaxone (2 g every 12 hours) and meropenem (2 g every 8 hours) intravenously, the patient was discharged with a normal temperature and brain MRI showed improvement of the lesion. Conclusion: Similar cases reported in previous studies were always associated with bacterial blood dissemination after dental surgery or myocarditis; however, the patient in our case had no any associated risk factors. As far as we know, this is the only case of central nervous system infection caused by H. aphrophilus and E. corrodens that has utilized combined mNGS and MALDI-TOF MS in the diagnosis.

Infratemporal abscess: a rare complication of a common procedure.

The infratemporal fossa (ITF) is an anatomically complex cavity that houses a variety of muscular and neurovascular structures at the base of the skull. Infections involving the ITF, though uncommon, can be fatal due to the difficulties of accessing this anatomical space and its proclivity to evolve into a cavernous venous thrombosis (CVT). As a result, a multi-disciplinary approach involving several surgical and medical subspecialists is often warranted. We present a case of an infratemporal fossa abscess (IFA) after wisdom teeth extraction with a very complicated clinical course and a distinct microbiologic profile.

Eikenella corrodens isolated from pleural effusion: A case report.

BACKGROUND: The bacterium Eikenella, classified as a gram-negative member of the phylum Proteobacteria, is distinguished by its rarity, corrosive nature, facultative anaerobic properties, and conditional pathogenicity. It represents the sole species within its genus-Eikenella corrodens (E. corrodens)-and can be found colonizing both human and animal oral and nasopharyngeal regions. Additionally, it occasionally inhabits the gastrointestinal or urogenital tracts. However, its slow growth rate can be attributed to its high nutritional requirements. However, there is an uneven distribution of construction and diagnostic capacity in China which poses undeniable challenges for the clinical examination and analysis of this case, especially in the basic hospitals. CASE SUMMARY: Here we presented a case of empyema associated with E. corrodens infection in a 67-year-old male patient without any previous history of infectious diseases in our primary hospital in Dongguan district of China. The patient was admitted due to recurrent worsening cough, sputum production, and dyspnea for 3 d, which had persisted for over 20 years. Moreover, the patient experienced a one-hour episode of unconsciousness. Upon admission, immediate comprehensive examinations were conducted on the patient which subsequently led to his admission to the intensive care unit. Meanwhile, the patient presented with drowsiness and profuse sweating along with bilateral conjunctival edema observed during initiation of non-invasive ventilation, suggesting empyema. A significant amount of coffee-colored malodorous pleural fluid was drained during the procedure above and sent to the laboratory department for inspection. Finally, laboratory culture results confirmed the presence of E. corrodens infection in the pleural fluid sample. The patient received antimicrobial therapy until died on day 22 in the hospital. CONCLUSION: In this report, we presented a case of empyema associated with E. corrodens infection. Multiple courses of morphological examination, viable culture analysis, and biochemical identification revealed its difficulties in detecting distinctive characteristics, as well as a detection model worth promoting. It's just that there were still certain deficiencies in terms of morphological assessment, biochemical identification, and drug susceptibility testing.

[Empyema thoracis, hemorrhagic pericarditis and acalculous cholecystitis caused by Eikenella corrodens sepsis]. / Empyemát, haemorrhagiás pericarditist és acalculosus cholecystitist okozó Eikenella corrodens szepszis.

The authors present a case of a 29-year-old woman who was diagnosed with pneumonia in the left side complicated with pleural effusion and hemorrhagic pericarditis one month after she had undergone tonsillectomy. Eikenella corrodens was identified as pathogenic agent when the empyema was removed during thoracotomy. After the patient was given antibiotic treatment she was discharged from the hospital without any symptoms or complaints. However, one month after she had left the hospital she was readmitted to the surgical unit as an emergency because of acute abdominal complaints. On admission acalculous cholecystitis as well as hemorrhagic pericarditis requiring pericardiocentesis were also observed. A rare cause of sepsis, Eikenella corrodens was identified which resulted in a severe disorder including polyserositis. Pericardiocentesis was performed two times and the patient was given targeted antibiotics and non-steroidal anti-inflammatory drugs. She was also treated with antimycotics as she had developed mycosis. After one month the patient recovered and was discharged from the hospital. No further recurrence of symptoms or complaints was observed during follow up.

Buccal Abscess Caused by Toothbrush Trauma: A Case Report of a Two-Year-Old.

Children often experience impalement trauma when they fall while holding objects in their mouths. While most cases heal without complications, here we report a case of buccal abscess formation after toothbrush trauma. A two-year-old boy fell while running with a toothbrush in his mouth, which punctured his right buccal mucosa. The following day, he presented to a pediatrician with a fever and buccal swelling and was treated with oral antibiotics. However, the buccal swelling did not improve, and the patient was referred to our department. Four days after the visit, the buccal swelling and fever worsened, requiring hospitalization, intravenous antibiotics, and drainage. The inflammation quickly disappeared following treatment, with no recurrence. Prophylactic antibiotic administration for oral impalement trauma is controversial. Our results suggest that prophylactic antibiotics covering both anaerobic and aerobic bacteria are necessary in cases of toothbrush-related oral trauma, where multiple bacterial infections may occur.

Secondary hand infection with Eikenella corrodens and Staphylococcus aureus in a patient with Behcet's disease: a case report.

We report the first case of a woman with Behcet's disease (BD) with multiple hand ulcers secondary to coninfection by Eikenella corrodens and Staphylococcus aureus resulting in necrotizing fasciitis. She had a long history of BD including long courses of prednisone and immunosuppressants. The patient was hospitalized for multiple superficial ulcers, swelling, and infection of the hands. After admission, pus culture examination revealed rare coinfection by E. corrodens and S. aureus. We administered moxifloxacin and vancomycin to control infection and methylprednisolone to control BD. We performed incision, drainage, and debridement of the ulcer surface on the hands to reduce the pus on the wound surface. E. corrodens infections occur in immunosuppressed patients and contribute to coinfections, particularly in patients with BD in whom destruction of the skin immune barrier increases risk to secondary infections. For severe and complicated hand infections, efforts should be made to identify pathogenic microorganisms so appropriate antibiotics and other interventions can be given to control the infection.

Zinc chloride inhibits lysine decarboxylase production from Eikenella corrodens in vitro and its therapeutic implications.

OBJECTIVES: Dentifrices containing zinc reduce gingival inflammation and bleeding better than control dentifrices (no zinc). How zinc might work is not understood. We have shown that lysine decarboxylase (LdcE), an enzyme from Eikenella corrodens, converts lysine to cadaverine in dental biofilms. The lack of lysine impairs the dentally attached cell barrier to biofilm, causing biofilm products to leak into junctional epithelium and stimulate inflammation. In year-old beagle dogs, immunization with LdcE, induces antibodies that inhibit LdcE activity and retard gingivitis development. We therefore examined whether a zinc-mediated loss of LdcE activity could explain the beneficial effect of zinc dentifrices. METHODS: We grew E. corrodens in modified tryptic soy broth with or without zinc chloride, and extracted LdcE from the cell surface using a Potter Elvehjem homogenizer. RESULTS: Up to 0.96 mM zinc chloride in the bacterial growth medium did not change cell yield, but reduced the extracted protein content by 41% (R2 = 0.27, p < 0.05) and LdcE activity/mg extracted protein by 85% (R2 = 0.90, p < 0.001). In extracts from cells grown without zinc, 78 times this zinc chloride concentration (73 mM) was required to reduce LdcE activity by 75%. CONCLUSIONS: Zinc ions inhibit the production of protein with LdcE activity at E. corrodens cell surfaces. The zinc ions may attach to cysteine residues that are unique to the N-terminal region of LdcE by interfering with the non-covalent polypeptide assembly that produces enzyme activity. CLINICAL SIGNIFICANCE: Zinc ion-mediated inhibition of LdcE assembly may provide a rationale for the improved control of gingival inflammation by zinc dentifrices.