Combinatorial effects of amoxicillin and metronidazole on selected periodontal bacteria and whole plaque samples

Objective

The aim of the present study was to analyze in vitro the combinatorial effects of the antibiotic combination of amoxicillin plus metronidazole on subgingival bacterial isolates.

Design

Aggregatibacter (Actinobacillus) actinomycetemcomitans, Prevotella intermedia/nigrescens, Fusobacterium nucleatum and Eikenella corrodens from our strain collection and subgingival bacteria isolated from patients with periodontitis were tested for their susceptibility to amoxicillin and metronidazole using the Etest. The fractional inhibitory concentration index (FICI), which is commonly used to describe drug interactions, was calculated.

Results

Synergy, i.e. FICI values ≤ 0.5, between amoxicillin and metronidazole was shown for two A. actinomycetemcomitans (FICI: 0.3), two F. nucleatum (FICI: 0.3 and 0.5, respectively) and one E. corrodens (FICI: 0.4) isolates. Indifference, i.e. FIC indices of >0.5 but ≤4, occurred for other isolates and the 14 P. intermedia/nigrescens strains tested. Microorganisms resistant to either amoxicillin or metronidazole were detected in all samples by Etest.

Conclusion

Combinatorial effects occur between amoxicillin and metronidazole on some strains of A. actinomycetemcomitans, F. nucleatum and E. corrodens. Synergy was shown for a few strains only.     

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

PurposeTo investigate clinical characteristics of six cases of Eikenella corrodens infection in Ningbo First Hospital in China in recent 2 years.MethodsWe 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.ResultsFive 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.     

HACEK endocarditis: state-of-the-art

The HACEK group of bacteria – Haemophilus parainfluenzae, Aggregatibacter spp. (A. actinomycetemcomitans, A. aphrophilus, A. paraphrophilus, and A. segnis), Cardiobacterium spp. (C. hominis, C. valvarum), Eikenella corrodens, and Kingella spp. (K. kingae, K. denitrificans) – are fastidious gram-negative bacteria, part of the normal microbiota of oral and upper respiratory tract in humans. Although their pathogenicity is limited, they are responsible for 1-3% of all infective endocarditis. HACEK endocarditis mostly affect patients with underlying heart disease or prosthetic valves, and are characterized by an insidious course, with a mean diagnosis delay of 1 month (Haemophilus spp.) to 3 months (Aggregatibacter and Cardiobacterium spp.). The advent of continuously monitored blood culture systems with enriched media has erased the need for extended incubation for the diagnosis of HACEK endocarditis. Medical treatment relies on third-generation cephalosporin, with a favorable outcome in 80-90% of cases, with or without cardiac surgery.     

The characterization of a (nutritionally important) proline iminopeptidase from Eikenella corrodens

Eikenella corrodens generates energy primarily through the oxidative deamination of specific amino acids, a process that is coupled to dissimilatory nitrate reduction to nitrite. Cell yields resulting from chemostat-growth of the organism in simple, chemically defined media containing varying amounts of proline confirm that this amino acid is a likely source of energy for E. corrodens in the oral environment. The importance of proline in ATP generation by the organism is reflected in molar growth yields, which showed that biomass production per mole of this amino acid was significantly higher than that for other amino acids. The organism was found to express, constitutively, the enzyme proline iminopeptidase, which releases proline from the N-terminus of small peptides. The enzyme was partially purified and characterized and found to exist in the cytoplasm as a 35 kDa monomer. Inhibition studies showed that the enzyme, although classified as a serine protease, also appears to require thiol groups for activity, a finding which is consistent with previous reports. The enzyme obeyed Michaelis-Menten kinetics and was found to have a Km value of 0.223 mM for the substrate proline-p-nitroanilide.     

Eikenella corrodens cervical spinal epidural abscess induced by a fish bone

Cervical spinal epidural abscess, caused by fish bone injury and a secondary infection by Eikenella corrodens which is part of the normal flora, has not been reported. A 72-yr-old man came to the hospital with pain in his posterior neck and both shoulders for 2 months. He also was experiencing weakness on his right side for 3 days. A fish bone had been stuck in his throat for about 2 months. Neurological examination revealed right hemiparesis, hypesthesia on the left extremities and neck stiffness. Laboratory findings showed an elevated ESR/CRP and leukocytosis, and magnetic resonance imaging revealed a retropharyngeal abscess and cervical myelitis. The patient was treated with emergency surgical decompression and antibiotics. A fish bone was removed from the C3-C4 intervertebral disc space. In the culture of chocolate blood agar and 5% sheep blood agar plate, E. corrodens was detected as a causative organism.     

DNA probe detection of periodontal pathogens in HIV-associated periodontal lesions

Recent studies have shown that an atypical gingivitis and a rapidly progressive periodontal disease may be early-occurring opportunistic infections associated with human immunodeficiency virus (HIV) infection. This study examined the prevalence of selected periodontal pathogens associated with these HIV-related periodontal lesions. Subgingival plaque samples were obtained from both HIV-seronegative and HIV-seropositive homosexual men and from presumably uninfected heterosexual men. DNA probes were used to detect Actinobacillus actinomycetemcomitans, Bacteroides intermedius, Bacteroides gingivalis, Eikenella corrodens and Wolinella recta in the plaque. The healthy sites in both the seronegative and seropositive homosexual groups showed a greater prevalence of all test bacteria, except for E. corrodens, than did the heterosexual group. HIV-associated periodontitis sites showed a microbial profile qualitatively similar to that of conventional periodontitis, except that B. gingivalis was more prevalent in conventional periodontitis. In contrast, HIV-associated gingivitis sites exhibited a greater prevalence of all bacteria tested than conventional gingivitis sites. In fact, HIV gingivitis generally showed a bacterial profile similar to that of the HIV periodontitis lesions, except that W. recta was significantly more prevalent in HIV periodontitis. These data suggest that the HIV gingivitis lesion is a precursor to HIV periodontitis. Thus, early identification and prophylactic treatment of high-risk individuals may prevent the destruction of periodontal tissues.     

Susceptibility of Eikenella corrodens to Antimicrobial Agents

Summary

Twelve Eikenella corrodens strains were isolated from dental infections and tested for their susceptibility to antimicrobial agents by an agar dilution method. All strains were susceptible to penicillin, ampicillin and tetracycline, and resistant to cephalexin and metronidazole and moderately resistant to erythromycin, gentamicin and cefaclor.     

啮蚀艾肯菌致鼻咽颅底感染1例报道

目的 总结1例啮蚀艾肯菌引起鼻咽颅底感染的诊疗经验,提高对该菌感染病的认识。方法 回顾性分析1例啮蚀艾肯菌致鼻咽颅底感染患者的病例资料,并结合文献进行讨论。结果 本例患者完善内镜检查、影像学检查以及实验室检查,鼻咽颅底组织2次病理报告均为慢性肉芽肿性炎,经实验室确诊为啮蚀艾肯菌感染,予清创引流、口服抗生素2个月后,患者痊愈,术后随访3个月未复发。结论 鼻咽颅底感染临床少见,临床症状、影像学检查与鼻咽癌相似。啮蚀艾肯菌为罕见致病菌,发病率低。诊治上,需结合病理学、病原学检查明确诊断,及早清创引流、选取合适的抗感染药物。     

The mechanisms of Eikenella corrodens aggregation by salivary glycoprotein and the effect of the glycoprotein on oral bacterial aggregation

The mechanism of aggregation of Eikenella corrodens 1073 with E. corrodens aggregating factor (EcAF) which was purified from submandibular-sublingual (SM-SL) saliva was investigated. Heating (100 degrees C, 10 minutes) or protease treatment of E. corrodens cells abolished the aggregating activity. The aggregation was inhibited by adding N-acetyl-D-galactosamine (GalNAc) and saccharides which contain a galactose residue at the non-reducing end. The aggregating activity was sensitive to EDTA and was restored by Ca2+ but not by Mn2+ or Mg2+. Neuraminidase treatment of EcAF increased their ability to aggregate. E. corrodens, suggesting that the sialic acids on EcAF interfere with aggregation. These data suggest that the aggregation of E. corrodens 1073 with EcAF is mediated by specific interactions between a bacterial cell surface lectin-like substance and a complementary GalNAc-like receptor. EcAF also aggregated 16 strains of oral bacteria including periodontopathic bacteria such as Porphyromonas (Bacteroides) gingivalis 381 and Actinobacillus actinomycetemcomitans ATCC29522; however, those aggregations were not inhibited by GalNAc. Therefore, EcAF appears to have more than two types of bacterial binding site and plays important roles in accumulation of dental plaque by forming a complex network of plaque bacteria including periodontopathic strains.