The First Known Case of Liver Abscess Caused by Aggregatibacter aphrophilus in Japan.

A 48-year-old man presented with a sustained fever. Abdominal computed tomography revealed multilocular liver abscesses. He underwent percutaneous needle aspiration, yielding straw-colored pus. Gram staining revealed Gram-negative coccobacilli. The organism grew only on chocolate II agar in a 7% carbon dioxide atmosphere. Identification of Aggregatibacter aphrophilus was confirmed using mass spectrometry and 16S rRNA gene sequencing. He was successfully treated with antibiotics. Liver abscess caused by A. aphrophilus is extremely rare. We herein report the first such case in Japan. Even fastidious organisms, such as A. aphrophilus, should be correctly identified using mass spectrometry or 16S rRNA gene sequencing for adequate treatment.

Genomic integration and expression of the Aggregatibacter actinomycetemcomitans catalase gene in Aggregatibacter aphrophilus.

OBJECTIVE: To test the hypothesis that virulence genes of Aggregatibacter actinomycetemcomitans can be expressed and confer fitness advantages in the closely related Aggregatibacter aphrophilus. DESIGN: Clinical isolates of A. aphrophilus were screened for natural competence with marked genomic DNA from A. actinomycetemcomitans and A. aphrophilus. The gene katA of A. actinomycetemcomitans D7S-1 and its flanking regions were constructed and inserted into a comparable locus in the genome of a naturally competent A. aphrophilus strain by a markerless protocol via natural transformation. Mutants of A. actinomycetemcomitans with or without katA were also constructed by a similar protocol. Discs soaked with either 0.03% hydrogen peroxide or broth culture of Streptococcus gordonii Challis were placed on the agar with cultures of A. actinomycetemcomitans or A. aphrophilus. The size of the growth inhibition zone associated with the disc was measured after 2-day culture. RESULTS: Five of the 13A. aphrophilus strains exhibited a transformation frequency of 10-6 or higher. The intra- and inter-species transformation frequencies were comparable. The inhibition zones for katA-negative strains of A. actinomycetemcomitans or A. aphrophilus were 3- to 7-fold larger than those associated with katA-positive strains (p<0.05). CONCLUSIONS: There was no apparent species barrier for the transfer and expression of A. actinomycetemcomitans katA in A. aphrophilus. The inserted A. actinomycetemcomitans-specific katA gene in A. aphrophilus strain NJ8700 conferred resistance to inhibition by hydrogen peroxide or S. gordonii. The potential to swap genes between these two closely related oral species may be an alternative approach for investigating the virulence determinants of A. actinomycetemcomitans.

Bartholinitis due to Aggregatibacter aphrophilus: a case report.

BACKGROUND: Aggregatibacter aphrophilus, a commensal of the oro-pharyngeal flora and member of the HACEK group of organisms, is an uncommonly encountered clinical pathogen. It has already been described as the causative agent of brain abscesses, empyema, meningitis, sinusitis, otitis media, bacteriemia, pneumonia, osteomyelitis, peritonitis, endocarditis and wound infections. Herein we report the first case of bartholinitis due to A. aphrophilus. CASE PRESENTATION: A 33-year-old woman was admitted for a 3-day genital pain without fever and urinary functional signs. The abscess was incised and drained; A. aphrophilus was the only micro-organism that grew from the pus. The patient received no antibiotics; the clinical course was favourable. CONCLUSION: This case highlights the importance of an effective treatment of recurrent bartholinitis such as a cold resection of the gland. It is presented for its rarity.

Aggregatibacter aphrophilus ventriculitis following C1-C2 transarticular screw fixation.

OBJECTIVE: Central nervous system (CNS) infections after cervical spine surgery are a rare but serious complication and may be caused by uncommon pathogens. We report the case of a 57-year-old male who developed slowly progressive mental confusion with headaches, increased daytime sleepiness and mild gait disturbance within the last 3 weeks. Six weeks prior to admission to our department, he underwent an atlantoaxial fusion by C1-C2 transarticular screw fixation for rheumatoid arthritis related C1-C2 multidirectional instability. METHODS: We analyzed clinical and neuroradiological findings. RESULTS: The findings were consistent with communicating hydrocephalus secondary to ventriculitis and the left C1-C2 screw was found to be misplaced with perforation of the dura. The situation was interpreted as implant related surgical site infection of the cerebrospinal fluid followed by ventriculitis and hydrocephalus. Bacterial broad range 16S rRNA gene PCR from the cerebrospinal fluid (CSF) followed by sequencing identified Aggregatibacter aphrophilus as the causative agent, while conventional cultures remained negative due to its fastidious growth. The patient was successfully treated with a lumbar drain and intravenous ceftriaxone. CONCLUSIONS: To our knowledge, this is the first report of Aggregatibacter aphrophilus ventriculitis following C1-C2 transarticular screw fixation.

Unconventional N-Linked Glycosylation Promotes Trimeric Autotransporter Function in Kingella kingae and Aggregatibacter aphrophilus.

UNLABELLED: Glycosylation is a widespread mechanism employed by both eukaryotes and bacteria to increase the functional diversity of their proteomes. The nontypeable Haemophilus influenzae glycosyltransferase HMW1C mediates unconventional N-linked glycosylation of the adhesive protein HMW1, which is encoded in a two-partner secretion system gene cluster that also encodes HMW1C. In this system, HMW1 is modified in the cytoplasm by sequential transfer of hexose residues. In the present study, we examined Kingella kingae and Aggregatibacter aphrophilus homologues of HMW1C that are not encoded near a gene encoding an obvious acceptor protein. We found both homologues to be functional glycosyltransferases and identified their substrates as the K. kingae Knh and the A. aphrophilus EmaA trimeric autotransporter proteins. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed multiple sites of N-linked glycosylation on Knh and EmaA. Without glycosylation, Knh and EmaA failed to facilitate wild-type levels of bacterial autoaggregation or adherence to human epithelial cells, establishing that glycosylation is essential for proper protein function. IMPORTANCE: This work emphasizes the importance of glycosylation for proper function of bacterial proteins. Here we show that the Kingella kingae Knh and the Aggregatibacter aphrophilus EmaA trimeric autotransporter proteins are N-glycosylated by novel homologues of the Haemophilus influenzae HMW1C glycosyltransferase, highlighting the first examples of trimeric autotransporters that are modified by HMW1C-like enzymes. In the absence of glycosylation, Knh and EmaA lack adhesive activity. This work has relevance to our understanding of bacterial pathogenicity and expression of potential vaccine antigens.

Aggregatibacter aphrophilus pacemaker endocarditis: a case report.

BACKGROUND: Aggregatibacter bacteria are a rare cause of endocarditis in adults. They are part of a group of organisms known as HACEK--Haemophilus, Aggregatibacter, Cardiobacter, Eikenella, and Kingella. Among these organisms, several Haemophilus species have been reclassified under the genus Aggregatibacter. Very few cases of Aggregatibacter endocarditis in patients with pacemaker devices have been reported. CASE PRESENTATION: We present here what we believe to be the first case of Aggregatibacter aphrophilus pacemaker endocarditis. A 62-year-old African American male with a medical history significant for dual-chamber pacemaker placement in 1996 for complete heart block with subsequent lead manipulation in 2007, presented to his primary care doctor with fever, chills, night sweats, fatigue, and ten-pound weight loss over a four-month period. Physical examination revealed a new murmur and jugular venous distension which prompted initiation of antibiotics for suspicion of endocarditis. Both sets of initial blood cultures were positive for A. aphrophilus. Transesophageal echocardiogram revealed vegetations on the tricuspid valve and the right ventricular pacemaker lead (Figure 1). This case highlights the importance of identifying rare causes of endocarditis and recognizing that treatment may not differ from the standard treatment for typical presentations. The patient received intravenous ceftriaxone for his endocarditis for a total of six weeks. Upon device removal, temporary jugular venous pacing wires were placed. After two weeks of antibiotic treatment and no clinical deterioration, a new permanent pacemaker was placed and the patient was discharged home. CONCLUSIONS: This is the first case of A. aphrophilus endocarditis in a patient with a permanent pacemaker. Our patient had no obvious risk factors other than poor dentition and a history of repeated pacemaker lead manipulation. This suggests that valvulopathies secondary to repeated lead manipulation can be clinically significant factors in morbidity and mortality in this patient population.