- Volume 1, Issue 8, 2019

The type II toxin–antitoxin (TA) modules, mazEF and relBE, in Streptococcus mutans have been implicated in stress response, antibiotic tolerance and persister cell formation. However, how S. mutans regulates these systems to prevent unwanted toxin activation and persister cell formation is unclear. In this study, we provide evidence that ClpP is required for the proteolytic regulation of these TA systems and persister cell formation in S. mutans following antibiotic challenge. A persister viability assay showed that S. mutans UA159 (WT) formed a larger quantity of persister cells than its isogenic mutant ΔclpP following antibiotic challenge. However, the lux reporter assay revealed that clpP deletion did not affect the transcriptional levels of mazEF and relBE, since no significant differences (P>0.05) in the reporter activities were detected between the wild-type and ΔclpP background. Instead, all antibiotics tested at a sub-minimum inhibitory concentration (sub-MIC) induced transcriptional levels of mazEF and relBE operons. We then examined the protein profiles of His-tagged MazE and RelB proteins in the UA159 and ΔclpP backgrounds by Western blotting analysis. The results showed that S. mutans strains grown under non-stress conditions expressed very low but detectable levels of MazE and RelB antitoxin proteins. Antibiotics at sub-MICs induced the levels of the MazE and RelB proteins, but the protein levels decreased rapidly in the wild-type background. In contrast, a stable level of MazE and RelB proteins could be detected in the ΔclpP mutant background, suggesting that both proteins accumulated in the ΔclpP mutant. We conclude that ClpP is required for the proteolytic regulation of cellular levels of the MazE and RelB antitoxins in S. mutans , which may play a critical role in modulating the TA activities and persister cell formation of this organism following antibiotic challenge.

Strains of Rotarix, a live attenuated monovalent oral rotavirus vaccine, replicate in the intestine and are shed for about one month in immunocompetent recipients. The current study aimed to identify genetic changes of shed strains to reveal any significant mutations and their clinical impact on recipients. Stool samples of recipients of the first dose of Rotarix were sequentially collected for one month from the day of administration. Sequence analyses of the VP7 gene in eight recipients revealed five amino acid substitutions. Among them, two were observed in aa123, which is located in antigenic region 7-1a. Since there were no associated clinical symptoms, the genetic changes were unlikely to have caused reversion of pathogenicity of vaccine strain. Of interest, the virus in one case became closer to wild-type rotavirus via an amino acid change at aa123 occurring 14 days after administration, which might have resulted from multiple replications and long-term shedding of the vaccine strain.

Background. Francisella tularensis is a rare zoonotic bacterium that spreads sporadically by various routes, including infected arthropod bites, ingestion of contaminated water and inhalation of contaminated dust. However, its occurrence in postoperative chest infection has never been reported. Pathogen isolation, serology and molecular detection methods are commonly used for the diagnosis of tularaemia.

Case presentation. We present the first case report of the isolation of F. tularensis from a patient with a chest infection (a boy in his teens) following cardiac surgery for closure of a ventral septal defect. It was isolated on blood and chocolate agar on the third day after the subculture of drain fluid collected in a blood culture bottle incubated in Bact T/Alert 3-D (bioMerieux, France). The organism was identified as F. tularensis by Vitek GN ID Cards (Vitek 2 Compact, bioMerieux, France). The patient made a smooth recovery with antibiotic therapy.

Conclusion. F. tularensis can cause post-operative infection, especially in patients with a rural background.

Introduction. Lactobacillus prosthetic valve endocarditis is a rare infection caused by Lactobacillus bacteria. This bacterium is found in the normal flora of the human mouth, gastrointestinal tract and female genital tract. While there have been isolated cases of Lactobacillus bacteraemia and endocarditis, the infections are associated with comorbidities, immune deficiency, dental manipulation procedures and other medical history. This case of bioprosthetic valve endocarditis caused by Lactobacillus paracasei is unusual, as the patient was immune-competent and treated with pre-procedural antibiotics.

Case. We present a case of a 65-year-old male who underwent a dental extraction. He presented after 3 months of fever, chills and fatigue. On initial presentation, blood cultures were positive for alpha-haemolytic streptococcus bacteraemia. He was treated with IV penicillin and underwent aortic valve replacement with a bioprosthetic valve and excision of the mitral vegetation with repair of the mitral valve. Two years later, he had a tooth extraction after being treated properly with antibiotics. Three months later he presented with difficulty speaking, left leg weakness and increased drooling. All testing was normal. Three months later he presented with left side lower extremity weakness and expressive aphasia. He was diagnosed with bioprosthetic aortic valve endocarditis and was treated with IV penicillin and gentamicin for 6 weeks and then switched to oral penicillin. He remained stable.

Conclusions. L. paracasei can potentially be a cause of complicated endocarditis in patients with prosthetic heart valves undergoing dental procedures. Timely culture-guided antibiotic therapy is critical and may obviate the need for valve surgery.

Chromobacterium violaceum is a rare cause of infection in immunocompromised patients in the tropics with a spectrum of disease manifestations, including severe disease. Early identification of this micro-organism is essential for appropriate management. We present a case of C. violaceum septicaemia in a patient with chronic granulomatous disease.

We report a case with infective endocarditis (IE) due to Cardiobacterium valvarum . The patient was a 57-year-old male, who was referred to our hospital based on suspected IE detected by transthoracic echocardiography at a neighbourhood clinic. Three sets of blood cultures obtained on admission yielded positive results, and revealed rather slender and linear Gram-negative bacilli with a rosette formation that dyed minimally, with a pale white appearance. Although no isolates were identified by conventional methods, C. valvarum was ultimately identified by 16 S ribosomal RNA genotyping. HACEK group strains are difficult to identify by conventional methods. Therefore, if Gram-negative bacilli are isolated from IE patients, 16 S ribosomal RNA genotyping will be necessary. Furthermore, IE due to C. valvarum is very rare. We thus discuss our case in comparison with previous reports.

Introduction. Visceral leishmaniasis, caused by the Leishmania donovani complex, is responsible for over 20 000 deaths per year. This disease often affects the immunocompromised with an increased prevalence in those with human immunodeficiency virus (HIV). The immunocompromised are not only more susceptible to infection, but disseminated disease including gastric leishmaniasis. This is a case of gastric leishmaniasis occurring in a non-endemic region in a patient with comorbid HIV.

Case Presentation. The patient is a 39 year old originally from Central America currently living in Southeast Georgia. His history is significant for HIV, alcohol abuse, tobacco dependency and bone marrow biopsy-proven leishmaniasis. He denied any recent travel. At initial presentation, he had abdominal pain, nausea/vomiting, chills and dysphagia along with leukopenia and thrombocytopenia. Treatment with amphotericin B was initiated for his leishmaniasis as well as highly active antiretroviral therapy (HAART). The patient was discharged home on a 3 month course of amphotericin B with continued HAART therapy. Following resolution of his acute symptoms, six months later, the patient developed acute abdominal pain with nausea prompting presentation to the emergency department. Leishmaniasis was found again following bone marrow biopsy and the patient restarted amphotericin B and HAART. Several years later the patient presented again with similar symptoms, this time with accompanying rectal bleeding. The patient received an esophagogastroduodenoscopy and on gastric mucosal biopsy was found to have gastric leishmaniasis.

Conclusion. This manuscript highlights the key features of this case, including recognizing leishmaniasis clinically, proving diagnosis through definitive testing and understanding the connection between leishmaniasis and HIV.

Introduction. Lymphatic filariasis (LF) and leprosy are both endemic in India. These diseases are on the World Health Organization (WHO) list of neglected tropical diseases (NTDs), as they affect the most marginalized communities in the world, resulting in deformities and functional limitation. We report the first case of asymptomatic filariasis and leprosy co-morbidity in a patient with suspected Guillain–Barré syndrome.

Case presentation. A 55-year-old male who was a farmer by occupation presented to the Neurology Outpatient Department (OPD) of our institute with complaints of weakness in all four limbs for the last 15 days. After admission, a detailed history revealed that the patient had been taking multi-drug therapy (MDT) for leprosy for the previous 6 months. After symptomatic management of the presenting complaints, the patient was sent to the Department of Microbiology for a consultation and six-site slit-skin sampling. The initial screening of Ziehl–Neelsen (ZN)-stained smears under a 10× objective led to the incidental finding of sheathed structures resembling microfilaria (Mf) on the smear made from ear lobules. In addition, short acid-fast bacilli (AFB) were also observed under the oil-immersion objective.

Conclusion. We emphasize that a high index of suspicion and thorough screening of smears by a microbiologist is essential in specimens obtained from any body site.

We present a case of Ruminococcus gnavus sepsis in a woman suffering from multiple myeloma and myelodysplastic syndrome. R. gnavus , a Gram-positive coccus and a gut commensal, has been described in nine cases of infection in the literature, with most infections having occurred in patients with either gastrointestinal symptoms or prosthesis infections. In this case, R gnavus was identified by mass spectrometry, and showed susceptibility to penicillin, meropenem, tetracycline, metronidazole and clindamycin. The patient was successfully treated initially with intravenous piperacillin/tazobactam and metronidazole, and then switched to oral penicillin and metronidazole. The cause of infection is hypothesized to have been a shift in the gut microbiota towards an excess growth of R. gnavus caused by immunosuppression, and bacterial translocation across a vulnerable mucosal barrier due to prednisolone treatment and severe thrombocytopenia.