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Huang M, Li S, Wu X, Xu D, Tang L, Chen Z. An isolated pulmonary nodule secondary to Streptococcus intermedius infection in an otherwise healthy 10-year-old boy: A case report and literature review. Front Pediatr 2022; 10:921258. [PMID: 36160793 PMCID: PMC9490049 DOI: 10.3389/fped.2022.921258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 08/05/2022] [Indexed: 12/02/2022] Open
Abstract
Streptococcus intermedius, as a Gram-positive commensal bacterium, tends to cause various infections, such as brain and liver abscesses, endocarditis, and empyema, especially in immunocompromised patients. However, an isolated pulmonary nodule caused by S. intermedius in previously healthy individuals without traditional risk factors is rarely reported. Herein, we present a case of a 10-year-old immunocompetent boy referred to our department with a 5-day history of intermittent, left-sided chest pain. Chest X-ray and computed tomography revealed a left lung nodule. Although his blood, sputum, and bronchoalveolar lavage fluid cultures were negative, metagenomic next-generation sequencing (mNGS) showed only the presence of S. intermedius in ultrasonography-guided lung biopsy tissue and pleural fluid (416 and 110 reads, respectively). He was then successfully treated with appropriate intravenous antibiotics and avoided surgical intervention. To the best of our knowledge, this is the first report of S. intermedius-related pulmonary nodule confirmed by mNGS analysis in healthy children. For achieving proper diagnosis and treatment, infection with S. intermedius should be included in the differential diagnosis when coming across such a similar pulmonary nodule. mNGS, as a valuable supplement to conventional culture methods, is an essential diagnostic tool for identifying pathogens without typical characteristics.
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Affiliation(s)
- Meixia Huang
- Department of Pulmonology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Shuxian Li
- Department of Pulmonology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Xiling Wu
- Department of Pulmonology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Dan Xu
- Department of Pulmonology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Lanfang Tang
- Department of Pulmonology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Zhimin Chen
- Department of Pulmonology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
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A Case of Multiple Culture-Negative, Rim Enhancing Abscesses in the Central Nervous System. INFECTIOUS DISEASES IN CLINICAL PRACTICE 2021. [DOI: 10.1097/ipc.0000000000000967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Wang Y, Guo H, Bai Y, Li T, Xu R, Sun T, Lu J, Song Q. Isolation and characteristics of multi-drug resistant Streptococcus porcinus from the vaginal secretions of sow with endometritis. BMC Vet Res 2020; 16:146. [PMID: 32434590 PMCID: PMC7238638 DOI: 10.1186/s12917-020-02365-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Accepted: 05/10/2020] [Indexed: 01/13/2023] Open
Abstract
Background Sow endometritis is a common disease in pig breeding farms after artificial insemination, which leads to gray-green vaginal secretions and decreased conception rates. It is important to perform an etiologic diagnosis for effective treatments and control of diseases. The aim of this study was to carry out a pathogenic detection in five specimens of vaginal secretions collected from sick pigs with endometritis, implement identification of the pathogens by phenotypic detection and 16 s rDNA sequence and phylogeny analysis, and determinate antibiotic susceptibility of the isolates. Results A Streptococcus strain was isolated and identified from all of the five specimens. The isolate was positive for Voges-Proskauer (V-P) and for the hydrolysis of arginine, esculin and myelin-associated glycoprotein (MAG). Acid formation was observed for sorbitol, mushroom sugar, sucrose, and glucose. The 16S rDNA sequence of the isolate possessed 99.93% similarity to that of Streptococcus porcinus. The phylogenetic analysis of 16S rDNA sequence showed that the isolate belonged to the same clade as the S. porcinus strains from humans, pigs, and other animals. The isolate exhibited multi-drug resistance to aminoglycosides, quinolones, macrolides and tetracyclines except being sensitive to some β- lactams such as penicillin G, cephalothin, cefazolin, cephradine and cefuroxime. Conclusions A S. porcinus isolate with multi-drug resistance was identified from vaginal secretions of sows with endometritis in one pig breeding farm, which suggests that the sow endometritis was caused by S. porcinus infection during artificial insemination. This study indicates that sensitive antibiotics such as penicillin G or some cephalosporins could be used for treatment of the diseases. In addition, the study hints that bacterial multi-drug resistance is a tough problem for disease treatment in pig farms.
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Affiliation(s)
- Yawen Wang
- Hebei Province Research Center of Veterinary Biological Engineering and Technology, College of Veterinary Medicine, Hebei Agricultural University, Baoding, 071000, China
| | - Haiyong Guo
- School of Life Science, Jilin Normal University, Siping, 136000, China
| | - Yun Bai
- Hebei Province Research Center of Veterinary Biological Engineering and Technology, College of Veterinary Medicine, Hebei Agricultural University, Baoding, 071000, China
| | - Tanqing Li
- Hebei Province Research Center of Veterinary Biological Engineering and Technology, College of Veterinary Medicine, Hebei Agricultural University, Baoding, 071000, China
| | - Ruitao Xu
- Hebei Province Research Center of Veterinary Biological Engineering and Technology, College of Veterinary Medicine, Hebei Agricultural University, Baoding, 071000, China
| | - Tairan Sun
- Baoding Animal Disease Control and Prevention Center, Baoding, 071000, Hebei, China
| | - Jicheng Lu
- Baoding Animal Disease Control and Prevention Center, Baoding, 071000, Hebei, China
| | - Qinye Song
- Hebei Province Research Center of Veterinary Biological Engineering and Technology, College of Veterinary Medicine, Hebei Agricultural University, Baoding, 071000, China.
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Infección espinal por una cepa defectiva de Streptococcus intermedius diagnosticada mediante PCR multiplex. Enferm Infecc Microbiol Clin 2020; 38:245-246. [DOI: 10.1016/j.eimc.2019.09.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Revised: 09/17/2019] [Accepted: 09/19/2019] [Indexed: 11/23/2022]
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Tomoyasu T, Matoba M, Takao A, Tabata A, Whiley RA, Maeda N, Nagamune H. Rapid screening method for detecting highly pathogenic Streptococcus intermedius strains carrying a mutation in the lacR gene. FEMS Microbiol Lett 2018; 365:4705894. [PMID: 29228148 DOI: 10.1093/femsle/fnx258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 11/30/2017] [Indexed: 11/12/2022] Open
Abstract
Streptococcus intermedius is a member of the normal human commensal flora and secretes a human-specific cytolysin intermedilysin (ILY) as a major virulence factor. Expression of ily is repressed by LacR and loss-of-function mutations of LacR are observed in many ILY high-producing strains isolated from deep-seated abscesses, suggesting that high ILY production is necessary for increased virulence. However, because ILY exhibits no β-hemolysis on animal blood agar plates, differentiating ILY high- and low-producing strains using conventional laboratory methods is not possible. Interestingly, S. intermedius also produces glycosidases, including MsgA and NanA, which exhibit N-acetyl-β-d-glucosaminidase and neuraminidase activities, respectively. Moreover, MsgA expression, but not NanA, is negatively regulated by LacR. Here we measured the activities of MsgA, NanA and ILY in strains isolated from clinical specimens and dental plaque to determine the correlation between these glycosidase activities and ILY hemolytic activity. Hemolytic activity showed a strong positive correlation with MsgA and a weak negative correlation with NanA activities. Therefore, we calculated the ratio of MsgA and NanA activity (M/N ratio). This value showed a stronger positive correlation (r = 0.81) with ILY hemolytic activity and many strains with high M/N ratios (>2) were ILY-high producers with loss-of-function mutations in LacR.
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Affiliation(s)
- Toshifumi Tomoyasu
- Field of Biomolecular Functions and Technology, Department of Bioscience and Bioindustry, Graduate School of Bioscience and Bioindustry, Tokushima University Graduate School, Minami-josanjima-cho, Tokushima 770-8513, Japan.,Department of Resource Circulation Engineering, Center for Frontier Research of Engineering, Tokushima University Graduate School, Minami-josanjima-cho, Tokushima 770-8506, Japan.,Department of Biological Science and Technology, Institute of Technology and Science, Tokushima University Graduate School, Minami-josanjima-cho, Tokushima 770-8506, Japan
| | - Masaki Matoba
- Department of Biological Science and Technology, Institute of Technology and Science, Tokushima University Graduate School, Minami-josanjima-cho, Tokushima 770-8506, Japan
| | - Ayuko Takao
- Department of Oral Microbiology, School of Dental Medicine, Tsurumi University, 2-1-3 Tsurumi, Tsurumi-ku 230-8501, Japan
| | - Atsushi Tabata
- Field of Biomolecular Functions and Technology, Department of Bioscience and Bioindustry, Graduate School of Bioscience and Bioindustry, Tokushima University Graduate School, Minami-josanjima-cho, Tokushima 770-8513, Japan.,Department of Biological Science and Technology, Institute of Technology and Science, Tokushima University Graduate School, Minami-josanjima-cho, Tokushima 770-8506, Japan
| | - Robert A Whiley
- Department of Clinical and Diagnostic Oral Sciences, Institute of Dentistry, Bart's and The London School of Medicine and Dentistry, Queen Mary University of London, 4 Newark Street, London E1 2AT, UK
| | - Nobuko Maeda
- Department of Oral Microbiology, School of Dental Medicine, Tsurumi University, 2-1-3 Tsurumi, Tsurumi-ku 230-8501, Japan
| | - Hideaki Nagamune
- Field of Biomolecular Functions and Technology, Department of Bioscience and Bioindustry, Graduate School of Bioscience and Bioindustry, Tokushima University Graduate School, Minami-josanjima-cho, Tokushima 770-8513, Japan.,Department of Biological Science and Technology, Institute of Technology and Science, Tokushima University Graduate School, Minami-josanjima-cho, Tokushima 770-8506, Japan
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A case of multiple empyema caused by Streptococcus intermedius. Auris Nasus Larynx 2017; 44:745-748. [DOI: 10.1016/j.anl.2016.10.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 10/22/2016] [Accepted: 10/31/2016] [Indexed: 11/19/2022]
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Positive- and Negative-Control Pathways by Blood Components for Intermedilysin Production in Streptococcus intermedius. Infect Immun 2017; 85:IAI.00379-17. [PMID: 28607101 DOI: 10.1128/iai.00379-17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 06/08/2017] [Indexed: 11/20/2022] Open
Abstract
Streptococcus intermedius is an opportunistic bacterial pathogen secreting a human-specific cytolysin called intermedilysin (ILY) as a major pathogenic factor. This bacterium can degrade glycans into monosaccharides using two glycosidases, multisubstrate glycosidase A (MsgA) and neuraminidase (NanA). Here, we detected a stronger hemolytic activity mediated by ILY when S. intermedius PC574 was cultured in fetal bovine serum (FBS) than when it was grown in the standard culture medium. FBS-cultured cells also showed higher MsgA and NanA activity, although overproduction of ILY in FBS was undetectable in mutants nanA-null and msgA-null. Addition of purified MsgA and NanA to the FBS resulted in a release of 2.8 mM galactose and 4.3 mM N-acetylneuraminic acid; these sugar concentrations were sufficient to upregulate the expression of ILY, MsgA, and NanA. Conversely, when strain PC574 was cultured in human plasma, no similar increase in hemolytic activity was observed. Moreover, addition of human plasma to the culture in FBS appeared to inhibit the stimulatory effect of FBS on ILY, MsgA, and NanA, although there were individual differences among the plasma samples. We confirmed that human plasma contains immunoglobulins that can neutralize ILY, MsgA, and NanA activities. In addition, human plasma had a neutralizing effect on cytotoxicity of S. intermedius toward HepG2 cells in FBS, and a higher concentration of human plasma was necessary to reduce the cytotoxicity of an ILY-high-producing strain than an ILY-low-producing strain. Overall, our data show that blood contains factors that stimulate and inhibit ILY expression and activity, which may affect pathogenicity of S. intermedius.
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De Simone M, Brogna B, Sessa G, Oliva G, Guida B, Magliulo M. Valuable contribution of magnetic resonance spectroscopy in differentiation of brain abscess from glioma. Infect Dis (Lond) 2017; 49:871-873. [PMID: 28574298 DOI: 10.1080/23744235.2017.1331464] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Affiliation(s)
- Marta De Simone
- a Neuroradiology Unit , "San Giuseppe Moscati" Hospital , Avellino , Italy
| | - Barbara Brogna
- b Department of Internal and Experimental Medicine "Magrassi-Lanzara", Institute of Radiology , Second University of Naples , Naples , Italy
| | - Giovanni Sessa
- c Neurosurgery Unit , "San Giuseppe Moscati" Hospital , Avellino , Italy
| | - Giovanni Oliva
- c Neurosurgery Unit , "San Giuseppe Moscati" Hospital , Avellino , Italy
| | - Bruno Guida
- a Neuroradiology Unit , "San Giuseppe Moscati" Hospital , Avellino , Italy
| | - Maurizio Magliulo
- d Neurosurgery Unit , "San Giuseppe Moscati" Hospital Avellino , Italy
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Aguilera-Arreola MG, Martínez-Peña MD, Hernández-Martínez F, Juárez Enriques SR, Rico Verdín B, Majalca-Martínez C, Castro-Escarpulli G, Albarrán-Fernández E, Serrano-López SC. Cultivation-independent approach for the direct detection of bacteria in human clinical specimens as a tool for analysing culture-negative samples: a prospective study. SPRINGERPLUS 2016; 5:332. [PMID: 27065040 PMCID: PMC4792836 DOI: 10.1186/s40064-016-1949-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 02/29/2016] [Indexed: 12/03/2022]
Abstract
Administration of empirical antibiotic therapy prior to microbiological diagnosis is thought to be associated the failure of subsequent bacterial growth in culture. The aim of this study was to detect bacterial pathogens via direct amplification and sequencing of the 16S rDNA gene in samples showing negative culture results as alternative diagnostic tools to troubleshoot difficult samples. Twenty-three (7.66 %) positive samples were detected, most of which were monomicrobial infections; 15 of the cases were identified as HAIs, 6 had catheter colonisation, and 2 had sample colonisation. The pathogens identified included Escherichia, Salmonella, Pseudomonas spp., Enterococcus spp. and coagulase-negative staphylococci (CoNS). The most frequent infections were bacteraemia and urinary tract infection, but meningitis, warm infection and soft tissue infection were also documented. These findings emphasise the efficacy and usefulness of molecular diagnosis, thus 16S rDNA gene analysis is strongly indicated by HAIs diagnostics.
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Affiliation(s)
- Ma Guadalupe Aguilera-Arreola
- Department of Microbiology, Instituto Politécnico Nacional (IPN), Escuela Nacional de Ciencias Biológicas (ENCB), Mexico City, D.F. Mexico
| | - Marcos Daniel Martínez-Peña
- Department of Microbiology, Instituto Politécnico Nacional (IPN), Escuela Nacional de Ciencias Biológicas (ENCB), Mexico City, D.F. Mexico ; Microbial Genetic Resources Laboratory, Centro Nacional de Recursos Genéticos (CNRG)-INIFAP, Tepatitlán de Morelos, Jalisco Mexico
| | - Fabiola Hernández-Martínez
- Department of Microbiology, Instituto Politécnico Nacional (IPN), Escuela Nacional de Ciencias Biológicas (ENCB), Mexico City, D.F. Mexico ; Department of Zoology, Escuela Nacional de Ciencias Biológicas - Instituto Politécnico Nacional, Mexico City, D.F. Mexico
| | - Sara R Juárez Enriques
- Special Test Laboratory, Centro Médico Nacional (CMN) 20 de Noviembre - Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado (ISSSTE), Mexico City, D.F. Mexico
| | - Beatriz Rico Verdín
- Department of Epidemiology, Centro Médico Nacional (CMN) 20 de Noviembre del Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado (ISSSTE), Mexico City, D.F. Mexico
| | - Cristina Majalca-Martínez
- Special Test Laboratory, Centro Médico Nacional (CMN) 20 de Noviembre - Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado (ISSSTE), Mexico City, D.F. Mexico
| | - Graciela Castro-Escarpulli
- Department of Microbiology, Instituto Politécnico Nacional (IPN), Escuela Nacional de Ciencias Biológicas (ENCB), Mexico City, D.F. Mexico
| | - Enrique Albarrán-Fernández
- Department of Epidemiology, Centro Médico Nacional (CMN) 20 de Noviembre del Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado (ISSSTE), Mexico City, D.F. Mexico
| | - S Cecilia Serrano-López
- Special Test Laboratory, Centro Médico Nacional (CMN) 20 de Noviembre - Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado (ISSSTE), Mexico City, D.F. Mexico
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Zhang C, Hu L, Wu X, Hu G, Ding X, Lu Y. A retrospective study on the aetiology, management, and outcome of brain abscess in an 11-year, single-centre study from China. BMC Infect Dis 2014; 14:311. [PMID: 24903315 PMCID: PMC4053580 DOI: 10.1186/1471-2334-14-311] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Accepted: 05/28/2014] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Brain abscesses continue to pose diagnostic and therapeutic challenges in developed and developing countries. Their aetiology and management remain complex and unclear, making improvement of treatments and outcome difficult. METHODS To determine the demographics, management, and the variables that affect the outcome in subjects with brain abscesses treated at a single centre over an 11-year period, we retrospectively analysed data in 60 patients with brain abscesses surgically treated with stereotactically guided aspiration or open craniotomy excision in Shanghai Changzheng Hospital between January 2001 and December 2011. Such variables as age, gender, Glasgow Coma Scale (GCS) score at admission, clinical presentation, location, number of lesions, predisposing factors, mechanism of infection, aetiological agent, and therapy were analysed independently. RESULTS Our analysis demonstrated that patient age and gender were factors that influence the occurrence of brain abscess; female patients and patients greater than 40 years of age were most likely to suffer a brain abscess. We also found that a patient's GCS score upon admission did not influence outcome. While frequency of successful culturing of the infectious agent was low, positive cultures were obtained in only 8 of the cases (13.33%), in which the most common isolate was Streptococcus milleri. Outcome was favourable in 78.33% of the subjects, while the mortality rate was 20%. The outcome of one patient was poor due to the abscess in the basal ganglia region. CONCLUSIONS Stereotactically guided aspiration is an effective treatment for brain abscess with an overall favourable outcome. Mortality due to brain abscess was not directly related to surgery nor surgical technique. Additional studies will continue to reveal patients trends that may improve treatment for brain abscess.
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Affiliation(s)
- Chenran Zhang
- Department of Neurosurgery, Changzheng Hospital, Second Military Medical University, No. 415, Feng-Yang Road, Shanghai 200003, China
| | - Liuhua Hu
- Department of Cardiology, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People’s Republic of China
| | - Xiaojun Wu
- Department of Neurosurgery, Changzheng Hospital, Second Military Medical University, No. 415, Feng-Yang Road, Shanghai 200003, China
| | - Guohan Hu
- Department of Neurosurgery, Changzheng Hospital, Second Military Medical University, No. 415, Feng-Yang Road, Shanghai 200003, China
| | - Xuehua Ding
- Department of Neurosurgery, Changzheng Hospital, Second Military Medical University, No. 415, Feng-Yang Road, Shanghai 200003, China
| | - Yicheng Lu
- Department of Neurosurgery, Changzheng Hospital, Second Military Medical University, No. 415, Feng-Yang Road, Shanghai 200003, China
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Krzyściak W, Pluskwa KK, Jurczak A, Kościelniak D. The pathogenicity of the Streptococcus genus. Eur J Clin Microbiol Infect Dis 2013; 32:1361-76. [PMID: 24141975 PMCID: PMC3824240 DOI: 10.1007/s10096-013-1914-9] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 06/11/2013] [Indexed: 12/11/2022]
Abstract
Streptococcus infections are still one of the important problems facing contemporary medicine. As the World Health Organization (WHO) warns, Streptococcus pneumoniae is responsible for the highest number of pneumonia cases all over the world. Despite an increasing number of pneumococcal vaccinations, incidences of disease connected to this pathogen's infection stay at the same level, which is related to a constantly increasing number of infections caused by nonvaccinal serotypes. Unfortunately, the pathogenicity of bacteria of the Streptococcus genus is also connected to species considered to be physiological flora in humans or animals and, additionally, new species exhibiting pathogenic potential have been discovered. This paper presents an opinion concerning the epidemiology of streptococci infections based on case studies and other publications devoted to this problem. It also sheds new light based on recent reports on the prevention of protective vaccinations application in the case of streptococci infections.
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Affiliation(s)
- W Krzyściak
- Department of Medical Diagnostics, Pharmacy Faculty, Jagiellonian University Medical College, 9 Medyczna St., 30-688, Krakow, Poland,
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LacR mutations are frequently observed in Streptococcus intermedius and are responsible for increased intermedilysin production and virulence. Infect Immun 2013; 81:3276-86. [PMID: 23798532 DOI: 10.1128/iai.00638-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Streptococcus intermedius secretes a human-specific cytolysin, intermedilysin (ILY), which is considered to be the major virulence factor of this pathogen. We screened for a repressor of ily expression by using random gene disruption in a low-ILY-producing strain (PC574). Three independent high-ILY-producing colonies that had plasmid insertions within a gene that has high homology to lacR were isolated. Validation of these observations was achieved through disruption of lacR in strain PC574 with an erythromycin cassette, which also led to higher hemolytic activity, increased transcription of ily, and higher cytotoxicity against HepG2 cells, compared to the parental strain. The direct binding of LacR within the ily promoter region was shown by a biotinylated DNA probe pulldown assay, and the amount of ILY secreted into the culture supernatant by PC574 cells was increased by adding lactose or galactose to the medium as a carbon source. Furthermore, we examined lacR nucleotide sequences and the hemolytic activity of 50 strains isolated from clinical infections and 7 strains isolated from dental plaque. Of the 50 strains isolated from infections, 13 showed high ILY production, 11 of these 13 strains had one or more point mutations and/or an insertion mutation in LacR, and almost all mutations were associated with a marked decline in LacR function. These results strongly suggest that mutation in lacR is required for the overproduction of ILY, which is associated with an increase in pathogenicity of S. intermedius.
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