Antibiotic Susceptibility of the First Streptococcus Constellatus Isolated from Epidural Abscess in Dakar

Streptococcus constellatus can sometimes cause serious invasive infections, as infections of the liver and lung, brain abscesses, bacteraemia, endocarditis and intra-abdominal infections. The study aimed to identify S.constellatus and to assess their susceptibility to several antibiotics. Methods: In a 59-year-old patient hospitalized in intensive unit care for an epidural abscess, pus was collected and bacterial were grown, then bacterial identifi cation was performed by routine laboratory methods. Antimicrobial susceptibility testing was performed using standard disk diffusion method and MIC of several antibiotics was determined by using the BioMérieux Vitek 2. Results: S.constellatus was identifi ed in abscess and was resistant to penicillin, aminoglycosides, macrolides, lincomycin, and fl uoroquinolones. Only vancomycin, pristinamycin and rifampin were active. Conclusion: S.constellatus is considered commensal organism, but identifi cation and antibiotic susceptibility of this species are necessary for good management of the abscess. Research Article Antibiotic Susceptibility of the First Streptococcus Constellatus Isolated from Epidural Abscess in Dakar Assane Dieng1*, Serigne ML Ndiaye1, Khadidiatou Gueye1, Frederic C Diaz1, Samba Diao1, Safi etou Ngom1, Habsa Diagne1, Moustapha Cisse1, Maguette Diop1, Pape I Ndiaye2, Makhtar Camara1 and Cheikh SB Boye1 1Bacteriology and Virology Laboratory, Aristide Le Dantec teaching Hospital, Dakar, Senegal 2Intensive care unit, Aristide Le Dantec teaching Hospital, Dakar, Senegal Dates: Received: 06 December, 2017; Accepted: 16 December, 2017; Published: 18 December, 2017 *Corresponding author: Assane Dieng, Bacteriology and Virology Laboratory, Aristide Le Dantec teaching Hospital, Dakar, Senegal, P.O. Box 3001,30 Avenue Pasteur Dakar, Senegal, Tel: +221338225919; E-mail:


Introduction
Streptococcus constellatus is member of the Streptococcus anginosus Group (SAG) that are considered commensal organisms [1]. SAG isolates are part of the normal fl ora of the human respiratory, gastrointestinal and genitourinary tracts [2]. However, they can sometimes cause serious invasive infections, as infections of the liver and lung, brain abscesses, bacteraemia, endocarditis and intra-abdominal infections [3,4].
One of the most striking features of species in the SAG is their tendency to cause abscesses and S. intermedius and S.
constellatus are the main causes of deep abscess [5].
In most care of abscess, some type of drainage procedure associated with appropriate antibiotic treatment is suffi cient [5].
SAG is generally considered to be susceptible to betalactam antibiotics and macrolides. However, increasingly; we are seeing the emergence of viridans and beta-haemolytic streptococci resistant to antibiotic [6].
In Senegal there is no data on S. Constellatus and this is the fi rst strains isolated from abscess in Dakar.
The study aimed to identify S.constellatus and to assess their susceptibility to several antibiotics.

Materials and Methods
In a 59-year-old patient hospitalized in intensive unit care for an epidural abscess, pus was collected and bacterial were grown. S.constellatus suspension were diluted to obtain a fi nal concentration of 10 5 CFU/mL (an optical density of 0.5 on the McFarland scale) and inoculated on Mueller-Hinton supplemented with 5% sheep blood.
Plates were incubated at 37 C under CO2 atmosphere for 18-24 hours.
Quality control for antimicrobial susceptibility testing was performed using the ATCC 49619 strains of S.pneumoniae.
Susceptibility was determined based on Clinical Laboratory Standards Institute (CLSI) break points [7].
Also, MIC of several antibiotics was determined by using the BioMérieux Vitek 2.

Results
Bacterial identifi cation was S. constellatus. However, cefotaxim, pristinamycin, rifampin and vancomycin showed good activity with low MIC values of 0.25 mg/l and 1mg/l respectively.

Discussion
In our study, S.constellatus was isolated from epidural abscess in patient hospitalized. This was the fi rst this strain has been isolated in Senegal. However in other countries, S.constellatus were identifi ed as the cause of infections, including infections of liver and lung, brain abscesses, bacteraemia, endocarditis, invasive pyogenic infection 3,4,8].
Diffi culties in identifi cation strains isolates of the "Streptococcus anginosus group" (SAG; Streptococcus intermedius, Streptococcus constellatus, and Streptococcus anginosus), have caused confusion in determining their pathogenic potential, but using new powerful tool for rapid identifi cation bacteria, makes it possible to differentiate these organisms [5]. Thus, it is necessary to equip the laboratories for good management of infectious diseases.
SAG was generally susceptible to penicillin, other betalactam antibiotics and macrolides [2, 9,10]. However, in our study S.constellatus were resistant to penicillin, aminoglycosides, macrolides, lincomycin and fl uoroquinolones. Macrolides and clindamycin resistance SAG were observed in other studies [11]. Also fl uoroquinolones resistance SAG were observed in Germany, while they are habitually used for the therapy of purulent infections [2]. Our fi ndings demonstrate that antibiotics resistance has emerged among SAG isolates.
Only vancomycin, pristinamycin and rifampin were active and should be therefore used in abscesses treatment.

Conclusion
S.constellatus is considered commensal organism, but identication and antibiotic susceptibility of this species are necessary for good management of the abscess.