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| Year : 2010 | Volume
: 53
| Issue : 1 | Page : 187-188 |
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| Biotype and antibiotic resistance pattern of group A streptococci |
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Yukthi Sharma, Shashidhar Vishwanath, Indira Bairy
Department of Microbiology, Kasturba Medical College, Manipal-576 104, India
Click here for correspondence address and email
| Date of Web Publication | 19-Jan-2010 |
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How to cite this article:
Sharma Y, Vishwanath S, Bairy I. Biotype and antibiotic resistance pattern of group A streptococci. Indian J Pathol Microbiol 2010;53:187-8 |
Sir,
Group A Streptococci (Streptococcus pyogenes) which includes several serotypes has remained a significant human pathogen for centuries. This organism causes several infections including pharyngitis, pyoderma, cellulitis, necrotizing fasciitis, osteomyelitis, septic arthritis, bacteremia and pneumonia, and also initiates post infectious sequelae like acute rheumatic fever and glomerulonephritis. Strain characterization has assumed great importance in view of resurgence in the incidence of invasive Group A Streptococci (GAS) infections and rheumatic heart disease all over the world. Typing of GAS strains is usually based on antigenic variations of two surface molecules, M protein and T protein and production of serum opacity factor. [1] Molecular methods used for typing GAS are expensive, time consuming and difficult to interpret. [2] Hence there is a need for more reliable, economical and simple methods of GAS strain differentiation. An association between serotypes and biotypes has been shown and biotyping was found to be an easy method for rapid and preliminary characterization of strains. [1]
Penicillin remains the drug of choice in treatment of GAS infections and their sequelae. However, in patients allergic to penicillin, alternative antibiotics such as macrolides and quinolones are prescribed.
There are very few reports on GAS biotypes in India and with increasing number of reports on resistance to penicillin alternatives among GAS, a study was carried out to characterize S. pyogenes strains isolated from throat and wound swabs by biotyping and assess the burden of antibiotic resistance among these strains. As recent studies suggest that biofilm may also have a role in S. pyogenes infections, [3] biofilm producing ability was also determined for all the isolates.
Throat swabs obtained from cases of pharyngitis and wound swabs from pyoderma cases were processed and b-hemolytic streptococci were identified following standard operating procedures. Grouping of strains was done using Streptex kit (Remel Europe Ltd, Dartford, Kent, UK). GAS isolates were biotyped as previously described by Bouvet et al. [4] according to the presence or absence of b-glucuronidase, combined with their ability to ferment mannitol, glycogen, cyclodextrin, pullulan and methyl-b-D-glucopyranoside. Minimum inhibitory concentration for penicillin, erythromycin and cefadroxil (Hi-Media Laboratories, Mumbai, India) were determined by agar dilution method on Mueller-Hinton blood agar and interpreted according to Clinical Laboratory Standards Institute (CLSI) guidelines. Biofilm production was determined by quantitative adherence assay. [3]
A total of 34 GAS isolates were obtained. Of these, 23 (67.6%) were from pharyngitis cases and 11 (32.4%) from pyoderma cases. Biotyping delineated six different biotypes among throat isolates and four different biotypes among isolates from pyoderma. Biotypes 4 and 10 were the most frequent (9/34, 26.5% each), followed by biotype 2 (6/34, 17.6%). Two strains (5.9%) were untypeable (As shown in [Table 1]). Of the few previous reports of GAS biotypes causing infections in India, Thangam Menon et al.[1] at Chennai reported biotype 4 as the most frequent biotype and Palani kumar et al.[2] observed biotype 10 as to be the most frequent among clinical isolates. This association of specific biotypes with clinical disease suggests that there may be a pathogenic association of some biotypic characteristics with virulence factors. [2]
MIC values for penicillin and cefadroxil in all the 34 isolates remained within the susceptible range. Physicians who treat streptococcal infections routinely have relied on the fact that GAS remain universally susceptible to penicillin. Despite the fact that penicillin has been used for several decades, there has never been a penicillin resistant strain of GAS isolated from a patient. Therefore, at present, penicillin is still considered the first-line therapy in the treatment of most GAS infections. The pattern of universal sensitivity to penicillin found in this study is similar to the findings in several earlier reports worldwide. [5],[6],[7] Erythromycin is the antibiotic of choice in penicillin-allergic patients and has been shown to be as effective as penicillin in eradicating GAS from the pharynx. However, in contrast to the universal susceptibility of GAS strains to penicillin in vitro, resistance to erythromycin and related antibiotics has been widely reported and the prevalence of erythromycin resistance has been reported to vary from 1.3% to greater than 45% in various studies in India and western countries. [7] The increase in resistance is mediated either through target modification caused by methylase activity encoded by two classes of methylase genes, ermAM and ermTR, or by an active drug-efflux pump encoded by the mefA gene. [5]
In the present study, 38.23% of the GAS isolates were resistant to erythromycin, which is much higher to that observed by Brahmadathan et al. [5] at Vellore (13.8%) and Charmaine A. C. Lloyd et al. [6] at Chennai (16.2%). The higher rates of resistance to erythromycin found in this study could be probably due to extensive use of macrolides. There are also reports of resistance to other important drug alternatives such as clindamycin and fluoroquinolones. [6]
In the present study, 22 of the 34 isolates (64.7%) showed biofilm production. Biofilm production was maximum with biotypes 4 and 10 (77.8% each). Of the 22 biofilm producing strains, seven (31.8%) were resistant to erythromycin. However, Baldassarri L et al. [3] found that up to 90% of the GAS isolates could form biofilm. These biofilms may have a role in successful colonization and in difficulty of eradication of GAS.
In conclusion, biotyping appears to be a simpler and more economical method of characterizing GAS strains. There is a need for continuous local monitoring of resistance patterns of GAS to macrolides and other alternative drugs so as to avoid possible treatment failures. Further studies are also required to understand the possible role of biofilms in the survival strategy of S. pyogenes as several cases of recurrent infections, treatment failures of Streptococcal pharyngitis, and persistent throat carriage of S. pyogenes have been reported in the absence of in vitro resistance to Penicillin.
 References | |  |
| 1. | Menon T, Shanmughasundaram S, Palani Kumar M, Girish Kumar CP. Group A Streptococcal infections of the pharynx in a rural population in south India. Indian J Med Res 2004;119:171-3.  |
| 2. | Kumar MP, Menon T, Lobo C, Anbumani N, Kumar CP, Shanmugasundaram S. Biotypes of group A Streptococci isolated from children. J Med Microbiol 2004;53:229-30. [PUBMED] [FULLTEXT] |
| 3. | Baldassarri L, Creti R, Recchia S, Imperi M, Facinelli B, Giovanetti E, et al. Therapeutic failures of antibiotics used to treat Macrolide-Susceptible Streptococcus pyogenes infections may be due to biofilm formation. J Clin Microbiol 2006;44:2721-7. [PUBMED] [FULLTEXT] |
| 4. | Bouvet A, Geslin P, Kriz-Kuzemenska P, Blanc V, Devine C, Grimont F. Restricted association between biotypes and serotypes within group A Streptococci. J Clin Microbiol 1994;32:1312-7. [PUBMED] [FULLTEXT] |
| 5. | Brahmadathan KN, Anitha P, Gladstone P. Increasing erythromycin resistance among group A Streptococci causing tonsillitis in a tertiary care hospital in southern India. Clin Microbiol and Infect 2005;11:335-7. |
| 6. | Lloyd CA, Jacob SE, Menon T. Antibiotic resistant b-hemolytic Streptococci. Indian J Pediatr 2007;74:1077-80. [PUBMED] [FULLTEXT] |
| 7. | Mathur P, Kapil A, Das B, Dhawan B, Dwivedi SN. Invasive b-hemolytic Streptococcal infections in a tertiary care hospital in northern India. J Med Microbiol 2002;51:791-2. [PUBMED] [FULLTEXT] |
Correspondence Address:
Indira Bairy
Department of Microbiology, Kasturba Medical College, Manipal - 576 104
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0377-4929.59233
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