Comparative Susceptibility of Clinical Group A, B, C, F, and G β-Hemolytic Streptococcal Isolates to 24 Antimicrobial Drugs

Abstract

A total of 312 clinical β-hemolytic streptococcal isolates (Streptococcus pyogenes, group A = 63; Streptococcus agalactiae, group B = 145; group C = 50; group F = 27; group G = 27) were examined for susceptibility to 23 and 24 antimicrobial drugs with the Bauer-Kirby agar disk diffusion and the agar dilution method, respectively. Sheep blood Mueller-Hinton agar served as the reference medium. Wilkins-Chalgren agar supported optimal growth of group A and B, but not of all group C, F, and G streptococci. The group A streptococci were susceptible to all β-lactam antibiotics, clindamycin, chloramphenicol, rifampin, teicoplanin, and vancomycin, but resistant to cotrimoxazole, fusidic acid, and, except for 2 strains, to fosfomycin. Resistance (R)/intermediate susceptibility (I) rates (R/I%) to ciprofloxacin (0/2%), ofloxacin (1/2%), erythromycin (1.6 / 0%), and clarithromycin (0/1%) were low. Higher resistance rates were noted with tetracyclines (doxycycline 23.8/15.9%; tetracycline 39.7/3.2%). Among the group B streptococcal isolates, one strain was resistant against oxacillin and of intermediate susceptibility to penicillin G and cefoxitin. All isolates were susceptible to teicoplanin and rifampin. Conversely, all group B isolates were resistant to cotrimoxazole and fusidic acid; 69% and 51 % of these isolates were susceptible to fosfomycin and rifampin, respectively. R/I rates of the group B streptococcal isolates were low for ciprofloxacin and ofloxacin (0/0.7%), clindamycin (0.7/0%), erythromycin (1.4/ 3.5%), clarithromycin (1.4/0%), and chloramphenicol (0.7/0%). Resistance to tetracyclines was significant (doxycycline: 72.4/2.1%; tetracycline: 74.5/1.4%). Among the non-A, non-B β-hemolytic streptococci, 2 group C strains were resistant to oxacillin and showed intermediate susceptibility to penicillin G. All isolates were susceptible to third and fourth-generation cephalosporins, imipenem, chloramphenicol, rifampin, teicoplanin, and vancomycin. R/I rates to the other antimicrobial drugs were: ciprofloxacin (3.9/1.9%), ofloxacin (2.9/1.9%), clindamycin (2.9/1%), erythromycin (5.8/0%), clarithromycin (3.8/2.9%), and cotrimoxazole (16.4/3.9%). Resistance against tetracyclines was more frequent (doxycycline: 18.3/2.9%; tetracycline: 20.2/6.7%). On the basis of various minor discrepancies between MIC and disk diffusion test results, it is proposed that the current NCCLS inhibition zone (diameter, mm) criteria indicative of intermediate susceptibility of β-hemolytic streptococci be changed for the following antimicrobial drugs: ampicillin: 22-27 mm (only for group A and B β-hemolytic streptococci); ciprofloxacin: 16-18 mm; clindamycin: 15-18 mm; doxycycline: 17-19 mm; tetracycline: 17-19 mm, and erythromycin: 14-19 mm.

Antimicrobial susceptibility pattern of beta-haemolytic group A, C and G streptococci isolated from North India

“…The high resistance (25.5 %) of GAS to tetracycline reported here is comparable to the global rise noticed (Aggarwal et al, 1984;Dhakal et al, 2010;Jain et al, 2008;Lloyd et al, 2007;Ray et al, 2010;Smeesters et al, 2010;Traub & Leonhard, 1997;Zaoutis et al, 1999) that has been assigned to polyclonal dissemination of resistance types, as antibiotic resistance encoded by transposable elements does occur in GAS. GAS resistance (3.9 %) to chloramphenicol and susceptibility to vancomycin reported in this study are similar to results from previous reports (Jain et al, 2008).…”

“…Worldwide data suggest an increased resistance of GAS to macrolides, ranging from 0. A Cd E At Cw T C Nv Ak G Throat isolates 11 + 2 2 2 2 2 + 2 2 2 57 2 2 2 + + + 2 2 2 2 85 2 + + 2 2 2 2 2 2 2 Skin isolates 12 2 2 2 2 + 2 + + 2 2 22.8 2 2 2 + 2 2 + 2 2 2 44 2 2 2 + 2 2 2 + 2 2 44 + 2 2 + 2 + 2 2 2 2 44 2 2 + 2 2 2 2 + 2 2 44 2 2 2 + 2 2 2 + 2 2 44 2 2 2 + + + 2 + 2 2 44 2 2 2 2 2 2 2 2 2 2 49 2 2 2 + + + 2 2 2 2 75.1 2 2 2 2 2 + 2 + 2 2 81 2 2 + 2 2 2 2 2 + 2 81 2 2 2 2 2 + 2 + 2 + 85 2 2 2 2 2 + 2 + 2 2 RF isolates 11 2 2 2 2 2 + 2 + 2 2 67 2 2 2 2 2 + 2 + 2 2 Invasive disease isolates 58 2 2 2 2 2 + + 2 2 2 87 2 2 + 2 2 + 2 2 + 2 95 2 2 2 2 2 + 2 + + 2 Rowe et al, 2009;Traub & Leonhard, 1997); a review of Indian literature showed a gradual increase upto 29.4 % up until 2010 (Brahmadathan et al, 2005;Capoor et al, 2006;Dhakal et al, 2010;Lloyd et al, 2007;Mathur et al, 2002). The absence of, or very low, erythromycin resistance among GAS from pharyngitis and RF patients in the present study is quite similar to previous findings (Brahmadathan et al, 2005;Rijal et al, 2009).…”

Susceptibility to antimicrobials and mechanisms of erythromycin resistance in clinical isolates of Streptococcus agalactiae from Rio de Janeiro, Brazil

“…By agar-dilution assay for MIC determination (National Committee for Clinical Laboratory Standards, 2000b), we observed that the results were similar to those of the disc-diffusion assay, except for one isolate that showed intermediate susceptibility to erythromycin by the discdiffusion test and resistance by MIC determination. Similar discrepancy has been reported before (Traub & Leonhard, 1997). Total erythromycin resistance in the period of study was 5·4 %, which is similar to values reported recently in other countries (Fernandez et al, 1998;de Azavedo et al, 2001).…”

“…Macrolides are a useful alternative therapy in penicillinallergic patients; however, emergence of strains resistant to macrolides has been observed in several countries, at a frequency ranging from 2 to 46 % (Traub & Leonhard, 1997;Hsueh et al, 2001). …”

Macrolide and tetracycline resistance in clinical strains of Streptococcus agalactiae isolated in Tunisia

“…A high rate of tetracycline resistance was noted in our study, as was described in other studies performed in different countries: USA (96 %), Germany (74.5 %) and France (88.1 %) (Lin et al, 2000;Traub & Leonhard, 1997;De Mouy et al, 2001).…”