Susceptibility to telithromycin in 1,011 Streptococcus pyogenes isolates from 10 central and Eastern European countries

Distribution of macrolide resistance mechanisms in Bulgarian clinical isolates of Streptococcus pyogenes during the years of 2013-2016

Streptococcus pyogenes, or group A streptococcus (GAS), is the main etiological agent of bacterial tonsillopharyngitis and a common cause of a wide variety of other mild to severe infections.

OBJECTIVES

Objectives of the present study was to determine and evaluate the distribution of genetic mechanisms associated with certain phenotypes of macrolide resistance in Bulgarian GAS isolated during the years of 2013-2016.

METHODS

All GAS strains were screened for the macrolide resistance genes erm(A), erm(B) and mef(A), using multiplex polymerase chain reaction (PCR). The minimal inhibitory concentrations (MICs) of erythromycin, azithromycin, clarithromycin, clindamycin were determined by E-tests.

RESULTS

Almost 23% of GAS isolates obtained in 2013-2014 and near 40% of them in 2015-2016 contained various elements of resistance. The predominant gene was mef(A), which encodes an efflux pump (M-phenotype), identified in 57.84% of the macrolide-resistant strains. The next frequently prevalent mechanism was a combination of mef(A) and erm(B) in 22.55%, which determined high-level inducible or constitutive resistance to macrolides, lincosamides and streptogramins (iMLSB or cMLSB). The highest MIC value (>256mg/L) was detected in association with erm(B) (p<0.05). The MIC range was observed to be much higher in the isolates with combinations of resistance genes vs. those with mef genes alone (p<0.05).

CONCLUSION

The data about the distribution and prevalence of macrolide resistance mechanisms obtained in this study can help in the treatment of persistent and recurrent GAS infections and in the correct choice of empiric therapy.

Group A beta-hemolytic streptococcal pharyngitis and carriage rate among Egyptian children: a case-control study

BACKGROUND

Improper prescription of antibiotics for treatment of acute pharyngitis predisposes to emergence of a carrier state and antibiotic-resistant strains of group A streptococci (GAS). We sought to identify the frequency and antimicrobial susceptibility patterns of group A streptococci among Egyptian children with acute pharyngitis compared with asymptomatic children.

DESIGN AND SETTING

Case-control study conducted from September 2013 to August 2014 at a pediatric outpatient clinic in Egypt.

PATIENTS AND METHODS

Throat swabs were collected from children with acute pharyngitis and from asymptomatic children. We evaluated the accuracy of McIsaac scores and the rapid antigen detection test (RADT) for diagnosis of GAS pharyngitis with throat culture as a reference test. Antimicrobial susceptibility testing of GAS isolates was done by the disc diffusion method.

RESULTS

Of 142 children with acute pharyngitis (cases) and 300 asymptomatic children (controls) (age range, 4-16 years), GAS pharyngitis was diagnosed in 60/142 children (42.2%); 48/300 (16%) were found to be carriers. All GAS isolates in the case group were sensitive to penicillin; however, an MIC90 (0.12 micro g/mL) for penicillin is high and an alarming sign. The resistance rate to macrolides was 70% with the cMLSB phenotype in 65.1%. The sensitivities and specificities were 78.3% and 73.2% for McIsaac score of >=4 and 81.1% and 93.9% for RADT, respectively. GAS isolates in the control group were 100% sensitive to penicillin, while 12.5% and 37.5% were resistant to macrolides and tetracycline, respectively.

CONCLUSION

An increased MIC90 for GAS isolates to penicillin is an alarming sign. A high frequency of resistance to macrolides was also observed.

Antibiotic susceptibility of streptococcus pyogenes isolated from respiratory tract infections in dakar, senegal

Group A Streptococcus (GAS) is one of the major causes of respiratory tract infections. The objectives of this study were to identify isolates of S. pyogenes obtained from respiratory tract infections, and to assess their susceptibility to several antibiotics. A total of 40 strains were isolated and their susceptibility to 17 antibiotics was tested using a standard disk diffusion method. The minimum inhibitory concentrations (MICs) were determined using the E-test. All isolates were sensitive to β-lactam antibiotics including penicillin, amoxicillin, and cephalosporins. Macrolides remain active with the exception of spiramycin, which showed reduced susceptibility. Out of the 40 isolates, 100% of the isolates were resistant to tetracycline. Interestingly, isolates were sensitive to chloramphenicol, teicoplanin, vancomycine, and levofloxacin, providing potential alternative choices of treatment against infections with S. pyogenes.

Alterations in regulatory regions of erm(B) genes from clinical isolates of enterococci resistant to telithromycin

We determined rates of resistance to the ketolide telithromycin in 56 Enterococcus faecalis isolates and 44 Enterococcus faecium isolates collected from hospitals in Korea between 2005 and 2006. Twenty nine (51.8%) isolates of E. faecalis and 35 (79.5%) isolates of E. faecium were resistant to telithromycin (minimum inhibitory concentrations, ≥ 4 μg/mL). All of the telithromycin-resistant E. faecalis carried the erm(B) gene only. Of the telithromycin-resistant E. faecium, 29 resistant strains carried erm(B) only, the other six carried erm(A) and erm(B) together. The nucleotide sequence of the erm(B) regulatory regions from 29 E. faecalis and 29 E. faecium isolates with erm(B) only was analyzed. Five types of alterations were detected. The first and second types had point mutations that destabilize the secondary structure of erm(B) mRNA sequestering the translation initiation region of the structural gene. The third type was identical to erm(Bv1), a previously reported variant of erm(B) with different induction specificity. The fourth and fifth types had point mutations within the critical sequence for induction and a point mutation destabilizing the stem-loop of erm(B) mRNA sequestering the translation initiation region of the structural gene.

Multistep resistance development studies of ceftaroline in gram-positive and -negative bacteria

Ceftaroline, the active component of the prodrug ceftaroline fosamil, is a novel broad-spectrum cephalosporin with bactericidal activity against Gram-positive and -negative isolates. This study evaluated the potential for ceftaroline and comparator antibiotics to select for clones of Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, Moraxella catarrhalis, Klebsiella pneumoniae, Staphylococcus aureus, and Enterococcus faecalis with elevated MICs. S. pneumoniae and S. pyogenes isolates in the present study were highly susceptible to ceftaroline (MIC range, 0.004 to 0.25 μg/ml). No streptococcal strains yielded ceftaroline clones with increased MICs (defined as an increase in MIC of >4-fold) after 50 daily passages. Ceftaroline MICs for H. influenzae and M. catarrhalis were 0.06 to 2 μg/ml for four strains and 8 μg/ml for a β-lactamase-positive, efflux-positive H. influenzae with a mutation in L22. One H. influenzae clone with an increased ceftaroline MIC (quinolone-resistant, β-lactamase-positive) was recovered after 20 days. The ceftaroline MIC for this isolate increased 16-fold, from 0.06 to 1 μg/ml. MICs for S. aureus ranged from 0.25 to 1 μg/ml. No S. aureus isolates tested with ceftaroline had clones with increased MIC (>4-fold) after 50 passages. Two E. faecalis isolates tested had ceftaroline MICs increased from 1 to 8 μg/ml after 38 days and from 4 to 32 μg/ml after 41 days, respectively. The parental ceftaroline MIC for the one K. pneumoniae extended-spectrum β-lactamase-negative isolate tested was 0.5 μg/ml and did not change after 50 daily passages.

In vitro activity of CEM-101 against Streptococcus pneumoniae and Streptococcus pyogenes with defined macrolide resistance mechanisms

CEM-101 had MIC ranges of 0.002 to 0.016 microg/ml against macrolide-susceptible pneumococci and 0.004 to 1 microg/ml against macrolide-resistant phenotypes. Only 3 strains with erm(B), with or without mef(A), had CEM-101 MICs of 1 microg/ml, and 218/221 strains had CEM-101 MICs of 64 microg/ml, while 17/19 strains had telithromycin MICs of 4 to 16 microg/ml; CEM-101 MICs were 0.015 to 1 microg/ml. By comparison, erm(A) and mef(A) strains had CEM-101 MICs of 0.015 to 0.5 microg/ml, clindamycin and telithromycin MICs of 64 microg/ml. Pneumococcal multistep resistance studies showed that although CEM-101 yielded clones with higher MICs for all eight strains tested, seven of eight strains had clones with CEM-101 MICs that rose from 0.004 to 0.03 microg/ml (parental strains) to 0.06 to 0.5 microg/ml (resistant clones); for only one erm(B) mef(A) strain with a parental MIC of 1 microg/ml was there a resistant clone with a MIC of 32 microg/ml, with no detectable mutations in the L4, L22, or 23S rRNA sequence. Among two of five S. pyogenes strains tested, CEM-101 MICs rose from 0.03 to 0.25 microg/ml, and only for the one strain with erm(B) did CEM-101 MICs rise from 1 to 8 microg/ml, with no changes occurring in any macrolide resistance determinant. CEM-101 had low MICs as well as low potential for the selection of resistant mutants, independent of bacterial species or resistance phenotypes in pneumococci and S. pyogenes.

In Vitro Activity of Antimicrobial Agents against Streptococcus Pyogenes Isolates from Patients with Acute Tonsillopharyngitis in Dakar, Senegal

Streptococcus pyogenes ( S. pyogenes) is the most important causative agent of tonsillopharyngitis. Beta-lactam antibiotics, particularly penicillin, are the drug of first choice and macrolides are recommended for patients who are allergic to penicillin. However, other antibiotics are also used for the treatment of streptococcal tonsillopharyngitis. In recent years, the increase in the incidence of respiratory tract pathogens that are resistant to current antibacterial agents highlights the need to monitor the evolution of the resistance of these pathogens to antibiotics. In this study, we assess the susceptibility of 98 isolates of S. pyogenes to 16 antibiotics. The pathogens were recovered from patients with acute tonsillopharyngitis in Dakar, the Senegalese capital city, who were recruited from May 2005 to August 2006. All strains were susceptible to penicillin with low Minimum Inhibitory Concentration (MIC = 0,016 mg/L). Amoxicillin had high activity (100%) showing its importance in treatment of streptococcal infections. Cephalosporins had MIC90 values ranging from 0.016 to 0.094 mg/L. Macrolides have shown high activity. All strains were resistant to tetracyclin. Other molecules such as teicoplanin, levofloxacin and chloramphenicol were also active and would represent alternatives to treatment of tonsillopharyngitis due to this pathogen. These results indicate that no significant resistance to antibiotics was found among patients with tonsillopharyngitis studied in Dakar. Limitations of this study were that the number of isolates tested was small and all isolates were collected from one hospital in Dakar. Hence, results may not be representative of the isolates found, in the wider community or other regions of Senegal. Further studies are needed in other parts of Dakar and other geographic regions of Senegal, in order to better clarify the antibiotic susceptibility profile of S. pyogenes isolates recovered from patients with tonsillopharyngitis.

Evidence of a conjugal erythromycin resistance element in the Lyme disease spirochete Borrelia burgdorferi

We report the identification of isolates of Borrelia burgdorferi strain B31 that exhibit an unusual macrolide-lincosamide (ML) or macrolide-lincosamide-streptogramin A (MLS(A)) antibiotic resistance pattern. Low-passage isolates were resistant to high levels (>100 microg/mL) of erythromycin, spiramycin and the lincosamides but were sensitive to dalfopristin, an analogue of streptogramin B. Interestingly, the high-passage erythromycin-resistant strain B31 was resistant to quinupristin, an analogue of streptogramin A (25 microg/mL). Biochemical analysis revealed that resistance was not due to antibiotic inactivation or energy-dependent efflux but was instead due to modification of ribosomes in these isolates. Interestingly, we were able to demonstrate high-frequency transfer of the resistance phenotype via conjugation from B. burgdorferi to Bacillus subtilis (10(-2)-10(-4)) or Enterococcus faecalis (10(-5)). An intergeneric conjugal system in B. burgdorferi suggests that horizontal gene transfer may play a role in its evolution and is a potential tool for developing new genetic systems to study the pathogenesis of Lyme disease.

Self-medication with antibiotics in Lithuania

OBJECTIVES

Excessive and not always proper use of antibiotic give rise to numerous problems, of which antimicrobial resistance, currently cause for worldwide concern, is the major one. Few single studies of antibiotic use have been carried out in some countries. This study was performed to estimate the prevalence of antibiotic use in the general population of Lithuania with special interest in self-medication with antibiotics and sources of their acquisition.

MATERIALS AND METHODS

Structured questionnaires on antibiotic use during the last 12 months were mailed to randomly selected adults and 746 of them were finally analyzed.

RESULTS

It was found that 39.9% of respondents reported antibiotic use during the last 12 months preceding the study and 53.2% of those used them in self-medication. In general, 22.0% (95%CI: 19.1-25.1) of respondents used antibiotics without prescription, whereas 45.0% (95%CI: 41.3-48.7) of them used antibiotics for intended self-administration. Adjustment for all the factors revealed the impact of the occupation, place of residence and presence of chronic disease on self-medication with antibiotics. Representatives of managerial, executive and professional occupations used non-prescribed antibiotics 8.38 times more often (95% CI: 1.76-39.91, p = 0.01) than retired people. Healthy people showed the tendency to self-medication 2.04 times more frequently than those with chronic diseases (95%CI: 1.11-3.75, p = 0.02). Rural people used non-prescribed antibiotics 1.79 times more often than inhabitants of urban areas (95%CI: 1.00-3.18, p = 0.049). Community pharmacies proved to be the most frequent (86.0%) source of over-the-counter antibiotics. Tonsillitis, bronchitis, and upper respiratory infections were the major reasons for self-medication with antibiotics.

CONCLUSIONS

The high prevalence of self-medication with antibiotics was found in Lithuania. The study indicated the need for more strict control of antibiotic sales and promotion of education of the correct use of antibiotic among Lithuanian people.

In vitro efficacy, resistance selection, and structural modeling studies implicate the malarial parasite apicoplast as the target of azithromycin

Azithromycin (AZ), a broad-spectrum antibacterial macrolide that inhibits protein synthesis, also manifests reasonable efficacy as an antimalarial. Its mode of action against malarial parasites, however, has remained undefined. Our in vitro investigations with the human malarial parasite Plasmodium falciparum document a remarkable increase in AZ potency when exposure is prolonged from one to two generations of intraerythrocytic growth, with AZ producing 50% inhibition of parasite growth at concentrations in the mid to low nanomolar range. In our culture-adapted lines, AZ displayed no synergy with chloroquine (CQ), amodiaquine, or artesunate. AZ activity was also unaffected by mutations in the pfcrt (P. falciparum chloroquine resistance transporter) or pfmdr1 (P. falciparum multidrug resistance-1) drug resistance loci, as determined using transgenic lines. We have selected mutant, AZ-resistant 7G8 and Dd2 parasite lines. In the AZ-resistant 7G8 line, the bacterial-like apicoplast large subunit ribosomal RNA harbored a U438C mutation in domain I. Both AZ-resistant lines revealed a G76V mutation in a conserved region of the apicoplast-encoded P. falciparum ribosomal protein L4 (PfRpl4). This protein is predicted to associate with the nuclear genome-encoded P. falciparum ribosomal protein L22 (PfRpl22) and the large subunit rRNA to form the 50 S ribosome polypeptide exit tunnel that can be occupied by AZ. The PfRpl22 sequence remained unchanged. Molecular modeling of mutant PfRpl4 with AZ suggests an altered orientation of the L75 side chain that could preclude AZ binding. These data imply that AZ acts on the apicoplast bacterial-like translation machinery and identify Pfrpl4 as a potential marker of resistance.

Activity of retapamulin against Streptococcus pyogenes and Staphylococcus aureus evaluated by agar dilution, microdilution, E-test, and disk diffusion methodologies

The in vitro activity of retapamulin against 106 Staphylococcus aureus isolates and 109 Streptococcus pyogenes isolates was evaluated by the agar dilution, broth microdilution, E-test, and disk diffusion methodologies. Where possible, the tests were performed by using the CLSI methodology. The results of agar dilution, broth microdilution, and E-test (all with incubation in ambient air) for S. aureus yielded similar MICs, in the range of 0.03 to 0.25 microg/ml. These values corresponded to zone diameters between 25 and 33 mm by the use of a 2-microg retapamulin disk. Overall, 99% of the agar dilution results and 95% of E-test results for S. aureus were within +/-1 dilution of the microdilution results. For S. pyogenes, the MICs obtained by the agar and broth microdilution methods (both after incubation in ambient air) were in the range of 0.008 to 0.03 microg/ml, and E-test MICs (with incubation in ambient air) were 0.016 to 0.06 microg/ml. For S. pyogenes, 100% of the agar dilution MIC results were within +/-1 dilution of the broth microdilution results. E-test MICs (after incubation in ambient air) were within +/-1 and +/-2 dilutions of the broth microdilution results for 76% and 99% of the isolates, respectively. E-test MICs for S. pyogenes strains in CO(2) were up to 4 dilutions higher than those in ambient air. Therefore, it is recommended that when retapamulin MICs are determined by E-test, incubation be done in ambient air and not in CO(2), due to the adverse effect of CO(2) on the activity of this compound. Diffusion zones (with incubation in CO(2)) for S. pyogenes were 18 to 24 mm. Retapamulin MICs for all strains by all methods (with incubation in ambient air) were < or =0.25 microg/ml. These results demonstrate that S. pyogenes (including macrolide-resistant strains) and S. aureus (including methicillin-resistant and vancomycin-nonsusceptible strains) are inhibited by very low concentrations of retapamulin and that all four testing methods are satisfactory for use for susceptibility testing.

Rapid inversion of the prevalences of macrolide resistance phenotypes paralleled by a diversification of T and emm types among Streptococcus pyogenes in Portugal

In Portugal erythromycin resistance of 26.6% (n = 352) remained constant during 1998 to 2003, however in 1998 the MLS(B) phenotype dominated (85%), whereas in 2003 the M phenotype prevailed (77%). A decline in T12/emm22 MLS(B) isolates could partially explain the drop in this phenotype, but the rise of the M phenotype was not due to clonal expansion.

Synthesis, Characterization and In Vitro Antimicrobial Activity of Novel Sulfonylureas of 15-Membered Azalides

Three series of the novel sulfonylurea derivatives of 15-membered azalides, i.e. 9a-N-[N'-(aryl)sulfonylcarbamoyl] (4a-4f, 5a-5f), 9a-N-{N'-[(aryl)sulfonylcarbamoyl-gamma-aminopropyl]} (10a-10f, 11a, 11c) and 9a-N-{N'-(beta-cyanoethyl)-N'-[(aryl)sulfonylcarabamoyl-gamma-aminopropyl]} (14a-14f, 15a, 15b, 15f) derivatives of 9-deoxo-9-dihydro-9a-aza-9a-homoerythromycin A (2) and 5-O-desosaminyl-9-deoxo-9-dihydro-9a-aza-9a-homoerythronolide A (3) were prepared and their structures elucidated by NMR and IR spectroscopic methods and mass spectrometry. Minimal inhibitory concentration (MIC) of these compounds was determined on a panel of sensitive and resistant Gram-positive and Gram-negative bacterial strains. Several compounds of the series of 9a-N-[N'-(aryl)sulfonylcarbamoyl] derivatives that showed significant improvements in activity against inducible resistant Streptococcus pyogenes strain were suggested for further optimization.

Alarming trend of clarithromycin-resistant Streptococcus pyogenes in Japan (1998-2002)

We investigated annual changes in clarithromycin resistance and resistance genes in 579 strains of Streptococcus pyogenes isolated from patients with symptomatic respiratory tract infections who visited primary medical institutions during the 5-year period from 1998 to 2002. The minimum inhibitory concentrations (MICs) of clarithromycin for S. pyogenes were measured using the standard broth microdilution method according to the National Committee for Clinical Laboratory Standards (NCCLS) guidelines, and strains showing MICs of 1 microg/ml or greater were regarded as being resistant to clarithromycin, according to the resistance standard specified by the NCCLS. The rates of S. pyogenes resistance to clarithromycin were 7.3% overall, 5.8% in 1998, 4.9% in 1999, 7.7% in 2000, 6.4% in 2001, and 11.1% in 2002. While the annual rates fluctuated slightly each year, an overall tendency to increase was observed during the 5-year period. Regarding the macrolide-resistance genes in the macrolide-resistant strains, mefA/E (+)/ ermB(-) was the most common genotype detected in these strains, while the ermB (+)/ mefA/E (-) and mef A/E (-)/ ermB (-) genotypes were detected at about the same rate. The MICs of clarithromycin for the ermB (+) strains tended to be higher than those of the mefA/E (+) strains, but some mefA/E (-) / ermB (-) strains also exhibited high MICs of clarithromycin, similar to those of the ermB (+) strains. The above results indicate that the number of clarithromycin-resistant strains of S. pyogenes is gradually increasing and that the resistance is becoming stronger; thus, special attention must be paid to the appearance of macrolide-resistant strains of S. pyogenes.

Ketolides: an emerging treatment for macrolide-resistant respiratory infections, focusing on S. pneumoniae

Resistance to antibiotics in community acquired respiratory infections is increasing worldwide. Resistance to the macrolides can be class-specific, as in efflux or ribosomal mutations, or, in the case of erythromycin ribosomal methylase (erm)-mediated resistance, may generate cross-resistance to other related classes. The ketolides are a new subclass of macrolides specifically designed to combat macrolide-resistant respiratory pathogens. X-ray crystallography indicates that ketolides bind to a secondary region in domain II of the 23S rRNA subunit, resulting in an improved structure-activity relationship. Telithromycin and cethromycin (formerly ABT-773) are the two most clinically advanced ketolides, exhibiting greater activity towards both typical and atypical respiratory pathogens. As a subclass of macrolides, ketolides demonstrate potent activity against most macrolide-resistant streptococci, including ermB- and macrolide efflux (mef)A-positive Streptococcus pneumoniae. Their pharmacokinetics display a long half-life as well as extensive tissue distribution and uptake into respiratory tissues and fluids, allowing for once-daily dosing. Clinical trials focusing on respiratory infections indicate bacteriological and clinical cure rates similar to comparators, even in patients infected with macrolide-resistant strains.

Antimicrobial susceptibility patterns and macrolide resistance genes of beta-hemolytic streptococci in Korea

In 540 beta-hemolytic streptococci, the rates of resistance to tetracycline, chloramphenicol, erythromycin, and clindamycin were 80.0, 22.8, 20.2, and 19.1%, respectively. Of the erythromycin-resistant isolates, 63.3% had the constitutive macrolide-lincosamide-streptogramin B (MLS(B)) resistance phenotype, 23.9% had the M phenotype, and 12.8% had the inducible MLS(B) resistance phenotype. The constitutive MLS(B) resistance phenotype with the erm(B) gene was dominant in Korea.

A rapid increase in macrolide resistance in Streptococcus pyogenes isolated in Poland during 1996-2002

OBJECTIVES

The aim of this study was to investigate Polish clinical isolates of Streptococcus pyogenes collected during a 7 year period using phenotypic and genotypic techniques.

METHODS

A total of 816 isolates of S. pyogenes recovered from 33 medical centres in Poland were tested for their susceptibility to various antimicrobial agents. Erythromycin-resistant isolates were analysed by PFGE, multilocus sequence typing and emm typing methods.

RESULTS

The tetracycline resistance rate was high (43%) among all S. pyogenes strains. Ninety-eight (12%) isolates were resistant to erythromycin. A low prevalence of the M phenotype (5.1%) associated with the presence of the mef(A) gene was found. All the isolates of the iMLSB phenotype harboured the erm(TR) gene. Out of the cMLSB isolates, 71.4% and 28.6% carried erm(TR) and erm(B), respectively. All isolates with erm(B) were resistant to telithromycin. PFGE analysis discerned 13 different patterns, A-N, with two predominant PFGE profiles--A (41 isolates) and B (25 isolates)--that in multilocus sequence typing corresponded, respectively, to a novel sequence type (ST) 367 and ST63. Overall, the representatives of these clones accounted for >90% of isolates of the iMLSB phenotype.

CONCLUSIONS

A significant increase in erythromycin resistance was observed among clinical S. pyogenes collected in Poland over a 7 year period driven by the spread of two epidemic clones.

Macrolide resistance in Streptococci and Haemophilus influenzae

Antimicrobial resistance is a growing problem among pathogens from respiratory tract infections. b-Lactam resistance rates are escalating among Streptococcus pneumoniae and Haemophilus influenzae. Macrolides are increasingly used for the treatment of respiratory tract infections, but their utility is compromised by intrinsic and acquired resistance. This article analyses macrolide-resistance mechanisms and their worldwide distributions in S pneumoniae, S pyogenes, and H influenzae.

Detection of multiple macrolide- and lincosamide-resistant strains of Streptococcus pyogenes from patients in the Boston area

Macrolide (including erythromycin and azithromycin) and lincosamide (including clindamycin) antibiotics are recommended for treatment of penicillin-allergic patients with Streptococcus pyogenes pharyngitis. Resistance to erythromycin in S. pyogenes can be as high as 48% in specific populations in the United States. Macrolide and lincosamide resistance in S. pyogenes is mediated by several different genes. Expression of the erm(A) or erm(B) genes causes resistance to erythromycin and inducible or constitutive resistance to clindamycin, respectively, whereas expression of the mef(A) gene leads to resistance to erythromycin but not clindamycin. We studied the resistance of S. pyogenes to erythromycin and clindamycin at an urban tertiary-care hospital. Of 196 sequential isolates from throat cultures, 15 (7.7%) were resistant to erythromycin. Three of these were also constitutively resistant to clindamycin and had the erm(B) gene. Five of the erythromycin-resistant isolates were resistant to clindamycin upon induction with erythromycin and had the erm(A) gene. The remaining seven erythromycin-resistant isolates were susceptible to clindamycin even upon induction with erythromycin and had the mef(A) gene. Pulsed-field gel electrophoresis analysis and emm typing demonstrated that the erythromycin-resistant S. pyogenes comprised multiple strains. These results demonstrate that multiple mechanisms of resistance to macrolide and lincosamide antibiotics are present in S. pyogenes strains in the United States.

Evaluation of 5-day therapy with telithromycin, a novel ketolide antibacterial, for the treatment of tonsillopharyngitis

A pooled analysis of two double-blind, multicentre, Phase III studies compared oral telithromycin 800 mg once-daily for 5 days with penicillin V 500 mg three-times-daily or clarithromycin 250 mg twice-daily for 10 days in the treatment of Streptococcus pyogenes (group A beta-haemolytic streptococcus; GABHS) tonsillopharyngitis. Patients aged > or = 13 years with acute GABHS tonsillopharyngitis were randomised to receive telithromycin (n = 430), penicillin (n = 197) or clarithromycin (n = 231). Clinical isolates of S. pyogenes (n = 590) obtained from throat swab samples on study entry were tested for their in-vitro susceptibility to telithromycin, clarithromycin and azithromycin. Telithromycin demonstrated in-vitro activity against the clinical isolates of S. pyogenes (MIC50/90 0.03/0.06 mg/L) higher than clarithromycin or azithromycin (MIC50/90 0.06/0.06 mg/L and 0.12/0.25 mg/L, respectively), including erythromycin-resistant strains. At the post-therapy/test of cure (TOC) visit (days 16-23), satisfactory bacteriological outcome was demonstrated for 88.3% (234/265) and 88.6% (225/254) of telithromycin- and comparator-treated patients, respectively (per-protocol population). Overall, GABHS eradication rates were 88.7% (235/265) for telithromycin and 89.0% (226/254) for comparators. The clinical cure rates at the post-therapy/TOC visit were 93.6% (248/265) and 90.9% (220/242) for telithromycin and pooled comparators, respectively. Telithromycin was generally well-tolerated. Most adverse events considered to be possibly related to study medication were gastrointestinal and of mild intensity. Discontinuations as a result of adverse events were few in both treatment groups. In conclusion, telithromycin 800 mg once-daily for 5 days was as effective as penicillin V or clarithromycin for 10 days in the treatment of GABHS tonsillopharyngitis.

Development of macrolide resistance by ribosomal protein L4 mutation in Streptococcus pyogenes during miocamycin treatment of an eight-year-old Greek child with tonsillopharyngitis

Streptococcus pyogenes isolates with the same pulsed-field patterns were recovered from the throat cultures of a child with tonsillopharyngitis before and after treatment with miocamycin, a 16-membered macrolide. The initial isolate was macrolide-susceptible, but the isolates after the treatment were resistant to 14 and 15-membered macrolides and had two amino acid (65WR66) deletions in ribosomal protein L4.

Antimicrobial susceptibility profile among beta-haemolytic Streptococcus spp. collected in the SENTRY Antimicrobial Surveillance Program--North America, 2001

The surveillance of antimicrobial resistance among beta-hemolytic Streptococcus spp. is an important health care concern due to the serious nature of the diseases that are caused by these pathogens and the emerging antimicrobial resistances. National and international studies have documented diverse rates of resistance to macrolide and lincosamide agents. The SENTRY Antimicrobial Surveillance Program evaluated the resistance rates of beta-hemolytic Streptococcus spp. to several drug classes including erythromycin and clindamycin during the 2001 study year. Twenty-five medical centers in North America contributed 787 isolates from serogroups A (SGA; 397 strains), B (SGB; 318 strains), G (SGG; 45 strains), C (SGC; 19 strains), and F (SGF; eight strains). Isolates were tested at a reference center by broth microdilution using NCCLS methods. A subset of isolates were characterized by molecular methods to determine the presence of erm and mef resistance mechanisms. All isolates were susceptible to beta-lactams, linezolid, vancomycin, chloramphenicol, quinupristin/dalfopristin, and fluoroquinolones. Garenoxacin (MIC(90,) 0.06 microg/ml) was the most potent fluoroquinolone tested. Tetracycline was inactive against SGB (14.8% susceptible) compared to SGC, SGG, SGF and SGA (48.9-85.6% susceptible). Resistance to erythromycin and clindamycin was highest among SGB isolates with M-phenotypes (mef) representing the majority (59.1%) of strains. Among isolates randomly selected for genotypic characterization, eight strains had mef (A), 16 had erm (A) [subclass erm (TR)], seven had erm (B) and one strain had erm (A) [subclass erm (TR)] and mef (A) present. These data when compared to previous SENTRY Program analysis showed macrolide resistance has remained stable over the last five years and M-phenotypes are the most prevalent expression of MLS(B) resistance in North America.

Relief of symptoms in patients with group A beta-hemolytic streptococcus tonsillopharyngitis: comparison between telithromycin and penicillin V

This study compared the resolution of symptoms in patients with group A beta-hemolytic streptococcus tonsillopharyngitis treated with 5 d of telithromycin 800 mg once daily, or 10 d of penicillin V 500 mg 3 times daily. At days 3-5 of treatment, the mean improvement in total symptom score was greater with telithromycin than with penicillin V (p = 0.042). Thus, telithromycin provided faster symptom relief than penicillin V.

Telithromycin and quinupristin-dalfopristin resistance in clinical isolates of Streptococcus pyogenes: SMART Program 2001 Data

This study evaluated the current status of antimicrobial resistance in clinical isolates of Streptococcus pyogenes in Taiwan as part of the SMART (Surveillance from Multicenter Antimicrobial Resistance in Taiwan) program. In 2001, 419 different isolates of S. pyogenes, including 275 from respiratory secretions, 87 from wound pus, and 31 from blood, were collected from nine hospitals in different parts of Taiwan. MICs of 23 antimicrobial agents were determined at a central location by the agar dilution method. All of the isolates were susceptible to penicillin (MIC at which 90% of the isolates were inhibited [MIC(90)], moxifloxacin > ciprofloxacin = levofloxacin = gatifloxacin > gemifloxacin) demonstrated potent activity against nearly all of the isolates of S. pyogenes tested. Thirty-two isolates (8%) were not susceptible to quinupristin-dalfopristin. Seventeen percent of isolates had telithromycin MICs of >or=1 microg/ml, and all of these isolates exhibited erythromycin MICs of >or=32 microg/ml. The high prevalence of resistance to telithromycin (which is not available in Taiwan) limits its potential use in the treatment of S. pyogenes infections, particularly in areas with high rates of macrolide resistance.

Activity of telithromycin compared with seven other agents against 1039 Streptococcus pyogenes pediatric isolates from ten centers in central and eastern Europe

In total, 1039 pediatric Streptococcus pyogenes isolates from Bulgaria, Croatia, the Czech Republic, Hungary, Latvia, Lithuania, Poland, Romania, Slovakia and Slovenia were studied. All strains were susceptible to penicillin G, levofloxacin, and quinupristin-dalfopristin, 91-100% to telithromycin, and 82-100% to erythromycin, azithromycin, and clarithromycin, and 90-100% to clindamycin. Macrolide resistance occurred mainly in Slovakia (25%), the Czech Republic (17.3%), and Croatia (15.8%). Overall, 9.7% of S. pyogenes isolates were erythromycin resistant due to erm(B)- or erm(A)-encoded methylases (72.3%) or to a mef(A)-encoded efflux pump (25.7%). One strain had alterations of both 23S rRNA (A2058G Escherichia coli numbering) and ribosomal protein L22 (G95D).

Efficacy and tolerability of 5-day, once-daily telithromycin compared with 10-day, twice-daily clarithromycin for the treatment of group A beta-hemolytic streptococcal tonsillitis/pharyngitis: a multicenter, randomized, double-blind, parallel-group study

BACKGROUND

Telithromycin, a ketolide antibacterial, has been developed for the treatment of community-acquired respiratory infections.

OBJECTIVE

This study compared the efficacy and tolerability of 5-day, once-daily telithromycin with 10-day, twice-daily clarithromycin in adolescents and adults with acute tonsillitis/pharyngitis caused by group A beta-hemolytic streptococci ([GABHS] Streptococcus pyogenes).

METHODS

In this multicenter, randomized, double-blind, parallel-group study, adolescent (aged > or = 13 years) and adult patients with a diagnosis of GABHS tonsillitis/pharyngitis received once-daily telithromycin 800 mg for 5 days (followed by placebo for 5 days) or twice-daily clarithromycin 250 mg for 10 days. Bacteriologic and clinical outcomes were assessed at a test-of-cure visit (days 16 to 23) and a late posttherapy visit (days 31 to 45).

RESULTS

A total of 526 patients were enrolled in the study, of which 463 (288 females, 175 males) were randomized to receive treatment (telithromycin, n = 232; clarithromycin, n = 231). The mean age of the telithromycin group was 30.9 years; in the clarithromycin group, it was 30.0 years. Bacterial eradication was achieved in 91.3% of telithromycin-treated patients and 88.1% of clarithromycin recipients (difference, 3.2%; 95% CI, -4.5 to 11.0). Clinical cure was achieved in 92.7% of telithromycin recipients and 91.1% of clarithromycin-treated patients (difference, 1.6%; 95% CI, -5.5 to 8.6). Bacteriologic and clinical cures for the 2 treatment groups also were similar at the late posttherapy visit. Treatment-related adverse events occurred more frequently in the telithromycin group than the clarithromycin group (67.2% vs 57.5%, respectively); diarrhea, nausea, and vomiting were significantly more common with telithromycin than with clarithromycin (P = 0.004, 0.010, and 0.001, respectively). Adverse events were generally mild.

CONCLUSION

This study demonstrates that telithromycin 800 mg once daily for 5 days was an effective and generally well-tolerated treatment for tonsillitis/pharyngitis caused by GABHS, providing similar bacteriologic and clinical efficacy to clarithromycin 250 mg twice daily for 10 days in the per-protocol population.

Clinical isolates of macrolide-resistant Streptococcus pyogenes in Central Greece

A total of 300 Streptococcus pyogenes isolates, collected during 2001 from five hospitals in the Thessalia district (Central Greece), were examined for their resistance to macrolides. Resistance to erythromycin was detected in 58 isolates (19.3%). Of these, 68.9% were susceptible to clindamycin (M-phenotype) and carried the mefA gene. Of the remaining isolates, 18 expressed the MLS(B) phenotype: 12 and six exhibited inducible and constitutive resistance to clindamycin, respectively. All of these strains were found to be ermA(TR) positive, except for four that had the ermB gene. Of the erythromycin-resistant strains, none was found to be resistant to penicillin, tetracycline or quinupristin-dalfopristin. Molecular typing by PFGE showed the presence of a limited number of clones.

Antistreptococcal activity of telithromycin compared with seven other drugs in relation to macrolide resistance mechanisms in Russia

The susceptibilities of 468 recent Russian clinical Streptococcus pneumoniae isolates and 600 Streptococcus pyogenes isolates, from 14 centers in Russia, to telithromycin, erythromycin, azithromycin, clarithromycin, clindamycin, levofloxacin, quinupristin-dalfopristin, and penicillin G were tested. Penicillin-nonsusceptible S. pneumoniae strains were rare except in Siberia, where their prevalence rate was 13.5%: most were penicillin intermediate, but for three strains (two from Smolensk and one from Novosibirsk) the MICs of penicillin G were 4 or 8 micro g/ml. Overall, 2.5% of S. pneumoniae isolates were resistant to erythromycin. Efflux was the prevalent resistance mechanism (five strains; 41.7%), followed by ribosomal methylation encoded by constitutive erm(B), which was found in four isolates. Ribosomal mutation was the mechanism of macrolide resistance in three isolates; one erythromycin-resistant S. pneumoniae isolate had an A2059G mutation in 23S rRNA, and two isolates had substitution of GTG by TPS at positions 69 to 71 in ribosomal protein L4. All S. pyogenes isolates were susceptible to penicillin, and 11% were erythromycin resistant. Ribosomal methylation was the most common resistance mechanism for S. pyogenes (89.4%). These methylases were encoded by erm(A) [subclass erm(TR)] genes, and their expression was inducible in 96.6% of isolates. The rest of the erythromycin-resistant Russian S. pyogenes isolates (7.6%) had an efflux resistance mechanism. Telithromycin was active against 100% of pneumococci and 99.2% of S. pyogenes, and levofloxacin and quinupristin-dalfopristin were active against all isolates of both species.