Macrolide-resistant Isolates Research Articles

Impact of intermittent preventive treatment in pregnancy with azithromycin-containing regimens on maternal nasopharyngeal carriage and antibiotic sensitivity of Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus: a cross-sectional survey at delivery.

Sulfadoxine-pyrimethamine (SP) plus azithromycin (AZ) (SPAZ) has the potential for intermittent preventive treatment of malaria in pregnancy (IPTp), but its use could increase circulation of antibiotic-resistant bacteria associated with severe pediatric infections. We evaluated the effect of monthly SPAZ-IPTp compared to a single course of SP plus chloroquine (SPCQ) on maternal nasopharyngeal carriage and antibiotic susceptibility of Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus at delivery among 854 women participating in a randomized controlled trial in Papua New Guinea. Serotyping was performed, and antibiotic susceptibility was evaluated by disk diffusion and Etest. Potential risk factors for carriage were examined. Nasopharyngeal carriage at delivery of S. pneumoniae (SPAZ, 7.2% [30/418], versus SPCQ, 19.3% [84/436]; P<0.001) and H. influenzae (2.9% [12/418] versus 6.0% [26/436], P=0.028), but not S. aureus, was significantly reduced among women who had received SPAZ-IPTp. The number of macrolide-resistant pneumococcal isolates was small but increased in the SPAZ group (13.3% [4/30], versus SPCQ, 2.2% [2/91]; P=0.033). The proportions of isolates with serotypes covered by the 13-valent pneumococcal conjugate vaccine were similar (SPAZ, 10.3% [3/29], versus SPCQ, 17.6% [16/91]; P=0.352). Although macrolide-resistant isolates were rare, they were more commonly detected in women who had received SPAZ-IPTp, despite the significant reduction of maternal carriage of S. pneumoniae and H. influenzae observed in this group. Future studies on SPAZ-IPTp should evaluate carriage and persistence of macrolide-resistant S. pneumoniae and other pathogenic bacteria in both mothers and infants and assess the clinical significance of their circulation.

Streptococcus pneumoniae carriage, resistance and serotypes among Jordanian children from Wadi Al Seer District, Jordan

Objectives: Isolation of Streptococcus pneumoniae from healthy children in Wadi Al Seer, Jordan before vaccination with prevenar.  Methods: Nasopharyngeal and throat swabs were colloected from 118 healthy children with age range from one to 50 months and mean age 13.4 months. Isolates were analysed for antimicrobial susceptibility, serotyping and macrolide resistant genotypes and phenotypes.Results: The overall nasopharyngeal carriage rate was 55.1% (n= 65/118). The percentage of resistance was as follows: Penicillin (80%), erythromycin (61.5%), clindamycin (33.8%), trimethoprim-sulfamethoxazole (73.8%), and tetracycline (53.8%). Vancomycin, Amoxicillin, cefotaxime, levofloxacin and telithromycin showed no resistance. 37/ 65 isolates (56.9%) were multiresistant. (MIC50, MIC90) were as follows (µg/ml): Penicillin (0.5, 2), erythromycin (2, >=32), clindamycin (0.06, >=32), trimethoprim-sulfamethoxazole (4, >=32), tetracycline (16, 32), and and levofloxacin (0.5, 1). Among macrolide resistant isolates 40 (61.5%), macrolide resistant phenotypes indicated were (n, %): M-Phenotypes (18, 45%), iMLSB (1, 2.5%) and cMLSB (21, 52.5%) with genotypes erm(B) 55%, and mef(A) 45%. The most common serotypes indicated were: 19F (18.5%), 6B (16.9%), 23F (12.3%), 35B (6.2%), 11A, NT and 15A (4.6%) each, and 14, 34, 23A, 6A, and 19A (3.1%) each. Coverage of PCV7, PCV10 and PCV13 was 52.3%, 52.3% and 58.5%, respectively.Conclusions: Carriage of pneumococci in Jordan is relatively high with high resistance rate which is a serious risk of future invasive and non invasive pneumococcal infections, and their spread is worrisome.

Utility of sequencing the erm(41) gene in isolates of Mycobacterium abscessus subsp. abscessus with low and intermediate clarithromycin MICs.

The erm(41) gene confers inducible macrolide resistance in Mycobacterium abscessus subsp. abscessus, calling into question the usefulness of macrolides for treating M. abscessus subsp. abscessus infections. With an extended incubation (14 days), isolates with MICs of ≥8 μg/ml are considered macrolide resistant by current CLSI guidelines. Our goals were to determine the incidence of macrolide susceptibility in U.S. isolates, the validity of currently accepted MIC breakpoints, and the erm(41) sequences associated with susceptibility. Of 349 isolates (excluding those with 23S rRNA gene mutations), 85 (24%) had clarithromycin MICs of ≤8 μg/ml. Sequencing of the erm(41) genes from these isolates, as well as from isolates with MICs of ≥16 μg/ml, including ATCC 19977T, revealed 10 sequevars. The sequence in ATCC 19977T was designated sequevar (type) 1; most macrolide-resistant isolates were of this type. Seven sequevars contained isolates with MICs of >16 μg/ml. The T28C substitution in erm(41), previously associated with macrolide susceptibility, was identified in 62 isolates (18%) comprising three sequevars, with MICs of ≤2 (80%), 4 (10%), and 8 (10%) μg/ml. No other nucleotide substitution was associated with macrolide susceptibility. We recommend that clarithromycin susceptibility breakpoints for M. abscessus subsp. abscessus be changed from ≤2 to ≤4 μg/ml and that isolates with an MIC of 8 μg/ml have repeat MIC testing or erm sequencing performed. Our studies suggest that macrolides are useful for treating approximately 20% of U.S. isolates of M. abscessus subsp. abscessus. Sequencing of the erm gene of M. abscessus subsp. abscessus will predict inducible macrolide susceptibility.

Current Opinions in the Treatment of Pulmonary Nontuberculous Mycobacteria in Non-Cystic Fibrosis Patients: Mycobacterium abscessus Group, Mycobacterium avium Complex, and Mycobacterium kansasii

Treatment of pulmonary infections caused by Mycobacterium avium complex (MAC) and Mycobacterium kansasii involves multidrug oral therapy with a macrolide (azithromycin or clarithromycin), ethambutol, and a rifamycin (rifampin or rifabutin). Patients with M. kansasii rapidly respond to a regimen of intermittent (three times weekly) or daily administration of this three-drug regimen. Patients with MAC respond more slowly and often require adjustment of the multidrug regimen because of drug intolerance. The usual treatment for patients with MAC nodular disease takes 15–18 months, with a goal of 12 months of negative cultures. Recent studies support the use of a three-times weekly oral treatment regimen for patients with macrolide-susceptible nodular MAC disease. Patients with upper lobe fibro-cavitary MAC, macrolide-resistant MAC, or severe nodular bronchiectatic disease are usually treated with a daily multidrug regimen supplemented with an injectable antibiotic (amikacin or streptomycin) or, most recently, inhaled preparations of amikacin. Patients with cavitary changes and/or those with macrolide-resistant isolates are often associated with poor treatment response and may require surgical resection in addition to their drug therapy. In contrast to patients with lung disease due to MAC and M. kansasii, the presence of a functional erythromycin ribosomal methylase (erm) gene in the majority of isolates of Mycobacterium abscessus (M. abscessus subsp. abscessus) blocks the activity of macrolides and precludes an effective oral drug regimen for most of these patients. Treatment regimens for macrolide-resistant M. abscessus require long-term intravenous access and parenteral drug combinations of amikacin, cefoxitin, imipenem, and/or tigecycline. Because of the inconvenience of dosing cefoxitin, a regimen of imipenem and amikacin may be preferred. Cure with these agents is infrequent because of the long-term toxicity and expense of these agents. Other treatment options are currently dismal. The role of newer antimicrobials such as tedizolid and bedaquiline has not been evaluated. Approximately 15 % of isolates of subsp. abscessus and all isolates of subsp. massiliense (infrequent in the USA) have a nonfunctional erm gene and are macrolide susceptible, making an oral macrolide an important treatment component and increasing the likelihood of long-term cure of the infection.

Molecular typing of Treponema pallidum in the Czech Republic during 2011 to 2013: increased prevalence of identified genotypes and of isolates with macrolide resistance.

From January 2011 to December 2013, a total of 262 samples, from 188 patients suspected of having syphilis were tested for the presence of treponemal DNA by PCR amplification of five chromosomal loci, including the polA (TP0105), tmpC (TP0319), TP0136, TP0548, and 23S rRNA genes. Altogether, 146 samples from 103 patients were PCR positive for treponemal DNA. A set of 81 samples from 62 PCR-positive patients were typeable, and among them, nine different genotypes were identified. Compared to a previous study in the Czech Republic during 2004 to 2010, the number of genotypes detected among syphilis patients in a particular year increased to six in both 2012 and 2013, although they were not the same six. The proportion of macrolide-resistant clinical isolates in this 3-year study was 66.7%.

Streptococcus agalactiae in Brazil: serotype distribution, virulence determinants and antimicrobial susceptibility.

BackgroundGroup B Streptococcus (GBS) remains a major cause of neonatal sepsis and is also associated with invasive and noninvasive infections in pregnant women and non-pregnant adults, elderly and patients with underlying medical conditions. Ten capsular serotypes have been recognized, and determination of their distribution within a specific population or geographical region is important as they are major targets for the development of vaccine strategies. We have evaluated the characteristics of GBS isolates recovered from individuals with infections or colonization by this microorganism, living in different geographic regions of Brazil.MethodsA total of 434 isolates were identified and serotyped by conventional phenotypic tests. The determination of antimicrobial susceptibility was performed by the disk diffusion method. Genes associated with resistance to erythromycin (ermA, ermB, mefA) and tetracycline (tetK, tetL, tetM, tetO) as well as virulence-associated genes (bac, bca, lmb, scpB) were investigated using PCR. Pulsed-field gel electrophoresis (PFGE) was used to examine the genetic diversity of macrolide-resistant and of a number of selected macrolide-susceptible isolates.ResultsOverall, serotypes Ia (27.6%), II (19.1%), Ib (18.7%) and V (13.6%) were the most predominant, followed by serotypes IV (8.1%) and III (6.7%). All the isolates were susceptible to the beta-lactam antimicrobials tested and 97% were resistant to tetracycline. Resistance to erythromycin and clindamycin were found in 4.1% and 3% of the isolates, respectively. Among the resistance genes investigated, tetM (99.3%) and tetO (1.8%) were detected among tetracycline-resistant isolates and ermA (39%) and ermB (27.6%) were found among macrolide-resistant isolates. The lmb and scpB virulence genes were detected in all isolates, while bac and bca were detected in 57 (13.1%) and 237 (54.6%) isolates, respectively. Molecular typing by PFGE showed that resistance to erythromycin was associated with a variety of clones.ConclusionThese findings indicate that GBS isolates circulating in Brazil have a variety of phenotypic and genotypic characteristics, and suggest that macrolide-resistant isolates may arise by both clonal spread and independent acquisition of resistance genes.

Impact of the pneumococcal conjugate vaccine on serotype distribution and susceptibility trends of pediatric non-invasive Streptococcus pneumoniae isolates in Tokai, Japan over a 5-year period

Introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in February 2010 markedly reduced the burden of invasive pneumococcal disease (IPD) and changed serotype distribution in Japan. We investigated the serotype distribution and susceptibility trends of non-invasive Streptococcus pneumoniae isolates collected from pediatric patients. A total of 564 pneumococcal isolates were collected over a 5-year period between 2008 and 2012. The coverage of PCV7 significantly decreased throughout the study period, from 49.3% in period 1 (between June 2008 and April 2009) to 23.4% in period 4 (between October 2011 and March 2012). This change was mainly due to a large decrease in the frequency of 19F (from 20.6% to 9.9%) and 6B (from 10.3% to 2.7%) and an increase in serotype 3 (from 5.1% to 13.5%) and serogroup 15 (from 4.4% to 9.0%). According to serotype replacement, the susceptible ratios of S.pneumoniae to β-lactams increased slightly while macrolide resistance remained high. The high frequency of macrolide-resistant pneumococcal isolates may continue because of the high frequency of erm(B) in replace serotypes such as serotype 3 and serogroup 15. The continuous surveillance study is essential following the introduction of a second generation 13-valent pneumococcal conjugate vaccine (PCV13).

Antimicrobial Resistance and Serotype Distribution of Nasopharyngeal Pneumococcal Isolates From Healthy Toddlers of Evros, Greece

Background: Streptococcus pneumoniae (SP) strains carried in the nasopharynx of healthy children reflect the circulating strains implicated in respiratory and invasive infections. Methods: We prospectively analyzed the serotype distribution of SP nasopharyngeal isolates in healthy toddlers aged 21 to 78 months (median age, 63 months) attending day care centers during the winters of 2010Y2012. All children were sampled once during the study period. Serotyping was performed by the Quellung reaction using the 12 pooled antisera Pneumotest panel and specific factor sera. We also studied the in vitro antimicrobial susceptibilities of the isolated pneumococci to several antibiotics by E-test, and for macrolide-resistant isolates of 2010 only, the resistance genes mef(A) and erm(B). Results: Among the 543 toddlers studied, 98.8% had received 1 or more doses of 7-valent pneumococcal conjugate vaccine (PCV7), whereas none was immunized with PCV10 or PCV13. Overall, 27.4% of the children tested were colonized with SP, whereas 22.8% and 52.3% of the isolates belonged to PCV7 and PCV13 serotypes, respectively. Overall, 25.5% of the isolates had intermediate resistance to penicillin (minimal inhibitory concentration, 0.12Y1 Kg/mL) and 3.4% were resistant to penicillin (minimal inhibitory concentration, 2 Kg/mL). All isolates were susceptible to amoxicillin, whereas 28.2% were resistant to macrolides, with the mef(A) geneYmediated M phenotype being the most common in 2010, the year that macrolide resistance genes were studied (93.4% of macrolideresistant isolates). Conclusions: Implementation of PCV13 will increase the coverage of children in our area for invasive pneumococcal serotypes by approximately 30%. Postlicensure serotyping and antimicrobial susceptibility surveillance are essential for designing rational immunization strategies.

Molecular mechanisms of quinolone, macrolide, and tetracycline resistance among Campylobacter isolates from initial stages of broiler production

The aim of this study was to investigate the resistance mechanisms of quinolones, macrolides and tetracycline in campylobacter isolates from grandparent and parent broiler breeders in Spain. Twenty-six isolates were investigated for quinolone resistance, three isolates for macrolide resistance and 39 for tetracycline resistance. All of the quinolone-resistant isolates possessed the mutation Thr86Ile in the quinolone resistance-determining region of gyrA and one isolate possessed the mutation Pro104Ser. Only one Campylobacter coli population (defined by restriction fragment length polymorphism–polymerase chain reaction of flaA and pulsed field gel electrophoresis) was resistant to erythromycin, and the mutation A2075G (23S rDNA) was responsible for macrolide resistance. The tetO gene was found in all of the tetracycline-resistant isolates. Twenty-two out of the 39 isolates investigated by Southern blot possessed chromosomic location of tetO and 17 were located on plasmids. Most of the plasmids with tetO were of around 60 kb and conjugation was demonstrated in a selection of them. In conclusion, we showed that Thr86Ile is highly prevalent in quinolone-resistant isolates as well as mutation A2075G in macrolide-resistant isolates of poultry origin. More variability was found for tetO. The possibility of horizontal transmission of tetO among campylobacter isolates is also an issue of concern in public health.

In Vitro Activity of Solithromycin against Erythromycin-Resistant Streptococcus agalactiae

The in vitro antibacterial activity of solithromycin (CEM-101) against macrolide-resistant isolates (n=62) of Streptococcus agalactiae (group B streptococcus [GBS]) was determined. Phenotypic characterization of macrolide-resistant strains was performed by double-disc diffusion testing. A multiplex PCR was used to identify the erm(B), erm(TR), and mef(A/E) genes, capsular genotypes, and alpha-like (Alp) protein genes from the GBS strains. Determination of MIC was carried out using the microdilution broth method. The Etest method was used for penicillin, azithromycin, clarithromycin, and erythromycin. Solithromycin had a MIC50 of ≤0.008 μg/ml and a MIC90 of 0.015 μg/ml against macrolide-susceptible S. agalactiae. These MICs were lower than those displayed by penicillin (MIC50 of 0.032 μg/ml and MIC90 of 0.047 μg/ml), the antibiotic agent of choice for prophylaxis and treatment of GBS infections. Against macrolide-resistant S. agalactiae, solithromycin had a MIC50 of 0.03 μg/ml and a MIC90 of 0.125 μg/ml. Against erm(B) strains, solithromycin had a MIC50 of 0.03 μg/ml and a MIC90 of 0.06 μg/ml, while against mef(A) strains, it had a MIC50 of 0.03 μg/ml and a MIC90 of 0.125 μg/ml. Most erythromycin-resistant GBS strains were of serotype V (64.5%) and associated significantly with alp2-3. Moreover, a statistically significant association was observed between the constitutive macrolide-lincosamide-streptogramin B resistance (cMLSB) phenotype and the erm(B) gene-carrying strains, the alp2-3 gene and the M phenotype, and the mef(A/E) gene and epsilon. Overall, our results show that solithromycin had lower or similar MICs than penicillin and potent activity against macrolide-resistant strains independent of their genotype or phenotype, representing a valid therapeutic alternative where β-lactams cannot be used.

Elementos genéticos móviles asociados con resistencia a eritromicina en aislamientos de Streptococcus pneumoniae en Colombia

Resistance to macrolide antibiotics is increasing in clinical isolates of Streptococcus pneumoniae and is associated with the presence of mobile genetic elements. Objetive: The aim of this study was to determine the distribution of serotypes and transposons among macrolide-resistant invasive isolates of S. pneumoniae in Colombia from 1994 to 2011.A total of 225 macrolide-resistant S. pneumoniae isolates were analyzed. The isolates had epidemiological data, serotyping and antimicrobial susceptibility patterns. The phenotypes were tested by erythromycin-clindamycin double-disk test. We investigated the presence of transposons by several multiplex PCRs to identify the genes erm (B), mef(A), mef(E), tet M, Cat , Aph3 -III, int -Tn 916 , xis -Tn 916 , TnpA -Tn 917 , TnpR -Tn 917 and int -Tn 5252 .Of all isolates, 62.7%, 2.7% and 34.6% of isolates exhibited cMLS B, iMLS B, and M phenotypes, respectively. Multiresistance was observed in 69.3% of these strains. The most prevalent genetic elements in MLS B were the Tn 5253 (34%), mostly carried in serotype 6B isolates and found to be related to the international clone Spain-ST90; Tn 1545 (18.4%), carried by serotype 19A and related to ST276, and Tn 3872 (14.9%), mainly detected in capsular types 6B and 14. Other seven transposons (32.7%) were associated with different serotypes. The mega element (62.8%) was associated to serotype 6A and ST473 in M phenotype.The majority of erythromycin-resistance isolates of S. pneumoniae in Colombia had the cMLS B phenotype and was associated with the presence of transposons, which carry multiple resistance determinants for other antibiotics. Moreover, isolates with M phenotype carried the gene mef( E) in the mega element.

Mobile genetic elements associated with erythromycin-resistant isolates of Streptococcus pneumoniae in Colombia

Resistance to macrolide antibiotics is increasing in clinical isolates of Streptococcus pneumoniae and is associated with the presence of mobile genetic elements. Objetive: The aim of this study was to determine the distribution of serotypes and transposons among macrolide-resistant invasive isolates of S. pneumoniae in Colombia from 1994 to 2011. A total of 225 macrolide-resistant S. pneumoniae isolates were analyzed. The isolates had epidemiological data, serotyping and antimicrobial susceptibility patterns. The phenotypes were tested by erythromycin-clindamycin double-disk test. We investigated the presence of transposons by several multiplex PCRs to identify the genes erm (B), mef(A), mef(E), tet M, Cat , Aph3 -III, int -Tn 916 , xis -Tn 916 , TnpA -Tn 917 , TnpR -Tn 917 and int -Tn 5252 . Of all isolates, 62.7%, 2.7% and 34.6% of isolates exhibited cMLS B, iMLS B, and M phenotypes, respectively. Multiresistance was observed in 69.3% of these strains. The most prevalent genetic elements in MLS B were the Tn 5253 (34%), mostly carried in serotype 6B isolates and found to be related to the international clone Spain-ST90; Tn 1545 (18.4%), carried by serotype 19A and related to ST276, and Tn 3872 (14.9%), mainly detected in capsular types 6B and 14. Other seven transposons (32.7%) were associated with different serotypes. The mega element (62.8%) was associated to serotype 6A and ST473 in M phenotype. The majority of erythromycin-resistance isolates of S. pneumoniae in Colombia had the cMLS B phenotype and was associated with the presence of transposons, which carry multiple resistance determinants for other antibiotics. Moreover, isolates with M phenotype carried the gene mef( E) in the mega element.

Kronik Akciğer Hastalığı Olan, Akut Alevlenme ve Pnömoni Tanısı ile Başvuran Çocuklarda Streptococcus pneumoniae Serotip Dağılımı ve Antimikrobiyal Duyarlılıkları

This study aimed to investigate serotype distribution and antimicrobial resistance of Streptococcus pneumoniae isolates obtained from children with chronic respiratory diseases admitted to hospital with a diagnosis of acute exacerbations between 2008-2010 at Marmara University Hospital, Istanbul, Turkey. Sixty one S.pneumoniae strains isolated from the respiratory samples of patients were studied for erythromycin, clindamycin, tetracyline, trimethoprim-sulphametoxazole (TMP-SMX), vancomycin, levofloxacin susceptibilities by disk diffusion method; MIC values of penicillin and ceftriaxone were determined by E-test (AB Biodisk, Sweden). Results were evaluated according to the CLSI standards. The erythromycin-clindamycin double disc method was applied for the detection of macrolide resistance phenotypes. The presence of macrolide resistance genes, ermB, mef(A)/(E), ermTR were determined by PCR using specific primers for each gene. The serotypes were determined by multiplex PCR using specific primers for 40 different serotypes. According to CLSI criteria, penicillin resistance in S.pneumoniae isolates were found to be 8.2% (5/61) and intermediate resistance rate was 54% (33/61) for oral penicillin. Penicillin resistance were found to be only 1.6% (1/61) for parenteral penicillin. Resistance rates of erythromycin, clindamycin, tetracyline, TMP-SMX were detected as 55.8%, 46%, 47.5% and 67.2%; respectively. No resistance was detected to vancomycin and levofloxacin. Constitutive macrolide-lincosamide-streptogramin B (cMLSB) phenotype and M phenotype were observed in 82.4% (n= 28) and 17.6% (n= 6) of the macrolide resistant isolates, respectively. Inducible macrolide-lincosamide-streptogramin B (iMLSB) phenotype was not detected. The macrolid resistance genotypes, ermB, mef(A)/(E), were positive 50% and 14.7%; respectively. Both ermB and mef(A)/(E) genes were detected 35.3% of the macrolid resistant isolates. None of the isolates were positive for ermTR gene. The most common S.pneumoniae serotypes were determined as serotype 19F, 23F and 6, furthermore penicillin (34%, 15.7% and 18.4%, respectively) and macrolide (38.2%, 20.6% and 14.7%, respectively) resistance rates of those serotypes were found relatively high. Serotype covarage of 7-, 10-, 13-valent conjugated pneumococcal vaccines and 23-valent pneumococcal vaccine were 65%, 67%, 69%, and 78.6%, respectively. In our country, use of the vaccines with these coverage rates has been observed to be effective in children exposed to intensive use of antibiotics with chronic lung disease.

Molecular Resistance Mechanisms of Macrolide-Resistant Invasive Streptococcus pneumoniae Isolates from Alaska, 1986 to 2010

The rapid emergence of antibiotic-resistant pneumococcal strains has reduced treatment options. The aim of this study was to determine antimicrobial susceptibilities, serotype distributions, and molecular resistance mechanisms among macrolide-resistant invasive pneumococcal isolates in Alaska from 1986 to 2010. We identified cases of invasive pneumococcal disease in Alaska from 1986 to 2010 through statewide population-based laboratory surveillance. All invasive pneumococcal isolates submitted to the Arctic Investigations Program laboratory were confirmed by standard microbiological methods and serotyped by slide agglutination and the Quellung reaction. MICs were determined by the broth microdilution method, and macrolide-resistant genotypes were determined by multiplex PCR. Among 2,923 invasive pneumococcal isolates recovered from 1986 to 2010, 270 (9.2%) were nonsusceptible to erythromycin; 177 (66%) erythromycin-nonsusceptible isolates demonstrated coresistance to penicillin, and 167 (62%) were multidrug resistant. The most frequent serotypes among the macrolide-resistant isolates were serotypes 6B (23.3%), 14 (20.7%), 19A (16.7%), 9V (8.9%), 19F (6.3%), 6A (5.6%), and 23F (4.8%). mef and erm(B) genes were detected in 207 (77%) and 32 (12%) of the isolates, respectively. Nineteen (7%) of the erythromycin-nonsusceptible isolates contained both mef and erm(B) genotypes; 15 were of serotype 19A. There was significant year-to-year variation in the proportion of isolates that were nonsusceptible to erythromycin (P < 0.001). Macrolide resistance among pneumococcal isolates from Alaska is mediated predominantly by mef genes, and this has not changed significantly over time. However, there was a statistically significant increase in the proportion of isolates that possess both erm(B) and mef, primarily due to serotype 19A isolates.

Seven-Year Surveillance of emm Types of Pediatric Group A Streptococcal Pharyngitis Isolates in Western Greece

BackgroundAn experimental 26-valent M protein Group A streptococcal (GAS) vaccine has entered clinical studies. Pharyngeal GAS emm type surveillances in different areas and time-periods enhance the understanding of the epidemiology of GAS pharyngitis. Moreover, these surveillances, combined with the data on GAS invasive disease, can play a significant role in the formulation of multivalent type-specific vaccines.MethodsDuring a 7-year period (1999–2005), 2408 GAS isolates were recovered from consecutive children with pharyngitis in Western Greece. The overall macrolide resistance rate was 22.8%. Along the study period we noted a tendency towards significantly decreased rates of resistance, with the lowest rates occurring in 2002 (15.3%), 2003 (15%) and 2004 (16.7%). A random sample of isolates from each year, 338 (61.7%) of the 548 macrolide-resistant and 205 (11%) of the macrolide-susceptible, underwent molecular analysis, including emm typing.ResultsThe 543 typed isolates had 28 different emm types. A statistically significant association was found between macrolide resistance and emm4, emm22 and emm77, whereas emm1, emm3, emm6, emm12, emm87 and emm89 were associated with macrolide susceptibility. A significant yearly fluctuation was observed in emm4, emm28 and emm77. The most common macrolide-resistant GAS were emm77 isolates harboring erm(A), either alone or in combination with mef(A), emm4 carrying mef(A), emm28 possessing erm(B), emm75 carrying mef(A), emm12 harboring mef(A) and emm22 carrying erm(A). We estimated that 82.8% of the isolates belonged to emm types included in the novel 26-valent M protein vaccine. The vaccine coverage rate was determined mainly by the increased frequency of nonvaccine emm4 isolates.ConclusionsA limited number of emm types dominated among macrolide-susceptible and macrolide-resistant GAS isolates. We observed seasonal fluctuations, which were significant for emm4, emm28 and emm77. This type of data can serve as baseline information if the novel 26-valent M protein GAS vaccine is introduced into practice.

O06.3 Macrolide Resistance of Mycoplasma Genitalium in France Directly Detected in Clinical Specimens by Real-Time PCR and Melting Curve Analysis

Objectives Mycoplasma genitalium (MG) is a sexually transmitted organism associated with non-gonococcal urethritis in men and several inflammatory reproductive tract syndromes in women. These infections are commonly treated with azithromycin....

Emergence of Macrolide-Resistant Campylobacter Strains in Chicken Meat in Poland and the Resistance Mechanisms Involved

In this study, we investigated the molecular mechanisms involved in erythromycin resistance in the first resistant Campylobacter strains isolated from chicken meat in Poland, and analyzed their genetic relatedness. A total of 297 samples of raw chicken meat and giblets from retail trade in the Warsaw area collected between 2006 and 2009 were examined. Among 211 Campylobacter strains (52 C. jejuni and 159 C. coli), 10 C. coli isolates (4.7%) were resistant to erythromycin. All the C. jejuni strains were susceptible. Among the high-level macrolide-resistant isolates, two different point mutations within the domain V of the 23S rRNA gene were observed. Eight of the strains had adenine→guanine transitions at position 2075, two other isolates at position 2074. Sequence analysis of ribosomal proteins L4 (rplD) and L22 (rplV) indicated that ribosomal protein modifications did not contribute to macrolide resistance. A mutation in the inverted repeat in the cmeR and cmeABC intergenic region was found in a single resistant strain. The genetic relatedness of Campylobacter isolates showed that two resistant strains obtained from the same production plant in a 2-month interval were genetically identical. The risk of transmission of resistant strains via the food chain highlights the need for constant monitoring of resistance in Campylobacter isolates of human and animal hosts.

Heterogeneous Macrolide Resistance in Methicillin-Resistant Staphylococcus aureus: Investigation of Resistance Mechanisms and Clonality

Staphylococcus aureus is one of the most important pathogens leading to hospital infections and has ability to gain multiple resistance to most of the antibiotics used as well as ability to spread clonally. In this study we aimed to investigate the mechanism of heterogenous macrolide resistance and clonality of 41 methicillin-resistant S.aureus (MRSA) strains isolated from clinical samples of inpatients between 2006 and 2008 in a tertiary care training hospital. Heterogenous macrolide resistance is defined as the isolates with colonies in the inhibiton zone of erythromycin, azithromycin, claritromycin discs, and named as hMLSB (heterogeneous macrolides, lincosamides, streptogramin-B) phenotype. A total of 63 macrolide-resistant MRSA strains isolated during the same period with non-hMLSB phenotype were included in the study as a control group. The susceptibilties of isolates to methicillin, erythromycin, azithromycin, claritromycin, clindamycin, quinupristin-dalfopristin, penicillin, vancomycin, teicoplanin, linezolide, gentamicin, amikacin, ciprofloxacin, trimethoprim-sulphamethoxazole, chloramphenicol, rifampin, tetracycline and telithromycin were determined by disc diffusion method according to the CLSI criteria. hMLSB isolates were also tested for erythromycin, clindamycin and quinupristin-dalfopristin susceptibility by Vitek-2 automated system (bioMerieux, France). Presence of erm(A), erm(B), erm(C), msr(A/B) resistance genes were investigated by PCR. The regulatory region of the erm(A) gene, which was found to be the only molecular mechanism of hMLSB, was sequenced. Sequence analysis of regulatory regions showed deletion of "guanine" base at position 149 in 34 strains and two point mutations namely "C368G" and "T377C" in 16 strains. Pulsed-field gel electrophoresis (PFGE) analysis indicated presence of a common clone and its variants; however this clone was also common among control group strains. Interestingly all heterogeneous macrolide resistant isolates were reported as susceptible to erythromycin, clindamycin, quinupristin-dalfopristin by the automated system. As a result a clone specific to heterogenous macrolide resistant strains was not detected. Although all hMLSB strains had erm(A) gene, a specific and common genetic modification could not be found in regulatory region of the isolates. The most important finding of this study is the detection of inability of the automated system to properly reflect the hMLSB phenotype. In addition it was suggested that longer incubation (at least 24 hours) of the antibiotic susceptibility test plates could help identification of hMLSB phenotype in disc diffusion tests.

Surveillance of Macrolide-Resistant Mycoplasma pneumoniae in Beijing, China, from 2008 to 2012

Macrolide resistance rates of Mycoplasma pneumoniae in the Beijing population were as high as 68.9%, 90.0%, 98.4%, 95.4%, and 97.0% in the years 2008 to 2012, respectively. Common macrolide-resistant mobile genetic elements were not detected with any isolate. These macrolide-resistant isolates came from multiple clones rather than the same clone. No massive aggregation of a particular clone was found in a specific period.

Decline in macrolide-resistant Streptococcus pyogenes isolates from French children

We studied the macrolide resistance and serotypes of 585 group A streptococcus (GAS) isolates collected from French children with pharyngitis. Nineteen isolates (3.2%) were erythromycin-resistant and harbored the following resistance genes: 31.6% mef(A), 15.8% erm(A), and 52.6% erm(B). The 19 isolates included 7 different emm types (4, 1, 11, 2, 28, 12, and 77) and 7 corresponding multilocus sequence types. The current fall in macrolide consumption has led to a very low rate of GAS macrolide resistance.