An analysis on biovars and antimicrobial susceptibility of 78 Ureaplasma strains isolated from respiratory tract of hospitalized infants / 预防医学

Objective To learn the biovars,antimicmbial susceptibility in Ureaplasma species isolated from respiratory tracts of infants hospitalized in tertiary children's hospital,and to provide evidences and clinical basis for the prevention and treatment of Ureaplasma infection in infants.Methods Ureaplasma species cultivation,identification and antibiotic susceptibility testing were performed using Mycoplasma IST2.The primers according to the conservative MB-Ag gene were designed to identify Ureaplasma biovars.Erythmmcin resistant genes (ermA,ermB and ermC) and active effiux transporter genes (mefA/E,msrA/B and mreA) were amplified using PCRs.Results A total of 78 Ureaplasma positive cases,of them,48 Ureaplasma strains were isolated from premature neonates.Biovar 1 was present in 51 (65.38％) strains,and biovar 2 was present in 27 (34.62％) strains.There were no significant differences among sex,premature infant,age,gestational age,birth weight,length of stay (P ＞ 0.05).The drug resistance rates to ciprofloxacin and ofloxacin were 80.77％,and to tetracycline was 1.28％.All strains were sensitive to doxycycline,josamycin and pristinomycin.The drug resistance rates to the macrolide antibiotics (erythromycin,azithromycinand and clarithromycin) were ＜ 12％.There was no statistically significant difference among the drug resistance rates of different biovars and these antibiotics (P ＞ 0.05).Only the methylated enzyme gene (ermB) and the active efilux pump gene (msrA/B) were detected,and the detection rate was 39.74％ and 12.82％ respectively.The ermB gene mainly exists in biovar 2,and the detection rate is 55.56％ (P ＜ 0.05).The msrA/B was balanced distributed between biovar 1 and 2 (P ＞ 0.05).A total of 78 Ureaplasma strains were isolated from 24 cases of neonatal septicemia,30 cases of congenital infection pneumonia,9 cases of retinopathy of prematurity,9 cases of neonatal intracranial hemorrhage,and 15 cases of bronchopulmonmT dysplasia.Conclusion Biovar 1 is more prevalent in Ureaplasma species isolated from infant respiratory tract,and higher detection rate of Ureaplasma is found in the preterm infants.All Ureaplasma strains have high drug resistance to both ciprofloxacin and ofloxacin,but low drug resistance to the macrolide antibiotics (erythromycin,azithromycin and clarithromyc),that could be used as a first choice for the treatment of Ureaplasma infection.Erythromycin resistance gene ermB,mainly exists in biovar 2.

Genotyping of erythromycin resistant group C & G streptococci isolated in Chennai, south India.

Background & objectives: Increasing resistance to erythromycin has been observed worldwide in group C and group G streptococci (GCS/GGS). The information available from India is scanty. The aim of the study was to identify erythromycin resistant GCS/GGS isolates in Chennai, south India, and to compare erythromycin resistant genotypes with emm types. Methods: One hundred and thirty one GCS/GGS isolates were tested for erythromycin resistance by disc diffusion and agar dilution methods. Erythromycin resistance genotypes [erm(A), erm(B) and mef(A)] were determined by a multiplex PCR. emm types of erythromycin resistant GCS/GGS isolates was also assessed using emm gene sequencing method. Results: Sixteen of the 131 isolates (12.21%) were resistant to erythromycin. Majority of the isolates were GGS (15/16). Eight of the 16 (50%) were S. dysgalactiae subsps. equisimilis. Twelve isolates (75%) were MLSB phenotype and four (25%) were M phenotype. Of the 12 isolates which exhibited MLSB resistance, seven showed cMLSB phenotype and were positive for erm(B) gene. The remaining five were iMLSB phenotype of which three were positive for erm(A) gene and two for erm(B) gene. erm(A) was common among carriers whereas erm(B) was common among clinical isolates. Interpretation & conclusions: MLSB was the predominant phenotype and erm(B) was the common genotype in the present study. The emm type stC1400.0 was frequently associated with erythromycin resistant GCS/GGS in our study.

Antimicrobial susceptibility of Streptococcus pneumoniae and genotypic characterization of erythromycin-resistant strains in Porto Alegre, Brazil

The antimicrobial susceptibility of 64 strains of S. pneumoniae obtained from three hospitals in Porto Alegre, Brazil, isolated between 2004 and 2005, was determined, using the agar-dilution method. The prevalence of resistant (intermediate and full resistance) strains to trimethoprim/sulphamethoxazole, penicillin, tetracycline, erythromycin, chloramphenicol, and ceftriaxone were 68 percent, 28 percent, 18 percent, 15 percent, 3 percent, and 1 percent, respectively. All strains were susceptible to vancomycin. Among 18 penicillin-resistant strains, 7 were resistant to at least two other antimicrobial drugs. All erythromycin-resistant strains, except one, contained the erm(B) and/or mef(A/E) genes, with a predominance of the former. The resistance rate to penicillin and erythromycin in Porto Alegre remained stable. The combination of trimethoprim/ sulphamethoxazole should not be recommended to treat pneumococcal infections, because of the high rate of resistant strains.

Resistance detection and macrolide antibiotic-resistant mechanism of Streptococcus pneumoniae isolates / 中国人兽共患病学报

In order to understand the resistance against common antibiotics in clinic and macrolide antibiotic-resistant mechanism of Streptococcus pneumoniae (S.pneumoniae) isolates in Zhejiang area,both K-B slip method and E-test were applied to determine the sensitivity of 138 S.pneumoniae isolates to nine antibiotics,and the ermB and mefE genes in those isolates which associated with macrolide antibiotics-resistance closely were detected by PCR.Subsequently,correlation among ermB and mefE genes and the erythromycin resistance were analyzed.For these 138 S.pneumoniae isolates,93.5% (129/138) of the strains were resistant to erythromycin,but only 2.9%～4.3% strains were resistant to cefotaxim,cefuroxime,amoxicillin and levofloxacin.The positive rate of ermB gene in the isolates (91.3%,126/138) was significantly higher than that of mefE gene (33.3%,46/138) (P<0.05).Both of these two genes existed in 27.5 % (38/138) of the strains and all of the strains without ermB and mefE genes were sensitive to erythromycin.The erythromycin resistance rate (62.5%) of mefE gene positive strains was remarkably lower than that of the mefE&ermB gene positive strains (100%) and the ermB gene positive strains (97.7%) (P<0.05).All the data mentioned above demonstrated that erythromycin is not an appropriate antibiotic to treat the infectious diseases caused by S.pneumoniae.Moreover,ermB is the predominant erythromycin resistance gene in S.pneumoniae isolates and ermB gene could inspire stronger erythromycin resistance than mefE gene.

Colonization Rate, Serotypes, and Distributions of Macrolide-Lincosamide-Streptogramin(B) Resistant Types of Group B Streptococci in Pregnant Women / 대한임상미생물학회지

BACKGROUND: The prevalence of neonatal group B streptococcal infection depends mainly on the colonization rate of pregnant women by group B streptococci (GBS). Although the colonization rate of Korean women by GBS is considered lower than in other countries, recent data on the maternal colonization rate of GBS are sparse. METHODS: From August 2008 to June 2009, swab specimens from the anorectus, vagina, and urethral orifice of a sample of 234 pregnant Korean women were placed in new Granada medium (NGM-H), tube medium (NGM-T), commercial NGM (NGM-B), and selective Todd-Hewitt broth (S-THB) for 18~24 hours in 5% CO2 at 35degrees C. Agar dilutional antimicrobial susceptibility tests, serotyping, and PCR were performed for GBS isolates. RESULTS: The colonization rate of GBS in pregnant women was 11.5% (27/234). Of the specimen cultures, 9.8% of anorectal cultures were positive, 8.1% of urethral orifice cultures were positive, and 7.3% of vagina cultures were positive. The detection rate of GBS in the different culture media was S-THB (96.3%), NGM-B (92.6%), NGM-H (88.9%), and NGM-T (85.2%). The distribution of GBS serotypes was as follows: III (29.6%), V and VI (22.2%), Ib and II (11.1%), and Ia (3.7%). 33.3% of GBS isolates were resistant to erythromycin and 44.4% to clindamycin. Among the nine erythromycin-resistant isolates, eight were serotype V and VI, which are erm(B) positive serotypes. CONCLUSION: The colonization of pregnant women by GBS, and the incidence of resistance of the GBS isolates to erythromycin and clindamycin were higher than those previously reported. Serotypes V and VI, GBS serotypes that carry the erm(B), are novel serotypes that have not previously been identified in pregnant Korean women.

Study on the relationship between erythromycin sensitivity and ermB gene in Ureaplasma urealyticum / 中华微生物学和免疫学杂志

Objective To study the relationship between erythromyein sensitivity and ermB gene in 143 Ureaplasma urealyticum (Uu) clinical isolates. Methods We detected the minimum inhabit concen-trations (MICs) of Uu to erythromycin by broth dilution method and MIC≥8 μg/ml was used as standard concentration of resistance to erythromycin. Polymerase chain reaction was used to detect the ermB gene and biotype Uu with primers based on multi-band antigen gene. Results The MICs, MIC50 MIC90 of Uu to erythromycin were ≤0. 125 μg/ml to ≥128 μg/ml, 16 μg/ml, and ≥128 μg/ml, respectively, with a high resistance rate of 64.38%. ermB gene, which was mainly detected in Uu with MIC≥8 μg/ml, was positively detected in 40 out of 143 Uu strains (27.97%). No significant differences of the resistance to erythromycin and positive rate of ermB gene were found between the two biovars in the study . Conclusion ermB gene may probably be one of the important genes conferring resistance to erythromycin in Uu. Further studies are needed to discover the difference of resistance and mechanism of erythromycin between the two bi-ovars.

The study on drug resistance and ermB gene of Enterococci isolated from animal and human / 中华微生物学和免疫学杂志

Objective To obtain better insights into transmission dynamics of macrolide resistance genes between human and animal Enterococcus strains.Methods The antimicrobial susceptibility to 8 anti-bioties of 52 Enterococci isolated from animal and 55 Enterococci isolated from human was determined.PCR was used to detect the macrolide resistance genes ermB and mefA,tetracycline resistance genes tetM,and the integrase gene int of Tnl545 of the total 107 strains.Forty-nine ermB positive strains were chosen to be se-quenced.Filter mating experiments were taken.Results The resistance rate to erythromycin were 89.09% and 80.77%for isolates from human and animal:and resistance rate to tetracycline were 80.00%and 67.3l%for isolates from human and animal.respectively.All isolated Enterococci strains were found sensi-tive to vancomycin ermB was detected in 61.82% human Enterococci and 53.85% porcine ones.Identical er-mB gene sequences were found in animal and human Enterococci.Transfer of the ermB gene from porcine E.faecalis to human E.feacalis was successful.and the transfer frequency is 1.2×10-5.Conclusion En-terococci have a high resistance rate to erythromycin and some other antibio tics,especially in pediatric iso-lates:but still very sensitive to glycopeptide.ermB was the predominant genes for macrolide and tetracy-cline.Identical ermB gene sequences were present in animal and human Enterococci and that transfer of the ermB gene from porcine E.faecalis to human E.faecalis and vice versa is possible.but probably occurs at a low frequency.

Antimicrobial Susceptibility Patterns and Macrolide Resistance Genes of beta-Hemolytic Viridans Group Streptococci in a Tertiary Korean Hospital

The aim of this study was to investigate antimicrobial susceptibilities and macrolide resistance mechanisms of beta-hemolytic viridans group streptococci (VGS) in a tertiary Korean hospital. Minimum inhibitory concentrations (MICs) of seven antimicrobials were determined for 103 beta-hemolytic VGS isolated from various specimens. The macrolide resistance mechanisms of erythromycin-resistant isolates were studied by the double disk test and polymerase chain reaction (PCR). The overall resistance rates of beta-hemolytic VGS were found to be 47.5% to tetracycline, 3.9% to chloramphenicol, 9.7% to erythromycin, and 6.8% to clindamycin, whereas all isolates were susceptible to penicillin G, ceftriaxone, and vancomycin. Among ten erythromycin-resistant isolates, six isolates expressed a constitutive MLSB (cMLSB) phenotype, and each of the two isolates expressed the M phenotype, and the inducible MLSB (iMLSB) phenotype. The resistance rates to erythromycin and clindamycin of beta-hemolytic VGS seemed to be lower than those of non-beta-hemolytic VGS in our hospital, although cMLSB phenotype carrying erm(B) was dominant in beta-hemolytic VGS.

A Decrease in Erythromycin Resistance Rate of Streptococcus pyogenes in 2004 in Jinju / 대한임상미생물학회지

BACKGROUND: The erythromycin (EM) resistance rates and emm genotypes of Streptococcus pyogenes could vary by geographical location and study period. The purpose of this study, involving a large number of children, was to determine EM resistance rate and its resistance mechanism of S. pyogenes, and to compare these results with those of previous studies performed at the same area. METHODS: Throat cultures were taken from 2,351 healthy children of four elementary schools from October through December, 2004 in Jinju. A total of 328 strains of S. pyogenes were isolated. Antimicrobial susceptibility test was performed by the agar dilution method against six antimicrobial agents. The phenotypes of EM resistance were evaluated by the double-disk diffusion test and the frequency of ermB and mefA genes was determined by polymerase chain reaction. RESULTS: Resistance rates of S. pyogenes to EM, clindamycin and tetracycline were 9.8%, 8.8% and 18.3%, respectively. Almost all isolates were susceptible to ofloxacin, levofloxacin and chloramphenicol. Constitutive resistance (CR) was observed in 87.5%, M phenotype in 9.4%, and inducible resistance only in 3.1%. The ermB and mefA genes were present in 90.6% and 9.4% of the isolates, respectively. CONCLUSION: The resistance rate to EM of S. pyogenes was 9.8% in 2004, which was a large drop from the 51% shown in 2002. CR with the ermB gene was predominant, suggesting that most of the EM resistant isolates have a high level of resistance.

Erythromycin Resistance Phenotype and Resistance Gene to Streptococcus pneumoniae / 中华医院感染学杂志

OBJECTIVE To investigate the prevalence of erythromycin resistance genes ermB and mefA and the relationship of drug resistance and genes in Streptococcus pneumoniae.METHODS Forty three strains of S. pneumoniae were collected from respiratory system infected children from Dec 2004 to Oct 2005 at Yuying Pediatric Hospital of Wenzhou Medical College.Erythromycin sensitivity test was done by using MIC method.The erythromycin resistance genes ermB and mefA were detected by PCR.RESULTS In all forty three strains,forty were erythromycin resistant(93%),three were erythromycin sensitive.The total detection rate of erythromycin resistance genes ermB and mefA was 76.7% and 23.3%,respectively.There were neither gene ermB nor gene mefA in 3 erythromycin-sensitive S.pneumoniae.In 40 strains the detection rate of gene ermB was 82.5% and that of gene mefA was 25%.The erythromycin resistance gene ermB or mefA were detected in 35 of the 43 strains.The total detection rate of erythromycin resistance gene was 81.4%.In the 35 erythromycin resistance strains there were 25 strains in which gene ermB existed lonely and 2 strains in which gene mefA existed lonely.There were both genes ermB and gene mefA in 8 of the 35 erythromycin resistance strains.CONCLUSIONS The erythromycin resistance of S.pneumoniae can be caused mainly by gene expression of ermB or mefA,but the gene mefA seems to be less important than gene ermB.Obviously the erythromycin isn′t useful in treating S.pneumoniae infection.

Antimicrobial Resistance of Streptococcus pneumoniae and Mechanisms of Resistance to Macrolides / 中华医院感染学杂志

OBJECTIVE To investigate the antimicrobial susceptibility of Streptococcus pneumoniae isolated in Yantai and their mechanisms of resistance to macrolides.METHODS Antimicrobial susceptibility of S.pneumoniae was determined by agar dilution method.Phenotypes of macrolide-resistant S.pneumoniae were determined using double disk test with erythromycin and clindamycin disks.ermB And mefE genes were amplified by PCR.RESULTS Among 42 strains of S.pneumoniae,65.0% were intermediate to and no strain was resistant to penicillin.The resistance rates to erythromycin and clindamycin were 93.0%,respectively.Of 41 erythromycin resistantstrains,93.0% were constitutive resistant.ermB Was detected in 40 strains and mefE in 1 strain,both ermB and mefE genes were found in 9 strains.CONCLUSIONS The resistance rate of S.pneumoniae to penicillin is high in Yantai area,the resistance rates to erythromycin and clindamycin are very high.Target modification by ermB methylase is the predominant mechanism in macrolide-resistant S.pneumoniae in Yantai.

Analysis of Phenotypic and Genotypic Distribution of Erythromycin and Clindamycin Resistance of Group A Streptococci Isolated from Acute Pharyngitis / 대한진단검사의학회지

BACKGROUND: Erythromycin (EM) or other macrolides have been used commonly for the treatment of bacterial pharyngitis. Recently, however, EM-resistant group A streptococci (GAS) are being reported with increasing frequency. The phenotypic expression of macrolide resistance is classified as constitutive, inducible, and M. EM resistance is mediated by ermB, ermTR, or mefA genes. The emm gene encoding M protein has variable sequences at 5'end terminus. METHODS: GAS was isolated from patients with acute pharyngitis at a local clinic in Jinju from November 2001 to May 2002. Antimicrobial susceptibility testing was performed using the disk diffusion method. The phenotypes of EM and clindamycin (CC) resistance were evaluated, and the frequency of ermB and mefA genes was determined by PCR. The emm genotype was identified with PCR and sequencing. RESULTS: A total of 125 strains of group A streptococci was isolated. The resistance rate to EM and CC was 44.8% and 19.2%, respectively. Constitutive resistance was observed in 42.1%, M phenotype in 57.9%, but inducible resistance was not seen. The ermB and mefA genes were positive in 39.3% and 58.9%, respectively. Most emm12 strains showed constitutive resistance, while emm18 and emm75 showed M phenotype. CONCLUSIONS: The EM and CC resistance rates of group A streptococci isolated from acute pharyngitis were remarkably high compared to the previous reports. M phenotype was more common than constitutive resistance in acute pharyngitis. The resistance pattern was variable according to the emm types, suggesting an association between the emm gene and resistant genes.

Antibiotic Resistance and Its Mechanism of Group A Streptococci in School Children of Jinju / 대한임상미생물학회지

BACKGROUND: Group A streptococci (GAS) is the most common cause of bacterial pharyngitis. Recently, a high frequency of resistance to erythromycin (EM), the drug of choice for penicillin-allergic patients, has been reported, especially in countries where antibiotics are overused. Resistance is classified as constitutive, inducible, or M according to the sensitivity results with EM and clindamycin (CC). These EM resistance phenotype is attributable to the erm , ermTR, and mefA genes, respectively. Although EM resistance of GAS is a serious problem in our country, there are very few reports regarding to its mechanism. METHODS: GAS were isolated from elementary school children of Jinju in 2002. Antibiotic sensitivity testing by disk diffusion was performed against tetracycline (TC), ofloxacin, EM and CC, and the results were compared to the previous one in 1995 at the same area. The phenotypes of EM resistance were evaluated, and the frequency of ermB and mefA genes was determined by PCR. The resistance pattern was analyzed by each emm genotype. RESULTS: The resistance rate to EM and CC was 51% and 34%, respectively, which is significantly higher than the rate of 25% and 9% recorded in 1995. Constitutive resistance was seen in 64% of the EM-resistant strains, the M phenotype in 34%, and inducible resistance in only 2%, compared to 38% of constitutive resistance and 62% of M phenotype in 1995. The ermB and mefA genes were present in 64% and 34% of strains, respectively. Most (88%) of the emm12 strains showed constitutive resistance, while emm18 and emm75 showed M phenotype. The organisms with most of the other emm genotypes were susceptible to EM. CONCLUSION: The EM and CC resistance rate had increased more than twofold. Constitutive resistance was twice as common as the M phenotype, whereas the mefA gene was more common in 1995. The resistance pattern was variable according to emm type, which suggests an association between the emm and resistance genes. Continuous microbiologic and epidemiological surveillance should be conducted and the seriousness of antibiotic resistance should be underscored in our community.

Distributions of Macrolide-Lincosamide-Streptogramin (MLS) Resistance Types in beta-hemolytic Streptococci / 대한임상미생물학회지

BACKGROUND: Macrolide resistance in beta-hemolytic streptococci has increased during the 1990s, and the proportion of MLS (Macrolide-lincosamide-streptogramin) resistance phenotypes and genotypes of beta-hemolytic streptococci are quite different by geographical variation and study period. The aim of the present study was to determine the distribution of MLS resistance phenotypes and genotypes in beta-hemolytic streptococci isolated from Wonju Christian Hospital. METHODS: The minimal inhibitory concentrations of erythromycin and clindamycin of 426 beta- hemolytic streptococci isolated from clinical specimens between 1990 to 1999 were determined by agar dilution method. MLS resistance phenotypes were determined by double disk diffusion method using erythromycin and clindamycin disk, and genotypes were determined by polymerase chain reaction (PCR). The PCR primers for erm(A), erm(B), erm(C), erm(TR), and mef(A) were used in these study. RESULTS: The proportion of MLS resistance phenotypes of 80 erythromycin-resistant beta-hemolytic streptococci were 60.0% for constitutive phenotype, 23.8% for M phenotype, and 16.2% for inducible phenotype. The proportion of three MLS resistance phenotypes of group A streptococci were nearly equal. About three-fourths of group B streptococci had the constitutive phenotypes, whereas three-fourths (75%) of group G streptococci had the M phenotypes. All MLS resistant strains carried the erm(B) genes in constitutive phenotypes, erm(TR) genes in inducible phenotypes, and mef(A) genes in M phenotypes, respectively. CONCLUSIONS: Mechanisms and phenotype proportions of MLS resistance are different by species in beta-hemolytic streptococci. It is possible that MLS resistance genes have transferred among beta- hemolytic streptococci because the erythromycin resistance genes are the same in beta-hemolytic streptococci.