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

Recent development and fighting strategies for lincosamide antibiotic resistance

SUMMARYLincosamides constitute an important class of antibiotics used against a wide range of pathogens, including methicillin-resistant Staphylococcus aureus. However, due to the misuse of lincosamide and co-selection pressure, the resistance to lincosamide has become a serious concern. It is urgently needed to carefully understand the phenomenon and mechanism of lincosamide resistance to effectively prevent and control lincosamide resistance. To date, six mobile lincosamide resistance classes, including lnu, cfr, erm, vga, lsa, and sal, have been identified. These lincosamide resistance genes are frequently found on mobile genetic elements (MGEs), such as plasmids, transposons, integrative and conjugative elements, genomic islands, and prophages. Additionally, MGEs harbor the genes that confer resistance not only to antimicrobial agents of other classes but also to metals and biocides. The ultimate purpose of discovering and summarizing bacterial resistance is to prevent, control, and combat resistance effectively. This review highlights four promising strategies, including chemical modification of antibiotics, the development of antimicrobial peptides, the initiation of bacterial self-destruct program, and antimicrobial stewardship, to fight against resistance and safeguard global health.

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 MLS B phenotype and four (25%) were M phenotype. Of the 12 isolates which exhibited MLS B resistance, seven showed cMLS B phenotype and were positive for erm(B) gene. The remaining five were iMLS B 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

MLS B 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.

Epidemiology of invasive Streptococcus pyogenes disease in Germany during 2003-2007

A nationwide laboratory-based surveillance study of invasive Streptococcus pyogenes infections was conducted in Germany. Invasive isolates (n=586) were obtained between 2003 and 2007. Most isolates were obtained from blood (53.9%) or skin lesions (17.6%). The most common emm types were emm 1 (30.5%), emm 28 (18.3%) and emm 3 (9.6%). Overall, speA was positive in 45.9%, speC in 44.7% and ssa in 14.8% of isolates. SpeA was common in emm type 1 (100%) and emm type 3 (96.4%), whereas speC was often observed in emm type 28 (93.5%). The most frequent clinical manifestations included sepsis (40.1%), necrotizing fasciitis (20.8%) and streptococcal toxic shock syndrome (16.6%). All isolates were susceptible to penicillin G, cefotaxime and levofloxacin. Tetracycline shows the highest rate of resistant or intermediate isolates with 11.6%, followed by clarithromycin (5.5%) and clindamycin (1.2%). The most prominent trend is the reduction of tetracycline-nonsusceptible isolates from 18.6% in 2003 to 8.9% in 2007.

Macrolide resistance trends in beta-hemolytic streptococci in a tertiary Korean hospital

PURPOSE

Erythromycin-resistant beta-hemolytic streptococci (BHS) has recently emerged and quickly spread between and within countries throughout the world. In this study, we evaluate the antimicrobial susceptibility patterns and erythromycin resistance mechanisms of BHS during 2003-2004.

MATERIALS AND METHODS

The MICs of seven antimicrobials were determined for 204 clinical isolates of BHS from 2003 to 2004. Resistance mechanisms of erythromycin-resistant BHS were studied by the double disk test as well as by polymerase chain reaction (PCR).

RESULTS

Compared with our previous study, resistance among Streptococcus pyogenes isolates to a variety of drugs decreased strikingly: from 25.7% to 4.8% in erythromycin; 15.8% to 0% in clindamycin; and 47.1% to 19.0% in tetracycline. The prevalent phenotypes and genotypes of macrolide-lincosamide-streptograminB (MLSB) resistance in Streptococcus pyogenes isolates have been changed from the constitutive MLSB phenotype carrying erm(B) to the M phenotype with mef(A) gene. In contrast with Streptococcus pyogenes, resistance rates to erythromycin (36.7%), clindamycin (43.1%), and tetracycline (95.4%) in Streptococcus agalactiae isolates did not show decreasing trends. Among the Streptococcus dysgalactiae subsp. equisimilis isolates (Lancefield group C, G), resistance rates to erythromycin, clindamycin, tetracycline and chloramphenicol were observed to be 9.4%, 3.1%, 68.8%, and 9.4%, respectively.

CONCLUSION

Continual monitoring of antimicrobial resistance among large-colony-forming BHS is needed to provide the medical community with current data regarding the resistance mechanisms that are most common to their local or regional environments.

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 MLS(B) (cMLS(B)) phenotype, and each of the two isolates expressed the M phenotype, and the inducible MLS(B) (iMLS(B)) 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.

Severe skin and soft tissue infections and associated critical illness

Skin and soft tissue infections (SSTIs) span a broad spectrum of clinical entities from limited cellulitis to rapidly progressive necrotizing fasciitis, which may be associated with septic shock or a toxic shock-like syndrome. These infections may manifest initially as pyodermas that then progress; alternatively, they may arise from metastatic spread of microorganisms from a distant focus. Regardless of the source, SSTIs may lead to critical illness. The complex interplay of environment, host, and pathogen are important to consider when evaluating SSTIs and planning appropriate therapy. The keys to a successful outcome are early identification of risk factors for specific pathogens and early initiation of empiric antimicrobial therapy. For certain types of SSTIs, surgical intervention for diagnosis and/or therapy is also required.

Resistance to erythromycin and telithromycin in Streptococcus pyogenes isolates obtained between 1999 and 2002 from Greek children with tonsillopharyngitis: phenotypic and genotypic analysis

Since the late 1990s, the prevalence of erythromycin-resistant Streptococcus pyogenes has significantly increased in several European countries. Between January 1999 and December 2002, 1,577 isolates of S. pyogenes were recovered from children with tonsillopharyngitis living in various areas of Western Greece. Erythromycin resistance was observed in 379 (24%) of the 1,577 isolates. All erythromycin-resistant strains along with 153 randomly selected erythromycin-susceptible S. pyogenes isolates were tested for their antimicrobial susceptibility, resistance phenotypes, and genotypes. Representative isolates underwent emm gene sequence typing. Isolates with reduced susceptibility to telithromycin (MIC, > or = 2 microg/ml) were studied for multilocus sequence type, L22, L4, and 23S rRNA mutations. Of the total 379 erythromycin-resistant isolates, 193 (50.9%) harbored the mef(A) gene, 163 (43%) erm(A), 1 (0.3%) mef(A) plus erm(A), and 22 (5.8%) the erm(B) gene. Among the erythromycin-susceptible isolates, emm 1 (25%), emm 2 (12.5%), and emm 77 (12.5%) predominated. Furthermore, among the erythromycin-resistant isolates, emm 4 (30.6%), emm 28 (22.2%), and emm 77 (12.5%) prevailed. Resistance to telithromycin was observed in 22 (5.8%) of the erythromycin-resistant isolates. Sixteen (72.7%) of the 22 isolates appeared to be clonally related, since all of them belonged to emm type 28 and multilocus sequence type 52. One of the well-known mutations (T2166C) in 23S rRNA, as well as a new one (T2136C), was detected in erythromycin- and telithromycin-resistant isolates. High incidence of macrolide resistance and clonal spread of telithromycin resistance were the characteristics of the Greek S. pyogenes isolates obtained from 1999 to 2002.

Molecular epidemiology of macrolide resistance in beta-haemolytic streptococci of Lancefield groups A, B, C and G and evidence for a new mef element in group G streptococci that carries allelic variants of mef and msr(D)

OBJECTIVES

To study the molecular mechanisms of erythromycin resistance in beta-haemolytic streptococci of Lancefield groups A, B, C and G.

METHODS

Erythromycin-resistant clinical isolates from North East Scotland were collected over 2 years. Resistance phenotypes were determined by disc diffusion and MICs by Etest. Resistance genes mef, msr(D), erm(B) and erm(TR) were identified by PCR and mef and msr(D) were sequenced.

RESULTS

Erythromycin resistance prevalence was 1.9% in group A streptococci (31 of 1625), 4.3% in group B (53 of 1233), 3.8% in group C (18 of 479) and 6.2% in group G (64 of 1034). The numbers of resistant isolates available were 26, 42, 9 and 52 in each group respectively. The majority of resistant isolates in groups A (57.7%, 15 of 26), B (88.1%, 37 of 42) and G (90.4%, 47 of 52) were MLS(B). The contribution of M phenotype was significant in groups C (77.8%, 7 of 9) and A (42.3%, 11 of 26). Group A isolates carried mef(A) and group B carried mef(E) exclusively. A mef sequence distinct from mef(A) and mef(E) was identified in group G and was associated with a new msr(D) sequence. These sequence variants appear to be part of a new genetic element that is inserted in the comEC gene. A bimodal distribution of erythromycin MICs was noted in erm(TR) isolates.

CONCLUSIONS

The results demonstrate significant differences in the mechanisms of macrolide resistance amongst different Lancefield groups in the same geographical area. New sequences show that resistance mechanisms are still evolving.

Abdominal wall cellulitis in the morbidly obese

Currently, almost two-thirds of the US population is either overweight or obese. In addition to non-infectious complications, obesity predisposes to infections, including lower extremity cellulitis. Although cases of abdominal wall cellulitis in the morbidly obese occur, to date there has been no formal address of this syndrome in the literature. We therefore reviewed our clinical experience of abdominal wall cellulitis complicating morbid obesity. A retrospective database search was performed to identify patients with both cellulitis and morbid obesity who were seen at the Mayo Clinic between January 1998 and August 2003. Clinical and microbiologic data were collected for these patients. Of the 260 cases of cellulitis identified, 24 (9.2%) had morbid obesity and abdominal wall cellulitis. The mean age of the 24 patients was 47 (range 22-70) y and over two-thirds of them were females. Their mean body mass index (BMI) was 62.3 (range 39.6-108.6). 17 (70.8%) had a remote history of abdominal surgery. 16 patients required 23 hospitalizations. Five patients developed cellulitis complications and 7 (29.1%) patients had recurrent bouts of cellulitis during the study period. Abdominal wall cellulitis is a unique infectious complication in patients with morbid obesity. Further study is needed to better define the pathogenesis of this illness to develop strategies in treatment and prevention.

Correlation of serotypes and genotypes of macrolide-resistant Streptococcus agalactiae

Despite the necessity for studies of group B streptococci (GBS), due to the increase in serious adult infections, the emergence of new serotypes, and the increased resistance to macrolide antibiotics, such studies have been limited in Korea. The primary purpose of the present study was to determine the frequency trends of GBS serotypes, including serotypes VI, VII, and VIII. The final objective was to elucidate the relationship between the genotypes and serotypes of macrolide-resistant GBS isolates from a Korean population. Among 446 isolates of Streptococcus agalactiae, isolated between January 1990 and December 2002 in Korea, the frequency of serotypes were III (36.5%), Ib (22.0%), V (21.1%), Ia (9.6%), VI (4.3%), II (1.8%), VIII (1.3%), IV (1.1%), and VII (0.9%). The resistance rates to erythromycin, by serotype, were 85% (V), 23% (III), 21% (VI), 3% (Ib), and 2% (Ia). Of 135 erythromycin- resistant S. agalactiae, ermB was detected in 105 isolates, mefA in 20 isolates, and ermTR in seven isolates; most type V isolates harbored the ermB gene, Ib type isolates had an equal distribution of resistance genes, type III isolates accounted for 70% of all isolates carrying mefA genes, and one fourth of type VI isolates had mefA genes.

Heterogeneity of genotype-phenotype correlation among macrolide-resistant Streptococcus agalactiae isolates

Seventy-four erythromycin-resistant group B Streptococcus isolates were analyzed regarding their phenotype-genotype and phenotype-serotype correlation. Four different phenotypes were assessed, one of them for the first time. ermB and ermTR were the most frequent genotypes (80%). The most prevalent serotype III showed great phenotypic variability while serotype V was strongly associated only with two different phenotypes.