Macrolide-lincosamide-streptogramin B Research Articles

Molecular analysis of meticillin-resistant Staphylococcus aureus strains isolated from different types of infections from patients hospitalized in 12 regional, non-teaching hospitals in southern Poland

Accumulated data indicate that meticillin-resistant Staphylococcus aureus (MRSA) infections are associated with a worse prognosis than methicillin-susceptible S.aureus infections. To assess the epidemiological profile of S.aureus infections and the genetic diversity of clinical strains of MRSA in 12 hospitals in southern Poland. Samples from bloodstream infections, pneumonia, and skin and soft tissue infections from adult patients were examined. S.aureus isolates were tested for MRSA and macrolide-lincosamide-streptogramin B (MLSB) phenotypes. Staphylococcal cassette chromosome mec (SCCmec) typing and S.aureus protein A (spa) typing were performed. Analysis of the genetic similarity was performed by pulsed-field gel electrophoresis. This study included 555 patients. An MRSA phenotype was detected in 15.1% of strains. The prevalence of MRSA infection was higher in patients aged >80 years. An MLSB phenotype was detected in 18.2% of strains. Analysis of SmaI profiles did not reveal a dominant clone. Spa typing showed 25 different spa types, and spa type t003 was the most common (49% of strains). Among MRSA strains, SCCmecII (49%) and SCCmecIV (27.4%) were predominant. The characteristics of MRSA showed considerable heterogeneity. The results demonstrate the need for caution when drawing conclusions on direct epidemiological relationships between isolates based on a single typing method. As the cases of infection in this study were not associated with the hospital environment and horizontal transfer, a focus on screening at hospital admission, and appropriate infection control, may help to reduce the risk of MRSA infections.

Phenotypic study of Macrolide-Lincosamide-Streptogramin B Resistance in Staphylococcus aureus and their relationship with Methicillin-Resistant Staphylococcus aureus (MRSA) at Tertiary Care in Eastern Nepal

Background Resistance to antimicrobial agents is prevalent among Staphylococci. This has led to wide uses of macrolide-lincosamide-streptogramin B (MLSB) antibiotics to Staphylococcus aureus (S. aureus) infections. MLSB though chemically distinct, have similar target site and mode of action. The multiple mechanisms are responsible for resistance to MLSB antibiotics which can lead to clinical failure. The aim of the study was to investigate the frequency of inducible and constitutive clindamycin resistance among clinical isolates of S. aureus and their relationship with Methicillin-resistant Staphylococcus aureus (MRSA).Material & Methods A total of 336 unique Staphylococcus aureus isolates from different clinical samples obtained from patients were studied. Antibiotic susceptibility test was performed by Kirby- Bauer disc diffusion method. “D test” was performed to detect inducible clindamycin resistance as per CLSI guidelines. MRSA was detected using Cefoxitin (30μg) and results were interpreted according to CLSI criteria.Results Inducible clindamycin resistance was seen in 45 (13.39%), constitutive clindamycin resistance was seen among 58 (17.26%) while MS phenotype was observed among 38(11.30%) of isolates. Inducible resistance as well as constitutive resistance was higher among MRSA as compared to MSSA (21.11%, 4.48% and 21.11%, 12.82%respectively).Conclusion The Successful use of clindamycin for the treatment of infection caused by S. aureus can be predicted based on the result of simple and inexpensive D test.Journal of Nobel Medical CollegeVolume 5, Number 1, Issue 8, January-July 2016, 1-5

A Low Prevalence of Inducible Macrolide, Lincosamide, and Streptogramin B Resistance Phenotype among Methicillin-Susceptible Staphylococcus aureus Isolated from Malaysian Patients and Healthy Individuals.

BackgroundAntibiotic resistance among Staphylococcus aureus is of great concern worldwide. This resistance is further complicated by the ability of S. aureus to confer cross-resistance to other antibiotics due to the presence of resistance genes, such as erythromycin resistance methylase (erm) genes, which render the bacterium resistant to macrolide-lincosamide-streptogramin B (MLSB) antibiotics. Resistance to these antibiotics can lead to therapeutic failure, resulting in significant morbidity and mortality in patients with S. aureus infections.ObjectivesThis study was performed to examine the distribution of MLSB-resistant strains of methicillin-susceptible S. aureus (MSSA), which were obtained from hospitalized patients and normal healthy individuals (carriers) using phenotypic methods, such as the double-disk diffusion (D-test) and the genotypic method by polymerase chain reaction (PCR).MethodsA total of 183 nonduplicative MSSA isolates obtained from hospitalized patients (133) and carriers (50) in our previous studies were randomly selected for the D-test. The guidelines of the Clinical and Laboratory Standards Institute (CLSI) were used for the interpretation of the results of this test. The detection of ermA, ermB, ermC and msrA genes by PCR was performed for isolates that had positive D-test results and that were resistant to erythromycin.ResultsOf the 183 MSSA isolates, 97.2% and 98.4% were highly susceptible to erythromycin and clindamycin, respectively. MSLB resistance was detected in four isolates (2.2%). Of the 133 MSSA isolated from hospitalized patients, only 3.0% (4/133) and 2.3% (3/133) exhibited resistance to erythromycin and clindamycin, respectively. With regard to the MLSB resistance phenotypes, only 1.6% and 0.6% exhibited inducible MLSB (iMLSB) and MS phenotypes, respectively. The ermC gene was detected in all three iMLSB phenotypes, and the msrA gene was detected in the MS phenotype. Surprisingly, all MSSA isolates (100%) from carriers exhibited extremely high susceptibility to both antibiotics.ConclusionsThe prevalence rates of iMLSB MSSA isolates vary according to geographical locations and the local antibiotic policy. The low prevalence rate of iMLSB MSSA isolates could probably be related to the judicious use of antibiotics for treating S. aureus infections in our studied population. Nonetheless, continuous antibiotic surveillance is still necessary to control any emergence of resistance isolates so that targeted therapy and effective control can be implemented accordingly.

Novel chromosome-encoded erm(47) determinant responsible for constitutive MLSB resistance in Helcococcus kunzii.

The aim of the study was to identify the determinant responsible for erythromycin resistance in Helcococcus kunzii clinical isolate UCN99 and to characterize the genetic support and environment of this novel gene. MICs were determined using the broth microdilution method according to EUCAST guidelines. The entire genome sequence of H. kunzii UCN99 was determined using a 454/Roche GS Junior sequencer. The fragment encompassing the new resistance gene and its own promoter was cloned into the pAT29 shuttle vector and the recombinant plasmid pAT29Ωerm(47) was expressed in both Staphylococcus aureus and Streptococcus agalactiae. The transcription start site (TSS) was experimentally determined by 5' RACE-PCR. UCN99 exhibited a constitutive macrolide/lincosamide/streptogramin B (MLSB) resistance phenotype, suggesting the presence of an Erm protein. WGS allowed the identification of a novel gene, named erm(47), encoding a protein sharing 44%-48% amino acid identity with known Erm methylases. In both S. aureus and S. agalactiae, the introduction of pAT29Ωerm(47) conferred a significant increase (≥16-fold) in MICs of all macrolides and lincosamides tested, as well as a 4-fold increase in MICs of quinupristin (streptogramin B), confirming the MLSB resistance. The TSS identification revealed the presence of a short leader peptide, potentially implicated in a translational attenuation mechanism. It was also demonstrated that erm(47) was harboured by a 81 kb genomic island integrated into a chromosomal gene. This is the first description of a novel MLSB resistance determinant, named erm(47). The prevalence of this gene among Gram-positive cocci must be further investigated to determine its clinical significance.

Healthcare-Associated Methicillin-Resistant Staphylococcus aureus: Clinical characteristics and antibiotic resistance profile with emphasis on macrolide-lincosamide-streptogramin B resistance.

Healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen worldwide and its multidrug resistance is a major concern. This study aimed to determine the clinical characteristics and antibiotic susceptibility profile of healthcare-associated MRSA with emphasis on resistance to macrolide-lincosamide-streptogramin B (MLSB) phenotypes and vancomycin. This cross-sectional study was carried out between February 2014 and February 2015 across four tertiary care hospitals in Mangalore, South India. Healthcare-associated infections among 291 inpatients at these hospitals were identified according to the Centers for Disease Control and Prevention guidelines. Clinical specimens were collected based on infection type. S. aureus and MRSA isolates were identified and antibiotic susceptibility tests performed using the Kirby-Bauer disk diffusion method. The minimum inhibitory concentration of vancomycin was determined using the Agar dilution method and inducible clindamycin resistance was detected with a double-disk diffusion test (D-test). Out of 291 healthcare-associated S. aureus cases, 88 were MRSA (30.2%). Of these, 54.6% were skin and soft tissue infections. All of the isolates were susceptible to teicoplanin and linezolid. Four MRSA isolates exhibited intermediate resistance to vancomycin (4.6%). Of the MRSA strains, 10 (11.4%) were constitutive MLSB phenotypes, 31 (35.2%) were inducible MLSB phenotypes and 14 (15.9%) were macrolide-streptogramin B phenotypes. Healthcare-associated MRSA multidrug resistance was alarmingly high. In routine antibiotic susceptibility testing, a D-test should always be performed if an isolate is resistant to erythromycin but susceptible to clindamycin. Determination of the minimum inhibitory concentration of vancomycin is necessary when treating patients with MRSA infections.

Molecular Markers of Antimicrobial Resistance in Methicillin-Resistant Staphylococcus aureus SCCmec IV Presenting Different Genetic Backgrounds.

Methicillin-resistant Staphylococcus aureus (MRSA) carrying SCCmec type IV has emerged in hospitals worldwide. The aim of this study was to evaluate phenotypic and molecular characteristics of antimicrobial resistance in MRSA SCCmec IV isolates, presenting different genetic backgrounds, isolated from hospitals in Rio de Janeiro. The antimicrobial resistance of 128 S. aureus type IV isolates from 11 hospitals was characterized by the disk diffusion test and minimum inhibitory concentration (MIC) test. Mutations in parC gene, which encodes ciprofloxacin resistance, and genes associated with macrolide-lincosamide-streptogramin B (MLSb) resistance were also investigated. MRSA isolates belonging to USA400/ST1 (60 isolates), USA800/ST5 (40), USA1100/ST30 (13), and other 11 (15) lineages were mainly resistant to erythromycin (68%), ciprofloxacin (56%), and clindamycin (50%). The highest antimicrobial resistance rates were found among USA400 isolates (p < 0.05). The majority of them (90%) carried only the erm(C) gene and mainly presented two mutation types in the parC gene. The msr(A) gene was most frequently found among USA800 isolates (p < 0.05). Among MRSA type IV isolates from Rio de Janeiro hospitals, multiresistance, including mutations in parC gene, was associated to the USA400/ST1, while the msr(A) gene was associated with USA800/ST5 isolates, highlighting that these lineages could have more potential to persist in a hospital environment.

Inducible Clindamycin Resistance in Methicillin Resistant Staphylococcus aureus

The resistance to antimicrobial agents among staphylococci is an increasing problem. This has led to renewed interest in the usage of macrolide-lincosamide-streptogramin B (MLSB) antibiotics to treat Staphylococcus aureus infections. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance thus necessitating the need to detect such resistance by a simple D-test on routine basis. The objective of this study was to investigate S. aureus collected isolates for MLSB phenotypes, in particular inducible clindamycin resistance (MLSBi). Methods: Four hundred and forty six S.aureus isolates from samples were evaluated and inducible resistance to clindamycin was detected by D-test as per CLSI guidelines (2012). Results: Among 224 isolates of staphylococci studied, 101 (21.4%) were methicillin-resistant S. aureus (MRSA) and 123 (26.1%) were methicillin-sensitive Staphylococcus aureus (MSSA). Of the 224 staphylococcal isolates 62 (27.7%) were resistant to erythromycin of which 10 (4.46%) showed inducible clindamycin resistance and belonged to the MLSBi phenotype. Among the 10 MLSBi phenotype 7 (6.93%) were MRSA and 3 (2.44%) were MSSA. Conclusion: D-test should be included as a mandatory method in routine disc diffusion testing to detect inducible clindamycin resistance in staphylococci for the optimum treatment of patients.

Distribution of erm genes among Staphylococcus aureus isolates with inducible resistance to clindamycin in Isfahan, Iran.

Background:The rising frequency of methicillin resistant Staphylococcus aureus (MRSA) has led to an increased use of antibiotics such as macrolide, lincosamide, streptogramin B (MLSB) for the treatment of S. aureus infections. Resistance to MLSB in S. aureus is commonly encoded by erm genes, which can be constitutive MLSB (cMLSB) or inducible MLSB (iMLSB). The purpose of this study was to determine the frequency of cMLSB, iMLSB, and MS phenotypes using D-test and polymerase chain reaction (PCR) methods.Materials and Methods:A total of 215 isolates of S. aureus were collected from January 2010 to May 2012 from Al-Zahra Hospital in Isfahan. PCR was performed for detection of mecA gene on all isolates using specific primers. The frequency of MLSB-resistant isolates was determined using D-test, and then a multiplex PCR was performed for detection of ermA, ermB, and ermC genes.Results:Among 215 S. aureus isolates examined, 82 (40.9%) were MRSA, and iMLSB, cMLSB, and MS resistance phenotypes had a frequency of 9 (4.18%), 58 (26.9%), and 11 (5.1%), respectively. Among nine isolates with iMLSB resistance phenotype, four isolates contained ermC gene, two isolates ermB gene, and one isolate ermA gene. Two isolates did not have any erm gene.Conclusion:In the current study, cMLSB was the most frequent phenotype and ermC was the most common gene in iMLSB resistant phenotypes.

Clindamycin microbial resistance in clinical isolates of Staphylococcus sp. derived from blood cultures of hospitalized patients

Introduction: Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) strains have become common in hospitals, and this resistance has limited patients' treatment with beta-lactam antibiotics. Clindamycin is an important therapeutic agent for MRSA infections; however, inducible macrolide-lincosamide-streptogramin B (MLSB) resistance (iMLSB) has resulted in therapeutic failures with the use of this antimicrobial, with a consequent increase in patient mortality and length of stay. Objective: This study was carried out in order to detect phenotypes of inducible and constitutive resistance to clindamycin in blood culture samples of Staphylococcus sp. from hospitalized patients. Material and methods: A hundred bacterial samples from blood cultures of adult patients were evaluated, identified by conventional phenotypic tests, and subject to determination of susceptibility and resistance profiles with cefoxitin, erythromycin, and clindamycin discs; and to phenotypic evaluation of iMLSB resistance using the D-test. The results were interpreted in accordance with the recommendations of the Clinical and Laboratory Standards Institute (CLSI) 2014. Results: In this study, 65% of 60 bacterial strains were susceptible to cefoxitin and 35%, resistant. The constitutive MLSB (cMLSB) resistance phenotype was observed in 15.56% of the methicillin-sensitive Staphylococcus aureus (MSSA) samples, 33.33% of methicillin-sensitive coagulase-negative Staphylococcus (MSCONS), 26.67% of MRSA and 20% of methicillin-resistant coagulase-negative Staphylococcus (MRCONS), while iMLSB resistance was observed only in strains susceptible to cefoxitin, corresponding to 80% in MSSA and 20% in MSCONS. Conclusion: The D-test is a key test for the constant monitoring of the inducible resistance phenotype (which may impair the effectiveness of treatment with clindamycin), minimizing potential medication errors and adverse clinical outcomes.

Inducible clindamycin resistance among clinical isolates of Staphylococcus aureus

Objective: The aim of the study was to detect the presence of inducible clindamycin resistance among clinical isolates of Staphylococcus aureus. Background: The resistance to antimicrobial agents among staphylococci is an increasing problem. This has led to renewed interest in the usage of macrolide–lincosamide–streptogramin B (MLSB) antibiotics to treat S. aureus infections. The resistance to macrolide can be mediated by the msrA gene coding for efflux mechanism or by the erm gene encoding for enzymes that confer inducible or constitutive resistance to MLSB antibiotics. Materials and methods: Ninety staphylococcal isolates were collected and were tested for antibiotic susceptibility using the disk diffusion method. Inducible resistance to clindamycin in S. aureus was tested by using the double disk diffusion test as per CLSI guidelines. Results: Inducible MLSBresistance (EryRClinInd) was seen in 7/90 (7.7%) isolates, the constitutive phenotype of MLSBresistance (EryRClinR) was detected in 6/90 (6.6%) isolates, and the MSBphenotype (EryRClinS) was seen in 34 (37.7%) isolates. In these isolates, inducible clindamycin resistance was detected in 4.3% (3/70) of S. aureus and 20% (4/20) of coagulase-negative staphylococci. Conclusion: This study showed that the double disk diffusion test should be used as a mandatory method in routine disk diffusion testing to detect inducible clindamycin resistance in staphylococci for the optimum treatment of patients.

The Rate of Inducible MLSBResistance in the Methicillin‐Resistant Staphylococci Isolated From Clinical Samples

BackgroundStaphylococci are one of the most common pathogens in nasocomial and community‐acquired infections. Methicillin‐resistant staphylococci are known to be resistant against all beta‐lactam antibiotics. Therefore, non‐beta‐lactam antibiotics such as macrolide and lincosamides can be used. Resistance to those antibiotics may lead to therapeutic failure. The purpose of the present study was to determine the prevalence of macrolide–lincosamide–streptogramin B (MLSB) resistance by usingD‐test in staphylococcal isolates from various clinical samples.MethodsSeventy‐one methicillin‐resistant Staphylococcus isolates (sixS. aureus, 65 coagulase negative staphylococci) were included in this study. Staphylococci were identified with conventional methods. According to Clinical Laboratory Standards Institute (CLSI) criteria, susceptibility testing was performed by Kirby–Bauer disk diffusion method.ResultsOne of six (16.6%) methicillin‐resistantS. aureusisolates and 19 of 65 (29.2%) methicillin‐resistant coagulase‐negative staphylococci (MR‐CNS) were detected asD‐test positive. Twenty of 71 (28.1%) staphylococcal isolates detected asD‐test positive. Inducible clindamycin resistance was found at a higher rate in MR‐CNS.ConclusionSince the resistant community and hospital acquired staphylococcal infections have become a therapeutic problem, it is very important to detect MLSBresistance routinely in microbiology laboratories.D‐test is a cheap and reliable diagnostic method that can be performed in every laboratory.

Molecular epidemiology and distribution of serotypes, genotypes, and antibiotic resistance genes of Streptococcus agalactiae clinical isolates from Guelma, Algeria and Marseille, France.

This study describes, for the first time, the genetic and phenotypic diversity among 93 Streptococcus agalactiae (group B Streptococcus, GBS) isolates collected from Guelma, Algeria and Marseille, France. All strains were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The molecular support of antibiotic resistance and serotyping were investigated by polymerase chain reaction (PCR). The phylogenetic lineage of each GBS isolate was determined by multilocus sequence typing (MLST) and grouped into clonal complexes (CCs) using eBURST. The isolates represented 37 sequence types (STs), 16 of which were novel, grouped into five CCs, and belonging to seven serotypes. Serotype V was the most prevalent serotype in our collection (44.1%). GBS isolates of each serotype were distributed among multiple CCs, including cps III/CC19, cps V/CC1, cps Ia/CC23, cps II/CC10, and cps III/CC17. All isolates presented susceptibility to penicillin, whereas resistance to erythromycin was detected in 40% and tetracycline in 82.2% of isolates. Of the 37 erythromycin-resistant isolates, 75.7% showed the macrolide-lincosamide-streptogramin B (MLSB)-resistant phenotype and 24.3% exhibited the macrolide (M)-resistant phenotype. Constitutive MLSB resistance (46%) mediated by the ermB gene was significantly associated with the Guelma isolates, whereas the M resistance phenotype (24.3%) mediated by the mefA/E gene dominated among the Marseille isolates and belonged to ST-23. Tetracycline resistance was predominantly due to tetM, which was detected alone (95.1%) or associated with tetO (3.7%). These results provide epidemiological data in these regions that establish a basis for monitoring increased resistance to erythromycin and also provide insight into correlations among clones, serotypes, and resistance genes.

Prevalence of MLSB Resistance and Observation of erm A & erm C Genes At A Tertiary Care Hospital.

The increasing resistance to macrolide, lincosamide, streptogramin B (MLSB) agents among Staphylococcus aureus is becoming a challenge to microbiologist. Clindamycin has been a useful drug for treatment of infection caused by the staphylococcus aureus, but change in clindamycin sensitivity pattern due to various mechanisms is leading to therapeutic failure. One of the important mechanisms is mediation of resistance by erm genes. Staphylococcus strains which have erm genes show inducible clindamycin resistance that cannot be determined by routine disk diffusion test resulting in treatment failure. This study was aimed to detect the prevalence of MLSBi and MLSBc resistance and observation of erm A & erm C genes among MLSBi isolates. A total 500 Staphylococcus aureus were isolated; they were checked by disk induction test (D- Test). Those isolates which showed inducible clindamycin resistance were randomly selected and subjected to PCR for the observation of erm A and erm C genes. Prevalence of MLSBi and MLSBc isolates were almost similar that is 10.8% and 11.6% respectively. MLSBi isolates showed more resistance to drugs when compared to MLSBc isolates. Neither of MLSBi and MLSBc isolates was resistant to Vancomycin and Linezolid. Inducible clindamycin was mainly due to presence of erm A gene. D- test should be mandatory at every microbiology laboratory and should be used in routine antibiotic procedure which will minimize the misuse of drug ultimately minimize the risk of treatment failure. PCR should be performed for the detection of genes responsible for erythromycin resistance as it is a quick and most sensitive method.

Study of Serotypes, Susceptibility to Macrolide and Virulence and Resistance Molecular Profiles in Invasive Strains of &amp;lt;i&amp;gt;Streptococcus agalactiae&amp;lt;/i&amp;gt; in Two Argentine Provinces

A study of invasive strains of Streptococcus agalactiae (GBS) from Cordoba and Misiones, Argentina; was conducted to determine serotypes, the susceptibility to macrolides and molecular profiles of virulence and resistance. We studied 17 strains, recovered from cerebrospinal fluid, blood and cellulite and, a strain of trophoblastic remnants from Misiones. The serotypes were determined by agglutination with sera and phenotypes of resistance to macrolide-lincosamide-streptogramin B (MLSB), were determined with the double-disk test (D-test). The confirmation was performed by E-test by ERI and CLI respectively that determined the minimum inhibitory concentration (MIC). Results were interpreted as recommended by the Clinical and Laboratory Standards Institute (CLSI) 2013. Resistance genes: ermB, ermTR and mefA and the virulence genes: bac, bca, rib, lmb, hylB, scpB, fbsA, fbsB and cylB were investigated by conventional PCR. Serotype III (50%) and Ia (50%) were detected in Cordoba. One strain showed cMLSB phenotype, confirmed by MIC. The same strains showed a resistance gene ermB. All studied virulence genes were detected in 100% of these strains. In Misiones, serotypes were III (72.7%), Ia (18.2%) and Ib (9.1%). All strains were susceptible to CLI and ERI by D-test, confirmed by MIC. None of the strains showed resistance genes. Virulence genes bca, rib, hylB, lmb, fbsA, fbsB and cylB were detected in 100% of the strains, bac in 81.8% and scpB in 90.9%. Our results are in accordance with international data, associating higher frequency of serotype III of invasive neonatal disease followed by Ia. The presence of serotype Ib could indicate a regional difference for Misiones. We highlight the macrolides susceptibility in strains of Misiones and consistency in the results for D-test, MIC and PCR for the single strain resistant phenotype cMLSB from Cordoba. The virulence genes studied were presented with high frequency as expected for invasive strains.

Hierarchal clustering yields insight into multidrug-resistant bacteria isolated from a cattle feedlot wastewater treatment system.

Forty-two percent of Escherichia coli and 58% of Enterococcus spp. isolated from cattle feedlot runoff and associated infiltration basin and constructed wetland treatment system were resistant to at least one antibiotic of clinical importance; a high level of multidrug resistance (22% of E. coli and 37% of Enterococcus spp.) was observed. Hierarchical clustering revealed a closely associated resistance cluster among drug-resistant E. coli isolates that included cephalosporins (ceftiofur, cefoxitin, and ceftriaxone), aminoglycosides (gentamycin, kanamycin, and amikacin), and quinolone nalidixic acid; antibiotics from these classes were used at the study site, and cross-resistance may be associated with transferrable multiple-resistance elements. For Enterococcus spp., co-resistance among vancomycin, linezolid, and daptomycin was common; these antibiotics are reserved for complicated clinical infections and have not been approved for animal use. Vancomycin resistance (n = 49) only occurred when isolates were resistant to linezolid, daptomycin, and all four of the MLSB (macrolide-lincosamide-streptogramin B) antibiotics tested (tylosin, erythromycin, lincomycin, and quinipristin/dalfopristin). This suggests that developing co-resistance to MLSB antibiotics along with cyclic lipopeptides and oxazolidinones may result in resistance to vancomycin as well. Effects of the treatment system on antibiotic resistance were pronounced during periods of no rainfall and low flow (long residence time). Increased hydraulic loading (short residence time) under the influence of rain caused antibiotic-resistant bacteria to be flushed through the treatment system. This presents concern for environmental discharge of multidrug-resistant organisms relevant to public health.

Detection of the efflux-mediated erythromycin resistance transposon in Streptococcus pneumoniae.

BackgroundThe present analysis focuses on phenotypic and genotypic characterizations of efflux-mediated erythromycin resistance in Streptococcus pneumoniae due to an increase in macrolide resistance in S. pneumoniae worldwide.MethodsWe investigated the prevalence of efflux-mediated erythromycin resistance and its relevant genetic elements from 186 specimens of S. pneumonia isolated from clinical and normal flora from Tehran, Iran. The presence of erythromycin resistance genes was tested by PCR with two sets of primers, specific for erm(B) and mef(A/E), and their genetic elements with tetM, xis, and int genes. Isolates were typed with the BOX PCR method and tested for resistance to six antibiotics.ResultsAntibiotic susceptibility tests revealed that 100% and 47% isolates were resistant to tetracycline and erythromycin, respectively. The erythromycin and clindamycin double-disc diffusion test for macrolide-lincosamide-streptograminB (MLSB) resistance phenotype showed 74 (84%) isolates with the constitutive MLSB phenotype and the remaining with the M phenotype. BOX PCR demonstrated the presence of 7 types in pneumococci with the M phenotype. Fourteen (16%) isolates with the M phenotype harbored mef(A/E), tetM, xis, and int genes.ConclusionsThe present results suggest dissemination of polyclonal groups of S. pneumoniae with the M phenotype carrying resistance genes attributed to transposon 2009.

Macrolide-Lincosamide-Streptogramin B Resistance Phenotypes in Staphylococcus Aureus

Staphylococcus aureus is one of the most frequently isolated pathogens in community and hospital-acquired infections. Macrolidelincosamide-streptogramin B (MLSB) group antibiotics have frequently been preferred. In this study, it was aimed to determine MLSB group antibiotics resistance phenotypes observed in S. aureus strains. A total of 182 S. aureus strains were included in the study. Methicillin resistance was assessed using the cefoxitin (30μg) disc, MLSB resistance phenotypes were assessed using D zone test with erythromycin (15μg) and clindamycin (2μg) discs according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. Of the strains included in the study, 38 (20.9%) methicillin-resistant S.aureus (MRSA) and 144 (79.1%) methicillin-susceptible S.aureus (MSSA) were identified. MLSB resistance phenotype was found in 65 (35.7%) strains. MLSB resis tance was found 84% in MRSA strains and 23% in MSSA strains: There was statistically significant between MRSA and MSSA strains. Constitutional MLSB resistance was found higher in MRSA strains (71%) and however, in MSSA strains was higher inducibleMLSB resistance (16.5%). It is suggested that, using the D test method in routine antibiotic susceptibility testing and determining resistance phenotypes in microbiology laboratories is the right approach and may play an important role in the prevention of treatment failure according to the substantial proportion of inducible resistance MLSB resistance observed.

Macrolide-lincosamide-streptogramin B (MLSB) resistance phenotypes in clinical Staphylococcus isolates and investigation of telithromycin activity

Staphylococci are one of the most common pathogens isolated from nosocomial and community acquired infections. Antibiotics such as clindamycin and erythromycin have been useful options for treating skin and soft-tissue infections caused by staphylococci. However, expression of macrolide-lincosamide-streptogramin B resistance (MLSB) can limit the effectiveness of these drugs. The aims of this study were to investigate the prevalence and phenotypes of MLSB resistance in staphylococcus strains isolated from clinical samples and to determine the telithromycin activity against these isolates. A total of 218 strains [92 Staphylococcus aureus and 126 coagulase-negative staphylococci (CNS)] isolated from different clinical samples (wound, abscess, blood, sterile body fluids, catheter, upper respiratory tract samples) between February 2011 to December 2012 were included in the study. The isolates were identified by using conventional methods and automated bacterial identification system (BD Phoenix 100™ System, Becton Dickinson, USA). Methicillin resistance of the isolates was determined with the use of cefoxitin (30 µg) disk and telithromycin (15 µg) activity was detected by Kirby-Bauer disk diffusion method. MLSB resistance phenotypes were investigated by the D-test method using erythromycin (15 µg) and clindamycin (2 µg) disks. Of 92 S.aureus isolates, 23 were methicillin-resistant (MRSA) and 69 were methicillin-susceptible (MSSA), whereas 78 of 126 CNS isolates were methicillin-resistant (MRCNS) and 48 were methicillin-susceptible (MSCNS). Hundred and seventy-two (79%) isolates were found as erythromycin-resistant, and the rates of erythromycin resistance in MRSA, MSSA, MRCNS and MSCNS strains were 83%, 71%, 95% and 63%, respectively. Inducible type of MLSB resistance (iMLSB type) was observed in 26%, 6%, 51% and 33%; chromosomal resistance (cMLSB type) in 32%, 27%, 27% and 17% and efflux pump connected resistance (MSB type) in 42%, 67%, 22% and 50% of the MRSA, MSSA, MRCNS and MSCNS, respectively. Forty-four (20%) strains were found susceptible to both clindamycin and erythromycin (S type resistance). Resistance due to enzymatic inactivation (L type) was observed only in two of the CNS strains (0.9%), one was methicillin-resistant and the other was susceptible. Total telithromycin resistance was detected as 26.6% (n= 58), while the resistance rates in MRSA, MSSA, MRCNS and MSKNS isolates were 35%, 35%, 28% and 8%, respectively. Telithromycin resistance rate was 34% (58/172) in erythromycin-resistant isolates. However, all erythromycin-susceptible isolates (n= 46) were also susceptible to telithromycin. Telithromycin-resistant isolates frequently exhibited cMLSB phenotype (39/44; 67.2%), followed by MSB (16/72; 27.6%) and iMLSB (3/56; 5.2%). In conclusion, clindamycin is still an effective antibiotic for the treatment of staphylococcal infections in our hospital, however, 34% resistance rate against telithromycin may limit the use of this agent which is an alternative for the treatment of infections caused by clindamycin and erythromycin-resistant strains.

Molecular characterization of Streptococcus pyogenes group A isolates from a tertiary hospital in Lebanon.

Streptococcus pyogenes [Group A Streptococcus (GAS)] is one of the most important human pathogens, responsible for numerous diseases with diverse clinical manifestations. As the epidemiology of GAS infections evolves, a rapid and reliable characterization of the isolates remains essential for epidemiological analysis and infection control. This study investigated the epidemiological patterns and genetic characteristics of 150 GAS isolates from a tertiary hospital in Lebanon by emm typing, superantigens (SAgs) detection, PFGE and antibiotic profiling. The results revealed 41 distinct emm types, the most prevalent of which were emm89 (16 %), emm12 (10 %), emm2 (9 %) and emm1 (8 %). Testing for the presence of superantigens showed that speB (87 %), ssa (36 %) and speG (30 %) were predominant. PFGE detected 39 pulsotypes when a similarity cut-off value of 80 % was implemented. Antibiotic-susceptibility testing against seven different classes of antibiotics showed that 9 % of the isolates were resistant to clindamycin, 23 % were resistant to erythromycin and 4 % showed the macrolide-lincosamide-streptogramin B (MLSB) phenotype. The emergence of tetracycline-resistant strains (37 %) was high when compared with previous reports from Lebanon. This study provided comprehensive evidence of the epidemiology of GAS in Lebanon, highlighting the association between emm types and toxin genes, and providing valuable information about the origin and dissemination of this pathogen.

Macrolide, lincosamide, and streptogramin B resistance in lipophilic Corynebacteria inhabiting healthy human skin.

Corynebacteria exist as part of human skin microbiota. However, under some circumstances, they can cause opportunistic infections. The subject of the study was to examine the macrolide-lincosamide-streptogramin B (MLSB) antibiotic resistance in 99 lipophilic strains of Corynebacterium genus isolated from the skin of healthy men. Over 70% of the tested strains were resistant to erythromycin and clindamycin. All of which demonstrated a constitutive type of MLSB resistance mechanism. In all strains, there were being investigated the erm(A), erm(B), erm(C), erm(X), lin(A), msr(A), and mph(C) genes that could be responsible for the different types of resistance to marcolides, lincosamides, and streptogramin B. In all strains with the MLSB resistance phenotype, the erm(X) gene was detected. None of the other tested genes were discovered. Strains harboring the erm(X) gene were identified using a phenotypic method based on numerous biological and biochemical tests. Identification of the chosen strains was compared with the results of API Coryne, MALDI-TOF MS, and 16S rDNA sequencing methods. Only 7 out of the 23 investigated resistant strains provided successful results in all the used methods, showing that identification of this group of bacteria is still a great challenge. The MLSB resistance mechanism was common in most frequently isolated from healthy human skin Corynebacterium tuberculostearicum and Corynebacterium jeikeium strains. This represents a threat as these species are also commonly described as etiological factors of opportunistic infections.