ABSTRACT
Abstract The aim of this study was to characterize phenotypically and genotypically 27 mecApositive Staphylococcus aureus strains with oxacillin MICs of ≤2 g/ml by Vitek 2, isolated indifferent regions of Uruguay. Susceptibility to oxacillin and cefoxitin was studied by gradient dif-fusion, disk diffusion to cefoxitin, and Phoenix and MicroScan systems. PBP2a was determined.SCCmec typing was performed and the isolates were compared by PFGE. Twenty-six isolateswere susceptible to oxacillin; one strain was susceptible to cefoxitin by disk diffusion and 3strains by gradient diffusion. Phoenix and MicroScan panels detected methicillin resistance in25 and 27 strains, respectively. Twenty-six strains tested positive for PBP2a. Twenty-six strainscarried SCCmec V and 24 belonged to pulsotype A. One strain carried SCCmec IV and did notbelong to pulsotype A. Cefoxitin disk diffusion test and PBP2a detection correctly identified 26of these 27 strains as MRSA. PFGE results suggest the dissemination of a cluster of MRSA carryingSCCmec V.
Resumen El objetivo de este estudio fue caracterizar fenotípicamente y genotípicamente 27 cepas de Staphylococcus aureus positivas para mecA y con CIM de oxacilina <2 pg/ml según Vitek 2, obtenidas en diferentes regiones del país. La sensibilidad frente a la oxacilina y la cefoxitina se estudió por difusión en gradiente, por disco-difusión (cefoxitina) y por los sistemas Phoenix y MicroScan. Se analizó la portación de PBP2a, se realizó la tipificación de SCCmec y las cepas se compararon mediante PFGE. Resultaron sensibles a oxacilina por difusión en gradiente 26 cepas; una fue sensible a cefoxitina por disco-difusión y 3 lo fueron por difusión en gradiente. Los sistemas Phoenix y MicroScan detectaron resistencia a meticilina en 25 y 27 cepas, respectivamente. Asimismo, 26 cepas portaban PBP2a y 26 cepas mostraron presencia de SCCmec V, 24 correspondieron al pulsotipo A. Una portaba SCCmec IV y no perteneció al pulsotipo A. La prueba de disco-difusión con cefoxitina y la detección de PBP2a identificaron 26 de 27 cepas como MRSA. La PFGE sugiere la diseminación de un grupo MRSA con SCCmec V. © 2022 Asociación Argentina de Microbiología. Publicado por Elsevier Espana, S.L.U. Este es un artículo Open Access bajo la licencia CC BY-NC-ND (https://creativecommons.org/licenses/by-nc-nd/4.0/).
ABSTRACT
BACKGROUND Mycobacterium abscessus complex (MABC) includes species with high resistance rates among mycobacterial pathogens. In fact, MABC infections may not respond to clarithromycin treatment, which has historically been very effective against MABC infection. Molecular markers have been proposed to detect both acquired (rrl polymorphisms) and inducible (erm(41) polymorphisms) clarithromycin resistance in MABC isolates. OBJECTIVES This study aimed to evaluate the susceptibility profile and molecular markers of clarithromycin resistance in MABC. METHODS The clarithromycin susceptibility profile was determined by broth microdilution with reads on days 3, 5, 7 and 14. Mutations in the rrl and erm(41) genes were evaluated by polymerase chain reaction (PCR) using specific primers, followed by sequencing. FINDINGS A total of 14 M. abscessus subsp. abscessus isolates and 28 M. abscessus subsp. massiliense isolates were evaluated, and clarithromycin resistance was observed in all isolates for up to three days of incubation. None of the 42 isolates exhibited a point mutation in the rrl gene, while all the isolates had a T28 polymorphism in the erm(41) gene. Moreover, all 28 M. abscessus subsp. massiliense isolates had a deletion in the erm(41) gene. MAIN CONCLUSIONS While all the MABC isolates exhibited acquired clarithromycin resistance, no isolates exhibited a point mutation in the rrl gene in this study. The M. abscessus subsp. massiliense isolates demonstrated clarithromycin resistance, which is an uncommon phenotype. The molecular data for the rrl and erm(41) genes were not consistent with the phenotypic test results of clarithromycin susceptibility, indicating a lack of correlation between molecular clarithromycin resistance markers for both acquired and inducible resistance.
Subject(s)
Humans , Clarithromycin/pharmacology , Drug Resistance, Bacterial/drug effects , Drug Resistance, Bacterial/genetics , Anti-Bacterial Agents/pharmacology , Mutation/genetics , Mycobacterium/drug effects , Mycobacterium/genetics , Microbial Sensitivity Tests , Genes, BacterialABSTRACT
Abstract Introduction There is a mechanism of macrolide resistance in Staphylococcus spp. which also affects the lincosamides and type B streptogramins characterizing the so-called MLSB resistance, whose expression can be constitutive (cMLSB) or inducible (iMLSB) and is encoded mainly by ermA and ermC genes. The cMLSB resistance is easily detected by susceptibility testing used in the laboratory routine, but iMLSB resistance is not. Therapy with clindamycin in cases of infection with isolated iMLSB resistance may fail. Objective To characterize the phenotypic (occurrence of cMLSB and iMLSB phenotypes) and molecular (occurrence of ermA and ermC genes) profiles of MLSB resistance of clinical isolates of susceptible and methicillin-resistant Staphylococcus aureus and CNS (coagulase-negative Staphylococcus) from patients of a university hospital, in Pernambuco. Methods The antimicrobial susceptibility of 103 isolates was determined by the disk diffusion technique in Mueller–Hinton agar followed by oxacillin screening. The iMLSB phenotype was detected by D test. Isolates with cMLSB and iMLSB phenotypes were subjected to polymerase chain reaction (PCR) for the detection of ermA and ermC genes. Results The cMLSB and iMLSB phenotypes were respectively identified in 39 (37.9%) and five (4.9%) isolates. The iMLSB phenotype was found only in four (10.8%) methicillin-susceptible S. aureus and one (4.5%) methicillin-resistant S. aureus. In the 44 isolates subjected to PCR, four (9.1%) only ermA gene was detected, a lower frequency when compared to only ermC 17 (38.6%) gene and to one (2.3%) isolate presenting both genes. Conclusion In the Staphylococcus spp. analyzed, the ermC gene was found more often than the ermA, although the iMLSB phenotype had been less frequent than the cMLSB. It was important to perform the D test for its detection to guide therapeutic approaches.
Subject(s)
Humans , Staphylococcus/drug effects , Staphylococcus/genetics , Macrolides/pharmacology , Streptogramin B/pharmacology , Drug Resistance, Multiple, Bacterial/genetics , Lincosamides/pharmacology , Phenotype , Brazil , Drug Resistance, Multiple, Bacterial/drug effects , Disk Diffusion Antimicrobial Tests , Genes, Bacterial/genetics , Hospitals, UniversityABSTRACT
Staphylococcus aureus es un importante patógeno involucrado en una serie de infecciones cuyo impacto se incrementa por sus múltiples factores de virulencia y su resistencia a los antimicrobianos. La resistencia a clindamicina inducida por eritromicina constituye un problema creciente en diversas partes del mundo. Este estudio fue de tipo retrospectivo y se analizó el comportamiento frente a los antimicrobianos de 4307 cepas de Staphylococcus aureus aisladas en un hospital de la ciudad de Maracaibo entre enero 2006 y diciembre de 2013. Se determinó la frecuencia de resistencia a clindamicina inducida por eritromicina, su asociación con la resistencia a oxacilina y el origen biológico de las muestras a partir de las cuales se aisló el microorganismo. La susceptibilidad a oxacilina se comprobó mediante el método de difusión con discos en agar y la resistencia inducida a clindamicina usando la prueba D-test. Se detectaron 60 cepas D-Test positivo (1,39%), de las cuales 38(63,33%) fueron sensibles a meticilina y 22 cepas fueron resistentes (36,67%). La resistencia total a clindamicina (constitutiva e inducida) representó el 31,43% (1354) del total de cepas evaluadas. La frecuencia de resistencia inducida a clindamicina en cepas de Staphylococcus aureus en la localidad es aún baja tanto en cepas sensibles como resistentes a meticilina.
Staphylococcus aureus is an important pathogen involved in a series of infections whose impact is increased by its multiple factors of virulence and antimicrobial resistance. Erythromycin-induced clindamycin resistance is a growing problem in various parts of the world. This study was retrospective and analyzed the behavior in response to antimicrobials of 4307 strains of Staphylococcus aureus isolated in a hospital in the city of Maracaibo between January 2006 and December 2013. The frequency of erythromycin-induced clindamycin resistance, its association with resistance to oxacillin and the biological origin of the samples from which the microorganism was isolated were determined. Susceptibility to oxacillin was checked by diffusion method with disk agar and the induced clindamycin resistance was evaluated using the D-test. 60 D-Test positive strains were detected (1.39%), of which 38 (63.33%) were sensitive to methicillin and 22 strains were resistant (36.67%. The total resistance to clindamycin (constitutive and induced) represented 31.43% (1354) of the total number of strains tested. The frequency of induced resistance to clindamycin in Staphylococcus aureus strains in the locality is still low for both methicillin sensitive and resistant strains.
ABSTRACT
OBJECTIVE To study the antibiotic resistance of Staphylococcus isolated from the burn patient wounds. METHODS The sensitivity to 14 common antimicrobial agents was deteded by K-B method. MRSA and MRCNS were detected by cefoxitin disk;the inducible resistance to clindamycin was detected by D-test. RESULTS There were 378 strains of Staphylococcus isolated from the burn patient wounds. The isolation rates of Staphylococcus epidermidis,S. aureus and S. haemolyticus were 43.1%,41.6% and 11.1%. Antibiotic resistance rate to vancomycin,teicoplanin,minocycline,rifapin and nitrofurantoin was 0.0-19.0%,the resistance rate to other antibiotics was 54.1-100.0%. The detection rate of MRSA was 81.5%,the detection rate of MRCNS among S. epidermidis and S. haemolyticus was 55.6% and 66.7%. The total positive rate of D-test was 48.2% in Staphylococcus which were sensitive to clindamycin but resistant to erythromycin. The positive rate of S. aureus,S. epidermidis and S. haemolyticus were 49.1%,44.2% and 57.1%. CONCLUSIONS Staphylococcus are ones of the important pathogens which make burn wound infection happen and the antimicrobial resistance is increasingly severe. The high positive results of MRSA and D-test make great trouble to therapy,and that should have taken more attention of clinic.
ABSTRACT
OBJECTIVE To study the antimicrobial agents resistance of Staphylococcus aureus isolated from clinic.METHODS To test the sensitivity of 20 common antimicrobial agents by K-B.MRSA was detected by cefoxitin disk;and the inducible resistance of clindamycin was detected by D-test.RESULTS The drug resistance rate of this term of S.aureus was high.Except vancomycin,minocycline,teicoplanin,nitrofurantoin and rifampin,the drug resistance rate was higher than 42.6%.From 312 strains of S.aureus 209 strains of MRSA were detected,the rate was 67.0%.The structural antimicrobial resistance rate of clindamycin was 29.5%,the detection rate of inducible resistance was 51.4%.CONCLUSIONS The antimicrobial resistance of S.aureus is increasingly severe.The high positive results of MRSA and D-test make great trouble to therapy,and should have taken more attention of clinic.
ABSTRACT
OBJECTIVE To investigate the drug resistance and the prevalence of inducible clindamycin resistance in clinical isolates of Staphylococcus aureus and evaluate the clinical value of cefoxitin disk diffusion method and oxacillin disk diffusion for detection of meticillin-resistant S.aureus(MRSA).METHODS Bacteria identification and susceptibility test were performed by VITEK-2 system and K-B disk method.The PBP2a was detected by latex agglutination and MRSA was identified by cefoxitin disk diffusion method and oxacillin disk diffusion.The inducible resistance of erythromycin to clindamycin was checked by D-test according to the standards of CLSI(NCCLS).The statistical analysis was performed by WHONET 5.4 and SPSS 13.0 software.RESULTS Resistant rate to penicillin and ampicillin was 98.9% and 100.0%,respectively.Vancomycin-resistant(VRE) or intermediate strains were not found.Of the 93 S.aureus isolates,MRSA and meticillin-sensitive S.aureus(MSSA) were 58(62.4%) and 35(37.6%),respectively.The resistant rate of MRSA to 11 antibiotics was higher than MSSA.The sensitivity and specificity of cefoxitin disk diffusion method were 98.3% and 97.1%,respectively,those of oxacillin disk diffusion were 75.9% and 94.3%.Of the 9 isolates resitant to erythromycin but susceptible to clindamycin,5(55.6%) showed inducible resistance to clindamycin.CONCLUSIONS Resistance of S.aureus is quite serious.Cefoxitin disc diffusion method is a simple and reliable method for the detection of MRSA.The inducible resistance of erythromycin to clindamycin in S aureus should be checked by D-test in clinical microbiology laboratory routinely.
ABSTRACT
OBJECTIVE To apply D-test for detection of inducible resistance of erythromycin to clindamycin in staphylococci and investigate their resistant rate to erythromycin and clindamycin. METHODS According to the standards of NCCLS to detect inducible resistance of erythromycin to clindamycin in staphylococci . RESULTS Co-resistance to erythromycin and clindamycin accounted for 50% and 22.8% in 77 strains of staphylococci (20 of S.aureus and 57 of coagulase-negative staphylococci). The rate of erythromycin resistance and clindamycin sensitivity accounted for 20% and 59.6%. D-test positive rate was 50% and 61.8% of which were erythromycin resistant and clindamycin sensitive respectively. CONCLUSIONS D-test for detection of inducible resistance of erythromycin to clindamycin in staphylococci should be checked in clinical microbiology laboratory in order to help physicians to select MLSb antimicrobial agents correctly.