Macrolide-lincosamide-streptogramin B resistance phenotypes and their associated genotypes in Staphylococcus aureus isolates from a tertiary level public hospital of Uruguay / Fenotipos de resistencia a macrólidos lincosamidas-estreptograminas B y sus genotipos asociados en Staphylococcus aureus aislados en un hospital público de nivel terciario en Uruguay

Abstract This study was undertaken to investígate the resistance phenotypes to macrolide-lincosamide-streptogramin B (MLSb) antibiotics and their associated genotypes in isolates of Staphylococcus aureus. We analyzed one hundred, consecutive, non-duplicate isolates (methicillin-susceptible MSSA, n = 53 and methicillin-resistant MRSA, n =47) obtained from var-ious clinical samples between July 2012 to December 2013. The resistance profile to MLSb antibiotics was determined by phenotypic methods and the resistance genes were detected by PCR assays. All of the isolates were subjected to pulsed-field gel electrophoresis (SmaI-PFGE). The overall prevalence of resistance to MLSb antibiotics was 38% and the resistance phenotype distribution was as follows: cMLSb, 22%; iMLSB, 10%; MSb, 5% and L, 1%. We detected ermA, ermC, ermB and mrsA/B genes in these resistant isolates. The single ermA gene was commonly observed mainly in those with a cMLSb R phenotype, whereas the combination ermA and ermC was more commonly observed in isolates with inducible expression. The patterns of SmaI-PFGE suggest a great genetic diversity in both MRSA and MSSA resistant to MLSb antibiotics. The results demonstrate the local presence of S. aureus resistant to MLSb antibiotics and its most frequently described responsible genes. Some of these isolates, especially those with the iMLSB phenotype, may be associated with therapeutic failure. Therefore, efforts should be directed to the correct detection of all MLSb resistant isolates using appropriate laboratory tests. PFGE results reveal a wide spread of resistance genes rather than the circulation of S. aureus clones resistant to MLSb antibiotics.

Resumen Los objetivos de este estudio fueron investigar en Staphylococcus aureus la presencia de fenotipos resistentes a los antibióticos macrólidos, lincosamidas y estreptograminas tipoB (MLSb) y conocer sus genotipos responsables. Analizamos 100 aislamientos consecutivos, no duplicados (53 sensibles a meticilina [MSSA] y 47 resistentes a meticilina [MRSA]), obtenidos entre 2012 y 2013 a partir de diferentes muestras clínicas. El perfil de resistencia a los antibióticos MLSb fue determinado por métodos fenotípicos y los genes de resistencia se detectaron por PCR. Todos los aislamientos fueron comparados por SmaI-PFGE. La prevalencia global de resistencia a los antibióticos MLSB fue del 38% y la distribución de los fenotipos de resistencia fue la siguiente: cMLSB, 22%; iMLSB, 10%; MSB, 5%; L, 1%. Se detectaron los genes ermA, ermC y mrsA/B en los aislamientos resistentes. El gen ermA se observó, sobre todo, en aislamientos con fenotipo resistente constitutivo R (cMLSB), mientras que la combinación ermA y ermC se detectó principalmente en aislamientos con resistencia inducible (iMLSB). Los patrones de Smal-PFGE sugieren una gran diversidad genética en los aislamientos resistentes a los antibióticos MLSb, tanto MRSA como MSSA. Los resultados demuestran la presencia local de S. aureus resistentes a los antibióticos MLSB y de sus genes responsables más frecuentemente descritos. Estos cultivos, especialmente aquellos con fenotipo resistente iMLSB, pueden asociarse con fallas terapéuticas. Por lo tanto, los esfuerzos deben dirigirse a la correcta detección de todos los cultivos resistentes a MLSB utilizando pruebas de laboratorio adecuadas. Los resultados de Smal-PFGE sugieren una amplia diseminación de genes de resistencia, más que la circulación de clones resistentes a los antibióticos MLSB.

Evaluation of Staphylococcus aureus resistance profile isolated from nursing students in an institution of higher education / Avaliação do perfil de resistência de staphylococcus aureus isolados de estudantes de enfermagem de uma instituição de ensino superior

Staphylococcus aureus causes a large variety of infections, where many of them are acquired in the hospital environment. A significant part of the population is a nasal carrier of this type of microorganism. The present study evaluated the nasal colonization by S. aureus, identifying its resistance profile in nursing students from a private educational institute of higher education. Nasal swab samples were collected and identified for S. aureus. Moreover, an antibiogram assay was performed, followed by the search for ermA and ermC genes using PCR. Sixty -two students were included and we isolated 20 positive samples (32,5%) for S. aureus. For the phenotypic profile, 30% were found to be resistant to Erythromycin and 10% to Oxacillin and Cefoxitin. For the D-test in the genotypic profile, 25% presented mecA gene (MRSA), 5% of ermA gene, 35% of ermC gene and 10% with ermC and mecA genes. These data reinforce the necessity of monitoring bacterial colonization in hospital environment, which are potentially resistant in health professionals.

Staphylococcus aureus causa uma grande variedade de infecções, muitas delas adquiridas no ambiente hospitalar. Uma parcela significativa da população é carreadora nasal desses micro-organismos. O presente trabalho avaliou a colonização nasal por S. aureus identificando seu perfil de resistência em estudantes de enfermagem de uma instituição privada de ensino superior. Foram coletadas e identificadas amostras de swab nasal para S. aureus e realizado o antibiograma e a detecção por PCR dos genes mecA, ermA e ermC. Foram incluídos 62 alunos e isoladas 20 amostras (32,3%) positivas para S. aureus, no perfil fenotípico, 30% apresentaram resistência à Eritromicina e 10% para Oxacilina, Cefoxitina e para o teste D, no perfil genotípico 25% apresentaram gene mecA (MRSA), 5% do gene ermA e 35% do gene ermC, e 10% com genes ermC e mecA. Esses dados reforçam a necessidade de monitoramento de colonização por bactérias potencialmente resistente em profissionais da saúde.

The prevalence of genotypes that determine resistance to macrolides, lincosamides, and streptogramins B compared with spiramycin susceptibility among erythromycin-resistant Staphylococcus epidermidis

Coagulase-negative staphylococci, particularly Staphylococcus epidermidis, can be regarded as potential reservoirs of resistance genes for pathogenic strains, e.g., Staphylococcus aureus. The aim of this study was to assess the prevalence of different resistance phenotypes to macrolide, lincosamide, and streptogramins B (MLSB) antibiotics among erythromycin-resistant S. epidermidis, together with the evaluation of genes promoting the following different types of MLSB resistance:ermA, ermB, ermC,msrA, mphC, and linA/A’. Susceptibility to spiramycin was also examined. Among 75 erythromycin-resistantS. epidermidis isolates, the most frequent phenotypes were macrolides and streptogramins B (MSB) and constitutive MLSB (cMLSB). Moreover, all strains with the cMLSB phenotype and the majority of inducible MLSB (iMLSB) isolates were resistant to spiramycin, whereas strains with the MSB phenotype were sensitive to this antibiotic. The D-shape zone of inhibition around the clindamycin disc near the spiramycin disc was found for some spiramycin-resistant strains with the iMLSB phenotype, suggesting an induction of resistance to clindamycin by this 16-membered macrolide. The most frequently isolated gene was ermC, irrespective of the MLSB resistance phenotype, whereas the most often noted gene combination wasermC, mphC, linA/A’. The results obtained showed that the genes responsible for different mechanisms of MLSB resistance in S. epidermidis generally coexist, often without the phenotypic expression of each of them.

Induced and Constitutive Clindamycin Resistance in Staphylococcus spp. Strains Isolated from a Neonatal Intensive Care Unit.

Aims: The hospital environment can act as a reservoir for microorganisms, which in turn can contaminate a range of hospital equipment and survive for long periods of time. One of these environments the Neonatal Intensive Care Unit (NICU), for the initial post partum period serving as a home for newborns of low birth weight and needing invasive procedures for administration of nutritional and medicinal substances, which makes the NICU a critical area for housing individuals with immune system. Thus, the aim of this study was to evaluate the phenotypic appearance of resistance of the Staphylococcus spp. compared to erythromycin and clindamycin, originating from isolated areas of a NICU in the city of Campina Grande - PB. Place and Duration of Study: Sample: Neonatal Intensive Care Unit of a public hospital in the city of Campina Grande – PB, Brazil. Processing and Analysis of Samples: Clinical Analysis Laboratory of the State University of Paraíba, between August and October 2012. Methodology: Samples were collected from surfaces present at the NICU. The samples were identified and strains of Staphylococcus spp. were subjected to sensitivity, and to verify erythromycin-induced resistance the D-test was used, following the CLSI standards-M100-S22 (2012). Results: Bacterial strains from all surfaces analyzed were isolated, 59.02% of isolates belong to the genus Staphylococcus spp., representing 36 bacterial strains, of which 31 were subspecies Staphylococcus aureus and 5 were coagulase-negative staphylococcus (CoNS). There was found more than 70% resistance to the group of penicillins and more than 30% to methicillin. Among the 36 strains of Staphylococcus spp. 19.45% were resistant to erythromycin. The rate found for constitutive resistance to macrolides (MLSBc) was 5.56% and was observed induced resistance to the macrolide type (MLSBi) in 2.78% the strains. Conclusion: The resistotyping of isolated strains for inducible and constitutive resistance may be considered a test of substantial importance not only as an epidemiologic marker in view of analyzing possible dissemination of hospital strains, but with respect to adequate, and precise determination of the antibiotic treatment of neonates.

Distributions of Macrolide-Lincosamide-Streptogramin B Resistance Phenotypes in Clinical Isolates of Staphylococi / 대한임상미생물학회지

BACKGROUND: Increased resistance rates to macrolide-lincosamide-streptogramin B (MLSB) antibiotics among clinical isolates of staphylococci are considered as a consequence of an expanded use of these antibiotics in the treatment of Gram-positive infections. The proportion of MLSB resistance phenotypes of staphylococci is quite different by geographical variations and study periods. The aim of the present study was to determine the distribution of MLSB resistance phenotypes among clinical isolates of staphylococci in a university hospital. METHODS: The MLSB resistance phenotypes of clinical isolates of staphylococci were investigated by the double-disk diffusion test using erythromycin and clindamycin disks. RESULTS: Of 7,916 isolates, 55.7% exhibited a constitutive resistance phenotype (cMLSB) whereas 8.1% expressed an inducible resistance phenotype (iMLSB). Among 3,419 coagulase-negative staphylococci (CNS), 32.6% and 10.0% exhibited cMLSB and iMLSB resistance phenotypes, respectively. Of 4,497 Staphylococcus aureus isolates, 73.1% and 6.8% were cMLSB and iMLSB resistance phenotypes, respectively. cMLSB was detected among 90.2% of methicillin-resistant S. aureus (MRSA), 46.5% of methicillin-resistant CNS (MRCNS), 3.2% of methicillin-susceptible CNS (MSCNS), and 2.2% of methicillin-susceptible S. aureus (MSSA). iMLSB was detected among 16.5% of MSSA, 11.5% of MRCNS, 6.7% of MSCNS, and 4.4% of MRSA. CONCLUSION: MLSB resistance was more prevalent among S. aureus isolates than CNS strains. Although cMLSB was the most frequently detected resistance phenotype among the total staphylococcal isolates, methicillin-susceptible strains exhibited somewhat higher iMLSB resistance rates compared with methicillin-resistant strains.