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.

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.