Phenotypic methods for screening carbapenem-resistant Enterobacteriaceae and assessment of their antimicrobial susceptibility profile

Abstract INTRODUCTION: In this study, we used phenotypic methods to screen carbapenem-resistant Enterobacteriaceae (CREs) and evaluated their antimicrobial sensitivity profile. METHODS: One hundred and seventy-eight CREs were isolated at a university hospital in south Brazil in a one-year period. Samples were assessed using disk diffusion tests with inhibitors of β-lactamases such as phenylboronic acid (AFB), cloxacillin (CLOXA), and ethylenediaminetetraacetic acid (EDTA). Strains with differences in zone diameters ≥ 5mm for disks supplemented or not were considered producers of carbapenemases. RESULTS: Klebsiella pneumoniae was the most prevalent CRE, which appeared in 80.3% cases (n = 143). Among clinical materials, the rectal swab was responsible for 43.4% of the isolations (n = 62), followed by urine (18.9%; n = 27). Among the CREs identified in this study, the growth of 56.7% (n = 101) isolates, which were putative producers of Klebsiella pneumoniae carbapenemase (KPC), were inhibited by AFB, whereas 7.3% (n = 13) isolates were inhibited by both AFB and CLOXA and were considered as putative producers of plasmid-mediated AmpC; approximately 3.4% (n = 6) were inhibited by EDTA, which possibly produced metallo-β-lactamase. Lastly, 32.6% (n = 58) cases showed negative results for AFB, CLOXA, and EDTA sensitivity, and represented another class of β-lactamases and/or mechanism of resistance. CONCLUSIONS: Phenotypic screening of CREs is important for clinical laboratories that monitor outbreaks of resistant microbes. Phenotypic tests that use carbapenemase inhibitors and enhancers such as AFB, CLOXA, and EDTA are necessary since they are good screening methods for the detection of carbapenemases.

Staphylococcal scalded skin syndrome in a premature newborn caused by methicillin-resistant Staphylococcus aureus: case report / Síndrome da pele escaldada estafilocócica em um recém-nascido prematuro causada por Staphylococcus aureus meticilina-resistente: relato de caso

CONTEXT: Staphylococcal scalded skin syndrome is an exfoliative skin disease. Reports of this syndrome in newborns caused by methicillin-resistant Staphylococcus aureus are rare but, when present, rapid diagnosis and treatment is required in order to decrease morbidity and mortality. CASE REPORT: A premature newly born girl weighing 1,520 g, born with a gestational age of 29 weeks and 4 days, developed staphylococcal scalded skin syndrome on the fifth day of life. Cultures on blood samples collected on the first and fourth days were negative, but Pseudomonas aeruginosa and Enterococcus sp. (vancomycin-sensitive) developed in blood cultures performed on the day of death (seventh day), and Pseudomonas aeruginosa and Serratia marcescens were identified in cultures on nasopharyngeal, buttock and abdominal secretions. In addition to these two Gram-negative bacilli, methicillin-resistant Staphylococcus aureus was isolated in a culture on the umbilical stump (seventh day). The diagnosis of staphylococcal scalded skin syndrome was based on clinical criteria.

CONTEXTO: A síndrome da pele escaldada estafilocócica é uma doença esfoliativa de pele. São raros os relatos desta síndrome causada por Staphylococcus aureusresistente à meticilina em neonatos, mas, quando presentes, exigem diagnóstico e tratamento rápidos para diminuir a morbidade e mortalidade. RELATO DE CASO: Uma menina recém-nascida prematura, pesando 1.520 g ao nascimento, com idade gestacional de 29 semanas e 4 dias, desenvolveu síndrome da pele escaldada estafilocócica no quinto dia de vida. As culturas de sangue coletadas no primeiro e quarto dias foram negativas, mas houve desenvolvimento de Pseudomonas aeruginosa e Enterococcus sp. (vancomicina sensível) na hemocultura realizada no dia do óbito (sétimo dia) e Pseudomonas aeruginosa e Serratia marcescens foram identificadas nas culturas de secreção da nasofaringe, nádega e da secreção abdominal. Na cultura do coto umbilical (sétimo dia), além desses dois bacilos Gram-negativos, foi isolado o Staphylococcus aureus resistente à meticilina. O diagnóstico da síndrome da pele escaldada estafilocócica foi baseado em critério clínico.

Prevalence of methicillin-resistant Staphylococcus aureus in a University Hospital in the South of Brazil

Methicillin-resistant Staphylococcus aureus (MRSA) stand out as one of the main agents causing nosocomial and community infections. This retrospective study aimed to analyze the MRSA predominance in a university hospital in the south of Brazil and it was carried out for five years (from 2007 to 2011). 616 MRSA (33,3% of the total) were isolated and an important reduction in the MRSA predominance was observed along the study. Although it was registered a reduction in the MRSA predominance, male adult patients (41-70 years old), who were in the Medical Clinic and Adult ICU, had the highest infection rates and concerning MRSA isolates rates, these were higher in blood and tracheal aspirates. In conclusion, studies of this type are becoming relevant to recognize pathogens like MRSA and to determine its predominance.

Staphylococcus aureus resistentes à meticilina (MRSA) destacam-se mundialmente como um dos mais frequentes patógenos nosocomiais e comunitários. Este estudo retrospectivo teve por objetivo analisar a prevalência de MRSA em um hospital universitário no sul do Brasil. Durante cinco anos (2007 a 2011), 616 MRSA (33,3% do total de S. aureus) foram isolados, sendo que sua frequência de isolamento apresentou considerável redução no decorrer do estudo. Nossos resultados demonstraram que as maiores taxas de isolamento dos MRSA ocorreram em amostras de sangue e secreção traqueal. As infecções prevaleceram em pacientes adultos (41 a 70 anos), do sexo masculino, internados na Clínica Médica e UTI adulto. Estudos como este se tornam importantes para o reconhecimento de patógenos resistentes, como o MRSA, e para a determinação da sua prevalência.

Evaluation of constitutive and inducible resistance to clindamycin in clinical samples of Staphylococcus aureus from a tertiary hospital

Introduction Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have become common in hospitals and the community environment, and this wide resistance has limited patient treatment. Clindamycin (CL) represents an important alternative therapy for infections caused by S. aureus. Antimicrobial susceptibility testing using standard methods may not detect inducible CL resistance. This study was performed to detect the phenotypes of resistance to macrolides-lincosamides-streptogramin B (MLSB) antibiotics, including CL, in clinical samples of S. aureus from patients at a tertiary hospital in Santa Maria, State of Rio Grande do Sul, Brazil. Methods One hundred and forty clinical isolates were submitted to the disk diffusion induction test (D-test) with an erythromycin (ER) disk positioned at a distance of 20mm from a CL disk. The results were interpreted according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI). Results In this study, 29 (20.7%) of the 140 S. aureus samples were resistant to methicillin (MRSA), and 111 (79.3%) were susceptible to methicillin (MSSA). The constitutive resistance phenotype (cMLSB) was observed in 20 (14.3%) MRSA samples and in 5 (3.6%) MSSA samples, whereas the inducible resistance phenotype (iMLSB) was observed in 3 (2.1%) MRSA samples and in 8 (5.8%) MSSA samples. Conclusions The D-test is essential for detecting the iMLSB phenotype because the early identification of this phenotype allows clinicians to choose an appropriate treatment for patients. Furthermore, this test is simple, easy to perform and inexpensive. .