Discrimination of methicillin-resistant Staphylococcus aureus from borderline-resistant and susceptible isolates by different methods

Resende, C A; Figueiredo, Agnes Marie Sá

doi:10.1099/00222615-46-2-145

Cited by 26 publications

(18 citation statements)

References 19 publications

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“…Both the disk diffusion test (oxacillin 1 mg/L) and the broth macro-dilution method failed to detect MRSA in this mixed population. Similar results were observed when truly heterogeneous MRSA class 1 and 2 were submitted to those recommended tests [20]. However, the agar screen (oxacillin 6 mg/L or methicillin 10 mg/L), as recommended by the NCCLS, was able to detect MRSA in all mixed cultures studied.…”

Section: Discussionsupporting

confidence: 68%

Occurrence of methicillin-resistant and -susceptible Staphylococcus aureus within a single colony contributing to MRSA mis-identification

Falcao

Texeira

Ferreira-Carvalho

et al. 1999

Journal of Medical Microbiology

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Many methods have been described for the detection of methicillin-resistantStaphylococcus aureus (MRSA), but the homogeneous or heterogeneous expression of methicillin resistance affects the reliability of those methods. This study demonstrates that close association between methicillin-susceptible S. aureus (MSSA) and MRSA strains in the host colonisation site can present additional problems for the detection of MRSA in clinical laboratories, which may contribute to failure in the control of MRSA infection in hospital. Worse, this association may also account for the emergence of MRSA during antibiotic therapy.

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Section: Discussionsupporting

confidence: 68%

Occurrence of methicillin-resistant and -susceptible Staphylococcus aureus within a single colony contributing to MRSA mis-identification

Falcao

Texeira

Ferreira-Carvalho

et al. 1999

Journal of Medical Microbiology

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“…**The antibiotics piperacillin+tazobactam, meropenem, imipenem, amikacin and ciprofloxacin were also screened, but there were no positive results. A -amoxicillin, B -amoxicillin-clav.acid, C -piperacillin, D -ticarcillin, E -ticarcillin-clav.acid, F -cephalothin, Gcefoxitin, H -cefotaxim, I -ceftazidim, J -cefepim, K -cefuroxim, L -ceftazidime 1, M -cotrimoxazol, O -tobramycin, Pgentamicin, Q-netilmicin 1996, Resende & Figueiredo 1997, Soares et al 1997.…”

Section: Streptococcus Acidominimus A(5)mentioning

confidence: 99%

Ants as carriers of antibiotic-resistant bacteria in hospitals

Moreira¹,

Morais²,

Vieira‐da‐Motta³

et al. 2005

Neotrop. Entomol.

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Neotropical Entomology 34(6): 999-1006 (2005) Formigas Como Agentes Carreadores de Bactérias Resistentes em Hospitais RESUMO -A presença de bactérias resistentes a antimicrobianos e carreadas por formigas isoladas em hospitais foi investigada em Campos dos Goytacazes, RJ. Três instituições de saúde foram visitadas nos períodos de 2001 a 2002 e amostras foram coletadas em áreas de cuidados médicos consideradas críticas baseando-se em critérios de maior risco para a aquisição de infecções por pacientes hospitalizados. Quatro espécies de formigas foram identificadas, Tapinoma melanocephalum (Fabricius) (63,1%), Paratrechina longicornis (Latreille) (21,1%), Monomorium pharaonis (L.) (10,5%) e Solenopsis saevissima (S. Smith) (5,3%) como carreadoras de 21 morfoespécies de bactérias. Os testes de identificação bacteriana e de perfil de resistência antimicrobiana foram realizados por meio de kits padronizados e avaliados por método automatizado. Entre as bactérias isoladas, algumas foram consideradas multirresistentes, incluindo o gênero Acinetobacter, Streptococcus, Gemella, e Klebsiella. Para análise antimicrobiana do gênero Enterobacter foi utilizado o método padrão de difusão em disco. Os resultados sugerem que existem riscos para pacientes que procuram por assistência de saúde nos hospitais estudados e a ocorrência de bactérias emergentes em hospitais carreadas por formigas devem ser consideradas. PALAVRAS-CHAVE: Infecçcão nosocomial, antimicrobiano, controle, formiga urbana ABSTRACT -The presence of antimicrobial-resistant bacteria and carried by ants isolated from hospitals was investigated in Campos dos Goytacazes, RJ, Brazil. Three health institutions were visited from 2001 to 2002 and samples were collected within critical areas of medical care based on criteria of greater risk of patient hospital acquired-infection. Four ant species were identified, Tapinoma melanocephalum (Fabricius) (63.1%), Paratrechina longicornis (Latreille) (21.1%), Monomorium pharaonis (L.) (10.5%), and Solenopsis saevissima (S. Smith) (5.3%) carrying 21 species of bacteria. The tests for bacteria species identification and antimicrobial-resistance profile were carried out by using standardized kits and evaluated by automated equipment. Among the bacteria isolates, some were considered multiresistant isolates, including genera Acinetobacter, Streptococcus, Gemella, and Klebsiella. For Enterobacter antibacterial analysis the disk diffusion standard method was used. The results suggest that there are risks for patients which seek for health assistance in the hospitals studied, and the presence of emerging bacteria isolates in hospital carried by ants must be considered.

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“…In studies performed since 1990 that used the presence of the mecA gene as the gold standard (1,2,4,5,9,10,11,12,15,16,18,19,23,24,26), the sensitivity of the agar screen test for the detection of resistant strains was excellent. However, two reports noted that when very heteroresistant strains were tested, the sensitivity decreased (2, 16).…”

mentioning

confidence: 99%

“…Conversely, the specificity among susceptible strains tested was very good unless strains with borderline MICs were included (9,12). Fewer studies have compared the detection of resistance by disk diffusion to the presence of mecA (2,8,11,15,16), but two studies (2,8) that included very heterogeneous strains found sensitivities of detection as low as 61% (2).…”

mentioning

confidence: 99%

Performance of Eight Methods, Including Two New Rapid Methods, for Detection of Oxacillin Resistance in a Challenge Set of Staphylococcus aureu s Organisms

et al. 2001

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Using a set of 55 Staphylococcus aureus challenge organisms, we evaluated six routine methods (broth microdilution, disk diffusion, oxacillin agar screen, MicroScan conventional panels, MicroScan rapid panels, and Vitek cards) currently used in many clinical laboratories and two new rapid methods, Velogene and the MRSAScreen, that require less than a day to determine the susceptibility of S. aureus to oxacillin. The methods were evaluated by using the presence of the mecA gene, as detected by PCR, as the "gold standard." The strains included 19 mecA-positive heterogeneously resistant strains of expression class 1 or 2 (demonstrating oxacillin MICs of 4 to >16 g/ml) and 36 mecA-negative strains. The oxacillin MICs of the latter strains were 0.25 to 4 g/ml when tested by broth microdilution with 2% NaCl-supplemented cation-adjusted Mueller-Hinton broth as specified by the NCCLS. However, when tested by agar dilution with 4% salt (the conditions used in the oxacillin agar screen method), the oxacillin MICs of 16 of the mecA-negative strains increased to 4 to 8 g/ml. On initial testing, the percentages of correct results (% sensitivity/% specificity) were as follows: broth microdilution, 100/100; Velogene, 100/100; Vitek, 95/97; oxacillin agar screen, 90/92; disk diffusion, 100/89; MicroScan rapid panels, 90/86; MRSA-Screen, 90/100; and MicroScan conventional, 74/97. The MRSA-Screen sensitivity improved to 100% if agglutination reactions were read at 15 min. Repeat testing improved the performance of some but not all of the systems.The oxacillin agar screen test has been used for many years to aid in the identification of oxacillin-resistant staphylococci. Recently, this test was shown to be ineffective for coagulasenegative staphylococci (20), and the NCCLS no longer recommends its use for these organisms. In a previous study, the inoculation methods for the oxacillin agar screen test were more clearly defined (19a), and recommendations were made to use a 1-l loop or an expressed swab inoculated into an area of 10 to 15 mm in diameter. In that study, a challenge group of Staphylococcus aureus isolates was tested, including several borderline oxacillin-resistant mecA-positive strains (n ϭ 19) that would be difficult to detect and mecA-negative strains (n ϭ 36) that might be falsely detected as resistant. Since several lots of oxacillin screen agar lacked specificity, the issue of the reliability of all methods for detection of oxacillin resistance was raised. Thus, using that same group of challenge organisms, we chose to examine the accuracy of the other routine methods for detecting oxacillin resistance. These methods were broth microdilution, disk diffusion, oxacillin agar screen, MicroScan conventional panels, MicroScan rapid panels, and Vitek. We also evaluated two new rapid methods, Velogene, a cycling probe assay, and MRSA-Screen, a latex agglutination method that detects the presence of PBP-2a (also known as PBP-2Ј), the penicillin-binding protein (PBP) responsible for the most common form of oxacillin resis...

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Discrimination of methicillin-resistant Staphylococcus aureus from borderline-resistant and susceptible isolates by different methods

Cited by 26 publications

References 19 publications

Occurrence of methicillin-resistant and -susceptible Staphylococcus aureus within a single colony contributing to MRSA mis-identification

Occurrence of methicillin-resistant and -susceptible Staphylococcus aureus within a single colony contributing to MRSA mis-identification

Ants as carriers of antibiotic-resistant bacteria in hospitals

Performance of Eight Methods, Including Two New Rapid Methods, for Detection of Oxacillin Resistance in a Challenge Set of Staphylococcus aureu s Organisms

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