Rapid laboratory methods provide optimal support for active surveillance efforts to screen for methicillinresistant Staphylococcus aureus (MRSA). Most laboratories struggle to determine the optimal use of resources, considering options to balance cost, speed, and diagnostic accuracy. To assess the performance of common methods, the first comparison of MRSASelect agar (MS) and CHROMagar MRSA (CA), with and without broth enrichment followed by a 24-h subculture to MS, was performed. Results were compared to those of the Xpert MRSA assay. For direct culture methods, the agreement between MS and CA was 98.8%. At 18 h, direct MS identified 93% of all positive samples from direct culture and 84% of those identified by the Xpert MRSA. For Trypticase soy broth-enriched MS culture, incubated overnight and then subcultured for an additional 24 h, the agreement with Xpert MRSA was 96%. The agreement between direct MS and Xpert MRSA was 100% when semiquantitative culture revealed a bacterial density of 2؉ or greater; however, discrepancies between culture and Xpert MRSA arose for MRSA bacterial densities of 1؉ or less, indicating low density as a common cause of false-negative culture results. Since 1؉ or less was established as the most common MRSA carrier state, broth enrichment or PCR may be critical for the identification of all MRSA carriers who may be reservoirs for transmission. In this active-surveillance convenience sample, the use of broth enrichment followed by subculture to MS offered a low-cost but sensitive method for MRSA screening, with performance similar to that of Xpert MRSA PCR.The spread of methicillin-resistant Staphylococcus aureus (MRSA) is a major concern in healthcare settings because human "carriers" can spread MRSA to others, resulting in increased morbidity, mortality, and costs (13,14,17). One strategy to help prevent and control MRSA infections is the use of active surveillance cultures to screen patients for nasal carriage of MRSA, a practice coupled with appropriate barrier precautions for colonized or infected patients. Active surveillance programs are growing in number in the United States (10,20,23,24), despite differences in opinions about the practice and reported gaps in the literature (19). Therefore, clinical microbiology laboratories must respond to provide support for active surveillance screening methods.There is continued debate about the practicality and cost benefit of different MRSA detection methods. Typically, agar culture or PCR methods are used (4); however, additional workload and costs cause laboratories to struggle with resource allocation issues, which often depend on the interplay between assay accuracy, turnaround time, cost per test, and workforce availability. While PCR results can be available in as little as 2 h and are known to provide excellent sensitivity and specificity for MRSA screening (4, 25, 28), PCR methods are more costly than culture methods (6). Alternately, selective and differential chromogenic agars have gained popularity because of lower cost and...
During an outbreak of influenza A, seven patients with Reye's syndrome and 16 ill classmate control subjects were evaluated for characteristics of the patients' prodromal illness and the control subjects illness and for medication usage. Patients during the prodrome and control subjects had similar rates of sore throat, coryza, cough, headache, and gastrointestinal complaints except for documented fever which occurred significantly more often in patients than in control subjects (P = .05). While medications which did not contain salicylate were taken as frequently by patients as control subjects, patients took more salicylate-containing medications than did control children (P < .01). All seven patients took salicylate whereas only eight of 16 control subjects did so (P < .05). Patients took larger doses of salicylate than did the entire control group (P < .01). When the eight control subjects who took salicylate were compared with the patients, the patients still tended to take larger doses (P = .08). Patients with fever took salicylate more frequently than control subjects with fever (P < .01). In addition, salicylate consumption was correlated with severity of Reye's syndrome (P < .05). It is postulated that salicylate, operating in a dose-dependent manner, possibly potentiated by fever, represents a primary causative agent of Reye's syndrome.
Objectives: Haemophilus parasuis is a commensal organism of the upper respiratory tract of conventional pigs that, under appropriate conditions, can cause the Glasser disease, characterized by severe systemic infection, fibrinous polyserositis, arthritis and meningitis. This is an emerging infection with increasing importance in swine production. In our laboratory, we are detecting an increase in the prevalence of resistance to beta-lactam antibiotics in H. parasuis, being this antimicrobial family the first clinical election against respiratory tract infections in swine. Resistance to beta-lactam antimicrobials has yet not been described nor characterized in H. parasuis. Methods: Antimicrobial susceptibility test and MICs were performed folowing NCCLS standard procedures. Identification by PCR was performed with modified procedure of Oliveira, S. et al, 2001. Nitrocefine test was done using OXOID beta-lactamase identification sticks. CAMP test was performed following standard procedures. DNA digestions and cloning manipulation were performed following standard procedures. Results: Phenotypic characteristics and specific tests were used for presumptive identification of H. parasuis. We have developed a PCR based on specific amplification of 821 pb from the coding gene of the 16S subunit rRNA. We confirmed 67 H. parasuis isolates and tested them for antimicrobial susceptibility, 10 were highly resistant to ampicillin (MIC ‡ 32 microg/ml). All resistant isolates showed positive reaction to the nitrocefine test, indicating that beta-lactamases enzymes are involved in this phenomenon. This kind of resistance mechanism is usually harboured in plasmid in other swine respiratory pathogens. The plasmid profile analysis of these strains in agarose gel electrophoresis, after digestion with PstI, was indifferenciable in 8 of the 10 strains. We attempted to transform plasmid DNA directly into E. coli altuogh results were negative, indicating that replication origin is specific to Haemophilus spp. Currently we are cloning the gene responsible for this phenotype in H. parasuis. Conclusion: We have identified beta-lactam resistance in H. parasuis. Resistance is due to beta-lactamases. We are characterizing the genetic determinants responsible for this emerging phenotype.
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