Background: Colonization with methicillin-resistant Staphylococcus aureus(MRSA) poses a hygiene risk that does not spare field hospitals or military medical field camps during military deployments. Diagnostic options ...Background: Colonization with methicillin-resistant Staphylococcus aureus(MRSA) poses a hygiene risk that does not spare field hospitals or military medical field camps during military deployments. Diagnostic options for unambiguously identifying MRSA isolates are usually scarce in military environments. In this study, we assessed the stepwise application of two different selective agars for the specific identification of MRSA in screening analyses.Methods: Nasal swabs from 1,541 volunteers were subjected to thioglycollate broth enrichment and subsequently screened on CHROMagar MRSA selective agar for the identification of MRSA. The MRSA identity of suspiciouslooking colonies was confirmed afterwards or excluded by another selective agar, chrom ID MRSA. All isolates from the selective agars with MRSA-specific colony morphology were identified by biochemical methods and mass spectrometry.Results: The initial CHROMagar MRSA screening identified suspicious colonies in 36 out of 1541 samples. A total of 25 of these 36 isolates showed MRSA-like growth on chrom ID agar. Out of these 25 isolates, 24 were confirmed as MRSA, while one isolate was identified as Staphylococcus kloosii. From the 11 strains that did not show suspicious growth on chrom ID agar, 3 were methicillin-sensitive Staphylococcus aureus(MSSA, with one instance of cocolonization with Corynebacterium spp.), 2 were confirmed as MRSA(with 1 instance of co-colonization with MSSA), 2 were lost during passaging and could not be re-cultured, one could not be identified by the applied approaches, and the remaining 3 strains were identified as Staphylococcus saprophyticus, Staphylococcus hominis(co-colonized with Macrococcus caseolyticus) and Staphylococcus cohnii, respectively.Conclusion: The application of the selective agar CHROMagar MRSA alone proved to be too non-specific to allow for a reliable diagnosis of the presence of MRSA. The combined use of two selective agars in a stepwise approach reduced this non-specificity with an acceptably low loss of sensitivity. Accordingly, such a stepwise screening approach might be an option for resource-restricted military medical field camps.展开更多
<b><span style="font-family:Verdana;">Background:</span></b><span style="font-family:Verdana;"> Early detection and accurate identification of foodborne pathogen outbr...<b><span style="font-family:Verdana;">Background:</span></b><span style="font-family:Verdana;"> Early detection and accurate identification of foodborne pathogen outbreaks is an important public health function. Increased clinical adoption of multiplex PCR assays or culture</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">independent diagnostic tests (CIDT) correlates to more stool specimens</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">sent to public health laboratories (PHL) for characterization. Isolation and confirmation of enteric bacterial </span><span style="font-family:Verdana;">pathogens can prove difficult to consistently recover. The purpose of this study</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">was to evaluate </span><span style="font-family:Verdana;">the </span><span style="font-family:;" "=""><span style="font-family:Verdana;">performance of a broad-use laboratory developed enrichment </span><span><span style="font-family:Verdana;">broth for isolation of </span><i><span style="font-family:Verdana;">Campylobacter</span></i><span style="font-family:Verdana;">, </span><i><span style="font-family:Verdana;">Salmonella</span></i><span style="font-family:Verdana;">, </span><i><span style="font-family:Verdana;">Shigella</span></i><span style="font-family:Verdana;">, and </span><i><span style="font-family:Verdana;">Yersinia</span></i> </span><span style="font-family:Verdana;">strains from stool specimens. </span><b><span style="font-family:Verdana;">Methods:</span></b><span style="font-family:Verdana;"> The study compared differences in positivity rates among media and enrichment combinations at specific time </span><span style="font-family:Verdana;">points. Comparison of direct inoculation (DI)</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> enrichment using a</span><span style="font-family:Verdana;"> lab-developed Enteric Bacterial Enrichment (EBE) broth and gold-standard isolation methods w</span><span style="font-family:Verdana;">ere</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> conducted to test current utility of this established practice with stool specimens heat injured and non-injured. </span><b><span style="font-family:Verdana;">Results:</span></b><span style="font-family:Verdana;"> A total of 234 spiked stool samples, 175 non-injured and 59 heat injured, were tested with</span><b> </b><span style="font-family:Verdana;">varying</span><b> </b><span style="font-family:Verdana;">bacterial concentrations. For non-injured stools, direct inoculation performed better for </span><i><span style="font-family:Verdana;">Campylobacter</span></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">Yersinia</span></i><span style="font-family:Verdana;"> than enrichment. Conversely, </span><i><span style="font-family:Verdana;">Salmonella</span></i><span><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">Shigella</span></i><span style="font-family:Verdana;"> recovery and limit of detection increased with</span></span><span style="font-family:Verdana;"> enrichment. </span><i><span style="font-family:Verdana;">Campylobacter</span></i><span style="font-family:Verdana;"> had the highest percent recovery while </span><i><span style="font-family:Verdana;">Shigella</span></i><span style="font-family:Verdana;"> being the lowest from direct plating at 6-hour and 24-hour enrichment periods. Among broths, EBE performed the best for </span><i><span style="font-family:Verdana;">Yersinia</span></i><span style="font-family:Verdana;"> and similar to Selenite broth for </span><i><span style="font-family:Verdana;">Salmonella</span></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">Shigella</span></i><span style="font-family:Verdana;">. Generally, heat injured stool had a significantly lower percent of recovery than non-heat injured with a higher limit of detection across organisms. </span><b><span style="font-family:Verdana;">Conclusion:</span></b><span style="font-family:Verdana;"> Our data suggest there is </span></span><span style="font-family:Verdana;">an </span><span style="font-family:;" "=""><span style="font-family:Verdana;">only utility for targeted enrichment of CIDT positive </span><i><span style="font-family:Verdana;">Salmonella</span></i><span style="font-family:Verdana;"> stool specimens. We highlight the difficulties of formulating an enrichment broth capable of supporting a variety of enteric pathogens with standardized incubation. Increasing demands on PHL infrastructure warrant further examination of enhancing organism isolation and cost analyses for CIDT positive specimens.</span></span>展开更多
文摘Background: Colonization with methicillin-resistant Staphylococcus aureus(MRSA) poses a hygiene risk that does not spare field hospitals or military medical field camps during military deployments. Diagnostic options for unambiguously identifying MRSA isolates are usually scarce in military environments. In this study, we assessed the stepwise application of two different selective agars for the specific identification of MRSA in screening analyses.Methods: Nasal swabs from 1,541 volunteers were subjected to thioglycollate broth enrichment and subsequently screened on CHROMagar MRSA selective agar for the identification of MRSA. The MRSA identity of suspiciouslooking colonies was confirmed afterwards or excluded by another selective agar, chrom ID MRSA. All isolates from the selective agars with MRSA-specific colony morphology were identified by biochemical methods and mass spectrometry.Results: The initial CHROMagar MRSA screening identified suspicious colonies in 36 out of 1541 samples. A total of 25 of these 36 isolates showed MRSA-like growth on chrom ID agar. Out of these 25 isolates, 24 were confirmed as MRSA, while one isolate was identified as Staphylococcus kloosii. From the 11 strains that did not show suspicious growth on chrom ID agar, 3 were methicillin-sensitive Staphylococcus aureus(MSSA, with one instance of cocolonization with Corynebacterium spp.), 2 were confirmed as MRSA(with 1 instance of co-colonization with MSSA), 2 were lost during passaging and could not be re-cultured, one could not be identified by the applied approaches, and the remaining 3 strains were identified as Staphylococcus saprophyticus, Staphylococcus hominis(co-colonized with Macrococcus caseolyticus) and Staphylococcus cohnii, respectively.Conclusion: The application of the selective agar CHROMagar MRSA alone proved to be too non-specific to allow for a reliable diagnosis of the presence of MRSA. The combined use of two selective agars in a stepwise approach reduced this non-specificity with an acceptably low loss of sensitivity. Accordingly, such a stepwise screening approach might be an option for resource-restricted military medical field camps.
文摘<b><span style="font-family:Verdana;">Background:</span></b><span style="font-family:Verdana;"> Early detection and accurate identification of foodborne pathogen outbreaks is an important public health function. Increased clinical adoption of multiplex PCR assays or culture</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">independent diagnostic tests (CIDT) correlates to more stool specimens</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">sent to public health laboratories (PHL) for characterization. Isolation and confirmation of enteric bacterial </span><span style="font-family:Verdana;">pathogens can prove difficult to consistently recover. The purpose of this study</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">was to evaluate </span><span style="font-family:Verdana;">the </span><span style="font-family:;" "=""><span style="font-family:Verdana;">performance of a broad-use laboratory developed enrichment </span><span><span style="font-family:Verdana;">broth for isolation of </span><i><span style="font-family:Verdana;">Campylobacter</span></i><span style="font-family:Verdana;">, </span><i><span style="font-family:Verdana;">Salmonella</span></i><span style="font-family:Verdana;">, </span><i><span style="font-family:Verdana;">Shigella</span></i><span style="font-family:Verdana;">, and </span><i><span style="font-family:Verdana;">Yersinia</span></i> </span><span style="font-family:Verdana;">strains from stool specimens. </span><b><span style="font-family:Verdana;">Methods:</span></b><span style="font-family:Verdana;"> The study compared differences in positivity rates among media and enrichment combinations at specific time </span><span style="font-family:Verdana;">points. Comparison of direct inoculation (DI)</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> enrichment using a</span><span style="font-family:Verdana;"> lab-developed Enteric Bacterial Enrichment (EBE) broth and gold-standard isolation methods w</span><span style="font-family:Verdana;">ere</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> conducted to test current utility of this established practice with stool specimens heat injured and non-injured. </span><b><span style="font-family:Verdana;">Results:</span></b><span style="font-family:Verdana;"> A total of 234 spiked stool samples, 175 non-injured and 59 heat injured, were tested with</span><b> </b><span style="font-family:Verdana;">varying</span><b> </b><span style="font-family:Verdana;">bacterial concentrations. For non-injured stools, direct inoculation performed better for </span><i><span style="font-family:Verdana;">Campylobacter</span></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">Yersinia</span></i><span style="font-family:Verdana;"> than enrichment. Conversely, </span><i><span style="font-family:Verdana;">Salmonella</span></i><span><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">Shigella</span></i><span style="font-family:Verdana;"> recovery and limit of detection increased with</span></span><span style="font-family:Verdana;"> enrichment. </span><i><span style="font-family:Verdana;">Campylobacter</span></i><span style="font-family:Verdana;"> had the highest percent recovery while </span><i><span style="font-family:Verdana;">Shigella</span></i><span style="font-family:Verdana;"> being the lowest from direct plating at 6-hour and 24-hour enrichment periods. Among broths, EBE performed the best for </span><i><span style="font-family:Verdana;">Yersinia</span></i><span style="font-family:Verdana;"> and similar to Selenite broth for </span><i><span style="font-family:Verdana;">Salmonella</span></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">Shigella</span></i><span style="font-family:Verdana;">. Generally, heat injured stool had a significantly lower percent of recovery than non-heat injured with a higher limit of detection across organisms. </span><b><span style="font-family:Verdana;">Conclusion:</span></b><span style="font-family:Verdana;"> Our data suggest there is </span></span><span style="font-family:Verdana;">an </span><span style="font-family:;" "=""><span style="font-family:Verdana;">only utility for targeted enrichment of CIDT positive </span><i><span style="font-family:Verdana;">Salmonella</span></i><span style="font-family:Verdana;"> stool specimens. We highlight the difficulties of formulating an enrichment broth capable of supporting a variety of enteric pathogens with standardized incubation. Increasing demands on PHL infrastructure warrant further examination of enhancing organism isolation and cost analyses for CIDT positive specimens.</span></span>
