In September of 2004, we investigated 7 cases of post-myelography meningitis. Streptococcal species were recovered from blood or cerebrospinal fluid in all cases. Our findings suggest that droplet transmission of the oral flora of the clinician performing the procedure was the most likely source of these infections. The Centers for Disease Control and Prevention recommends the use of face masks by those performing myelograms.
Background
Although intestinal colonization precedes most extraintestinal Escherichia coli infections, colonization-promoting factors are incompletely understood. We compared within-household E. coli colonization patterns with host and bacterial traits.
Methods
Twenty-two veterans with a clinical E. coli isolate and their 46 human and animal household members underwent longitudinal fecal sampling. Distinct E. coli strains were characterized for phylogenetic background, virulence genes, antibiotic resistance, and colonization behaviors. Host and bacterial traits were assessed statistically as predictors of colonization behaviors.
Results
Among the 139 unique-by-household fecal E. coli strains, univariable predictors of colonization behavior included (i) host demographics, (ii) matching the index clinical isolate, and (iii) bacterial characteristics (2 phylogroups, 5 clonal lineages, 18 virulence genes, and molecular extraintestinal pathogenic E. coli status). Multivariable predictors of colonization behavior included: veteran host, spouse host, matching the index clinical isolate, phylogroup F, ST73, hlyD (alpha hemolysin), hlyF (variant hemolysin), H7 fliC (flagellar variant), vat (vacuolating toxin), and iha (adhesin-siderophore).
Conclusions
Host demographics, multiple bacterial "virulence" traits, and matching the index clinical isolate predicted E. coli fecal colonization behaviors. Thus, certain bacterial characteristics may promote both colonization and pathogenicity. Future interventions directed toward such traits might prevent E. coli infections both directly and by disrupting antecedent colonization.
For patients with possible Staphylococcus aureus infection, providers must decide whether to treat empirically for methicillin-resistant S. aureus (MRSA). Nares MRSA colonization screening tests could inform decisions regarding empiric MRSA-active antibiotic use.1,2
BackgroundProviders often must decide whether to empirically treat hospitalized patients for MRSA. The results of routine MRSA nares swabs often are available prior to clinical culture results, so could conceivably help guide antibiotic selection. However, the reported predictive value of nares swabs is mixed. Therefore, we sought to define the predictive characteristics of MRSA nares swabs for the MRSA status of clinical Staphylococcus aureus(SA) isolates at the Minneapolis Veterans Affairs Medical Center (MVAMC).MethodsWe retrospectively reviewed electronic health records (EHRs) of 599 MVAMC inpatients with a clinical SA isolate between 2013 and 2016. The SA isolates were from skin/soft tissue (n = 281), blood (n = 99), respiratory (n = 90), urine (n = 62), and bone/joint (n = 27). We recorded each isolate’s MRSA vs. MSSA status and the result of the temporally closest MRSA nares swab, then compared swab and culture results in relation to culture site and swab-to-culture interval.ResultsOverall, for identifying MRSA among patients with a clinical SA isolate, the MRSA nares swab’s sensitivity was 65.1%, specificity 96.2%, positive predictive value (PPV) 91.4%, and negative predictive value (NPV) 81.9%. The odds ratio (OR) of a positive MRSA nares swab for a MRSA-positive culture was 47.9 (95% confidence interval [CI] 25.7–89.2). Exclusion of the 70 nares swabs that were collected > 14 days before the clinical isolate increased the NPV to 84.0%, with a corresponding sensitivity 68.0%, specificity 83.9%, and PPV 90.3%. Test performance varied significantly by culture site (Table).Culture SiteOR (95% CI)Sens. (%)Spec. (%)PPV (%)NPV (%)All47.9 (25.7–89.2)65.196.291.481.9Skin/soft tissue59.7 (22.5–158.3)63.497.293.081.9Blood65.9 (13.6–319.9)95.896.992.085.1Respiratory64.1 (13.3–309.5)73.295.993.881.0Urine13.5 (3.7–49.5)64.388.281.875.0Bone/jointN/A20.0100.0100.084.6ConclusionA positive MRSA nares swab greatly increased the odds that a SA isolate was MRSA. However, sensitivity and NPV were lower than some prior studies. Our findings suggest that, for veterans with a severe infection that might be due to SA, a negative MRSA nares screen provides insufficient NPV to allow confident omission of empiric MRSA-active antibiotics.Disclosures
All authors: No reported disclosures.
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