Utilizing Moist or Dry Swabs for the Sampling of Nasal MRSA Carriers? An <i>In Vivo</i> and <i>In Vitro</i> Study

<div><p>This study investigates the quantitative bacterial recovery of Methicillin-resistant S<i>taphylococcus aureus</i> (MRSA) in nasal screenings by utilizing dry or moistened swabs within an <i>in vivo</i> and an <i>in vitro</i> experimental setting. 135 nasal MRSA carriers were each swabbed in one nostril with a dry and in the other one with a moistened rayon swab. Quantitative bacterial recovery was measured by standard viable count techniques. Furthermore, an anatomically correct artificial nose model was inoculated with a numerically defined suspension of MRSA and swabbed with dry and moistened rayon, polyurethane-foam and nylon-flocked swabs to test these different settings and swab-materials under identical laboratory conditions. <i>In vivo</i>, quantities of MRSA per nostril in carriers varied between <10¹ and >10⁷ colony forming units, with a median of 2.15x10⁴ CFU. However, no statistically significant differences could be detected for the recovery of MRSA quantities when swabbing nasal carriers with moist or dry rayon swabs. <i>In vitro</i> testing confirmed the <i>in vivo</i> data for swabs with rayon, polyurethane and nylon-flocked tips, since pre-moistening of swabs did not significantly affect the quantities of retrieved bacteria. Therefore, pre-moistening of swabs prior to nasal MRSA sampling provides no advantage in terms of recovering greater bacterial quantities and therefore can be omitted. In addition, this situation can be mimicked in an <i>in vitro</i> model, thereby providing a useful basis for future <i>in vitro</i> testings of new swab types or target organisms for screening approaches.</p></div

Recovered MRSA quantities from the artificial nose model utilizing dry or moist rayon, polyurethane foam and nylon-flocked swabs.

<p>Nose models were swabbed utilizing either dry or moistened rayon, polyurethane foam or nylon-flocked swabs. Data results from n = 10 swabs for each setting. p-value (comparing dry and moist swabs within one swab-type) = 0.62 (Nerbe plus, rayon); 0.90 (MWE, polyurethane); 0.72 (Copan, nylon-flocked); 0.96 (MWE, rayon) (Wilcoxon-Mann-Whitney U-test).</p

Quantities of MRSA per nostril.

<p>Quantities of MRSA per nostril.</p

Recovered MRSA quantities from patients utilizing dry or moistened rayon swabs.

<p>Patients were swabbed in the nostrils utilizing either dry or moist rayon swabs. CFU = colony forming units. Data result from n = 135 patients. p-value = 0.17 (Wilcoxon-Mann-Whitney U-test).</p

Test quality of CRP levels for the prediction of parasitemia, malaria and septicemia.

<p>Test quality of CRP levels for the prediction of parasitemia, malaria and septicemia.</p

Classification and comparison of CART model and IMCI algorithm.

a<p>IMCI-algorithm for identification of children with malaria in high-risk areas: Fever by history of fever or feeling hot/elevated body temperature of ≥37.5°C on admission and/or some palmar pallor.</p>b<p>CART-model: For calculation only those variables were used, which were included in the CART-analysis for the certain age group.</p>c<p>PPV = Positive predictive value.</p>d<p>NPV = Negative predictive value.</p

CART – model for children between 12 and 60 months of age (N = 4143).

<p>¹ Number of patients with the respective combination of variables given by the branches of the decision tree. ² Number of patients positive for <i>P. falciparum</i> parasitaemia. ³ Odds Ratio for <i>P. falciparum</i> parasitaemia with the combination of variables in comparison to all other combinations.</p

Distribution of haemoglobin-values in patients of different ages with and without palmar pallor.

<p>p-value was calculated assuming a Student's t distribution.</p

Signs and symptoms and their association with <i>P. falciparum</i> parasitaemia in children.

a<p>To be positive for this (inverse) variable patients must not present <i>malnourished condition</i>.</p>b<p>To be positive for this (inverse) variable patients must not present <i>skin abnormalities</i>, <i>skin rash</i>, <i>skin depigmentation</i> and <i>other skin problem</i>.</p>c<p>To be positive for this (inverse) variable patients must not present <i>vomiting</i> and <i>diarrhoea</i>.</p>d<p>To be positive for this (inverse) variable patients must not present <i>respiratory distress, breathing difficulties, fast breathing, deep breathing, chest indrawing, running nose</i>, blocked nose and <i>cough</i>.</p>e<p>CI: 95% Confidence interval.</p

Enrollment and exclusion of patients for analysis.

<p>^a A patient is defined as an individual visiting the OPD. ^b Case report forms must have information for each variable in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036678#pone-0036678-t002" target="_blank">Table 2</a> available.</p