Test page

HTML

<table class="amhtable">
    <thead>
        <tr class="heading">
            <th class="width-16">Modifying circumstance</th>
            <th class="width-16">Common pathogens</th>
            <th class="width-16">First choice</th>
            <th class="width-16">Alternative</th>
            <th class="width-36">Additional information</th>
        </tr>
        <tr>
            <th colspan="5">SECTION TITLE</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>column 1</td>
            <td>column 2</td>
            <td>column 3</td>
            <td>column 4</td>
            <td>column 5</td>
        </tr>
    </tbody>
</table>

CSS

.amhtable,
.amhtable thead,
.amhtable tbody,
.amhtable tr,
.amhtable th,
.amhtable td {
    border: 1px solid #000;
    border-collapse: collapse;
    font-weight: normal; 
    color: #000;
}
.amhtable {
    width: 100%;
}
.amhtable .width-16 {
    width: 16%;
}
.amhtable th,
.amhtable td {
    padding: 3px;
}
.amhtable th {
    background-color: #82a3e7;
    border: 1px solid #777;
    font-family: Verdana, Arial, Helvetica, DejaVu Sans, Bitstream Vera Sans, sans-serif;
    font-weight: bold;
}
.amhtable .heading th {
    background-color: #567ac4;
    font-style: italic;
}