user-1: How do I deal with my mind accusing me of something I’m not doing?
For example, if you are walking, and your mind tells you that you are killing insects or bacteria, how do you deal with it?
Or
For example, if your skin gets itchy and you want to scratch but your mind tells you that you are killing ants or bacteria that might be causing your skin to be itchy. Your original intention was to scratch your skin because it’s itchy but your mind tells you that you are going to kill insects or bacteria that might be on your skin, you don’t listen to your mind and scratch your skin anyway. Is this bad karma?
Sorry if this is hard to understand. I try to make it clear.

user8157: Bacteria do not appear to be "breathing creatures" therefore appear excluded from the 1st precept.
The 1st precept is about intentional killing therefore excludes non-intentional killing of insects.

user471: The commentary to Dhammapada 1 precisely addresses the topic of unintentionally killing insects:

On one occasion, Thera Cakkhupala (who was blind) came
to pay homage to the Buddha at
the Jetavana monastery. One night, while pacing up and down in
meditation, the thera accidentally stepped on some insects. In the
morning, some bhikkhus visiting the thera found the dead insects. They
thought ill of the thera and reported the matter to the Buddha.
The
Buddha asked them whether they had seen the thera killing the insects.
When they answered in the negative, the Buddha said, "Just as you
had not seen him killing, so also he had not seen those living
insects. Besides, as the thera had already attained arahatship he
could have no intention of killing and so was quite innocent." .....
Then the Buddha spoke in verse as follows:
Verse 1: All mental phenomena have mind as their forerunner; they have
mind as their chief; they are mind-made. If one speaks or acts with an
evil mind, 'dukkha' follows him just as the wheel follows the
hoofprint of the ox that draws the cart.


-1: <p>How do I deal with my mind accusing me of something I’m not doing?
For example, if you are walking, and your mind tells you that you are killing insects or bacteria, how do you deal with it?</p>
<p>Or</p>
<p>For example, if your skin gets itchy and you want to scratch but your mind tells you that you are killing ants or bacteria that might be causing your skin to be itchy. Your original intention was to scratch your skin because it’s itchy but your mind tells you that you are going to kill insects or bacteria that might be on your skin, you don’t listen to your mind and scratch your skin anyway. Is this bad karma?</p>
<p>Sorry if this is hard to understand. I try to make it clear.</p>
 8157: <p>Bacteria do not appear to be &quot;breathing creatures&quot; therefore appear excluded from the 1st precept.</p>
<p>The 1st precept is about intentional killing therefore excludes non-intentional killing of insects.</p>
 471: <p>The commentary to <a href="https://www.tipitaka.net/tipitaka/dhp/verseload.php?verse=001" rel="nofollow noreferrer">Dhammapada 1</a> precisely addresses the topic of unintentionally killing insects:</p>
<blockquote>
<p>On one occasion, Thera Cakkhupala (who was blind) came
to pay homage to the Buddha at
the Jetavana monastery. One night, while pacing up and down in
meditation, the thera accidentally stepped on some insects. In the
morning, some bhikkhus visiting the thera found the dead insects. They
thought ill of the thera and reported the matter to the Buddha.</p>
<p>The
Buddha asked them whether they had seen the thera killing the insects.
When they answered in the negative, the Buddha said, &quot;<strong>Just as you
had not seen him killing, so also he had not seen those living
insects.</strong> Besides, as the thera had already attained arahatship he
could have <strong>no intention of killing</strong> and so was quite innocent.&quot; .....</p>
<p>Then the Buddha spoke in verse as follows:</p>
<p>Verse 1: All mental phenomena have mind as their forerunner; they have
mind as their chief; they are mind-made. If one speaks or acts with an
evil mind, 'dukkha' follows him just as the wheel follows the
hoofprint of the ox that draws the cart.</p>
</blockquote>
