Final answer:
The clean-catch or midstream urine collection method is optimal for bacterial culture as it reduces contamination with external microbiota.
Step-by-step explanation:
The optimal method for urine collection for bacterial culture is clean-catch or midstream urine (B). This technique involves cleaning the genital area first to minimize contamination with normal microbiota and then collecting the urine midstream. This method ensures that the sample is representative of the bladder's content rather than contaminants from the external genitalia. While catheterization and suprapubic aspiration can also provide uncontaminated samples, they are more invasive. The choice of collection method may be influenced by the patient's condition and the clinical setting.