Final answer:
The communicable condition considered a nationally notifiable infectious disease in the list provided is Chlamydia trachomatis, which must be reported by healthcare providers to public health authorities such as the CDC.
Step-by-step explanation:
The condition among those listed that is considered a nationally notifiable infectious disease is d) Chlamydia trachomatis. The Centers for Disease Control and Prevention (CDC) categorizes certain infectious diseases as notifiable at a national level, and chlamydia is one of them.
This means that healthcare providers are legally required to report cases of chlamydia to public health authorities, aiding in data collection and the monitoring of disease prevalence. While other diseases like MRSA and Clostridium difficile are concerning due to their resistance to antibiotics, they are not on the national notifiable list. RSV is a common cause of childhood illness but is not considered a notifiable disease at the national level either.