**Core Concept**
Proper hand hygiene is the cornerstone of preventing nosocomial infections, which are infections acquired in healthcare settings. Effective hand hygiene involves the use of hand sanitizer or soap and water to eliminate pathogens on the hands.

**Why the Correct Answer is Right**
The simplest and most effective method to prevent nosocomial infection is hand hygiene. Hand hygiene removes pathogens from the hands, thereby preventing the transmission of these pathogens to patients. This is especially crucial in healthcare settings where patients are often immunocompromised. The Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) recommend hand hygiene as the primary method for preventing nosocomial infections.

**Why Each Wrong Option is Incorrect**
**Option A:** Using personal protective equipment (PPE) is essential in preventing nosocomial infections, but it is not the simplest or most effective method. While PPE can reduce the transmission of pathogens, it is often cumbersome and may not be feasible in all situations.
**Option B:** Cleaning and disinfecting surfaces is an important component of infection control, but it is not the simplest or most effective method to prevent nosocomial infections. Hand hygiene is more effective in reducing the transmission of pathogens.
**Option C:** Implementing isolation precautions is a critical component of infection control, but it is not the simplest or most effective method to prevent nosocomial infections. Hand hygiene is more effective in reducing the transmission of pathogens.

**Clinical Pearl / High-Yield Fact**
Remember the "5 Moments for Hand Hygiene" as recommended by the WHO: before touching a patient, before clean/aseptic procedures, after body fluid exposure, after touching a patient, and after touching patient surroundings.

**Correct Answer: A. Proper hand hygiene is the cornerstone of preventing nosocomial infections.**