Acinetobacter pittii is a Gram-negative bacterium that has drawn attention in medical settings due to its involvement in serious infections. Gram-negative means it possesses a thin cell wall that does not retain the crystal violet stain used in laboratory procedures. As an opportunistic pathogen, A. pittii typically causes disease only in individuals with weakened defenses or when it accesses parts of the body it does not normally inhabit. It has emerged as a cause of hospital-acquired infections, often complicating recovery for vulnerable patients.
Identification and Natural Habitat
Acinetobacter pittii belongs to the Acinetobacter calcoaceticus–Acinetobacter baumannii (ACB) complex. Species in this complex are genetically similar and difficult to differentiate using standard laboratory methods, often requiring advanced molecular techniques for precise identification.
A. pittii is ubiquitous, found widely throughout the natural environment, particularly in soil and water sources. It has also been isolated from various environmental sources, including food, plants, and animals. Furthermore, it can transiently colonize the skin and upper respiratory tract of humans without causing immediate illness.
Clinical Significance and Types of Infections
A. pittii primarily causes infections in hospitalized patients, often recognized as severe hospital-acquired infections. Its ability to survive on surfaces contributes to its persistence in healthcare facilities, posing a risk to vulnerable individuals.
The most frequent infections are linked to invasive medical procedures or devices. A. pittii is a known cause of ventilator-associated pneumonia (VAP) and bloodstream infections (bacteremia), which carry a significant risk of mortality.
A. pittii can also cause infections in other sites throughout the body. These include:
- Urinary tract infections (UTIs), often associated with indwelling urinary catheters.
- Wound infections, especially following surgery or traumatic injury.
- Soft tissue infections.
Clinicians must determine whether the bacterium is causing an active infection or merely colonizing a site, such as an open wound or the respiratory tract.
How It Spreads and Who Is At Risk
Transmission within healthcare settings occurs through multiple routes, leveraging the bacterium’s ability to survive for extended periods on dry surfaces. Environmental contamination is a significant factor, with direct contact with contaminated medical equipment (ventilators, catheters, intravenous lines) serving as a primary mechanism.
Person-to-person spread is also a major concern, often facilitated by the hands of healthcare workers moving between patients and equipment. This underscores the importance of stringent hand hygiene and infection control practices in preventing outbreaks.
The risk of developing a symptomatic infection is not uniform across the population, as A. pittii primarily targets the most vulnerable individuals. Patients who are immunocompromised, meaning they have a weakened immune system, are at the highest risk. Other major risk factors include:
- A prolonged stay in an intensive care unit (ICU).
- Use of invasive medical devices.
- Undergoing mechanical ventilation.
- Having central venous catheters or open surgical wounds.
Managing Infection and Antibiotic Resistance
The primary challenge in treating A. pittii infections is its high rate of multidrug resistance (MDR). The bacterium possesses genes that confer resistance to multiple classes of antibiotics, severely limiting treatment options. This resistance is frequently encoded on mobile genetic elements like plasmids, allowing resistance genes to be easily shared among bacterial strains.
Resistance to carbapenems, broad-spectrum antibiotics preferred for severe Gram-negative infections, is a major concern. When isolates are carbapenem-resistant, clinicians must use alternative, last-resort antibiotics. Diagnosis is crucial, involving culturing the bacteria and performing susceptibility testing to determine which antibiotics remain active.
Alternative treatments for resistant strains include specialized antibiotics such as polymyxins (colistin) or tigecycline. Sulbactam/durlobactam is a newer option approved to treat certain types of Acinetobacter pneumonia, including carbapenem-resistant strains. The high resistance rate emphasizes the need for rigorous infection prevention strategies to control the spread of this pathogen.