Acinetobacter junii

Acinetobacter junii is an opportunistic pathogen within the Acinetobacter genus, a group of aerobic Gram-negative coccobacilli commonly found in soil, water, and human flora. 

This species is less clinically significant than others like Acinetobacter baumannii, but it can still cause serious infections, particularly in immunocompromised individuals and hospital settings. 

A. junii is known for causing catheter-related bloodstream infections and occasional point-source outbreaks linked to contaminated medical solutions. 

It generally has lower virulence and higher antimicrobial susceptibility compared to more notorious Acinetobacter species. Nonetheless, A. junii can form biofilms, which contribute to its persistence and potential for infection in healthcare environments. 

Effective treatment relies on susceptibility testing and may involve a range of antibiotics, although its infections usually have a benign course with low associated mortality.

What is Acinetobacter junii?

Acinetobacter spp. are aerobic Gram-negative coccobacilli commonly found in soil, water, and as part of the human skin and throat flora. [2.] 

The genus has undergone extensive taxonomic revisions, and modern molecular techniques have identified over 34 species. [2.] 

Acinetobacter spp. are non-motile, although some exhibit twitching motility, and are strictly aerobic, thriving optimally at 33-37°C. [2., 3.] 

Although generally low in virulence, it can cause serious infections in immunocompromised patients and those with multi-organ disease. [3.] 

Clinically, Acinetobacter baumannii, A. nosocomialis, and A. pittii are the most significant, with A. baumannii being particularly notorious for its high virulence and multidrug resistance, often leading to severe infections and high mortality rates. [3., 6.] 

Acinetobacter junii is one of the less common species of the Acinetobacter genus found in clinical settings. It is primarily associated with catheter-related bloodstream infections and point-source infections. [2.] 

These infections are relatively rare compared to those caused by A. baumannii and other more clinically significant Acinetobacter species. [2., 3.] 

‍Acinetobacter junii is generally more susceptible to antimicrobials and considered to have lower virulence than other Acinetobacter species. [2., 3.] 

Infections caused by this species usually run a benign clinical course with low associated mortality. Additionally, small outbreaks caused by A. junii have occasionally been linked to contaminated infusion fluids such as heparin solution. [2.] 

Acinetobacter junii Infections

Acinetobacter junii is an opportunistic pathogen that can cause various infections, particularly in healthcare settings and among immunocompromised individuals.

Common Types of Infections

Acinetobacter junii has been implicated in a range of infections including bacteremia, septicemia, meningitis, peritonitis, urinary tract infections, and ocular infections, and it has been associated with rare cases of corneal ulcers. [4., 5., 7., 8., 11., 12.]

Acinetobacter is primarily associated with health care-associated infections, especially in ICU patients and long-term care facility residents. Risk factors include recent surgery, central vascular catheterization, tracheostomy, mechanical ventilation, enteral feeding, and treatment with broad-spectrum antibiotics. [14.] 

Antibiotic Resistance Concerns Regarding Acinetobacter junii [10., 13.] 

 Like other Acinetobacter species, A. junii has the potential to develop resistance to multiple antibiotics. However, it is generally considered less resistant than A. baumannii. [2.] 

However, carbapenem-resistant A. junii strains producing OXA-type carbapenemases and IMP-4 have been described, indicating potential horizontal gene transfer between A. junii and A. baumannii. [12.] 

A. baumannii is the best-studied strain of the Acinetobacter genus; like A. junii, it has developed a well-known antibiotic resistance to carbapenem.  Carbapenem belongs to the beta-lactam family of antibiotics, which includes penicillins and cephalosporins.

The rising trend of carbapenem resistance in Acinetobacter spp. is concerning due to limited therapeutic options. This resistance is attributed to several mechanisms.  

While these mechanisms are best-known due to research on A. baumannii, A. junii may also utilize similar antibiotic resistance methods through mobile genetic elements and integrons, similar to A. baumannii. [12.] 

Metallo-β-lactamases (MBLs)

These enzymes hydrolyze carbapenems efficiently, rendering them ineffective against A. baumannii by breaking down the antibiotic molecules.

Carbapenem-Hydrolyzing Class D β-Lactamases (CHDLs)

These enzymes hydrolyze carbapenems, with varying efficiencies, contributing significantly to resistance by deactivating the antibiotic.

Intrinsic Oxacillinase

The OXA-51/69 variants, when overexpressed, can hydrolyze carbapenems and reduce the susceptibility of A. baumannii to these antibiotics.

Porin Modifications

Loss or alteration of the CarO protein and other porins reduces carbapenem uptake into the bacterial cell, thereby decreasing the antibiotic's effectiveness.

Penicillin-Binding Protein (PBP) Modifications

Alterations in PBPs reduce the binding affinity of carbapenems, thereby diminishing their antibacterial activity.

Acinetobacter junii and Biofilm Formation

Most research on Acinetobacter virulence factors has focused on A. baumannii, which is considered more clinically significant. Additionally, A. junii is not considered as virulent a strain as A. baumannii, so it is difficult to determine whether the many virulence factors known to be produced by A. baumannii are also produced by A. junii.

It is known that Acinetobacter junii creates biofilms as a protective mechanism and virulence factor. [9.] 

Biofilms are complex communities of microorganisms (bacteria, fungi, algae or protozoa) that adhere to surfaces and are encased in a self-produced matrix of extracellular polymeric substances (EPS).

The biofilm matrix is composed of polysaccharides, proteins, extracellular DNA, and other molecules that form a protective environment for the microorganisms.

‍A. junii does exhibit the capacity to form biofilms at both the solid-liquid and air-liquid interfaces, but the extent and clinical relevance of this ability were not as prominent as those seen in more clinically relevant species. [9.] 

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Laboratory Testing for Acinetobacter junii

Test Type, Sample Collection and Preparation

The presence of Acinetobacter junii is typically assessed by culturing samples taken from the nasopharynx, wounds, or body fluid samples.

Because Acinetobacter junii is typically a hospital-acquired infection, sample collection and testing most commonly occur in a hospital and/or clinical setting.  

Interpretation of Acinetobacter junii Testing

Optimal Levels of Acinetobacter junii 

Acinetobacter junii is a potentially pathogenic species that is tested in clinical or hospital settings when there is concern for nosocomial infection with this organism.  Optimal levels of this bacterium are undetectable.  

Clinical Significance of Elevated Levels of Acinetobacter junii 

The presence of elevated levels of Acinetobacter junii in cultured tissue or fluid indicates the presence of colonization or an infection with this organism.  

Treatment of Acinetobacter junii Infection

Due to increasing antibiotic resistance of Acinetobacter spp., selecting the appropriate treatment for an individual is essential.

Treatment decisions will be guided by the individual's potential medication allergies, as well as susceptibility of the organism present to various antibiotic therapies.  

Common Antibiotic Therapies Used for Acinetobacter junii Infection [1.] 

Acinetobacter junii is a far less clinically-relevant strain of the Acinetobacter genus; focus is more heavily placed on treatment of Acinetobacter baumannii, a more virulent and common infectious agent.  

Cultured samples with a positive finding of Acinetobacter junii may include followup testing for antibiotic resistance genes, aiding in treatment decisions.

Acinetobacter baumannii, the most common strain of Acinetobacter spp. infection, is inherently multidrug-resistant with limited antibiotics effective against it. 

Avoid treating colonization; however, infections require treatment.

Bacterial colonization is defined as the presence and growth of bacteria on or in a host without causing disease or eliciting an immune response. Colonization generally does not trigger an inflammatory response or symptoms.

Colonization often occurs on external surfaces like skin or mucous membranes, and it can be beneficial or neutral to the host (e.g., normal gut flora).

In contrast, an infection is the invasion and multiplication of bacteria in host tissues, causing cellular injury and eliciting an immune response that is ultimately harmful to the host.

Medications to which Acinetobacter is usually sensitive include: [1.]

• Amikacin

• Colistin

• Meropenem

• Minocycline

• Polymyxin B

• Rifampin

• Sulbactam/durlobactam

• Tigecycline

First-, second-, and third-generation cephalosporins, macrolides, and penicillins generally have little or no activity against Acinetobacter and may predispose to colonization. 

Some strains are sensitive to cefepime, ceftazidime, and some combination antibiotics.

Both monotherapy and combination therapy (e.g., amikacin, minocycline, or colistin ± rifampin) have been used successfully. 

While combination therapy is often suggested, conclusive data on its superiority in preventing failure or resistance development are lacking. It can be considered for empiric therapy in areas with high antimicrobial resistance rates or for isolates resistant to multiple antibiotic classes.

FAQ: Understanding Acinetobacter junii

Acinetobacter junii is a lesser-known but clinically significant bacterium belonging to the Acinetobacter genus. 

This FAQ section addresses common questions about Acinetobacter junii, its characteristics, symptoms, and the types of infections it can cause. Understanding this bacterium can help in recognizing and managing related infections effectively.

What is Acinetobacter junii?

Acinetobacter junii is a gram-negative bacterium that is part of the Acinetobacter genus. While not as well-known as Acinetobacter baumannii, it can still cause various infections, particularly in immunocompromised individuals or those with underlying health conditions.

What are Acinetobacter Bacteria?

Acinetobacter bacteria are a group of gram-negative, aerobic bacteria commonly found in soil and water. They have emerged as important pathogens in hospitals and healthcare settings due to their ability to cause a range of infections, especially in immunocompromised populations, and due to their increasing resistance to antibiotics.

How is Acinetobacter junii Different From Other Acinetobacter Species?

Acinetobacter junii is less frequently encountered in clinical settings compared to Acinetobacter baumannii. However, it can still cause serious infections, particularly in vulnerable populations. 

What Types of Infections Can Acinetobacter junii Cause?

Acinetobacter junii can cause various types of infections, including:

• Skin infections: These can manifest as cellulitis, abscesses, or wound infections.

• Pneumonia: Respiratory infections, particularly in individuals with compromised lung function or those on mechanical ventilation.

• Bloodstream infections: Also known as bacteremia, which can occur in hospitalized patients with invasive devices such as catheters.

What are the Symptoms of an Acinetobacter Skin Infection?

Symptoms of an Acinetobacter skin infection include:

• Redness and swelling at the site of infection

• Pain or tenderness in the affected area

• Pus or other drainage from the wound

• Fever and general malaise in more severe cases

What are the Symptoms of Acinetobacter Pneumonia?

Symptoms of Acinetobacter pneumonia include:

• Cough, often producing sputum

• Fever and chills

• Shortness of breath

• Chest pain

• Fatigue and weakness

How is an Acinetobacter junii Infection Diagnosed?

Diagnosis typically involves collecting samples from the suspected site of infection (e.g., skin, respiratory tract, blood) and performing laboratory tests, such as cultures and molecular methods, to identify the presence of Acinetobacter junii.

How is Acinetobacter junii Infection Treated?

Treatment of Acinetobacter junii infections can be challenging due to its potential resistance to multiple antibiotics. Treatment options may include:

• Empiric antibiotic therapy, adjusted based on the sensitivity profile of the isolated bacterium

• Use of antibiotics that are typically successful in eradicating other Acinetobacter spp. Infections

• Supportive care and removal of any infected or colonized medical devices

What Measures Can Prevent Acinetobacter junii Infections?

Preventive measures include:

• Strict adherence to hand hygiene protocols

• Implementing robust infection control practices in healthcare settings

• Appropriate use and sterilization of medical equipment

• Judicious use of antibiotics to minimize resistance development

Why is it Important to Monitor Acinetobacter junii?

Monitoring Acinetobacter junii is crucial because it helps in understanding the prevalence, resistance patterns, and clinical impact of this bacterium. 

Effective monitoring aids in developing targeted treatment protocols and infection control measures to reduce the burden of infections.

When Should I Seek Medical Attention for Acinetobacter junii Symptoms?

Seek medical attention if you experience symptoms of an infection, particularly if you have been hospitalized or have risk factors such as a compromised immune system. 

Early diagnosis and appropriate treatment are key to managing Acinetobacter junii infections effectively.

How Can I Stay Informed About Acinetobacter junii?

Stay informed by following updates from health organizations such as the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO). Healthcare providers and infectious disease specialists can also provide valuable information and guidance.