Klebsiella aerogenes: PCR Detection and Clinical Overview

Klebsiella aerogenes is a Gram-negative, short rod-shaped bacterium with rounded ends. Cells are typically observed singly, in pairs, or occasionally in short chains.

Unlike classical Klebsiella species, it may possess peritrichous flagella, contributing to motility. Some strains can produce a polysaccharide capsule, which enhances environmental survival and influences colony morphology.

Gram staining yields a characteristic red or pink appearance, consistent with the structure of Gram-negative bacteria.

Klebsiella aerogenes is a facultative anaerobe, capable of growth in both aerobic and anaerobic environments. This adaptability allows it to thrive in diverse habitats, including soil, water, and host-associated environments.

It exhibits active metabolic capabilities, fermenting carbohydrates such as glucose and lactose to produce acid and gas. These metabolic byproducts can be used as key indicators in laboratory identification.

The organism can utilize a variety of carbon and nitrogen sources, demonstrating metabolic flexibility that supports its survival in fluctuating environmental conditions.

Clinically, some strains produce extended-spectrum beta-lactamases (ESBLs), conferring resistance to beta-lactam antibiotics such as penicillins and cephalosporins, which presents challenges in antimicrobial therapy.

On nutrient agar, colonies typically appear after 18–24 hours at 35–37°C as round, smooth, moist, and glistening structures with diameters of approximately 2–3 mm.

Colonies are usually gray-white, opaque, and exhibit a viscous, mucoid texture. Due to capsule production, colonies may demonstrate a characteristic “stringing” phenomenon when lifted with an inoculation loop.

On blood agar, hemolytic activity varies by strain. Some isolates exhibit beta-hemolysis, others show alpha-hemolysis, while some are non-hemolytic, providing additional differentiation criteria.

Traditional identification methods include culture, colony morphology observation, and biochemical testing. However, differentiation from closely related Enterobacteriaceae species can be complex.

Real-time PCR (qPCR) offers a rapid, sensitive, and specific approach for detecting Klebsiella aerogenes, enabling accurate identification in clinical microbiology, environmental monitoring, and antimicrobial resistance surveillance.

Klebsiella aerogenes is an opportunistic pathogen associated with healthcare-associated infections, particularly in immunocompromised individuals or patients with invasive medical devices.

Infections may include respiratory tract infections, urinary tract infections, bloodstream infections, and wound infections.

Effective management requires appropriate antimicrobial therapy guided by susceptibility testing, as well as strict infection control measures to prevent hospital transmission.