Burkholderia pseudomallei, Burkholderia cepacia Complex, Stenotrophomonas maltophilia. Acinetobacter species. Flashcards
(17 cards)
Burkholderia pseudomallei: morphology and identification
Burkholderia pseudomallei is a Gram-negative, non-fermentative, bipolar staining bacillus that appears as a ‘safety pin’ on Gram stain. It is motile, oxidase-positive, and has a characteristic earthy odor. It can grow on a variety of media, including blood agar and MacConkey agar, forming smooth, creamy colonies. This bacterium is facultative intracellular and can survive within macrophages.
Burkholderia pseudomallei: antigenic structure
Burkholderia pseudomallei possesses a complex antigenic structure that includes lipopolysaccharide (LPS), which contributes to its pathogenicity. The bacterium also has outer membrane proteins that facilitate adhesion to host tissues. There is antigenic variation between strains, which can complicate immune responses and diagnostics.
Burkholderia pseudomallei: pathogenesis
Burkholderia pseudomallei is the causative agent of melioidosis, an infectious disease transmitted primarily through soil and water contaminated with the bacteria. It enters through cuts, inhalation, or ingestion. The bacteria can cause a wide range of clinical manifestations, including pneumonia, abscesses, septicemia, and chronic infections. Its ability to form biofilms and survive intracellularly in host cells contributes to its virulence.
Burkholderia pseudomallei: clinical findings
Clinical manifestations of melioidosis include acute pneumonia with fever, cough, and chest pain, abscess formation in multiple organs (liver, spleen, bones), septicemia, and sometimes chronic infections. The disease can range from mild to severe and is often fatal if untreated, especially in immunocompromised individuals.
Burkholderia pseudomallei: diagnostic laboratory tests
Diagnosis of Burkholderia pseudomallei involves culture of clinical specimens (e.g., blood, sputum, wound exudate) on selective media. PCR and serological tests can also be used. The bacterium’s characteristic ‘safety pin’ appearance on Gram stain helps in preliminary identification. Serology and molecular methods can aid in diagnosis, especially in endemic areas.
Burkholderia pseudomallei: treatment
Melioidosis is treated with antibiotics, typically starting with intravenous ceftazidime or meropenem, followed by oral antibiotics such as trimethoprim-sulfamethoxazole (TMP-SMX) for extended therapy. Treatment duration is long, often requiring several months to prevent relapse.
Burkholderia pseudomallei: epidemiology
Burkholderia pseudomallei is endemic in Southeast Asia, northern Australia, and parts of Africa. The disease is acquired through environmental exposure, especially in areas where the bacterium is prevalent in soil and water. It affects both humans and animals, particularly in regions with heavy rainfall and flooding.
Burkholderia pseudomallei: prevention and control
Preventive measures include avoiding contact with contaminated soil or water, especially in endemic areas. Protective clothing and footwear should be worn when handling soil or working outdoors in these regions. Public health education and early diagnosis are key to controlling the spread of melioidosis.
Burkholderia cepacia complex: morphology and identification
Burkholderia cepacia complex is a group of genetically related, Gram-negative bacilli, which are motile and oxidase-positive. The bacteria are capable of growing on various media, producing colonies that range from pale yellow to cream-colored. Some strains produce a characteristic fruity odor. B. cepacia complex is known for its ability to form biofilms and its resistance to many antibiotics.
Burkholderia cepacia complex: pathogenesis
Burkholderia cepacia complex is an opportunistic pathogen, especially in patients with cystic fibrosis (CF). It can cause chronic lung infections, particularly in CF patients, and can lead to rapid decline in pulmonary function. It is also associated with catheter-related infections, wound infections, and sepsis in immunocompromised individuals.
Stenotrophomonas maltophilia: morphology and identification
Stenotrophomonas maltophilia is a Gram-negative, non-fermentative, oxidase-negative rod. It forms colonies on MacConkey and blood agar that are usually smooth, pale, or greenish. It is known for its resistance to multiple antibiotics, including cephalosporins, and has a distinctive earthy odor.
Stenotrophomonas maltophilia: pathogenesis
Stenotrophomonas maltophilia is an opportunistic pathogen, commonly infecting immunocompromised patients, especially those with cystic fibrosis, cancer, or prolonged hospital stays. It can cause pneumonia, urinary tract infections, wound infections, and sepsis. Its resistance to many antibiotics, including beta-lactams, makes it challenging to treat.
Acinetobacter species: morphology and identification
Acinetobacter species are Gram-negative, non-fermentative, oxidase-negative, and typically appear as short, plump rods. These bacteria are commonly found in hospital environments and can be cultured from blood, sputum, or wound exudate. They grow well on various media, producing colonies that are generally smooth and either colorless or pale.
Acinetobacter species: pathogenesis
Acinetobacter species are opportunistic pathogens that can cause a wide range of infections, including pneumonia, urinary tract infections, wound infections, and bloodstream infections. Acinetobacter baumannii is particularly known for its resistance to multiple antibiotics, making infections difficult to treat. It is a common cause of nosocomial infections, especially in ICU settings.
Acinetobacter species: treatment
Acinetobacter infections require appropriate antibiotic therapy, often involving carbapenems (e.g., imipenem) or amikacin for multidrug-resistant strains. In some cases, colistin or tigecycline may be used for extensively drug-resistant strains. Antibiotic resistance patterns must be assessed before treatment initiation.
Acinetobacter species: epidemiology
Acinetobacter species are ubiquitous in the environment, commonly found in soil, water, and hospital environments. Acinetobacter baumannii is a frequent cause of hospital-acquired infections, particularly in patients with ventilator-associated pneumonia, wound infections, and catheter-related bloodstream infections. It is more common in immunocompromised patients.
Acinetobacter species: prevention and control
Control of Acinetobacter infections involves strict infection control measures, including hand hygiene, environmental cleaning, and isolation of infected patients in healthcare settings. Antibiotic stewardship programs are crucial to prevent the development of multidrug-resistant strains. Surveillance of antibiotic resistance patterns is essential for guiding treatment.
