Barkholderia diseases and transmission Gardenerella vagainalis diseases and transmission

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Burkholderia - Diseases and Transmission

The Organism

Burkholderia is a genus of >115 species of oxidase- and catalase-positive, non-lactose-fermenting, Gram-negative bacilli. Most species are environmentally derived. Two species - B. pseudomallei and B. mallei - are primary pathogens; the rest cause opportunistic infections.

Harrison's Principles of Internal Medicine 22E, p. 1314

Key Species and Their Diseases

1. Burkholderia cepacia Complex (Bcc)

A complex of at least 22 species (B. cenocepacia, B. multivorans, etc.)

Diseases:

Chronic lung infections in cystic fibrosis (CF) patients - can cause a rapidly fatal necrotizing pneumonia ("cepacia syndrome")
Infections in chronic granulomatous disease (CGD)
Nosocomial (hospital-acquired) pneumonia, bacteremia, urinary tract infections
Septicemia in immunocompromised patients

Transmission:

Person-to-person spread - documented at CF camps and social events; CF patients can spread Bcc to each other
Environmental sources - soil and water; organism survives for prolonged periods in moist environments
Contaminated medical products - intrinsic resistance to preservatives allows it to contaminate mouthwash, liquid docusate sodium, inhaled medications, disinfectant solutions used on bronchoscopes and pressure transducers, and skin antiseptics
Nosocomial spread via contaminated fomites and lapses in infection control

2. Burkholderia pseudomallei - MELIOIDOSIS

Disease: Melioidosis - ranges from asymptomatic infection to fulminant septicemia

Clinical presentations include:

Presentation	Details
Pneumonia	Most common in adults
Localized cutaneous infection	Most common in immunocompetent children
Genitourinary infection	Including prostatic abscesses
Septic arthritis / osteomyelitis
CNS involvement	Brain abscesses
Acute suppurative parotitis	Common in Thai and Cambodian children
Hepatic / splenic abscesses	In disseminated infection
Necrotizing fasciitis	In severe cutaneous infection
Bacteremia	~50% of adults on admission

Geography: Northeast Thailand, northern Australia, Indian Subcontinent, southern China, Hong Kong, Taiwan, Pacific/Indian Ocean islands, parts of South/Central America. More than 75% of cases occur during the rainy season.

Transmission:

Inhalation of aerosolized organisms or dust containing the organism
Percutaneous inoculation through skin wounds in contact with contaminated soil or water
Ingestion of contaminated soil, water, or food
Rare breastfeeding transmission - 2 cases reported from mothers with mastitis
Laboratory exposure without proper PPE
Children are exposed early in life; highest seroconversion rates between 6 months and 4 years
Red Book 2021, p. 428-429

3. Burkholderia mallei - GLANDERS

Disease: Glanders - a zoonosis primarily of horses, mules, and donkeys; rare in humans

Clinical forms:

Cutaneous/nasal glanders - nodular lesions with ulceration
Pulmonary glanders - pneumonia, lung abscesses
Septicemic glanders - rapidly fatal; pustular skin lesions

Transmission:

Direct contact with infected animals (horses, mules, donkeys)
Inhalation of infected aerosols
Laboratory exposure (considered a bioterrorism agent)
B. mallei is the only non-motile Burkholderia species (lacks flagellum)

4. Other Species

Species	Association
B. gladioli	CF lung infections; poor outcome in lung transplant recipients
B. thailandensis	Rare, mild melioidosis-like disease
B. oklahomensis	Rare, resembles melioidosis

Gardnerella vaginalis - Diseases and Transmission

The Organism

Gardnerella vaginalis (formerly Haemophilus vaginalis) is a thin, Gram-variable rod or coccobacillus that is part of the normal vaginal flora of reproductive-age women. It is:

Nonmotile
Catalase-negative
Slow fermentative metabolism
Grows best in 5% CO2 at 48 hours
Forms small, faint beta-hemolytic colonies on rabbit or human blood agar
Henry's Clinical Diagnosis and Management by Laboratory Methods, p. 1423

Primary Disease: Bacterial Vaginosis (BV)

BV is not caused by G. vaginalis alone - it is a polymicrobial syndrome characterized by a major shift in vaginal flora from normal Lactobacillus-dominant flora to a mixed anaerobic environment. G. vaginalis is the organism most specifically associated with the condition.

Co-pathogens in BV

Gardnerella vaginalis, Mycoplasma, Prevotella, Atopobium, Mobiluncus, Sneathia, Leptotrichia, and BV-associated bacteria (BVAB1-3)

Creasy & Resnik's Maternal-Fetal Medicine, p. 3347

Clinical Features of BV

Finding	Details
Discharge	Thin, homogeneous, gray/white, malodorous
Fishy odor	Caused by amines; accentuated by KOH (whiff test) or after coitus
Vaginal pH	>4.5 (normal <4.5)
Clue cells	Vaginal epithelial cells covered with bacteria (>20% of cells)
WBCs	Few/absent (hence "vaginosis" not "vaginitis")

Amsel Criteria - 3 of 4 required for diagnosis:

Amine-like/fishy odor (±KOH)
Thin, gray homogeneous discharge
Elevated pH (>4.5)
Clue cells on saline microscopy

Complications of BV

Preterm birth (OR 1.4-8.0 in pregnant women)
Chorioamnionitis (clinical and histologic)
Endometritis
Pelvic inflammatory disease (PID)
Increased susceptibility to other sexually transmitted infections (STIs), including HIV
Postpartum septicemia - G. vaginalis can cause bacteremia in postpartum women and neonates
BV affects 10-30% of pregnant women; half are asymptomatic

Transmission

G. vaginalis is part of normal vaginal flora in reproductive-age women - its mere presence does not indicate disease
Sexual transmission is increasingly supported by evidence - BV is more common in sexually active women and those with new or multiple partners; it is rarely seen in virgins
The condition can occur in women who have sex with women, supporting sexual transmission
Not a classical STI - not transmitted by non-sexual routes under normal circumstances
Overgrowth is promoted by: douching, loss of lactobacilli, antibiotic use, alkaline semen exposure
Jawetz, Melnick & Adelberg's Medical Microbiology 28E, p. 2984
Henry's Clinical Diagnosis, p. 1428

Treatment

Condition	Drug
Bacterial vaginosis	Metronidazole 500 mg twice daily x 7 days (90% cure rate) OR vaginal metronidazole gel 0.75% x 5 days
Alternative	Oral clindamycin 300 mg BD x 7 days, or vaginal clindamycin cream 2% x 5 days
Systemic infection (septicemia)	Ampicillin or amoxicillin (no beta-lactamase produced)
Single-dose metronidazole 2g	No longer recommended (only 60-80% cure rate)

Creasy & Resnik's Maternal-Fetal Medicine, p. 3366; Henry's Clinical Diagnosis, p. 1438

Quick Comparison Summary

Feature	Burkholderia	Gardnerella vaginalis
Gram stain	Gram-negative bacillus	Gram-variable rod/coccobacillus
Primary pathogen?	Only B. pseudomallei and B. mallei	No (normal flora that overgrows)
Main populations affected	CF, CGD, immunocompromised; travelers to endemic regions	Reproductive-age women
Key diseases	Melioidosis, glanders, CF lung infections, nosocomial infections	Bacterial vaginosis, postpartum septicemia, preterm birth
Main transmission route	Soil/water (environmental), person-to-person (CF), contaminated medical products	Sexual transmission (increasingly supported); overgrowth of endogenous flora
Key diagnostic feature	Culture, PCR, serology	Clue cells, Amsel criteria, pH >4.5, fishy odor
First-line treatment	Ceftazidime/meropenem (B. pseudomallei); TMP-SMX maintenance	Metronidazole

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