Lecture 40 - Actinomyces - 7 Nov 2006

ACTINOMYCETACEAE

Objectives At the end of the lecture the students should be able to:  Describe the general characteristics of the organisms  Understand and recall their pathogenesis  Enumerate the infections they cause  Describe the laboratory diagnosis  List the treatment options

Genera 

Comprises 3 potentially pathogenic genera: Actinomyces Nocardia Streptomyces

Actinomyces israelii Pathogenesis and clinical disease Actinomycosis  Endogenous infection  Causes abscesses in the jaw, thorax, abdomen and cutaneous  Injury to the oral mucosa, e.g. tooth abscess or extraction, penetrates deep tissue – abscess formation

Clinical presentations  Cervicofacial  Thoracic

actinomycosis

actinomycosis

 Abdominal

actinomycosis

 Cutaneous

actinomycosis

Diagnosis  Macroscopic

examination

– typical yellow granules (“Sulfur granules”)

 Culture

– anaerobically at 37oC for 48h –2

wks  Gram-positive

branching bacilli

Treatment Rx:  Debridement and drainage  Large

doses of penicillin G (20 million unit/day) or ampicillin

2

– 3 months

NOCARDIA  Branched,

strictly aerobic, Gram positive  Environmental saprophytes - soil  Usually weakly acid-fast  Infection in immunosuppressed persons Important species: – Nocardia asteroides and N. brasiliensis

 Clinical

disease:

– Pulmonary nocardiosis – Cutaneous nocardiosis

Pulmonary nocardiosis  Multiple

abscesses in the lung; necrotic and confluent - Atypical pneumonia  Spread by blood stream to other organs, e.g. brain abscess.  N. asteroides in the usual causative agent  Most common presentation

Cutaneous nocardiosis  Mycetoma:

- Subcutaneous draining abscess  Contains white granules  N. brasiliensis is the frequent cause  Madura foot:  Chronic granulomatous infection - foot - bones and soft tissue.  Occurs amongst those who walk bare footed. Sudan, N. Africa and West Coast of India.  Caused by Actinomadura (Nocardia) madurae.  Also caused by other Actinomyces and fungi.

Diagnosis  Sputum  Culture

on blood agar  Colonies cream, orange, pink or whitish dry chalky and adhere firmly to the medium.  Gram stain – pleomorphic Gram-positive  ZN stain - weakly acid-fast branching filamentous organisms from the sputum, pus or biopsy tissue

Treatment  Surgical  Sulfa

drainage of abscesses

drugs e.g. Trimethoprimsulfamethoxazole (“Septrin”), amikacin, imipenem

Case presentation -1 A 18-year slightly malnourished boy came to the hospital Casualty with the C/O discharging swelling in the right check and neck of about 2 months duration. PMH: he has extracted a tooth about 2 weeks prior to onset of symptoms.     

What is your provisional diagnosis? Name 3 other forms of this infection Which organism is the infecting agent? How would you investigate a case like this? What is the treatment option?

Case presentation -2 A 46-year man who had undergone renal transplantation about 6 years ago presented with multiple abscesses in the forearm and chest. A Gram-stain of the pus aspirated from the lesions revealed Gram-positive beaded and some branching bacilli which also could be seen with ZN staining.     

What is the likely diagnosis? Which organism is responsible for this infection? Why did this man develop this type of infection? What is the source of the infection? What are the treatment options?