The answer

• Anaerobic
• Filamentous bacteria which are beaded and non branching
• Actino is a Gram-positive bacteria.
• These are filamentous bacteria which can be recognized on tissue sections 
• Not acid fast

• Actinomyces are normal inhabitants of the oral cavity and can become a pathogen. .
• They are commensal organisms and frequently found in dental caries and at gingival margins with poor oral hygiene. 
• Not found in soil. They do not thrive at temperature below 30 degree C. 
• They are extremely host specific and A israelli causing infection in humans is never found in animals.

What are the common sites for infection with Actinomyces israelii ?

The answer

• Most commonly in the jaw or neck (Cervicofacial area 55%)
• Abdominopelvic region 20% 
  • abdominal disease-abscess or mass secondary to disruption of the bowel mucosa 
  • rare pelvic form has been associated with Intrauterine contraceptive devices
• Thorax 15% :
  • The indolent infection progresses to necrotizing pneumonia. 
  • If untreated abscesses develop with extensive parenchymal destruction. 
  • Predilection to bases and peripheral portion of lungs is due to aspiration as the initiating process. 
  • Disease spreads through pleura to chest wall as in our patient. 
  • In untreated cases sinus tracts can form with characteristic sulfur granules. 
  • Think Actino whenever a lesion crosses fissure or pleura, extends to contiguous mediastinum or chest wall.

If they are normal inhabitants of oral flora, why do they become pathogenic? Describe the clinical picture of actinomycosis of jaw.

The answer

• Actinomyces are normal inhabitants of the oral cavity.
• Gingivitis and caries of teeth contain aerobic and anaerobic bacteria. 
  • They provide a milieu suitable for growth of Actinomyces.
• If there is an injury to jaw they are able to invade the soft tissue of Jaw and progress.
• Hard, very slow-growing swellings form and eventually turn into abscesses
• When the abscesses break down, pus is discharged through several openings in the skin (Sulfur granules)

How common is actnomycosis?

The answer

• Disease is relatively uncommon. 
• Actinomycosis occurs worldwide with no racial predilection. 

How do you differentiate Actinomyces israelii from Nocardia?

The answer

• Nocardia is a branching filamentous, gram-positive bacterium and is weakly acid-fact.

• Inflammation is neutrophilic in both infections

• Actinomycosis looks similar on gram stain to Nocardia, but generally is not acid fast.

Is Actinomyces israelii  a fungus or bacteria?

The answer

• Actino exhibits some features typical of fungus branching mycelia formation 
• However they are Gram-positive bacteria.
  • Lack of nuclear membrane, the cell wall characteristics and absence of mitochondria are all bacterial characteristics.
  • It reproduces by bacterial fission than sporogenic or filamentous budding.

• It is more common in patients with poor oral hygiene. 
• There is a male predominance of 4:1. 
• Patients with actinomycosis are generally normal hosts 
• NOT immunocompromised. It is an uncommon infection in transplanted patients. 

Is Actinomyces israelii an opportunistic infection?

The answer

• It is not an opportunistic infection.  
• It is due to aspiration of organisms from oral cavity. 
• Patients with a predisposition to aspiration e.g. seizure disorder, mental retardation, episodes of unconsciousness, alcoholism etc are more prone to develop infection. 
• This statement refers to pulmonary infection.

Describe the pathology of  infection with Actinomyces israeli

The answer

• Necrotizing inflammation with abscess formation.

The answer

• They must be cultured strictly in anaerobic environment for at least one week.
•  In only 50% of cases organisms are successfully cultured. 
• The other concomitant organisms perhaps work in synergy to produce the necessary anaerobic environment for Actinomyces. 
• In actinomycosis there are sulphur granules which are ball-shaped bacterial colonies, gram-positive, with club-shaped ends of radially oriented filaments. 

The answer

• Treatment with penicillin is usually effective.
• For protracted period of time

What measures can we take to prevent infection with Actinomyces israeli?

The answer

• It is not a contagious infection. These organisms are normal inhabitants of the oral cavity.
• Proper care of Teeth and Gingiva should prevent a situation favoring growth of these organisms 

Describe the morphological and cultural characteristics of  Nocardia asteroides

The answer

• Branching filamentous 
• gram-positive bacterium 
• Weakly acid-fact. 
• Long, delicate not beaded.
• Aerobic bacterium.  
• Does not form spores

What is the source for Nocardia?

The answer

• Found worldwide in soil and decaying organic material 

• Nocardia infects humans through the respiratory tract. 
• Nocardia may also be introduced through the skin.
• Nocardia will disseminate via the blood or lymphatic channels. 

The answer

Susceptible hosts

• Approx. 1,000 cases of nocardiosis diagnosed annually in the U.S. 
  • Increasing incidence of infection with Nocardia
    • Follows increase in organ transplantation and the attendant immunosuppressive therapy
  • 2.5 times more common in males than females 
• Increased incidence in people with deficient cell mediated immunity 
  • immunosuppressive therapy for transplantation. (45%)
  • long term use of steroids Lymphoma / leukemia
  • HIV
  • post splenectomy 

The answer

Human defenses

• Immune T-cells are important in clearing Nocardia from the lung and preventing dissemination.
• Inflammation is also neutrophilic but infections progress unless antimicrobial agents are given or cell mediated immunity takes over.
• Nocardia is an opportunistic infection. 
• They can thrive only if there is defect in cell mediated response

The answer

•  Subacute or chronic abscess 

The answer

• Aspiration of lesion
  • Transthoracic percutaneous fine needle aspirate  (Under CT guidance) or bronchoscopy.
• Biopsy 

The answer

Clinical infections 

• Lungs 
  • most common site of involvement 
  • 70-80% of cases Pulmonary nocardiosis 
  • subacute (may have acute onset in immunocompromised hosts)
  • cough, sputum, fever , anorexia , wt. loss
  • CXR >> variable infiltrates , nodules, cavities 
• The CNS 
  • is infected in about 1/3 of all cases.
  •   Nocardial Brain Abscess 
  • Usually one or more supratentorial brain abscesses, often multiloculated with satellite extensions 
  • Rupture into ventricles can lead to acute deterioration -- meningitis 
  • Common presenting features -- headaches, seizures, confusion and focal neurologic findings
• Dissemination to nearly every organ has been reported i.e., kidney, bone, muscle, peritonitis, endocarditis 
• Extrapulmonary dissemination typically presents as subacute or chronic abscess 

What is the therapeutic strategy for Nocardia infection?

The answer

• Trimethoprim-sulfamethoxazole
• Imipenem / Amikacin 
  Cefotaxime / Amikacin  I.V. for at least 6 wks. 
• Immunocompromised ---- 1 yr. of oral Antibiotics
  (following I.V. Tx) 
• Brain abscess
  • Stereotactic aspiration / decompression of brain abscesses
  • Craniotomy to excise the entire abscess and wall 

The answer

• It is not a contagious infection.
• It is an opportunistic infection
• No preventive measures can be taken

What is/are the sources for Pseudomonas aeruginosa?

The answer

• Environment.: common inhabitants of soil and water

• Gastrointestinal tract 

The answer

Pathogenicity 

Invasive and Toxinogenic

• Bacterial attachment and colonization
  • fimbrial adherence to injured epithelial cells (opportunistic adherence) / pseudomonas pili
  • Biofilm (alginate slime) Pseudomonas forms a biofilm which protects the bacteria from host defenses. (phagocytes, Lymphocytes, Complement)
• Extracellular enzymes and Toxins  contributing to bacterial invasion
  • Local invasion (Elastase, Alkaline protease, hemolysins, cytotoxin)
  • Disseminated systemic disease (exotoxins A, lipopolysaccharide)

The answer

• Intact skin and mucous membrane. (Never infects uncompromised tissues)
• Require both humoral and cell mediated immunity
  • Phagocytes
  • Lymphocytes
  • Complement

What are the clinical infections with Pseudomonas aeruginosa?

The answer

• Urinary tract infections (Catheterization, instrumentation)
• Pneumonia (Neutropenic)
• Lower respiratory tract colonization (Cystic fibrosis)
• Eye infection: 
• Swimmers ears.
• Endocarditis (IV drug users and prosthetic heart valves)
• Osteochondritis
• Dermatitis and soft tissue infections (Burns, trauma, dermatitis)
• Systemic infections/Septicemia 

How does infection with Pseudomonas aeruginosa lead to septic shock?

The answer

• The lipopolysaccharide (LPS) in gram negative organism triggers complement, clotting, fibrinolytic and kinin pathways. 
• Fever and inflammation are mediated by cytokines that are released in response to LPS. 
• Cytokines which are released include TNF-" , interleukin-1 (IL-1) interferon-m ).
• Interleukin-1 is the endogenous pyrogen. TNF-" is the most potent mediator of the pathophysiology of the gram negative sepsis syndrome.

How do you diagnose inefction with Pseudomonas aeruginosa?

The answer

• Gram stain and culture of appropriate secretions/blood.

What is the pathogenesis of  ecthyma gangrenosum?

The answer

• Is the result of direct invasion and destruction of the blood vessel walls by Pseudomonas aeruginosa

The answer

• Resistance to many of the common antibiotics due to changes in porins
• Combination therapy of cell wall active agent and aminoglycoside
• Piperacillin and gentamicin were given to provide bactericidal antibiotic activity against the pseudomonas. 
• The combination results in synergy. MIC of either drug is decreased by the addition of the second drug, hence the organisms are killed at lower concentrations of the drug.
• Other drugs which may be used are imipenem, ceftazidime and aminoglycosides.

What are the determinants of poor outcome in patients with Pseudomonas sepsis?

The answer

• Sepsis, pneumonia
• Persistent neutropenia.