Archive for the ‘Anti-Infectives’ Category

DIAGNOSIS FOR ANTHRAX

Saturday, January 1st, 2011
Clinical diagnosis of anthrax requires a high index of suspicion. During the recent postal-related outbreak of anthrax in the United States, the CDC used surveillance case definitions, which established a confirmed case of anthrax as a patient with a compatible clinical illness combined with either isolation of B. anthracis from a culture or laboratory evidence of infection based on at least two supportive tests (polymerase chain reaction [PCR], immunohistochemistry, or serology). A suspected case was defined as a patient with a compatible clinical illness combined with either a single non-culture laboratory test or epidemiologic linkage to a source.
Gram stain and culture of B. anthracis can be obtained from blood, cerebrospinal fluid, vesicular fluid, and biopsy material from a cutaneous specimen. Growth of the bacillus is usually noted within 6 to 24 hours, and it is non-motile and non-hemolytic and demonstrates spores in nutritionally deficient media. Serologic testing requires the acquisition of acute and convalescent specimens and is not commercially available. Confirmation of identification can also occur with PCR, direct fluorescent antibody analysis, or immunohistochemical testing, which are generally available only through public health laboratories. Nasal swabs have been used in epidemiologic outbreak investigations but have no clinical utility in making treatment decisions. Although community laboratories can provide presumptive identification, confirmatory testing is available only through state health department laboratories.
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DIAGNOSIS FOR ANTHRAXClinical diagnosis of anthrax requires a high index of suspicion. During the recent postal-related outbreak of anthrax in the United States, the CDC used surveillance case definitions, which established a confirmed case of anthrax as a patient with a compatible clinical illness combined with either isolation of B. anthracis from a culture or laboratory evidence of infection based on at least two supportive tests (polymerase chain reaction [PCR], immunohistochemistry, or serology). A suspected case was defined as a patient with a compatible clinical illness combined with either a single non-culture laboratory test or epidemiologic linkage to a source.Gram stain and culture of B. anthracis can be obtained from blood, cerebrospinal fluid, vesicular fluid, and biopsy material from a cutaneous specimen. Growth of the bacillus is usually noted within 6 to 24 hours, and it is non-motile and non-hemolytic and demonstrates spores in nutritionally deficient media. Serologic testing requires the acquisition of acute and convalescent specimens and is not commercially available. Confirmation of identification can also occur with PCR, direct fluorescent antibody analysis, or immunohistochemical testing, which are generally available only through public health laboratories. Nasal swabs have been used in epidemiologic outbreak investigations but have no clinical utility in making treatment decisions. Although community laboratories can provide presumptive identification, confirmatory testing is available only through state health department laboratories.*208/348/5*

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CAUSES OF INFECTIOUS ARTHRITIS

Tuesday, December 21st, 2010
There are a number of causes of infectious arthritis. Gram-positive aerobes are implicated in the majority of cases of infectious arthritis and are seen in an estimated 70% to 80% of patients. Staphylococcus aureus is the most common pathogen in this group and is responsible for about 60% of infections in the joint space. The organism can also cause an acute septic bursitis following trauma. Streptococcal infections are also common and may be due to group A B-hemolytic streptococci as well as groups В, C, and G streptococci.
Gram-negative bacilli are responsible for about 9% to 20% of cases of infectious arthritis. These infections typically occur in the elderly and in patients with comorbid conditions such as immunocompromised states or chronic arthritis. Pseudomonas aeruginosa is often the underlying cause in intravenous drug users with sternoclavicular or sacroiliac infections. Brucella can also cause arthritis of the sacroiliac joint in patients exposed to unpasteurized dairy products. Pasteurella multocida should be considered in patients who present with an animal bite to a joint.
Neisseria gonorrhoeae remains the predominant cause in adults younger than 30 years of age. Disseminated gonococcal infection often manifests as a triad of polyarthritis, dermatitis (vesiculopustular skin lesions), and tenosynovitis. Synovial cultures yield the diagnosis in less than 50% of patients. N. gonorrhoeae can be recovered from pharyngeal, rectal, urethral, or cervical cultures. Gonococcal infection can also result in a monoarticular purulent arthritis without skin involvement. Synovial cultures are more often positive in these cases.
Chronic monoarticular arthritis of the large joints, most commonly the knee, can be present in the later stages of Lyme disease. The organism, Borrelia burgdoferi, is rarely detected in synovial fluid, and the diagnosis is made through serologic testing.
Mycobacterial infections can manifest as a more indolent and progressive monoarthritis. Tendon sheaths can be involved as well, particularly in infections with atypical mycobacteria. Potential organisms include Mycobacterium tuberculosis, Mycobacterium kansasii, and Mycobacterium marinum. Diagnosis is primarily made through culture of the synovial tissue.
Chronic monoarthritis can occasionally be caused by fungal organisms, usually in immunocompromised patients. Disseminated coccidioidomycosis, blastomycosis, and sporotrichosis (particularly in people exposed to soil) have all been reported. Candidal infections may also occur, typically via hematogenous seeding, and are more acute in onset.
Arthritis can be a significant feature of a number of viral illnesses. Polyarthritis can occur in patients with infection with mumps and parvovirus B19. It has also been reported during the preicteric period in patients with hepatitis B. Infections with rarer arthropod-borne alpha viruses endemic to East Africa, such as Chikungunya and O’nyong-nyong fever, are abrupt and can cause severe pain in large joints.
*134/348/5*

CAUSES OF INFECTIOUS ARTHRITISThere are a number of causes of infectious arthritis. Gram-positive aerobes are implicated in the majority of cases of infectious arthritis and are seen in an estimated 70% to 80% of patients. Staphylococcus aureus is the most common pathogen in this group and is responsible for about 60% of infections in the joint space. The organism can also cause an acute septic bursitis following trauma. Streptococcal infections are also common and may be due to group A B-hemolytic streptococci as well as groups В, C, and G streptococci.Gram-negative bacilli are responsible for about 9% to 20% of cases of infectious arthritis. These infections typically occur in the elderly and in patients with comorbid conditions such as immunocompromised states or chronic arthritis. Pseudomonas aeruginosa is often the underlying cause in intravenous drug users with sternoclavicular or sacroiliac infections. Brucella can also cause arthritis of the sacroiliac joint in patients exposed to unpasteurized dairy products. Pasteurella multocida should be considered in patients who present with an animal bite to a joint.Neisseria gonorrhoeae remains the predominant cause in adults younger than 30 years of age. Disseminated gonococcal infection often manifests as a triad of polyarthritis, dermatitis (vesiculopustular skin lesions), and tenosynovitis. Synovial cultures yield the diagnosis in less than 50% of patients. N. gonorrhoeae can be recovered from pharyngeal, rectal, urethral, or cervical cultures. Gonococcal infection can also result in a monoarticular purulent arthritis without skin involvement. Synovial cultures are more often positive in these cases.Chronic monoarticular arthritis of the large joints, most commonly the knee, can be present in the later stages of Lyme disease. The organism, Borrelia burgdoferi, is rarely detected in synovial fluid, and the diagnosis is made through serologic testing.Mycobacterial infections can manifest as a more indolent and progressive monoarthritis. Tendon sheaths can be involved as well, particularly in infections with atypical mycobacteria. Potential organisms include Mycobacterium tuberculosis, Mycobacterium kansasii, and Mycobacterium marinum. Diagnosis is primarily made through culture of the synovial tissue.Chronic monoarthritis can occasionally be caused by fungal organisms, usually in immunocompromised patients. Disseminated coccidioidomycosis, blastomycosis, and sporotrichosis (particularly in people exposed to soil) have all been reported. Candidal infections may also occur, typically via hematogenous seeding, and are more acute in onset.Arthritis can be a significant feature of a number of viral illnesses. Polyarthritis can occur in patients with infection with mumps and parvovirus B19. It has also been reported during the preicteric period in patients with hepatitis B. Infections with rarer arthropod-borne alpha viruses endemic to East Africa, such as Chikungunya and O’nyong-nyong fever, are abrupt and can cause severe pain in large joints.*134/348/5*

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