Question

A 31 year old male presented to the Emergency Department (ED) after experiencing gross hemoptysis. He had a 2 month history of productive cough, a 25 pound weight loss, night sweats, and fatigue. A chest X-ray (CXR) revealed bilateral cavitary infiltrates. The patient had a history of heavy alcohol and drug use with a long history of cigarette use and a chronic smoker's cough. The patient reports no permanent residence. The patient was admitted and tested for bacterial pneumonia. Routine Gram stain from sputum was negative. AFB cultures on three consecutive morning sputum samples were subsequently ordered. While AFB cultures are kept for 8 weeks, direct microscopic examination by Ziehl Neelsen staining can allow for an AFB diagnosis within 24 hours of sample collection. Between 5,000 and 10,000 tubercle bacilli per ml of sputum are required for direct microscopy to be positive. Sputum specimens from patients with pulmonary tuberculosis, particularly those with cavitary disease, often contain sufficiently large numbers of acid-fast bacilli to be readily detected by direct microscopy. The sensitivity can further be improved by examination of more than one smear from a patient. Many studies have shown that examination of two smears will on average detect more than 90% of infectious tuberculosis cases. The incremental yield of acid-fast bacilli from serial smear examinations has been shown to be 80-83% from the first, 10-14% from the second and 5-8% from the third specimen. Therefore three sputum specimens are recommended for suspects of pulmonary tuberculosis. A negative smear result does not exclude the diagnosis of tuberculosis as some patients harbor fewer tubercle bacilli than can be detected by microscopy. A poor quality specimen (salvia, contaminated, quantity too small, specimen not stored properly, etc.) may also produce negative results. Table 1. Acid Fast Bacilli (AFB) Smear Classifications Using the Ziehl Neelsen Staining Method, Amerkan Thoracic Society Scale Chassification of Smear Type 1 ATS Standards > 9 AFB per field 1-9 AFB per field 1-9 AFB per 10 fields 1-9 AFB per 100 fields 1-2 organisms per 300 fields seen per 300 fields 3+ Infectiousness of Patient Probably very infectious Probably very infectious Probably infectious Probably infectious Smear Result Strongly positive Strongly positive Moderately positive Weakly positive in condusive repeattest Negative Report exact AFB count Probably infectious May not be infectious NO AFB seen Answer the following questions: 1. Explain how the clinical presentation of the patient in the ED is indicative of TB. 2. Explain why the Gram stain was negative for the patient.

Answer 1

1. Clinical presentation in the ED is indicative of TB

Tuberculosis is associated with symptoms such as Malaise, fever, weight loss, sweating, anorexia, dyspnea, cough, productive cough with sputum.The patient in the given case is experiencing productive cough, weight loss, fatigue and night sweats which states that he is suffering from TB.

2. Gram stain was negative for the patient because , patient had undergone routine sputum culture. Direct microscopy was suggested but was not performed on the sputum of the patient. Thus gram stains are negative.Where as direct microscopy will show positive results with in 24hrs.

3.Significance of direct microscopic examination of sputum sample in Acid Fast Bacillus culture is faster results in short time frame, the results can be exactly detected irrespective of the amount of sputum collected, and also irrespective the quality of specimen.

4. Usually 10 to 100 Bacillus are needed for the sputum to be positive.Below 4+ only Bacillus are in between 1 to 9 which grades from negative to slightly infectious. Where as 4+ shows patient have Bacillus more than 9 and thus indicating infectious.