3.1.1 Transportation The terms Category A (for positive cultures) and Category B (for specimens) are limited to classifying samples / microbial cultures being transported to another laboratory (see Table below). Sample Description Packaging Requirement Category A samples are or suspected to contain a microbial agent with the following definition “an infectious substance which is transported in a form that if exposure to it occurs, is capable of causing permanent disability, life-threatening or fatal disease to humans or animals”. The majority are Hazard Group 3 or 4 Assign to UN2814 (Humans) Packaging Instructions P620 Supporting documentation as per ADR Transport as category A ADR licensed courier For practical reasons to referral / reference services to continue a limited number of Category A agents have exempted from being transported as Category A. These are Vero-cytotoxin producing Escherichia coli (VTEC), Mycobacterium tuberculosis and Shigella dysenteriae 1 Assign UN3373 Packaging instruction P650 Send by courier Royal Mail will NOT accept Category B samples are that do not meet the definitions of Category A Assign UN3373 Packaging instruction P650 Post or courier Royal Mail WILL accept 4 Specimen Processing/Procedure77,78 4.1 Test Selection If there is sufficient volume, specimens being processed for AFBs should normally have AFB microscopy (a ‘smear’) prior to, and in addition to, culture; with the exception of samples received already pre-inoculated into a mycobacterial culture bottle. Direct microscopy of urine is also of questionable value; and moreover, depending on the clinical setting, can be misleading due to the presence of mycobacteria10,26. If sample volume is insufficient for both, culture is usually preferred to microscopy due to greater sensitivity. It may be appropriate to process a sample for AFBs, depending on specimen type and available clinical details, even if these tests were not specifically requested when submitted1. Such specimen types in particular would include pleural biopsies or material from lymph nodes1. 4.2 Appearance Sterile site body fluids Note the presence of any clot and, if present, include it in the processing. Tissue biopsies Process the entire tissue if the sample is small.
Rapid diagnostic tests should be conducted for rifampicin resistance Infection control measures and treatment for MDR TB should be started as outlined by NICE Rapid diagnostic tests for M. tuberculosis complex identification should be conducted on biopsy material only if: all the samples has been inappropriately placed in formalin acid-fast bacilli are visible on microscopy All NAATs should be carried out in accordance with manufacturer’s instructions. Suitable clinical samples should also ideally be sent for conventional AFB microscopy and culture investigations as outlined above. 4.5.5 Culture media, conditions and organisms Clinical details/ conditions Specimen Standard Incubation Cultures read Target organism(s) ‡ Temp oC Atmos Time Bone and joint, including spinal tuberculosis All bone marrow aspirates Wound swab Pus or Pus swabs** Automated liquid systems* and LJ + pyruvate 35 – 37 Air 8 weeks extending to 12 weeks if required 45 Weekly Mycobacterium species Tuberculous meningitis CSF Ascites fluid Pleural fluid Automated liquid systems* and LJ + pyruvate*** 35 – 37 Air 8 weeks extending to 12 weeks if required 45 Weekly Mycobacterium species Pulmonary tuberculosis Sputum Brochoalveolar lavage/bronchial washings Gastric washings 42 Air 8 weeks extending to 12 weeks if required 45 Weekly M. xenopi tuberculosis Urine Automated liquid systems* and LJ + pyruvate 35 – 37 Air 8 weeks extending to 12 weeks if required 45 Weekly Mycobacterium species Consider for bone and joint fluids eg from extremities and/or direct smear positive Automated liquid systems* and LJ + pyruvate 28 - 30 Air 8 weeks extending to 12 weeks if required 45 Weekly Non-tuberculous mycobacteria