Invasive pneumococcal disease in the Australian Capital Territory and Queanbeyan region: do high infant rates reflect more disease or better detection?

OBJECTIVE: To describe the epidemiology of invasive pneumococcal disease in the Australian Capital Territory (ACT) and Queanbeyan region prior to the introduction of conjugate pneumococcal vaccines. METHODOLOGY: Residents with sterile site isolates of Streptococcus pneumoniae from 1998 to 2000 were identified from a prospective bacteraemia surveillance project involving all ACT public hospitals, supplemented by retrospective laboratory-based detection of other sterile site isolates. RESULTS: Incidence of invasive pneumococcal disease was 15.2 cases per 105 per year, and 193.4 per 105 per year in infants under 2 years. Primary bacteraemia was significantly more common in infants and young children than in older subjects. Reduced penicillin susceptibility was observed in 9.6% of isolates, and no high-level penicillin resistance was observed. CONCLUSIONS: Infants in the ACT and Queanbeyan have a higher invasive pneumococcal disease incidence than similar populations worldwide. Better detection is the most likely explanation. This population would be ideal for studies of the 'real life' effectiveness of infant conjugate vaccination.

Laboratory cross-contamination of Mycobacterium tuberculosis: an investigation and analysis of causes and consequences.

BACKGROUND: The misdiagnosis of Mycobacterium tuberculosis infection has many ramifications. These include medical and psychological implications for patients and their families and financial and public health implications for health-care institutions. Microbiology laboratory procedures should minimize the possibility of laboratory cross-contamination of specimens and maximize the ability to recognize a cluster of false-positive cultures. Newer molecular typing methods provide rapid, accurate and effective means of identifying false-positive M. tuberculosis cultures. AIMS: To investigate a cluster of patients with positive M. tuberculosis cultures that were processed in the mycobacteriology laboratory on the same day. METHODS: Five patients' medical records and radiology results were reviewed to determine whether the cases were epidemiologically linked and whether there was clinical suspicion of tuberculosis. Restriction fragment length polymorphism (DNA fingerprinting) was performed using repetitive elements IS6110 and pTBN12. Laboratory processing procedures were analysed. RESULTS: On the basis of DNA fingerprinting using IS6110, the isolates from all five patients were identical. Molecular typing using pTBN12 was performed on four of the five isolates. All four had identical patterns. There was no epidemiological link between the patients. At least three (and probably four) of the five patients were misdiagnosed with tuberculosis. CONCLUSION: Microbiology laboratories should ensure that appropriate methodologies are in place to avoid cross-contamination of specimens. Clinicians need to critically interpret any positive laboratory result, especially in an unlikely clinical setting.