Clonal Associations among Staphylococcus aureus Isolates from Various Sites of Infection

A molecular epidemiological analysis was undertaken to identify lineages of Staphylococcus aureus that may be disproportionately associated with infection. Pulsed-field gel electrophoresis analysis of 405 S. aureus clinical isolates collected from various infection types and geographic locations was performed. Five distinct S. aureus lineages (SALs 1, 2, 4, 5, and 6) were identified, which accounted for 19.01, 9.14, 22.72, 10.12, and 4.69% of isolates, respectively. In addition, 85 lineages which occurred with frequencies of <2.5% were identified and were termed “sporadic.” The most prevalent lineage was methicillin-resistant S. aureus (SAL 4). The second most prevalent lineage, SAL 1, was also isolated at a high frequency from the anterior nares of healthy volunteers, suggesting that its prevalence among clinical isolates may be a consequence of high carriage rates in humans. Gene-specific PCR was carried out to detect genes for a number of staphylococcal virulence traits. tst and cna were found to be significantly associated with prevalent lineages compared to sporadic lineages. When specific infection sites were examined, SAL 4 was significantly associated with respiratory tract infection, while SAL 2 was enriched among blood isolates. SAL 1 and SAL 5 were clonally related to SALs shown by others to be widespread in the clinical isolate population. We conclude from this study that at least five phylogenetic lineages of S. aureus are highly prevalent and widely distributed among clinical isolates. The traits that confer on these lineages a propensity to infect may suggest novel approaches to antistaphylococcal therapy

Bacterial Infection in Chronic Obstructive Pulmonary Disease in 2000: a State-of-the-Art Review

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States. The precise role of bacterial infection in the course and pathogenesis of COPD has been a source of controversy for decades. Chronic bacterial colonization of the lower airways contributes to airway inflammation; more research is needed to test the hypothesis that this bacterial colonization accelerates the progressive decline in lung function seen in COPD (the vicious circle hypothesis). The course of COPD is characterized by intermittent exacerbations of the disease. Studies of samples obtained by bronchoscopy with the protected specimen brush, analysis of the human immune response with appropriate immunoassays, and antibiotic trials reveal that approximately half of exacerbations are caused by bacteria. Nontypeable Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae are the most common causes of exacerbations, while Chlamydia pneumoniae causes a small proportion. The role of Haemophilus parainfluenzae and gram-negative bacilli remains to be established. Recent progress in studies of the molecular mechanisms of pathogenesis of infection in the human respiratory tract and in vaccine development guided by such studies promises to lead to novel ways to treat and prevent bacterial infections in COPD