Many cystic fibrosis patients have long-term Staphylococcus aureus infections, with the bacteria’s resistance to antibiotics fluctuating over time, a study reports.
Chronic and recurrent infection of the airways is the most severe consequence of cystic fibrosis. The most prevalent bacteria is Staphylococcus aureus. There are different types of it, however, and studies have not looked extensively at which types cause the most damage over the long term.
Previous studies have shown that small colony variants (SCVs) and methicillin-resistant S. aureus (MRSA) have the most severe impact on CF patients’ lung function. But few studies have looked at S. aureus infections’ long-term effect on lung function. A German team decided to remedy this.
Their research, “Staphylococcus aureus in the airways of cystic fibrosis patients – A retrospective long-term study,” appeared in the International Journal of Medical Microbiology,
The team studied 283 CF patients in the city of Munster who had had S. aureus infections as early as 1994. Their analysis showed that 18 percent of the patients had rarely been infected with the bacteria, 20 percent had been intermittently infected, and 61 percent had had persistent infections.
They studied samples of the patients’ bacteria to determine antibiotic resistance. Its resistance to antibiotics ranged from 9 percent for methicillin to 80 percent for penicillin. Closer inspection showed that it fluctuated over the years, suggesting gain and loss of resistance over time.
Analysis of specific S. aureus cultures showed that 11 percent were SVCs and 1 percent were mucoid S. aureus species.
The study also indicated that patients only with S. aureus had better lung function and were younger than patients only with P. aeruginosa or those infected with both bacteria. This observation came during the last year of the study.
Researchers said the study was the first to determine S. aureus’s persistence in CF patients’ airways over time.
“We determined a high percentage of patients with persistent S. aureus infection within the CF patients treated at the two centers in Munster on a long-term scale,” the team wrote. “S. aureus isolates with different resistance patterns were isolated, indicating fluctuation of resistance against various antibiotics by acquisition and loss of resistance genes or by replacement with other S. aureus strains with different resistance profiles.”