Broad spectrum drugs spur growth of resistant bugs

Sydney, Oct 15 : Doctors should avoid prescribing expensive broad-spectrum antibiotics for pneumonia to avert the development of more drug-resistant super bugs, according to a new study.

The study, by PhD researcher Patrick Charles, shows that only five percent of patients hospitalised with community-acquired pneumonia had infections caused by organisms that could not be successfully treated with penicillin, combined with an "atypical" antibiotic such as doxycycline or erythromycin.

In the world's largest study of its kind, Charles - an infectious diseases consultant at Austin Health - studied almost 900 people admitted to six hospitals over 28 months from 2004 to 2006.

His research analysed samples of blood, urine, sputum and viral swabs of the nose and throat taken from 885 patients at the Austin, Alfred, Monash and West Gippsland hospitals in Victoria, the Royal Perth Hospital and Princess Alexandra Hospital, Brisbane.

He found that most cases of pneumonia were caused by easy-to-treat bacteria such as the pneumococcus or mycoplasma, or alternatively by respiratory viruses which do not require antibiotic therapy.

Only five percent of cases were caused by organisms which would require more expensive and broad-spectrum antibiotics, and these cases were nearly all in patients who'd had frequent hospital admissions or were residents of nursing homes, according to a Melbourne University release.

"It shows that . . . doctors should resist the push which is occurring in some parts of the world - particularly the USA - to prescribe broad-spectrum antibiotics to treat essentially all possible causes."

Charles said the trend towards broad-spectrum antibiotics is being driven by lab-based studies of resistance rates in bacteria sent to the labs, rather than clinical studies of patients with pneumonia.

"By continuing to use more traditional antibiotics to treat most cases of pneumonia, doctors can limit or delay the emergence of more resistant strains of bacteria.

"By using the broad-spectrum antibiotics less often, we can also prolong the effective lifespan of these drugs."

His study was recently published in Clinical Infectious Diseases and he was recently conferred with a PhD for his research by the University of Melbourne.