In the case of Australia, only five per cent of hospital patients 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, Dr. Patrick Charles, a PhD researcher at the university of Melbourne, analysed samples of blood, urine, sputum and viral swabs of the nose and throat taken from 885 patients admitted to six Australian hospitals over 28 months from 2004 to 2006.
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 per cent 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.
"The study results show that current Australian guidelines for prescribing antibiotics for pneumonia are appropriate," Dr Charles says.
"It shows that Australian 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."
Dr Charles says the trend towards broad-spectrum antibiotics is being driven by laboratory-based studies of resistance rates in bacteria sent to the labs, rather than clinical studies of patients with pneumonia.
In the laboratory-based studies, the bacterial isolates often come from highly selected patients with more difficult to treat disease.
In addition, the fear of litigation made some doctors unnecessarily opt for more aggressive treatments.
However, the more frequently these broad-spectrum antibiotics were used, the more likely it was that bacteria would be become resistant to them.
"The emergence of antibiotic-resistant bacterial pathogens is one of the biggest threats to Australian health care standards and is closely linked to the inappropriate use of antibiotics," says Dr Charles.
"By continuing to use more traditional antibiotics to treat most cases of pneumonia, Australian 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.
"Furthermore, in the USA, Canada and some parts of Europe, they are seeing some serious complications which appear to be related to the overuse of some classes of broad-spectrum antibiotics which are frequently used there to treat respiratory infections."
Dr Charles is a physician in Infectious Disease and General Medicine at the Austin Hospital in Melbourne. He is also an Honorary Lecturer in the University of Melbourne's Department of Medicine at the Hospital.
His study was recently published in the journal Clinical Infectious Diseases and he was recently conferred with a PhD for his research at the University of Melbourne.