Antibiotics used to treat a variety of common bacterial infections are becoming more difficult to access, mostly because the drugs are less profitable for manufacturers to produce and market, say experts.

Writing in a commentary in Clinical Microbiology and Infection, researchers including those at St George’s, University of London, say the problem is particularly acute for formulations needed to treat sick babies and children.

They say doctors increasingly have to use alternative antibiotic treatments, which may have worse side-effects for patients, including encouraging the growth of drug-resistant bacteria – one of the greatest threats to public health.

Professor Mike Sharland, Paediatric Infectious Diseases Research Group at St George's University of London, who was a co-author of the study, said: “Considerable attention has been correctly focussed on the need to develop new antibiotics.

“However it is increasingly clear that insufficient attention has been paid to the optimal use of older off patent antibiotics.

“There are increasing global shortages of older antibiotics, the optimal choice of antibiotic, dose and duration for most common infections are very poorly evidence based.

“Many older narrow spectrum antibiotics are becoming unavailable forcing wider use of broader spectrum agents.”

Some of these older drugs, for example IV fosfomycin and colistin, have an important role to play in treating multidrug resistant bacteria.

The authors found that absence of marketing of older antibiotics is primarily caused by the high costs involved in registering medicines in multiple countries. This is combined with the relatively small market for these antibiotics, which are sold as low-cost generics and for short courses of treatment.

Previous research in 38 countries has shown that out of 33 older but effective antibiotics, 22 were marketed in fewer than 20 countries, and that the situation was deteriorating.

Research has also revealed repeated and prolonged shortages of many antibiotics. For example, in the USA between 2001 and 2013, 148 different antibiotics were in shortage, many on multiple occasions. The authors say little is known about the situation in poorer nations but evidence suggests it is even worse.

Read the paper here