The WHO on Monday said it it has published the first-ever list of antibiotic-resistant "priority pathogens", 12 families of bacteria that pose the greatest threat to human health, to guide and promote research and development of new antibiotics.

The Geneva-based World Health Organisation (WHO) said that list was drawn up as part of its efforts to address growing global resistance to antimicrobial medicines. According to the global health body, the list is divided into three categories according to the urgency of need for new antibiotics: critical, high and medium priority.

The most critical group of all includes multi-drug resistant bacteria that pose a particular threat in hospitals, nursing homes, and among patients whose care requires devices such as ventilators and blood catheters. They include Acinetobacter, Pseudomonas and various Enterobacteriaceae (including Klebsiella, E. coli, Serratia, and Proteus), said a WHO statement.

It said that all the bacteria can cause severe and often deadly infections such as bloodstream infections and pneumonia. "These bacteria have become resistant to a large number of antibiotics, including carbapenems and third generation cephalosporins - the best available antibiotics for treating multi-drug resistant bacteria," said the report.

The second tier which includes antibiotics of high priority includes for Enterococcus faecium, which is vancomycin-resistant, Staphylococcus aureus which is methicillin-resistant, Helicobacter pylori which is clarithromycin-resistant, Campylobacter spp which is fluoroquinolone-resistant, Salmonellae which is fluoroquinolone-resistant, Neisseria gonorrhoeae which is cephalosporin and fluoroquinolone-resistant.

The third tier which includes medium priority includes Streptococcus pneumoniae which is penicillin-non-susceptible, Haemophilus influenzae, which is ampicillin-resistant and Shigella spp which is fluoroquinolone-resistant.

This list is a new tool to ensure research and development responds to urgent public health needs, said WHO's Assistant Director-General for Health Systems and Innovation Marie-Paule Kieny in the statement.

Evelina Tacconelli, Head of the Division of Infectious Diseases at the University of Tübingen and a major contributor to the list, said :"New antibiotics targeting this priority list of pathogens will help to reduce deaths due to resistant infections around the world. "Waiting any longer will cause further public health problems and dramatically impact on patient care."