Study Suggests Antibiotics Effective in Southern India Might Not be as Effective in Eastern India

New Delhi: Antibiotic resistance of bacteria is rising globally and this resistance shows differential patterns. Some antibiotics work well against some bacteria in a particular geographical region, while they may not work well against the same bacteria in a different region. In India also, this trend has been observed. A recent study published in the Elsevier journal Gene suggests that antibiotics that are effective against Helicobacter pylori in South India may not be as useful in the Eastern regions.

H pylori is a bacterium that infects the stomach and can cause chronic gastritis, peptic ulcer as well as gastric cancer in extreme cases. India has a high prevalence of infection by this bacterium and over 20 million people are estimated to suffer from peptic ulcer. 

It is worth mentioning here that H pylori has numerous strains circulating in India with a differential prevalence of strains in different regions. To know which strains (or variants) are prevalent at what places, scientists have to carry out the sequencing of the whole genomes of the strains. Remember, strains of a pathogen (a bacterium or a virus or any other agent that can cause disease) are slight genetic variations of the same species. In this case, the species is H pylori and the various strains of it contain slight differences in their genetic architecture. The genetic variations that bring in different strains are acquired by the process known as a mutation, where random changes in the genetic material (DNA or RNA) occur naturally or are induced by other environmental factors. To know about the genetic makeup of the strains, deciphering the sequences of their genomes (all the genetic information of an organism) is the way scientists resort to. 

In the latest study also, the team of researchers applied the technique of finding out the genome sequences of 143 H pylori strains from across India. Out of these strains, 32 were isolated from eastern (Kolkata) and southern India. They compared the sequences in order to reveal the distinctness of the genetics of the strains circulating in different regions. In total, the study conducted the whole genome sequencing of 74 genomes from Kolkata (East India) and these sequences were compared with 12 previously reported sequences from South India. The findings suggest that the gene called AMR was present in greater numbers among the strains isolated from east India in comparison to the isolates of South India. The comparative genome analysis also revealed that the genes involved in disease virulence and drug resistance are different in South and East India isolates.

Moreover, the study analysed the resistance to a variety of antibiotics of the strains from the regions. They found a differential pattern of resistance to antibiotics offered by the strains in different regions. The antibiotics that were considered in the study included those used frequently in H pylori infection like metronidazole, levofloxacin, amoxicillin, tetracycline, clarithromycin and furazolidone. 

The results of the study showed that among East Indian isolates, resistance against amoxicillin, tetracycline and furazolidone was low, while high resistance was observed to metronidazole and clarithromycin. The authors warn of “judicial use of metronidazole and clarithromycin antibiotics in eastern India.”

The study's corresponding author Bhabatosh Das, associate professor at Translational Health Science and Technology Institute, Faridabad, while speaking to NewsClick commented on the antibiotic use in different regions of the country. “Several of my recent articles, including one recently submitted multicentric study, clearly indicate that clinicians must be very vigilant before prescribing an antibiotic to patients. We observed >90% resistance against a few routinely used antibiotics. Such antibiotics may not continue to treat MDR (multi drug resistance) infections,” Das said.

When asked for his suggestions and about whether the observed differential antibiotic resistance in different geographic locations arose due to unaware and reckless use of antibiotics, Dr Das said, “Multiple factors contribute to the emergence of MDR pathogens. In addition to the healthcare sector, the use of antibiotics in livestock, agriculture, and the release of industrial effluent from the pharma sector may also provide selective advantages to resistant pathogens. XDR infections in community-acquired pathogens suggest that the current antibiotic resistance crisis is the result of a multi-sectoral effect.”

It is noteworthy that similar studies were conducted previously, where differential antibiotic resistance was observed in different regions. When asked about the difference between the earlier study and the new one, Dr Das said, “The previous study was based on the phenotype, and the identity of resistance traits was not explored. We sequenced the genome of H pylori and identified the bacterial functions that contribute to drug resistance. In addition, we reported that antibiotic resistance is continuously evolving. The current strains are multidrug-resistant compared to the previous single-drug-resistant isolates.”

On the other hand, Professor Satyajit Rath, adjunct faculty of the Indian Institute of Science Education and Research (IISER), Pune, raised the issue that the studies are relatively small. “So will have only moderate impact,” Rath told NewsClick.

However, prof. Rath agreed that the findings do provide some basis for choosing antibiotics for H. pylori treatment in different locations. “While the studies identify both the extent of resistance to some antibiotics and the tendency of clusters of strains in geographical locations of Helicobacter, and while both are useful to know, neither finding is particularly surprising, and these descriptive studies do not really provide any insights about the bigger picture/s of antibiotic resistance,” Rath further commented.