We report the persistent circulation of third-generation cephalosporin resistant Salmonella Typhi in Mumbai, linked to the acquisition and maintenance of a previously characterized IncX3 plasmid carrying the ESBL gene blaSHV-12 and the fluoroquinolone resistance gene qnrB7 in the genetic context of a triple mutant also associated with fluoroquinolone resistance.

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Introduction: Tigecycline Evaluation and Surveillance Trail (TEST) study is an on-going global surveillance. The study was performed to determine the susceptibility of common pathogens to tigecycline and comparator antibiotics by broth microdilution (BMD) at two tertiary care centres in India from 2015 to 2017. Methodology: Total of 989 isolates collected from various clinical specimens between January 2015 and September 2017 from two centres in India were included. BMD was performed to determine the minimum inhibitory concentration (MIC) for tigecycline and comparator antibiotics. Results: Among Gram-negative bacteria, susceptibility to tigecycline was lowest among Klebsiella spp. being 84% while others such as E. coli, Enterobacter spp., Serratia spp. and H. influenzae showed susceptibility of 98%, 95%, 98% and 100% respectively. Overall, 99 isolates among Enterobacteriaceae (E. coli, Klebsiella spp. and Enterobacter spp.) were ESBL producers, susceptible to tigecycline. Among the 101 meropenem resistant Enterobacteriaceae, 85 were susceptible to tigecycline (84%). Among the Gram-positive bacteria, S. aureus and Enterococcus spp. were 99% and 98% susceptible to tigecycline respectively. Among 68 MRSA isolates in the study, 66 (97%) were susceptible to tigecycline. Seven vancomycin resistant E. faecalis were isolated and all were susceptible to tigecycline. Conclusion: Tigecycline has retained activity over both Gram-positive and Gram-negative organisms with MIC values comparable to global reports. About 98% of the MDR Gram-positive and Gram-negative bacteria in the study are susceptible to tigecycline. With increased incidence of extensively drug resistant organisms, tigecycline is a potential reserve drug.

Antibiotic resistance is a global threat caused by factors such as overuse of antibiotics, lack of awareness, development of biofilms etc. World Health Organization released a list of global priority pathogens which consisted of 12 species of bacteria categorized as expressing critical, high and medium resistance. Several Gram-negative and Gram-positive species are known to cause wide varieties of infections and have become multidrug or extremely drug resistant. Pathogens causing infections associated with invasive medical devices are biofilm producers and hence their treatment becomes difficult due to a structurally stable matrix which prevents antibiotics from penetrating the biofilm and thereby showing its effects. Factors contributing to tolerance are inhibition of penetration, restricted growth and activation of biofilm genes. Combination drug therapies has also shown potential to eradicate biofilm infections. A combination of inhaled Fosfomycin/tobramycin antibiotic strategy has been effective against Gram-negative as well as Gram positive organisms. Along with antibiotics, use of natural or synthetic adjuvants shows promising effects to treat biofilm infections. Fluroquinolone activity on biofilms is disrupted by low oxygen tension in the matrix, a strategy known as hyperbaric oxygen treatment that can enhance efficacy of antibiotics if well optimized. Adjuvants such as Ethylenediaminetetraacetic acid (EDTA), Sodium Dodecyl Sulphate (SDS) and chlorhexidine act by killing non-growing microbial cells aggregated on the inner layer of the biofilm. This review aims to list down current combination therapies used against Gram-negative and Gram-positive biofilm forming pathogens and brief about comparison of combination drugs and their efficacies.