Abstract
Extended-Spectrum β-Lactamase (ESBL) producing bacteria are becoming increasingly prevalent in biofilmassociated infections. Bacteria form biofilms that allow their survival in hostile environments. The amount of formed biofilm is affected by external environmental factors. This study investigates the effect of specific parameters (media type, incubation condition, and growth stage) on the amount of produced biofilm on antibiotic resistant bacterial strains, Escherichia coli (CTX-M-15, TEM-3, and IMP-type) and Klebsiella pneumoniae (OXA-48, SHV-18, NDM-1, and KPC-3). The amount of biofilm formed was measured at different time points (6, 12, 24 and 48 h) of incubations under static and shaking conditions, using three different types of media (nutrient broth, LB broth, and AB broth). Statistical tests showed that there was a significant difference in biofilm level (p<0.01) for 64 out of 80 tests (80%) when grown under different types of media. Growing under different incubation conditions also showed a statistical difference in biofilm level (p<0.05) for 76 out of 120 tests (63%). Stage of growth of the same species also showed statistical difference, 20 out of 24 tests (83%) for E. coli and 24 out of 24 tests (100%) for K. pneumoniae. These findings suggested that biofilm formation is highly affected by incubation conditions, strains’ stage of growth, and media type demonstrating that these conditions may play a role in adaptability of the ESBLs on different environmental conditions and their increased prevalence in biofilm associated infections.
Highlights
Over the years, the increase in the incidence of antibiotic resistance in many pathogens has been reported and in many areas worldwide [1]
We emphasized our understanding of measuring biofilm by using antibiotic-resistant strains and we tried to find out how biofilm amount could be affected by different growth parameters, will those parameters be agreed with all the tested strains, and which strain among those selected antibioticresistant can give the highest amount of biofilm and under which conditions
As we proposed that those selected time-stages would not be the same for all strains regarding biofilm development as each strain differs from another phenotypically and genotypically, our results confirmed this in that 100% of K. pneumoniae strains and 83% of E. coli strains showed a significant difference at the selected growth stages and for both static and shaking incubation
Summary
The increase in the incidence of antibiotic resistance in many pathogens has been reported and in many areas worldwide [1]. This increase has been attributed to the changing of microbial characteristics, selective pressure and technological and societal changes that have enhanced the development and spread of antibioticresistant microorganisms. Antibiotic resistance represents one of most significant healthcare problems. Healthcare suppliers are obligated to use more toxic doses of antibiotics, more expensive and less effective antibiotics when all options have been exhausted, i.e. first and the second line antibiotic treatment is limited by resistance or is unavailable [3]
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