For instance, I've been looking at the interaction between K. pneumoniae and E. Coli but can't find anything substantial. Specifically, I am looking at antibiotic resistance - if beta-lactamase production from K. pneumoniae confers antibiotic resistance to E. Coli in vitro.
Thanks!
Dear Zhe Yuan Tay,
Looking at interactions between strains is very interesting and has obvious implications for microbial ecology and co-evolution, as well as the more practical considerations about the development and transfer of antibiotic resistances.
Perhaps you should evaluate the impact of co-cultures by fitness measurements in both liquid broth (where antibiotic and beta-lactamase can freely diffuse) and semi-solid agar where spatial heterogeneity will be important - in particular, you would expect to see a positive interaction when Kp and Ec colonies are close and at higher antibiotic levels.
The impact of spatial heterogeneity has been investigated by others using agar-based systems - it would be interesting to see whether your system is similar, and whether different pairs of Kp and Ec have different outcomes when testes at a range of cell densities and antibiotic levels.
Regards, Andrew.
The answer that Andrew provides is accurate, but let me add a point of clarification. Since the antibiotic can readily diffuse into and out of the periplasm where beta-lactamase is located, in a liquid culture the antibiotics are going to be inactivated fairly readily. Once this happens the growth of non-resistant strains can readily occur. This is less true on plates where the rate of diffusion is much less.
Beta-lactamases are inducible enzyme produced when penicillin or its derivatives contact the bacterial cells. The enzymes themselves may not induce resistance in non producers. Their production has molecular basis (plasmid based) and it depends on presence or otherwise of these genes. The type of beta-lactamase gene present would determine the type of beta lactamase produced and the range of beta lactam antibiotics resitance would occur. blaTEM, blaCTX and blaSHV for examples confer resistance to third generation cephalosporin and lower penicillins through the production of extended spectrum beta lactamases (ESBLs) .
Organisms interacting with the bearer of ESBLs gene or any other beta-lactamase genes may fortunately receive genes by genetic recombination and begin to show resistance through the production of appropriate beta-lactamase. This is however not guaranteed.
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