Beta-Lactamase Fitness Costs: Bacterial Growth Rates (2013-2015)

This dataset, sourced from Zenodo (#4987501), documents the fitness consequences of beta-lactamase-mediated antibiotic resistance — a critical mechanism by which bacteria survive beta-lactam antibiotics like penicillin and cephalosporins. Across 1,284 measurements, bacterial growth rates under ceftazidime (CAZ) pressure were recorded, revealing a median growth rate of just 0.0029 per unit time and a striking range from near-zero (−0.0001) up to 0.13 — meaning the fastest-growing resistant strains grow roughly 45× faster than the median. Sixty outliers were flagged in the growth rate distribution (mean 0.01, σ=0.03), pointing to rare but highly fit resistant variants that could seed the spread of resistance in clinical or agricultural settings. The data underscores a key tension in antibiotic resistance biology: resistance mutations often impose metabolic penalties, yet selection pressure can rapidly surface high-fitness exceptions. Understanding which mutations escape that cost is essential for designing antibiotics and treatment regimens that are harder for pathogens to tolerate.

• 212 beta-lactamase-producing isolates were measured with 6 replicates each across 157 isolation dates (Jun 2013 to Mar 2015)
• The growth rate distribution is sharply bimodal: 120 isolates cluster below 0.005, while 23 isolates form a distinct fast-growing group above 0.05
• The middle range (0.01-0.05) is nearly empty with only 2 isolates, suggesting a fitness threshold rather than a continuum
• Fast growers are concentrated in summer months (Aug-Sep 2013, May-Jun 2014), while late 2014 and early 2015 isolates are almost exclusively slow growers
• The 3,000x growth rate difference between the fastest (R10399: 0.125) and slowest (R14933: 0.00004) isolates implies dramatically different fitness costs of resistance