Tubes ok, plate contaminated

Well, what can I say? Same work yet different results. I wouldn't like to consider that the plate itself may have been contaminated, but otherwise how can this result be explained...? A bit tired of serial dilution, I made up some fresh CSA (no antibiotics added) and something other for Campy's MIC test preparation. As it's impossible to incubate them in microplate reader or even to obtain its growth curve, I would have to modify my antiseptic protocol especialized to them. # Made up: 1. Single strength CSA w/o antibiotics --- 200 ml (~16 plates) 2. Double strength CSA w/o antibiotics --- 25 ml x4 (for agar dilution) 3. Serial diluted 0.5A Campy (79, 84, 89, 90). Serial diluted by 10-folds in Muller-Hinton broth => 0.5A, 10^-1, 10^-2, 10^-3, 10^-4, 10^-5, 10^-6. Duplicate, incubate in both 37C and 42C.