Which antibiotic combination is used as an adjunct for aggressive (Grade C) periodontitis?

Metronidazole plus amoxicillin (the so-called 'Winkelhoff cocktail') is the well-established systemic antibiotic combination used as an adjunct to scaling/root planing for aggressive (Grade C) periodontitis, particularly effective against Aggregatibacter actinomycetemcomitans.