This genus is always associated with disease. It is usually subject to aggressive antibiotic treatment. It appears to be present is some 20-30% of CFS patient’s uBiome seen so far.
“Enterobacteriaceae like Kluyvera are not very friendly and tend to thrive in the inflamed gut. ”
There are 230+ studies on PubMed — this is just from a select sampling.
- Ineffectual: Lemongrass, Artemesia vulgaris (wormwood), Nutmeg oil, Selinum wallichianum Essential oil (or) Milk Parsley 
- study which shows that oil of Mexican oregano works against kluyvera cryocrescens. the active ingredient of Mexican oregano and common oregano are the same, carvacrol. From a reader, Study
- “. Successful treatment options include third-generation cephalosporins, aminoglycosides, betalactams with beta-lactamase inhibitors and carbapenems. ” 
- “In contrast, the resistance to ampicillin, extended-spectrum penicillins, and first- and second-generation cephalosporins is significant. Kluyvera is a potentially virulent pathogen that deserves aggressive treatment designed with an awareness of the organism’s antimicrobial resistance patterns.” 
This is a tough genus to reduce without using antibiotics. No known probiotics impacts it.
- Aspartame (Nutrasweet)
- L-Glutamic acid ( monosodium glutamate – MSG) and possibly gluten
- L-Phenylalanine (Good sources of phenylalanine are eggs, chicken, liver, beef, milk, and soybeans.)
- Pomegranate ellagitannins
- Oregano (Mexican or common)