Cross-resistance can be one way or two way, one-way resistance can be seen in:: (A) Neomycin and streptomycin, (B) Tetracycline and doxycycline, (C) Sulphadiazine and sulphadoxine, (D) None of the above
Answer is A. Organisms that develop resistance to an antimicrobial agent may also show resistance to other  chemically related AMAs. The cross-resistance among AMAs could either be one-way or two-way.  Cross-resistance among tetracyclines and sulphonamides is usually ‘two-way’.