MB = Medical Bachelor?

Bachelor of Medicine, an academic degree (Medicinae Baccalaureus)

A professor with only a bachelor degree? That is what confused me.
Perhaps he had a PhD degree in other field?

Professor Peter Collignon
Director of Infectious Diseases & Microbiology

MB BS(Hons), BSc(Med), FASM, FRACP, FRCPA
Professor, Australian National University Medical School.

Professionals holding MBBS Degrees are referred to by the title of "Doctor" and use the prefix "Dr".

Bachelor of Medicine, Bachelor of Surgery, or in Latin Medicinae Baccalaureus, Baccalaureus Chirurgiae (abbreviated in various ways, viz. "BMBS", MB BChir, BM BCh, MB BCh, MB ChB, MB BS, BM, BMed, MBBS etc.), are the two first professional degrees awarded upon graduation from medical school in medicine and surgery by universities in various countries that follow the tradition of the United Kingdom. The naming suggests that they are two separate degrees; however, in practice, they are usually treated as one and awarded together. Usually, students who have graduated with a "Bachelor of Medicine" degree may also practice surgery, because it is equivalent to the "Bachelor of Medicine, Bachelor of Surgery" degree

Most Australian medical schools confer MBBS degrees. However, The University of Newcastle confers BMed. This degree is equivalent to MB BS and any BMed graduate may practice in any field of Medicine of their own choice including surgery.
In Australia, Doctor of Medicine (MD) is an advanced research degree requiring two years' full time enrolment, compared to a PhD which requires three years' full time enrolment. The University of Melbourne will soon award "MD" to their MBBS equivalent graduates as will several others including The University of Western Australia located in Perth.
http://en.wikipedia.org/wiki/Bachelor_of_Medicine,_Bachelor_of_Surgery

I just learned something new by checking this out for you--I didn't realize that Australian medical schools haven't typically awarded MD degrees.

The MB BS degree in Australia