Alternative Growth Behavior of Mycobacterium Avium Subspecies and Staphylococci with Implications for Clinical Microbiology and Blood Culture

Rapid culture of Mycobacterium avium subspecies paratuberculosis (MAP) from patients remains a challenge. During the process of developing a rapid culture method for MAP, we found that there is an alternative growth behavior present in MAP, MAH (Mycobacterium avium subspecies hominissuis) and other bacteria such as Staphylococcus aureus, and Staphylococcus pseudintermedius. The bacterial DNA, RNA and proteins are present in the supernatants of the liquid culture media after routine microcentrifugation. When cultured in the solid media plate, there are a limited number of colonies developed for MAP and MAH disproportionate to the growth. We believe there is an alternative growth behavior for MAP, MAH and other bacteria similar to “phenoptosis”. Based on the alternative bacterial growth behavior, we tested 62 blood culture specimens that have been reported negative by routine automated blood culture method after 5 days of incubation. We used alternative culture media and molecular diagnostic techniques to test these negative culture bottles, and we found a large percentage of bacterial growth by alternative culture media (32%) and by molecular PCR amplification using 16s rDNA primer set and DNA sequencing (69%). The sensitivity of detection by the molecular PCR/sequencing method is significantly higher than by routine automated blood culture. Given the challenge of early diagnosis of sepsis in the hospital setting, it is necessary to develop more sensitive and faster diagnostic tools to guide clinical practice and improve the outcome of sepsis management.