Infections caused by gram-negative bacteria such as salmonella, pneumococcus, and cholera are a major problem for patients with compromised immune systems, as well as for premature babies. Bdellovibrio and like organisms (BALOs) are bacterial predators that attack and feed on other gram-negative bacteria without harming humans. Therefore, the use of predatory bacteria has been suggested as an alternative approach to tackle a range of drug-resistant, gram-negative bacterial infections that can develop in hospitalized patients. However, recent studies have revealed that some gram-negative bacteria appear to be resistant to BALOs.