ORLANDO, FLA—The advantages and drawbacks of the therapeutic use of viruses to treat bacterial infections was one focus of the 101st General Meeting of the American Society for Microbiology (ASM). Also highlighted was the survival of triclosan-resistant bacteria in common antibacterial products.

In addition, presenters provided details about a broad, interagency plan to cope with antimicrobial resistance. The use of nicotine against antibiotic-resistant mycobacteria was explored during the meeting, which took place in Orlando, Florida, as was the reemergence of whooping cough (a result of the mutation of genes encoding two proteins in the coat of Bordetella pertussis, which has reduced the organism’s susceptibility to currently available vaccines).

USING VIRUSES TO FIGHT BACTERIAL INFECTION

As antibiotic resistance becomes more of a concern, researchers are exploring alternatives to conventional infection-fighting tactics. According to an investigative team lead by Rial Rolfe, PhD, Assistant Dean and Professor in the Texas Tech University Health Sciences Center in Amarillo, using bacterial viruses, or bacteriophages, to stop infection could have significant advantages over standard antibiotic treatments.

For instance, while antibiotic treatments require multiple doses, bacteriophages could be administered once, after which the viruses would reproduce in their bacterial hosts until all of the targeted bacteria were destroyed. The destruction of beneficial bacteria, a frequent consequence of antibiotic treatment, could also be avoided by bacteriophage use.

The team presented research on the benefits of bacteriophage therapy for Clostridium difficile diarrhea in hamsters. C difficile did develop bacteriophage resistance, but the viruses were able to maintain their efficacy by evolving along with the bacterial species. Although the researchers were able to produce promising results with bacteriophage experiments in hamsters, they acknowledge that real-world scenarios will be more complex and difficult to manage.

BACTERIA SURVIVE DESPITE DISINFECTANT USE

Triclosan is a popular antimicrobial substance used in a variety of household and institutional cleaning products. But Maura Meade, PhD, and coworkers at Allegheny College in Meadville, Pennsylvania, have identified certain bacteria that defy the substance’s toxicity and enable others to resist it as well.

Dr. Meade, Assistant Professor of Biology, voiced concern that such triclosan-resistant organisms as Serratia marcescens and Pseudomonas putida were able to survive for longer than 16 weeks in hand soaps, dishwashing liquids, and acne creams containing triclosan. She also noted that P putida and Alcaligenes xylosoxidans formed biofilms on antibacterial substances in which triclosan was incorporated. These organisms are known to decrease triclosan’s ability to kill bacteria.

This finding, Dr. Meade said, could have serious implications for home and health care settings in which triclosan is used.

GUIDELINES TO HELP FIGHT ANTIBIOTIC RESISTANCE

David Bell, MD, of the Centers for Disease Control and Prevention (CDC), Atlanta, presented the Public Health Action Plan to Combat Antimicrobial Resistance, a strategy developed by the CDC, the Food and Drug Administration, the National Institutes of Health, the ASM, and others. Part 1 of the plan, released in January 2001, relates to antimicrobial resistance on a national level. Part 2 has an international focus and will be developed between 2001 and 2002.

The action plan is organized in four sections: surveillance, prevention and control, research, and product development. Seven of the plan’s 13 top-priority action items have already been implemented; there are 84 initiatives in the plan altogether. Six more will be implemented within the next two years with the cooperation of the federal, state, and local agencies named in the plan’s pages. It was noted that implementation of stated goals was contingent upon future resource availability.

Seventy-five percent of the CDC’s $25 million 2001 budget for antimicrobial resistance will be disbursed to health departments and universities that will assist in investigator-initiated and peer-reviewed programs intended to fight the emerging threat of antibiotic resistance.

NICOTINE TO FIGHT MYCOBACTERIAL INFECTION?

Citing indications that such antimycobacterial drugs as isoniazid, rifabutin, clarithromycin, and others have been increasingly ineffective in treating mycobacterial infections, researchers are looking for alternative treatment strategies.

Nicotine was investigated in vitro as an agent for use against six Mycobacterium variants, including those responsible for tuberculosis and Crohn’s disease. Saleh A. Naser, PhD, and coworkers at the University of Central Florida in Orlando found that all of the organisms were susceptible to minimum inhibitory concentrations (MIC) of 2.0 to 3.0 µg/mL. The human body can tolerate higher concentrations of the substance: Salivary nicotine levels in smokers and others who use tobacco products may range from 70 to 1,560 µg/mL. (Salivary nicotine levels of 70 µg/mL result when a minimum of 10 cigarettes are smoked daily.)

Given this, said Dr. Naser, and pending determination of nicotine’s toxicity levels in human tissue, the lower MIC may turn out to be a useful nicotine dose for treatment of infectious disease.

THEORY ON WHOOPING COUGH REEMERGENCE POSITED

In an effort to understand recent outbreaks of whooping cough in the United States, Australia, Canada, and the Netherlands, researchers lead by Frits Mooi of the Netherlands’ National Institute of Public Health and the Environment suggested that proteins in the coat of the B pertussis bacterium—pertactin and pertussis toxin—had changed, making the organism less recognizable to the antibodies primed by currently available vaccines.

In a mouse infection model, Dr. Mooi’s team evaluated the efficacy of the vaccine against both the earlier form of B pertussis and the evolved form. They focused particularly on the variable domain of pertactin and found that the whooping cough vaccine, which was developed in the 1950s, was more effective against bacteria with the old pertactin type.

Therefore, the researchers believe that recent whooping cough outbreaks were indeed attributable to the bacteria’s adaptation to the vaccine.

—Owen McCarthy

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