Multiple benefits derived from a peer teacher program in two undergraduate microbiology lab courses.

A peer teaching program was implemented to alleviate the problem of a limited number of lab instructors attempting to teach large numbers of students in two different undergraduate microbiology lab courses. The benefit of having peer teachers was immediately obvious to the lab instructors, faculty and staff who were responsible for conducting the labs, but it was soon evident that there were also benefits for everyone else involved in the program. The students enrolled in the labs reported that having peer teachers in the lab enhanced their learning, and they felt comfortable receiving help from a peer teacher who had recently completed the course. The peer teachers discovered that they gained valuable experience and confidence while teaching other students, and they appreciated the chance to gain hands-on experience. The lab instructors received the qualified help they needed in order to give more individual attention to the large numbers of students in the labs. The feedback from this program has been positive from everyone involved.

The destruction of Escherichia coli biofilms using high-intensity focused ultrasound.

High-intensity focused ultrasound (HIFU) has shown great potential for replacing surgery in many applications. In this work, HIFU was used to destroy Escherichia coli (E. coli) biofilms that had been grown on chambered microscope slides. Biofilms are central to the pathogenesis and persistence of nosocomial (hospital-acquired) infections associated with indwelling medical devices. The slides were exposed to 9.1 mus pulses at a pulse repetition frequency of 1000 Hz. The pulses were generated by a 1.1 MHz spherically focused source with a focal length of 6.3 cm and an active diameter of 7 cm. The peak rarefactional pressure for the pulses was varied as 3.1, 4.1, 5.2, 6.2 and 7.6 MPa in addition to a sham where the biofilms were not exposed. The effectiveness of the treatment was assessed by determining the number of colony forming units (CFU) remaining following exposure of the bacteria to HIFU. Most of the biofilms treated at the higher exposures of 6.2 and 7.6 MPa had no detectable CFU, indicating that bacteria in the biofilm were killed by the treatment or that treatment disrupted the biofilm and released bacteria from the slide. However, the ability of some bacteria to survive at the higher exposure settings needs to be resolved prior to implementing the treatment clinically.

Ultrasound histotripsy and the destruction of Escherichia coli biofilms.

Ultrasound histotripsy has shown great potential for replacing surgery in many applications. In this work, a modification of ultrasound histotripsy was used to destroy Escherichia coli (E. coli) biofilms that had been grown on chambered microscope slides. Biofilms are central to the pathogenesis and persistence of nosocomial (hospital-acquired) infections associated with indwelling medical devices. The slides were exposed to 9.1 micros pulses at a pulse repetition frequency of 1000 Hz. The pulses were generated by a 1.1 MHz spherically focused source with a focal length of 6.3 cm and an active diameter of 7 cm. The peak rarefactional pressure for the pulses was varied as 3.1, 4.1, 5.2, 6.2, and 7.6 MPa in addition to a sham where the biofilms were not exposed. The effectiveness of the treatment was assessed by determining the viable number of colony forming units (CFU) remaining in the biofilm. Most of the biofilms treated at the higher exposures of 6.2 and 7.6 MPa had no remaining CFU indicating that the biofilm was completely destroyed. However, the persistence of some CFU for some of the biofioms at the higher exposure settings needs to be resolved prior to implementing the treatment clinically.

beta-Lactam induction of colanic acid gene expression in Escherichia coli.

An unexpected observation led us to examine the relationship between beta-lactam exposure and synthesis of colonic acid capsular polysaccharide in Escherichia coli. Strains containing a cps-lacZ transcriptional fusion were challenged with antibiotics having various modes of action, and gene expression was detected by a disk-diffusion assay and in broth cultures. The cps genes were induced by a subset of beta-lactams but not by agents inhibiting protein synthesis or DNA replication, indicating that cps expression was specific and not due to stresses accompanying cell death or by a general inhibition of peptidoglycan synthesis. A narrow concentration just below the MIC triggered cps expression in liquid culture, suggesting the response may be triggered by near-lethal levels of antibiotic. Because colanic acid is important for maturation of biofilm architecture, antibiotics that increase its synthesis might exacerbate the formation or persistence of biofilms.