Catherine Loc-Carrillo

Pros and cons of phage therapy.

Many publications list advantages and disadvantages associated with phage therapy, which is the use of bacterial viruses to combat populations of nuisance or pathogenic bacteria. The goal of this commentary is to discuss many of those issues in a single location. In terms of “Pros”, for example, phages can be bactericidal, can increase in number over the course of treatment, tend to only minimally disrupt normal flora, are equally effective against antibiotic-sensitive and antibiotic-resistant bacteria, often are easily discovered, seem to be capable of disrupting bacterial biofilms, and can have low inherent toxicities. In addition to these assets, we consider aspects of phage therapy that can contribute to its safety, economics, or convenience, but in ways that are perhaps less essential to the phage potential to combat bacteria. For example, autonomous phage transfer between animals during veterinary application could provide convenience or economic advantages by decreasing the need for repeated phage application, but is not necessarily crucial to therapeutic success. We also consider possible disadvantages to phage use as antibacterial agents. These “Cons”, however, tend to be either relatively minor.

Genotypic and Phenotypic Analysis of Enterobacter sakazakii Strains from an Outbreak Resulting in Fatalities in a Neonatal Intensive Care Unit in France

ABSTRACT In 1994, an outbreak of Enterobacter sakazakii infections occurred in a neonatal intensive care unit in France from 5 May to 11 July. During the outbreak, 13 neonates were infected with E. sakazakii, resulting in 3 deaths. In addition, four symptomless neonates were colonized by E. sakazakii. The strains were subjected to 16S rRNA gene sequence analysis, genotyped using pulsed-field gel electrophoresis, and phenotyped for a range of enzyme activities. E. sakazakii was isolated from various anatomical sites, reconstituted formula, and an unopened can of powdered infant formula. A fourth neonate died from septic shock, attributed to E. sakazakii infection, during this period. However, 16S rRNA gene sequence analysis revealed that the organism was Enterobacter cloacae. There were three pulsotypes of E. sakazakii associated with infected neonates, and three neonates were infected by more than one genotype. One genotype matched isolates from unused prepared formula and unfinished formula. However, no pulsotypes matched the E. sakazakii strain recovered from an unopened can of powdered infant formula. One pulsotype was associated with the three fatal cases, and two of these isolates had extended-spectrum β-lactamase activity. It is possible that E. sakazakii strains differ in their pathogenicities, as shown by the range of symptoms associated with each pulsotype.

Characterization of an extended-spectrum beta-lactamase Enterobacter hormaechei nosocomial outbreak, and other Enterobacter hormaechei misidentified as Cronobacter (Enterobacter) sakazakii

Enterobacter hormaechei is a Gram-negative bacterium within the Enterobacter cloacae complex, and has been shown to be of clinical significance by causing nosocomial infections, including sepsis. Ent. hormaechei is spread via horizontal transfer and is often associated with extended-spectrum beta-lactamase production, which increases the challenges associated with treatment by limiting therapeutic options. This report considers 10 strains of Ent. hormaechei (identified by 16S rDNA sequencing) that had originally been identified by phenotyping as Cronobacter (Enterobacter) sakazakii. Seven strains were from different neonates during a nosocomial outbreak in a California hospital. PFGE analysis revealed a clonal relationship among six of the seven isolates and therefore a previously unrecognized Ent. hormaechei outbreak had occurred over a three-month period. Antibiotic-resistance profiles were determined and extended-spectrum beta-lactamase activity was detected. The association of the organism with powdered infant formula, neonatal hosts and Cr. sakazakii suggested that the virulence of these organisms may be similar. Virulence traits were tested and all strains were shown to invade both gut epithelial (Caco-2) and blood-brain barrier endothelial cells (rBCEC4), and to persist in macrophages (U937). Due to misidentification we suggest that Ent. hormaechei may be an under-reported cause of bacterial infection, especially in neonates. Also, its isolation from various sources, including powdered infant milk formula, makes it a cause for concern and merits further investigation.

Development of a broad spectrum polymer-released antimicrobial coating for the prevention of resistant strain bacterial infections.

More than 400,000 primary hip and knee replacement surgeries are performed each year in the United States. From these procedures, approximately 0.5-3% will become infected and when considering revision surgeries, this rate has been found to increase significantly. Antibiotic-resistant bacterial infections are a growing problem in patient care. This in vitro research investigated the antimicrobial potential of the polymer released, broad spectrum, Cationic Steroidal Antimicrobial-13 (CSA-13) for challenges against 5 × 10(8) colony forming units (CFU) of methicillin-resistant Staphylococcus aureus (MRSA). It was hypothesized that a weight-to-weight (w/w) concentration of 18% CSA-13 in silicone would exhibit potent bactericidal potential when used as a controlled release device coating. When incorporated into a polymeric device coating, the 18% (w/w) broad-spectrum polymer released CSA-13 antimicrobial eliminated 5 × 10(8) CFU of MRSA within 8 h. In the future, these results will be utilized to develop a sheep model to assess CSA-13 for the prevention of perioperative device-related infections in vivo.

Use of phages to control Campylobacter spp.

The use of phages to control pathogenic bacteria has been investigated since they were first discovered in the beginning of the 1900s. Over the last century we have slowly gained an in-depth understanding of phage biology including which phage properties are desirable when considering phage as biocontrol agents and which phage characteristics to potentially avoid. Campylobacter infections are amongst the most frequently encountered foodborne bacterial infections around the world. Handling and consumption of raw or undercooked poultry products have been determined to be the main route of transmission. The ability to use phages to target these bacteria has been studied for more than a decade and although we have made progress towards deciphering how best to use phages to control Campylobacter associated with poultry production, there is still much work to be done. This review outlines methods to improve the isolation of these elusive phages, as well as methods to identify desirable characteristics needed for a successful outcome. It also highlights the body of research undertaken so far and what criteria to consider when doing in-vivo studies, especially because some in-vitro studies have not been found to translate into to phage efficacy in-vivo.

Model development for determining the efficacy of a combination coating for the prevention of perioperative device related infections: A pilot study

Antibiotic resistant bacterial infections are a growing problem in patient care. These infections are difficult to treat and severely affect the patients quality of life. The goal of this translational experiment was to investigate the antimicrobial potential of cationic steroidal antimicrobial-13 (CSA-13) for the prevention of perioperative device-related infections in vivo. It was hypothesized that when incorporated into a polymeric device coating, the release of CSA-13 could prevent perioperative device-related infection without inhibiting skeletal attachment. To test this hypothesis, 12 skeletally mature sheep received a porous coated titanium implant in the right femoral condyle. Group 1 received the titanium implant and an inoculum of 5 × 10(8) CFU of methicillin-resistant Staphylococcus aureus (MRSA). Group 2 received a CSA-13 coated implant and the MRSA inoculum. Group 3 received only the CSA-13 coated implant and Group 4 received only the implant-without the CSA-13 coating or MRSA inoculum. In conclusion, the CSA-13 combination coating demonstrated bactericidal potential without adversely affecting skeletal attachment. The CSA-13 containing groups exhibited no evidence of bacterial infection at the conclusion of the 12 week study and established skeletal attachment consistent with Group 4. In contrast, all of the Group 1 animals became infected and required euthanasia within 6-10 days. The significance of this finding is that this combination coating could be applied to implanted devices to prevent perioperative device-related infections. This method may facilitate significantly reduced incidences of device-related infections as well as a new method to treat and prevent resistant strain bacterial infections.

Local Intramedullary Delivery of Vancomycin Can Prevent the Development of Long Bone Staphylococcus aureus Infection

Current treatments for methicillin-resistant Staphylococcus aureus (MRSA) infections require intravenously delivered vancomycin; however, systemically delivered vancomycin has its problems. To determine the feasibility and safety of locally delivering vancomycin hydrochloride (~25 mg/Kg) to the medullary canal of long bones, we conducted a pharmacokinetics study using a rat tibia model. We found that administering the vancomycin intraosseously resulted in very low concentrations of vancomycin in the blood plasma and the muscle surrounding the tibia, reducing the risk for systemic toxicity, which is often seen with traditional intravenous administration of vancomycin. Additionally, we were able to inhibit the development of osteomyelitis in the tibia if the treatment was administered locally at the same time as a bacterial inoculum (i.e., Log10 7.82 CFU/mL or 6.62x107 CFU/mL), when compared to an untreated group. These findings suggest that local intramedullary vancomycin delivery can achieve sufficiently high local concentrations to prevent development of osteomyelitis while minimizing systemic toxicity.