Microorganisms develop biofilms on indwelling medical devices and are associated with device-related infections, resulting in substantial morbidity and mortality. This study investigated the effect of pretreating hydrogel-coated catheters with Pseudomonas aeruginosa bacteriophages on biofilm formation by P. aeruginosa in an in vitro model. Hydrogel-coated catheters were exposed to a 10 log 10 PFU ml ؊1 lysate of P. aeruginosa phage M4 for 2 h at 37°C prior to bacterial inoculation. The mean viable biofilm count on untreated catheters was 6.87 log 10 CFU cm ؊2 after 24 h. The pretreatment of catheters with phage reduced this value to 4.03 log 10 CFU cm ؊2 (P < 0.001). Phage treatment immediately following bacterial inoculation also reduced biofilm viable counts (4.37 log 10 CFU cm ؊2 reduction; P < 0.001). The regrowth of biofilms on phage-treated catheters occurred between 24 and 48 h, but supplemental treatment with phage at 24 h significantly reduced biofilm regrowth (P < 0.001). Biofilm isolates resistant to phage M4 were recovered from catheters pretreated with phage. The phage susceptibility profiles of these isolates were used to guide the development of a five-phage cocktail from a larger library of P. aeruginosa phages. The pretreatment of catheters with this cocktail reduced the 48-h mean biofilm cell density by 99.9% (from 7.13 to 4.13 log 10 CFU cm ؊2 ; P < 0.001), but fewer biofilm isolates were resistant to these phages. These results suggest the potential of applying phages, especially phage cocktails, to the surfaces of indwelling medical devices for mitigating biofilm formation by clinically relevant bacteria.Indwelling medical devices of various kinds may become colonized with microorganisms, resulting in the formation of microbial biofilms (16). Biofilm-associated organisms are tolerant to antimicrobial agents, can evade the host immune system, and can act as a nidus for infection (16). As a result, device-related infections, such as catheter-associated bloodstream infections, cause substantial morbidity and mortality among specific patient populations (9). Attributable mortality rates for healthcare-associated bloodstream infections have been estimated to be 25% (44).A number of novel strategies have been proposed to more effectively prevent and control device-associated biofilms, either by minimizing microbial attachment to device surfaces or by targeting the biofilm after it has developed. One such strategy is to use bacteriophages (phages) (17). Phages have been used for the treatment of infectious diseases in plants (26), animals (6), and humans (33,39,43). The use of phages to control biofilms has potential for several reasons. Phages can replicate at the site of an infection, thereby increasing in numbers where they are most required. During the lytic replication cycle, the infection of a bacterial host cell by a single phage virion will result in the production of dozens or hundreds of progeny phage, depending on the particular phage and host strains. Some phages also have been shown to...

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Mycobacteriophage DS6A is unique among the more than 8,000 isolated mycobacteriophages due to its ability to form plaques exclusively on mycobacteria belonging to the Mycobacterium tuberculosis complex (MTBC). Speculation surrounding this specificity has led to unsupported assertions in published studies and patents that nontuberculous mycobacteria (NTM) are wholly resistant to DS6A infection. In this study, we identified two independent nonessential regions in the DS6A genome and replaced them with an mVenus-expressing plasmid to generate fluorescent reporter phages ⌽ 2 GFP12 and ⌽ 2 GFP13. We show that even though DS6A is able to form plaques only on MTBC bacteria, infection of various NTM results in mVenus expression in transduced cells. The efficiency of DS6A in delivering DNA varied between NTM species. Additionally, we saw a striking difference in the efficiency of DNA delivery between the closely related members of the Mycobacterium abscessus complex, M. abscessus and Mycobacterium massiliense. We also demonstrated that TM4 and DS6A, two phages that do not form plaques on M. massiliense, differ in their ability to deliver DNA, suggesting that there is a phage-specific restriction between mycobacterial species. Phylogenetic analysis reveals that the DS6A genome has a characteristically mosaic structure but provided few insights into the basis for the specificity for MTBC hosts. This study demonstrates that the inability of the MTBC-specific phage DS6A to form plaques on NTM is more complex than previously thought. Moreover, the DS6A-derived fluorophages provide important new tools for the study of mycobacterial biology. IMPORTANCEThe coevolution of bacteria and their infecting phages involves a constant arms race for bacteria to prevent phage infection and phage to overcome these preventions. Although a diverse array of phage defense systems is well characterized in bacteria, very few phage restriction systems are known in mycobacteria. The DS6A mycobacteriophage is unique in the mycobacterial world in that it forms plaques only on members of the Mycobacterium tuberculosis complex. However, the novel DS6A reporter phages developed in this work demonstrate that DS6A can infect nontuberculous mycobacteria at various efficiencies. By comparing the abilities of DS6A and another phage, TM4, to infect and form plaques on various mycobacterial species, we can begin to discern new phage restriction systems employed within the genus. The standard treatment for a drug-susceptible Mycobacterium tuberculosis infection is four drugs (rifampin, isoniazid, pyrazinamide, and ethambutol) for 2 months, followed by 4 months of two drugs (rifampin and isoniazid). One of the key aspects of successfully treating tuberculosis is ensuring that the infecting strain is susceptible to each of the antibiotics given; therefore, quickly diagnosing antibiotic resistance is important for successful patient outcome as well as for lowering the incidence of the generation of drug-resistant mutants from improper antibiotic administra...

Background: In early 2020, an outbreak of coronavirus disease 2019 occurred among passengers and crew of the Diamond Princess cruise ship. During February 16 and 17, some US citizens, residents, and their partners voluntarily repatriated to the US from Japan. Methods: We conducted a retrospective, longitudinal evaluation of repatriated travelers where the outcome of interest was a positive test for SARS-CoV-2. Travelers who tested positive for SARS-CoV-2 were isolated in hospitals or at home under county isolation orders and underwent serial testing by real-time reverse transcription polymerase chain reaction (RT-PCR) approximately every other day, as contemporaneous US guidance required two consecutive negative tests collected greater than or equal to 24 hours apart and symptom improvement before release from isolation. Results: Among quarantined repatriated travelers, 14% tested positive for SARS-CoV-2. One-fifth of infected travelers initially tested negative but were identified on subsequent testing. All infected travelers remained asymptomatic or developed mild symptoms during isolation. Many travelers remained in prolonged isolation because of persistent viral detection based on contemporaneous policies. Conclusion: Our findings support testing within 3-5 days after possible SARS-CoV-2 exposure to comprehensively identify infections and mitigate transmission and lend support to symptom- and time-based isolation recommendations, rather than test-based criteria.