Pseudomonas aeruginosa (Pa) and Candida albicans (Ca) are major bacterial and fungal pathogens in immunocompromised hosts, and notably in the airways of cystic fibrosis patients. The bacteriophages of Pa physically alter biofilms, and were recently shown to inhibit the biofilms of Aspergillus fumigatus. To understand the range of this viral–fungal interaction, we studied Pa phages Pf4 and Pf1, and their interactions with Ca biofilm formation and preformed Ca biofilm. Both forms of Ca biofilm development, as well as planktonic Ca growth, were inhibited by either phage. The inhibition of biofilm was reversed by the addition of iron, suggesting that the mechanism of phage action on Ca involves denial of iron. Birefringence studies on added phage showed an ordered structure of binding to Ca. Electron microscopic observations indicated phage aggregation in the biofilm extracellular matrix. Bacteriophage–fungal interactions may be a general feature with several pathogens in the fungal kingdom.

Background: Pseudomonas aeruginosa (Pa) and Aspergillus fumigatus (Af) compete with each other for nutrients and survival in natural environments, and have been extensively studied because of their intermicrobial interactions in the human microbiome. These are the principal microbes infecting immunocompromised patients and persons with cystic fibrosis, particularly the airways. These intermicrobial studies have largely been conducted in liquid medium or on agar, and thus focus on soluble or diffusible microbial products. Several key inhibitory molecules were defined in such studies. Methods: in the present report, we examine several methodologies which can be conveniently used to study the interaction of microbial volatiles, including capture methods and kinetics. Results: Pa volatiles inhibit Af, and the inhibitory mechanism appears to be the incorporation of the inhibitory molecules into the substrate nourishing the Af, rather than directly onto Af structures. We define by mass spectroscopy some specific volatile Pa products that can inhibit Af. Some of these molecules are selected for interest by the study of gene deletion mutants, producing a few Pa strains that were impaired in inhibition. We presumed the volatiles of these latter strains could be excluded from the search for inhibitors. Conclusion: the Pa inhibition of Af via a gaseous phase could be critical components in their competition, particularly in airways, where more direct contact may not be extensive.

The aim of this study was to search for three plasmid-encoded, quinolone-resistant determinants: qnrA, qnrB, and qnrS. Thus, 460 Gram-negative strains belonging to 11 different genera (clinical, 347; non-clinical, i.e., from a rectal swab, 113), of which 40% were ciprofloxacin-resistant, were recovered from patients in an intensive care unit at the Istanbul Medical Faculty, Turkey, in the years 2000 and 2006. PCR with primers specific for qnrA, qnrB, and qnrS genes and primers specific for a series of ESBL genes were used. One qnrB1 and two qnrS1 genes were identified in three ESBL-positive isolates, whereas no qnrA-positive strain was found. The qnrB1 determinant was identified in a ciprofloxacin-susceptible Enterobacter cloacae isolate that expressed CTX-M-15 β-lactamase. Two qnrS1-determinants were found in two ciprofloxacin-susceptible E. cloacae isolates that were clonally related, but that had been isolated from different patients; both of these isolates expressed the same ESBL, CTX-M-3. This study detected the first plasmid-mediated quinolone-resistance determinants qnrB1 and qnrS1, among clinical strains obtained from patients in Turkey.

Aspergillus and Pseudomonas compete in nature, and are the commonest bacterial and fungal pathogens in some clinical settings, such as the cystic fibrosis lung. Virus infections of fungi occur naturally. Effects on fungal physiology need delineation. A common reference Aspergillus fumigatus strain, long studied in two (of many) laboratories, was found infected with the AfuPmV-1 virus. One isolate was cured of virus, producing a virus-free strain. Virus from the infected strain was purified and used to re-infect three subcultures of the virus-free fungus, producing six fungal strains, otherwise isogenic. They were studied in intermicrobial competition with Pseudomonasaeruginosa. Pseudomonas culture filtrates inhibited forming or preformed Aspergillus biofilm from infected strains to a greater extent, also seen when Pseudomonas volatiles were assayed on Aspergillus. Purified iron-chelating Pseudomonas molecules, known inhibitors of Aspergillus biofilm, reproduced these differences. Iron, a stimulus of Aspergillus, enhanced the virus-free fungus, compared to infected. All infected fungal strains behaved similarly in assays. We show an important consequence of virus infection, a weakening in intermicrobial competition. Viral infection may affect the outcome of bacterial–fungal competition in nature and patients. We suggest that this occurs via alteration in fungal stress responses, the mechanism best delineated here is a result of virus-induced altered Aspergillus iron metabolism.

This study evaluated the presence of carbapenem hydrolysing β-lactamase genes and plasmid-mediated quinolone resistance (PMQR) determinants in 22 Klebsiella pneumoniae isolates collected from the Istanbul Medical Faculty, Turkey, which reduced the susceptibility or resistance to carbapenem. The VITEK® 2 system and E-tests were used to determine the minimum inhibitory concentrations needed to inhibit bacterial growth. Genes were screened by polymerase chain reaction, and gene transferability was evaluated by transconjugation. Strain clonality was investigated by pulsed-field gel electrophoresis (PFGE). All strains were OXA-48 β-lactamase producers and three (13.6%) were also positive for the aac(6′)-Ib-cr gene. Most of the strains harboured other b-lactamase (bla) genes such as ^blaTEM, ^blaSHV, ^blaCTX-M and ^blaVEB-1. The transconjugants mostly harboured bla_OXA-48 and other β-lactamases separately. PFGE revealed eight pulsotypes among the isolates. The coexistence of bla_OXA-48 and PMQR in K. pneumoniae isolates may present a significant threat to health, especially in the nosocomial setting.

The paucity of effective antifungals against Aspergillus and increasing resistance, the recognition of the importance of Aspergillus biofilm in several clinical settings, and reports of verapamil—a calcium channel blocker—efficacy against Candida biofilm and hyphal growth, and synergy with an azole antifungal in vitro, led to a study of verapamil ± voriconazole against Aspergillus. Broth macrodilution methodology was utilized for MIC (minimum inhibitory concentration) and MFC (minimum fungicidal concentration) determination. The metabolic effects (assessed by XTT [2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt]) on biofilm formation by conidia were studied upon exposure to verapamil, verapamil plus voriconazole, or voriconazole alone. For biofilm formation, we found less inhibition from the combinations than with either drug alone, or less inhibition from the combination than that of the more potent drug alone. For preformed biofilm, we found no significant change in activity comparing voriconazole alone compared to added verapamil, and no significant alteration of activity of the more potent voriconazole, at any concentration in the range tested, by addition of a concentration of verapamil that is inhibitory alone. In full checkerboard assays with planktonic fungus, there was no indication of any effect of one drug on the other (indifference). Although verapamil was similarly inactive against planktonic Aspergillus, as with Candida, verapamil was indeed active against Aspergillus biofilm. However, indifference and antagonism was found with voriconazole.