SUMMARY: All humans are colonized with Candida species, mostly Candida albicans , yet some develop diseases due to Candida , among which genitourinary manifestations are extremely common. The forms of genitourinary candidiasis are distinct from each other and affect different populations. While vulvovaginal candidiasis affects mostly healthy women, candiduria occurs typically in elderly, hospitalized, or immunocompromised patients and in neonates. Despite its high incidence and clinical relevance, genitourinary candidiasis is understudied, and therefore, important questions about pathogenesis and treatment guidelines remain to be resolved. In this review, we summarize the current knowledge about genitourinary candidiasis.

Candidiasis can be present as a cutaneous, mucosal or deep-seated organ infection, which is caused by more than 20 types of Candida sp., with C. albicans being the most common. These are pathogenic yeast and are usually present in the normal microbiome. High-risk individuals are patients of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), organ transplant, and diabetes. During infection, pathogens can adhere to complement receptors and various extracellular matrix proteins in the oral and vaginal cavity. Oral and vaginal Candidiasis results from the overgrowth of Candida sp. in the hosts, causing penetration of the oral and vaginal tissues. Symptoms include white patches in the mouth, tongue, throat, and itchiness or burning of genitalia. Diagnosis involves visual examination, microscopic analysis, or culturing. These infections are treated with a variety of antifungals that target different biosynthetic pathways of the pathogen. For example, echinochandins target cell wall biosynthesis, while allylamines, azoles, and morpholines target ergosterol biosynthesis, and 5-Flucytosine (5FC) targets nucleic acid biosynthesis. Azoles are commonly used in therapeutics, however, because of its fungistatic nature, Candida sp. evolve azole resistance. Besides azoles, Candida sp. also acquire resistance to polyenes, echinochandins, and 5FC. This review discusses, in detail, the drug resistance mechanisms adapted by Candida sp.

Background. Novel therapies are urgently needed to treat carbapenem-resistant Klebsiella pneumoniae (CR-Kp)-mediated infection, which constitute a major health threat in the United States. In order to assess if it is feasible to develop anticapsular antibodies as a potential novel therapy, it is crucial to first systematically characterize capsular polysaccharide (CPS) and virulence traits in these strains. Methods. Forty CR-Kp were genotyped by pulsed field gel electrophoresis, multilocus sequence typing (MLST), and molecular capsule typing (C-patterns and wzi sequencing). Their biofilm formation, serum resistance, macrophage-mediated killing, and virulence in Galleria mellonella were compared. MAb (1C9) was generated by co-immunization with 2 CPSs, and cross-reactivity was investigated. Results. MLST assigned 80% of CR-Kp isolates to the ST258-clone. Molecular capsule typing identified new C-patterns, including C200/wzi-154, which was widely represented and associated with bla_KPC-3-bearing strains. Heterogeneity was detected in biofilm formation and macrophage-mediated killing. Differences in serum resistance correlated with virulence in G. mellonella. ST258 strains carrying bla_KPC-3 were less virulent than those with bla_KPC-2. MAb 1C9 cross-reacted with 58% of CR-Kp CPSs. Conclusions. CR-Kp ST258 strains exhibit variability of virulence-associated traits. Differences were associated with the type of KPC gene and CPS. Identification of cross-reacting anti-CPS mAbs encourages their development as adjunctive therapy.

Candida auris is an emerging multi-drug resistant yeast that causes systemic infections. Here we show that C. auris undergoes replicative aging (RA) that results from asymmetric cell division and causes phenotypic differences between mother and daughter cells similar to other pathogenic yeasts. Importantly, older C. auris cells (10 generations) exhibited higher tolerance to fluconazole (FLC), micafungin, 5- flucytosine and amphotericin B compared to younger (0–3 generation) cells. Increased FLC tolerance was associated with increased Rhodamine 6G (R6G) efflux and therapeutic failure of FLC in a Galleria infection model. The higher efflux in the older cells correlated with overexpression of the efflux pump encoding gene CDR1 (4-fold). In addition, 8-fold upregulation of the azole target encoding gene ERG11 was noted in the older cells. Analysis of genomic DNA from older cells by qPCR indicates that transient gene duplication of CDR1 and ERG11 causes the observed age-dependent enhanced FLC tolerance in C. auris strains. Furthermore, older cells exhibited a thickened cell wall, decreased neutrophil killing (24% vs 50%), increased epithelial cell adhesion (31.6% vs 17.8%) and upregulation of adhesin protein Als5p. Thus, this study demonstrates that transient gene duplication can occur during RA, causing increased FLC tolerance in old C. auris cells.

Staphylococcal enterotoxins (SE) can cause toxin-mediated disease, and those that function as superantigens are implicated in the pathogenesis of allergic diseases. The prevalence of 19 enterotoxin genes was determined by PCR in clinical S. aureus strains derived from wounds (108) and blood (99). We performed spa typing and multilocus sequence typing (MLST) to determine clonal origin, and for selected strains staphylococcal enterotoxin B (SEB) production was measured by enzyme-linked immunosorbent assay. Strains carried a median of five SE genes. For most SE genes, the prevalence rates among methicillin-resistant and methicillin-sensitive S. aureus isolates, as well as wound- and blood-derived isolates, did not differ. At least one SE gene was detected in all except two S. aureus isolates (>99%). Complete egc clusters were found in only 11% of S. aureus isolates, whereas the combination of sed , sej , and ser was detected in 24% of clinical strains. S. aureus strains exhibited distinct combinations of SE genes, even if their pulsed-field gel electrophoresis and MLST patterns demonstrated clonality. USA300 strains also showed considerable variability in SE content, although they contained a lower number of SE genes (mean, 3). By contrast, SE content was unchanged in five pairs of serial isolates. SEB production by individual strains varied up to 200-fold, and even up to 15-fold in a pair of serial isolates. In conclusion, our results illustrate the genetic diversity of S. aureus strains with respect to enterotoxin genes and suggest that horizontal transfer of mobile genetic elements encoding virulence genes occurs frequently.

Hypervirulent Klebsiella pneumoniae (hv Kp ) strains are predicted to become a major threat in Asia if antibiotic resistance continues to spread. Anticapsular antibodies (Abs) were developed because disseminated infections caused by hv Kp are associated with significant morbidity and mortality, even with antibiotic-sensitive strains. K1-serotype polysaccharide capsules (K1-CPS) are expressed by the majority of hv Kp strains. In this study, K1-CPS-specific IgG Abs were generated by conjugation of K1-CPS to immunogenic anthrax protective antigen (PA) protein. Opsonophagocytic efficacy was measured in vitro and in vivo by intravital microscopy in murine livers. In vivo protection was tested in murine models, including a novel model for dissemination in hv Kp -colonized mice. Protective efficacy of monoclonal antibodies (MAbs) 4C5 (IgG1) and 19A10 (IgG3) was demonstrated both in murine sepsis and pulmonary infection. In hv Kp -colonized mice, MAb treatment significantly decreased dissemination of hv Kp from the gut to mesenteric lymph nodes and organs. Intravital microscopy confirmed efficient opsonophagocytosis and clearance of bacteria from the liver. In vitro studies demonstrate that MAbs work predominantly by promoting FcR-mediated phagocytosis but also indicate that MAbs enhance the release of neutrophil extracellular traps (NETs). In anticipation of increasing antibiotic resistance, we propose further development of these and other Klebsiella -specific MAbs for therapeutic use.