Comparative Study of Vaginal Lactobacillus Phages Isolated from Women in the United States and Turkey: Prevalence, Morphology, Host Range, and DNA Homology

Abstract

Lactobacilli play an important role in maintaining vaginal health. However, during bacterial vaginosis lactobacilli decrease for unknown reasons. Our preliminary study showed that phages could infect vaginal lactobacilli. Therefore, the aim of this study was to analyze the distribution, virulence, and types of vaginal Lactobacillus phages isolated from women of two countries: the United States and Turkey. A total of 209 vaginal lactobacilli were isolated from reproductive-aged women in the United States (n ‫؍‬ 107) and Turkey (n ‫؍‬ 102). By analysis of 16S rRNA gene sequence and by comparison of protein profiles, most lactobacilli were identified as L. crispatus, L. gasseri, and L. jensenii. After mitomycin C induction, 28% of American lactobacilli and 36% of Turkish lactobacilli released phages. A total of 67 phages were isolated and further characterized by their host range, electron microscopy, and DNA homology. All 67 phages were infective against lactobacilli from both collections. The host ranges of most phages were broad, including multiple Lactobacillus species. Even though the phages were all temperate, they were able to cause lytic infection in various strains. The electron micrographs of these phages showed a hexagon-shaped head and a long tail with or without a contractile tail sheath. Based on their morphology, these phages belonged to Bradley's phage groups A and B, and could be further classified into four morphotypes. All four types were found among American phages, but only three were found among Turkish isolates. DNA hybridization with labeled probes of the four types of phages revealed that additional genetic types existed within each morphotype among these phages. The phage genomic sizes ranged between 34 and 55 kb. Many of the lysogenic Lactobacillus strains released phages spontaneously at a high frequency of 10 ؊3 to 10 ؊4 PFU/cell. In conclusion, lysogeny in vaginal lactobacilli is widely spread. Some lysogenic lactobacilli spontaneously release phages with a broad host range, which can be lytic against other vaginal lactobacilli regardless of their geographic origin.Lactobacilli indigenous to the human vagina are beneficial to women's health (35). These bacteria can inhibit other potentially harmful microorganisms by producing lactic acid, hydrogen peroxide (H 2 O 2 ), and antimicrobial substances (12,23,43). In most healthy women, lactobacilli are the dominant species in the vagina. Theoretically, the anaerobic bacteria are suppressed by lactobacilli (12, 23) and cannot replace lactobacilli unless the latter is first diminished. However, the group of anaerobic bacteria commonly outnumber lactobacilli, causing a microbial imbalance called bacterial vaginosis (BV) (3,9,10,15,38,40).BV is a clinical condition that is characterized by decreased lactobacilli and an increased number of anaerobic gram-negative rods, Gardnerella species, and genital mycoplasmas (10,38,40). Women who suffer from BV may have an increased discharge that often has an unpleasant fishy odor. BV has been associated w...

Phage-Host Interaction: an Ecological Perspective

“…Furthermore, about 30% of lactobacilli constituting the major commensals in the vagina of healthy women were lysogenic. Many lysogens could be induced by mitomycin C, and some phages could infect up to five different Lactobacillus species, which dominate the vaginal flora (36).…”

“…The high number of prophages in Lactococcus lactis offers in fact a large supply of new genetic material to superinfecting phages which is accessible via homologous recombination. Interestingly, the rich knowledge on phage resistance mechanisms acquired in the dairy field could also contribute to the understanding of the coexistence of phages and bacteria in the marine environment or the management of phage infections in humans (e.g., the cigarette smoke-induced prophage propagation purportedly linked to a decline of the protective Lactobacillus flora in the vagina which might open the way to vaginosis and candida superinfections) (36).…”

Sexually transmitted infections: challenges ahead

“…[277][278][279][280][281][282] species (infection with bacteriophages) in women was common, but that the rate of lactobacillus phage detection was higher in women with BV than without. 283,284 has good sensitivity and specificity for both treponemal (90·1-98·2% and 91·8-98·0%, 1399 respectively) and non-treponemal (80·6-98·2% and 89·4%, respectively) tests. 365 …”

Prevalence of Staphylococcus aureus and Lack of Its Lytic Bacteriophages in the Anterior Nares of Patients and Healthcare Workers at a Rural Clinic

“…18 Lytic bacteriophages against different bacterial species have been isolated and even suggested to be part of the complex microbiome of the human gut, 19,20 oral cavity, 21,22 and vagina. 23 The lytic phages are likely to modulate the rate of prevalence for one or more bacteria in different microbiological niches in the body. While lytic bacteriophages against S. aureus and MRSA have been isolated from different sources such as milk, 24 sewage influent, 25 cow slurry, 26 and septic wounds, 27 it is not known if they are prevalent in the anterior nares.…”