**4.** *E. coli* **directly affects human sperm function**

donor insemination [1]. Approximately 50% of infertility cases are attributed to the male [2, 3] due to conditions such as varicocele, cryptorchidism, obstructive problems, hormonal disor‐ ders, ejaculatory dysfunction as well as infectious causes classified under male genital tract

72 *Escherichia coli* Escherichia coli - Recent Advances on Physiology, Pathogenesis and Biotechnological Applications - Recent Advances on Physiology, Pathogenesis and Biotechnological Applications

MGTI accounts for 15% of male infertility cases [4]. MGTIs are an important problem in male reproductive health because they cause negative changes in semen parameters [5]. A consequence of MGTI is the inflammatory response evidenced by leukocytospermia, where a treatment with antibiotics and anti‐inflammatory drugs may be helpful to try to recover the patient's fertilizing potential [6]. Principal causes of MGTI are bacteria such as *Staphylococcus epidermidis*, *Streptococcus viridans*, *Staphylococcus aureus* and *Escherichia coli* (*E. coli*), which have a negative effect on the fertilizing potential of a man and are strongly associated with MGTI [7, 8]. However, *E. coli has* been shown to exert greater damaging effects on human sperma‐

*E. coli* is the causal agent in 65–80% of cases of chronic bacterial prostatis [12], and these bacte‐ ria have been isolated from semen in 69% of the patients with this pathology [13]. Moreover, *E. coli* causes diverse MGTIs such as urethritis, epididymitis and orchitis, and it is the most

With this background, this chapter discusses the negative effect of *E. coli on* sperm quality and male fertility. The chapter will be developed by first addressing the uropathogenic *E. coli strains* associated with male infertility. Then, the evidence of the *in vitro* effects of *E. coli on* the male gamete will be analyzed. Evidences will be described, obtained after *in vitro* co‐incu‐ bation of normal human spermatozoa with *E. coli and* with polymorphonuclear leukocytes, emulating infection. Next, the effects of *E. coli* on human sperm functions observed by direct incubation of spermatozoa with bacteria and without leukocytes will be discussed. Also, evi‐ dence of the effects of the metabolic and soluble products of *E. coli* on human sperm function will be analyzed. To complete the picture of the evidence of the effects of this bacterium on

**2. Uropathogenic strains of** *E. coli* **are associated with male infertility**

Among the different pathogenic strains of *E. coli,* the uropathogenic strains are mainly associ‐ ated with urinary tract infections (UTI). The pathogenic *E. coli* is classified according to the O antigens. Some of these have been associated with uropathogenic *E. coli* (UPEC) being the serotypes O1, O2, O4, O6, O7, O8, O16, O18, O25, and O75 preferentially associated with these strains [14]. Similarly, the most frequently O antigens associated among the serotypes isolated from patients with prostatitis are O1, O2, O4, O16, O18, O22, O25 and O75 serotypes [15], which coincide with *E. coli* strains isolated in cases of infections to the urinary tract. Regarding to the strains isolated from semen of infertile men, the described prevalent antigens are O1, O2, O4 and O6 [16]. These data indicate that the *E. coli* that infects the male reproductive tract is uropathogenic strain, which is not surprising considering the proximity of the urinary and

male fertility, some studies on animal models will be reviewed.

infection (MGTI).

tozoa [7, 9–11].

reproductive tracts.

frequently isolated bacterium [4].

The direct effect of *E. coli* on sperm was demonstrated through *in vitro* studies performed by directly incubating both cells. It has been demonstrated by several authors that *E. coli* com‐ ing into contact with spermatozoa causes decreased sperm motility [7, 24–26]. The decrease in sperm motility due to *E. coli* has been attributed for many years to an agglutinating effect on sperm [27]. Sperm agglutination can be caused by bacterial type 1 and P fimbriae; specifi‐ cally, the type 1 fimbriae of *E. coli* cause a pattern of head‐head type agglutination because they bind mannose residues in the head region of sperm. Instead, type P fimbriae of *E. coli* cause a head‐tail agglutination pattern because they bind gal‐gal receptors present along the sperm [28].

Electron microscopy has revealed that this bacterium causes damage primarily in the head of spermatozoa, such as rupture of the plasma membrane, vesicle formation and rupture of the inner and outer membranes of the acrosome [29].

Consistent with the plasma membrane damages observed, another report showed that *E. coli* per se causes phosphatidylserine translocation, a cell death indicator [9]. From the point of view of sperm cell death, it was observed that *E. coli* endotoxins such as lipopolysaccha‐ ride (LPS), peptidoglycan and porins produce loss of sperm viability [30]. Moreover, it has been shown that LPS and porins cause sperm DNA fragmentation [31]. The effects of these endotoxins are mediated by the toll‐like receptor (TLR)‐2 and TLR‐4, both present in sperm. After TLR‐2 and TLR‐4 stimulation, sperm damage highlighting DNA fragmentation can be observed [32].

Another direct effect of *E. coli* is at the level of mitochondrial membrane potential (ΔΨm). The *in vitro* observation that contact with *E. coli* decreases the ΔΨm together with the motility in spermatozoa [33] was followed by another report showing, also *in vitro,* that *E. coli* directly reduces sperm ΔΨm and alters plasma membrane stability [34]. From the point of view of sperm function, it has been observed that ΔΨm is positively correlated with sperm motility *in vivo* [35, 36]. However, after contact with some strains of *E. coli*, which decrease sperm motility *in vitro*, they had no effect on ΔΨm [37]. This study also found that some *E. coli* isolated from different patients was unable to decrease sperm motility, remarkably even an O6, which is thought to be a highly uropathogenic strain in urinary tract infections [38]. These facts con‐ trast with the notion that *E. coli* in general alters sperm function. These differences could be attributed to the fact that different strains bear specific but different characteristics from other *E. coli* strains. Evidence confirming this was observed in our work, when sperm were incu‐ bated with a hemolytic strain of *E. coli.* This strain caused a decrease in motility, ΔΨm, vitality and an increase in intracellular ROS in normal spermatozoa. These effects were not observed with other strains non‐hemolysis producers [39]. These differences among strains highlight the importance of knowing what kind of toxins are effectively produced by the *E. coli* strain infecting a patient, because it could indicate the level of sperm damage to be expected. As example, hemolytic *E. coli* strains produce the alpha‐hemolysin (HlyA) toxin [40], a calcium‐ dependent pore‐forming toxin which has intracellular effects, inactivating pathways related to cell survival [41]. This toxin can be highly relevant, particularly if we consider that between 40 and 50% of *E. coli* strains isolated from patients with epididymitis release this toxin [42].

soluble factor described is the sperm agglutinating factor (SAF) of 71 kDa, which produces sperm agglutination, decreases ATPase activity and can cause sperm death [48]. A toxin candidate to be further investigated is HlyA, because this toxin is produced by *E. coli* strains most pathogenic to

Effect of Uropathogenic *Escherichia coli* on Human Sperm Function and Male Fertility

http://dx.doi.org/10.5772/intechopen.68312

75

*In vitro* investigations have the disadvantage of not necessarily representing what would happen *in vivo*. Hence, *in vivo* studies in animal models allow us to get closer to the reproductive reality of a man with accessory glands infected by *E. coli.* That is how the progressive reduction of testic‐ ular size with a consequent decrease in sperm count caused by the necrotic death of the testicular germ cell has been described in rats inoculated with *E. coli* [49]. After three days of injecting rats with HlyA producing *E. coli,* the epididymis had epithelial damage, leukocyte infiltration and edema and the sperm‐fertilizing potential was lost, because despite being motile, the spermato‐ zoa had a premature acrosome reaction [50]. The above‐mentioned greater pathogenicity of the HlyA‐producing *E. coli* strains was reported in the work of Lang [50], where the *E. coli* strains that did not produce HlyA induced only slight damage to the epididymis. As already stated, sperm recognize peptidoglycans and LPS through TLR‐2 and TLR‐4, and this recognition event induces sperm cell death. This was confirmed by using knockout mice for both TLR‐2 and ‐4 and by observing that in these animals LPS or peptidoglycans did not induce sperm death [32]. Further evidence of the contribution of some *E. coli* strains to infertility was observed after inoculating the vaginal tract of rats with SAF‐producing strains. Control rats were inoculated with *E. coli* non‐SAF producers. It was observed that the rats inoculated with SAF‐producing strains were incapable of pregnancy, demonstrating that these toxin‐producing strains affect

It is clear that *E. coli* has an important role in causing male infertility associated with genital tract infections. The main mechanism postulated for male infertility by *E. coli* is the profound damage to different sperm processes and function, either by direct contact and/or through

While today there is a consensus that *E. coli* is an important causal agent of MGTI that may actually cause infertility, from the latest evidence presented above, it is clear that this would not be completely true for all UPEC. Due to these differences among the various strains, it seems important to develop molecular studies that can clarify what specific features of the *E. coli* strains are associated with the pathogenic effects on sperm or with an aggressive

To date, there have only been a few studies at the molecular level to try to explain how *E. coli*

inflammatory response this point should be followed.

sperm both *in vitro* and *in vivo* [42].

**6. Animal model research**

fertility profoundly [51].

**7. Conclusion**

secreted toxins.

causes infertility.

Evidence of *E. coli* effects on human spermatozoa shows that this bacterium impairs sperm qual‐ ity, principally causing decreased motility; nevertheless, there are other consequences for sperm quality, specifically the incubation of sperm with *E. coli* decreases the ability of the male gamete to penetrate the oocyte, the most important step in the function of the spermatozoon [43].
