Microorganisms can reach the urinary tract by hematogenous or lymphatic dissemination, although there are abundant clinical and experimental data that show that the rise of microorganisms from the urethra is the most frequent pathway produced by UTI, especially by microorganisms of intestinal origin (that is tos say, Escherichia coli and other enterobacteria). ^{10 , 11} This offers a logical explanation of the greater frequency of UTI in women than in men and of the increased risk of infection after catheterization or bladder instrumentation.

From the concept of bacterial virulence or pathogenicity in the urinary tract it follows that not all bacterial species are equally capable of causing an infection. The more compromised are the natural defense mechanisms (for example, obstruction or bladder catheterization), the lower the need for virulence of a bacterial strain to cause infection. Bacterial infection is a complex process, in which not only the infectious bacterium has an important role, but also the host. In fact, an important part of the problems arising from the ITU are due to the host's response to it.

Urinary tract infections are the second cause of infectious processes in human pathology, affecting mostly women. From the age of 50, the incidence is equated with the male sex, ¹² Its diagnosis of certainty and adequate treatment, immediately after having taken the sample for bacteriological study, is especially important to prevent kidney damage.The positivity of this study was superior to that reported by Guzman W and colaborados, ^{12 , 13} in a study conducted in 2017 to the populations of Zumbahua, Colta and Guamote in Ecuador, and found in a similar study in the community of Navarra, ¹² both lower than 22%.

The urinary tract is a sterile space. Retrograde ascent of bacteria is the most common mechanism of infection. In women, they can more easily ascend to the urinary tract, due to the relative proximity of the urethral orifice to the anus and to the shorter length of the urethra, congenital urinary tract abnormalities, neurogenic bladder, patients who have a susceptible urothelium, which facilitates increased bacterial colonization, or certain immunodeficiency associated with low levels of IgA and IgG. ^{11 , 12}

The predisposition to colonization in patients with recurrent UTI, in the absence of anatomical or functional alterations, is related to a greater capacity of adhesion of bacteria, such as Escherichia coli, to the internal prepucial skin, to the perineum, to the vaginal introite and to the urethra; Often, these microorganisms have type P fimbriae, a bacterial adhesion mechanism that makes them more virulent and related to the urothelium. These patients may also have some immunodeficiency associated with low levels of IgA and IgG. ^{12 , 13}

The literature reviewed allows us to verify that Escherichia coli is still the predominantly isolated uropathogen, followed in a variable order by Proteus mirabilis, Enterococcus faecalis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterobacter cloacae, Streptococcus agalactiae, Staphylococcus saprophyticus, Serratia marcescens y Morganella morganii. ^{4 , 6 , 14 , 15}

The values ​​reported in this study, regarding the isolates of Escherichia coli, coincide with what is reported by the scientific literature. ^{4 , 6 , 14 , 15} and the values ​​reported by Sánchez, in the study carried out in the Colombian microbiology laboratory in 2009-2013, where Klebsiella ranked second. ⁴ When assessing the resistance pattern obtained in this study, it is thought that it could be related to the protocols for the use of antimicrobials for urinary sepsis in recent years.

The resistance of the main uropathogen causing ITU, the Escherichia coli bacteria, to the antibiotics used in the Microbiology Laboratory of the Provincial Teaching Hospital “Celia Sánchez Manduley” in Manzanillo, showed a resistance pattern with values ​​far superior to the results produced by the researches consulted. ^{4 , 6 , 7 , 12 )} Inthe study carried out in Quito, enteropathogens showed resistance levels higher than those of this research for cotrimoxazole (56.7%) and nalidixic acid (53.3%). In the last decade there has been a significant increase in resistance from E. coli to ampicillin, first-generation cephalosporins and cotrimoxazole. ^{5 , 7 , 12} In general, more than half of Escherichia coli strains are resistant to ampicillin and amoxacillin, which invalidates these antibiotics for empirical use.

With respect to cotrimoxazole, in our environment the sensitivity is in a range greater than 40% (table 3). This greater resistance is not only observed in vitro, but also has an increased risk of clinical and bacteriological failure in urinary tract infections treated with cotrimoxazole. ^{( 13} Escherichia This work also shows a high resistance pattern for second and third generation cephalosporins.

It is important to highlight that literature shows that nitrofurantoin is only recommended for ambulatory oral therapy in low infections, not high infections, due to its low concentration in plasma and renal tissue. ^{4 , 8 , 16 , 17} Bacteria acquire the ability to resist the action of antibiotics through various mechanisms, such as antigenic variability, modification of the permeability of the inner membrane, extraction of the compound and enzymatic inhibition, as well as by modification of the ribosomal white, or alteration of the composition and content of bacterial wall glycoproteins.

This resistance is transmitted between microorganisms of the same genus and between microorganisms of different genera. ^{4 , 8 14 , 15 , 16} These results coincide with the criteria that justify resistance to an antimicrobial and may be supported by the following criteria: extensive and indiscriminate use of antimicrobials, irrational or inappropriate prescription of antibiotics, tendency to multiresistance, that exhibit the germs associated with in-hospital infections, and the high existence of cross resistance. ¹⁵

The knowledge of the prevalence of in vitro resistance patterns of Escherichia coli to some antimicrobials, observed in the present study, allows the doctor to orient himself in his daily practice when starting the empirical treatment (without bacteriological confirmation) of the UTI. The correct diagnosis, as well as the early treatment of these infections, is of the utmost importance, since in addition to beingresolve the signs and symptoms of the acute condition, secondary complications are avoided.