Risk factors and predisposing conditions for urinary tract infection

Understanding individual and population-specific risk factors associated with recurrent urinary tract infections (UTIs) can help physicians tailor prophylactic strategies. Frequent intercourse, vulvovaginal atrophy, change of the local bacterial flora, history of UTIs during premenopause or in childhood, family history, and a nonsecretor blood type are substantiated risk factors for recurrent uncomplicated UTIs. This is a narrative review based on relevant literature according to the experience and expertise of the authors. Asymptomatic bacteriuria is generally benign; however, during pregnancy it is more common and is associated with an increased likelihood of symptomatic infection, which may harm the mother or fetus. Screening of pregnant women and appropriate treatment with antimicrobials must be balanced with the potential for adverse treatment-related outcomes; appropriate prophylaxis should be considered where possible. High-quality data are currently lacking on risks related to asymptomatic bacteriuria in pregnancy and further data in this hard-to-study population should be a primary concern for researchers. Incomplete voiding represents the primary risk factor for UTIs associated with conditions such as urinary incontinence and prolapse. Correcting the presence of residual urine remains the most effective prophylaxis in these populations. Bladder function alters throughout life; however, changes in function may be particularly profound in clinical populations at high risk of UTIs. Patients with neurogenic bladder will also likely have other evolving medical issues which increase the risk of UTIs, such as repeated catheterization and increasing residual urine volume. More aggressive antimicrobial prophylactic strategies may be appropriate in these patients. Again, the paucity of data on prophylaxis in these high-risk patients requires the attention of the research community.

Structural and functional comparison of toxins from the venom of the scorpions Centruroides infamatus infamatus, Centruroides limpidus limpidus and Centruroides noxius

Two novel toxins containing 66 amino acid residues each were isolated from the venom of the scorpions Centruroides infamatus infamatus and Centruroides limpidus limpidus, respectively. Their full amino acid sequences were determined. Comparison of primary structures showed that they share 97% similarity among themselves and 83% to that of toxin 2 from Centruroides noxius. The three toxins studied compete with each other for the same binding sites on membranes prepared from rat brain synaptosomes, suggesting that they are all beta-scorpion toxins. Toxin action was assayed into the microI-2 rat skeletal muscle Na+ channel heterologously expressed into Xenopus oocytes. All three toxins block this Na+ channel in a similar fashion, without affecting inactivation, and showed IC50 values in the micromolar concentration range.

Isolation of a toxin from Centruroides infamatus infamatus Koch scorpion venom that modifies Na+ permeability on chick dorsal root ganglion cells

A novel toxin was isolated and characterized from the venom of the Mexican scorpion Centruroides infamatus infamatus. It has an apparent mol. wt of 7600, compatible with the presence of 66 amino acid residues per molecule. The N-terminal amino acid sequence was determined (up to residue 48) and showed approximately 95% similarity with toxins from other Mexican scorpions of the gnus Centruroides. Experiments conducted with chick dorsal root ganglion cells showed that toxin 1 is a Na+ channel effector, causing a decrease in the peak Na+ permeability, similar to decreases observed for typical beta-scorpion toxins.

Scorpionism and serotherapy in Mexico

In Mexico, scorpionism is an endemic public health problem. The exact number of human accidents is unknown, but partial statistics suggests numbers close to 200,000 per year. The documented number of fatality cases is in the order of 310 people per year. We currently use horse antiserum in patients who show a clear picture of intoxication. Our personal experience in treating 38,068 people, from which over 20,000 received serotherapy, shows that the antiserum is very effective, in that none of the patients died.

Epidemiological characteristics of scorpion sting in León, Guanajuato, México

Poisoning with scorpion venom in the city of León, Guanajuato state, México, is a significant public health problem. The hospital of the Mexican Red Cross gave medical attention to 38,068 cases of envenomation by scorpion sting during 1981-1986; 77% of all accidents occurred among persons under 30 years of age. The 100% survival rate can be attributed to prompt serotherapy. Most stings were due to scorpions from the species Centruroides infamatus infamatus. Scorpion stings increase dramatically in the spring and are lowest during winter. The distribution of scorpions throughout the city is uniform and accidents occur at any time of day or night with no preference in regard to the sex of the affected persons. The epidemiological aspects of scorpion poisoning are emphasized.