Escherichia coli is the predominant nonpathogenic facultative flora of the human intestine. Some E. coli strains, however, have developed the ability to cause disease of the gastrointestinal, urinary, or central nervous system in even the most robust human hosts. Diarrheagenic strains of E. coli can be divided into at least six different categories with corresponding distinct pathogenic schemes. Taken together, these organisms probably represent the most common cause of pediatric diarrhea worldwide. Several distinct clinical syndromes accompany infection with diarrheagenic E. coli categories, including traveler’s diarrhea (enterotoxigenic E. coli), hemorrhagic colitis and hemolytic-uremic syndrome (enterohemorrhagic E. coli), persistent diarrhea (enteroaggregative E. coli), and watery diarrhea of infants (enteropathogenic E. coli). This review discusses the current level of understanding of the pathogenesis of the diarrheagenic E. coli strains and describes how their pathogenic schemes underlie the clinical manifestations, diagnostic approach, and epidemiologic investigation of these important pathogens.

Diarrheagenic Escherichia coli

ETEC is an underrecognized but extremely important cause of diarrhea in the developing world where there is inadequate clean water and poor sanitation. It is the most frequent bacterial cause of diarrhea in children and adults living in these areas and also the most common cause of traveler's diarrhea. ETEC diarrhea is most frequently seen in children, suggesting that a protective immune response occurs with age. The pathogenesis of ETEC-induced diarrhea is similar to that of cholera and includes the production of enterotoxins and colonization factors. The clinical symptoms of ETEC infection can range from mild diarrhea to a severe cholera-like syndrome. The effective treatment of ETEC diarrhea by rehydration is similar to treatment for cholera, but antibiotics are not used routinely for treatment except in traveler's diarrhea. The frequency and characterization of ETEC on a worldwide scale are inadequate because of the difficulty in recognizing the organisms; no simple diagnostic tests are presently available. Protection strategies, as for other enteric infections, include improvements in hygiene and development of effective vaccines. Increases in antimicrobial resistance will dictate the drugs used for the treatment of traveler's diarrhea. Efforts need to be made to improve our understanding of the worldwide importance of ETEC.

https://cmr.asm.org/content/cmr/18/3/465.full.pdf

Enterotoxigenic escherichia coli in developing countries: epidemiology, microbiology, clinical features, treatment, and prevention

https://www.scielo.br/pdf/bjm/v47s1/1517-8382-bjm-47-s1-0003.pdf

Diarrheagenic Escherichia coli.

PCR has revolutionized the field of infectious disease diagnosis. To overcome the inherent disadvantage of cost and to improve the diagnostic capacity of the test, multiplex PCR, a variant of the test in which more than one target sequence is amplified using more than one pair of primers, has been developed. Multiplex PCRs to detect viral, bacterial, and/or other infectious agents in one reaction tube have been described. Early studies highlighted the obstacles that can jeopardize the production of sensitive and specific multiplex assays, but more recent studies have provided systematic protocols and technical improvements for simple test design. The most useful of these are the empirical choice of oligonucleotide primers and the use of hot start-based PCR methodology. These advances along with others to enhance sensitivity and specificity and to facilitate automation have resulted in the appearance of numerous publications regarding the application of multiplex PCR in the diagnosis of infectious agents, especially those which target viral nucleic acids. This article reviews the principles, optimization, and application of multiplex PCR for the detection of viruses of clinical and epidemiological importance.

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Multiplex PCR: Optimization and Application in Diagnostic Virology

Information on age- and sex-specific prevalence of herpes simplex virus (HSV) types 2 and 1 infections is essential to optimize genital herpes control strategies, which increase in importance because accumulating data indicate that HSV-2 infection may increase acquisition and transmission of human immunodeficiency virus. This review summarizes data from peer-reviewed publications of type-specific HSV seroepidemiologic surveys. HSV-2 prevalence is, in general, highest in Africa and the Americas, lower in western and southern Europe than in northern Europe and North America, and lowest in Asia. HSV-2 and -1 prevalence, overall and by age, varies markedly by country, region within country, and population subgroup. Age-specific HSV-2 prevalence is usually higher in women than men and in populations with higher risk sexual behavior. HSV-2 prevalence has increased in the United States but national data from other countries are unavailable. HSV-1 infection is acquired during childhood and adolescence and is markedly more widespread than HSV-2 infection. Further studies are needed in many geographic areas.

Age-Specific Prevalence of Infection with Herpes Simplex Virus Types 2 and 1: A Global Review

A multiplex PCR (M-PCR) assay with colorimetric detection was devised for the simultaneous amplification of DNA targets from Haemophilus ducreyi, Treponema pallidum, and herpes simplex virus (HSV) types 1 and 2. By using target-specific oligonucleotides in a microwell format, 298 genital ulcer swab specimens collected in New Orleans during three intervals from 1992 through 1994 were evaluated. The results of the M-PCR assay were compared with the results of dark-field microscopy and H. ducreyi culture on two different culture media. HSV culture results were available for 99 specimens collected during the third interval. Confirmatory PCR assays targeting different gene sequences for each of the three organisms were used to validate the M-PCR results. Specimens were resolved as positive for the determination of sensitivity if the reference diagnostic test was positive or if the results of both the M-PCR and the confirmatory PCR were positive. The resolved sensitivities of M-PCR for HSV, H. ducreyi, and T. pallidum were 100, 98.4, and 91%, respectively. The resolved sensitivities of HSV culture, H. ducreyi culture, and dark-field microscopy were 71.8, 74.2, and 81%, respectively. These results indicate that the M-PCR assay is more sensitive than standard diagnostic tests for the detection of HSV, H. ducreyi, and T. pallidum from genital ulcers.

Simultaneous PCR detection of Haemophilus ducreyi, Treponema pallidum, and herpes simplex virus types 1 and 2 from genital ulcers.

Infection with enterotoxigenic Escherichia coli (ETEC) is a common cause of diarrhea among travelers and residents of developing countries. ETEC produces either a heat-stable toxin or a heat-labile toxin, or both, encoded by plasmid-borne ST and LT genes, respectively. Diagnosis of infection with this subclass of E. coli can be performed with oligonucleotide hybridization probes; however, the sensitivity and specificity of this method are insufficient. A nonradioactive multiplex PCR assay that provides a sensitive and specific method for detecting the presence of either or both toxin genes has been developed. A simple procedure that removed inhibitors of the PCR while efficiently releasing ETEC DNA from stool specimens for subsequent amplification was used. The results for samples from a human volunteer study of ETEC infection indicated that this method of sample preparation results in greater clinical sensitivity than conventional total nucleic acid extraction and ethanol precipitation. Detection of ETEC by a multiplex PCR assay in stool specimens directly processed with a glass matrix and chaotropic solution had greater sensitivity than culture.

Multiplex PCR assay and simple preparation method for stool specimens detect enterotoxigenic Escherichia coli DNA during course of infection.

This cross-sectional study of 558 men with genital ulcer disease (GUD) and 602 men with urethritis aimed to determine the etiology of GUD in HIV-infected and noninfected men attending sexually transmitted disease (STD) clinics in Durban Johannesburg and Cape Town South Africa. Statistical analysis shows that patients with GUD were more likely to be infected with HIV than patients with urethritis (39.4% vs. 21.4%). Most importantly it was found that herpes simplex virus 2 (HSV-2) is a more common cause of GUD than has been suggested by previous studies conducted in South Africa. In addition serologic evidence of HSV-2 infection and current initial or recurrent genital herpes are strongly associated with HIV infection among men who attended STD clinics with GUD or urethritis. In view of these findings it is suggested that future approaches for reducing HIV transmission by STD control should include efforts to address HSV-2 infection.

Human immunodeficiency virus infection and genital ulcer disease in South Africa: the herpetic connection.

DNA probe and PCR-based assays to identify and detect parasites are technically complex; however, they have high sensitivity, directly detect parasites independent of the immunocompetence or previous clinical history of the patient, and can distinguish between organisms that are morphologically similar. Diagnosis of parasites is often based on direct detection by microscopy, which is insensitive and laborious and can lack specificity. Most PCR-based assays were more sensitive than DNA probe assays. The development of PCR-based diagnostic assays requires multiple steps following the initial selection of oligonucleotide primers and reporter probe. Generally, the ability to detect the DNA of one parasite was attained by PCR; however, advances in the preparation of samples for PCR (extraction of DNA while removing PCR inhibitors) will be required to achieve that sensitivity with human specimens. Preliminary PCR systems have been developed for many different parasites, yet few have been evaluated with a large number of clinical specimens and/or under field conditions. Those evaluations are essential for determination of clinical and field utility and performance and of the most appropriate application of the assay. Several situations in which PCR-based diagnosis will result in epidemiologic, medical, or public health advances have been identified.

DNA probes and PCR for diagnosis of parasitic infections

Chlamydia trachomatis and Neisseria gonorrhoeae are universally acknowledged as urethral pathogens, yet the etiology in the majority of cases of urethritis is unclear. Our case-control study assessed the association of Mycoplasma genitalium, Ureaplasma urealyticum, and other potential pathogens with acute nongonococcal urethritis (NGU) in heterosexual men presenting to an urban sexually transmitted diseases clinic. M. genitalium was detected in 27 (22%) of 121 NGU case patients and in 5 (4%) of 117 control subjects (P<.01). Although C. trachomatis was detected in 36 (30%) of 121 NGU case patients and in 4 (3%) of 117 control subjects (P<.01), only 3 men with NGU were infected with both C. trachomatis and M. genitalium. U. urealyticum was not associated with NGU. By multivariate analyses, controlling for age, race, history of prior urethritis, and chlamydial infection, M. genitalium was associated with a 6.5-fold increased risk of urethritis (95% confidence interval, 2.1-19.5), which supports a role of this organism in the etiology of NGU.

Judith B. Weiss

Papers

Simultaneous PCR detection of Haemophilus ducreyi, Treponema pallidum, and herpes simplex virus types 1 and 2 from genital ulcers.

Multiplex PCR assay and simple preparation method for stool specimens detect enterotoxigenic Escherichia coli DNA during course of infection.

Human immunodeficiency virus infection and genital ulcer disease in South Africa: the herpetic connection.

DNA probes and PCR for diagnosis of parasitic infections

Association of Mycoplasma genitalium with nongonococcal urethritis in heterosexual men.