Epidemiology and molecular analysis of herpes simplex keratitis requiring primary penetrating keratoplasty.

AIMS: To determine whether herpes simplex keratitis (HSK) has declined as an indication for penetrating keratoplasty (PKP) at the University of California San Francisco (UCSF) over the past 30 years. METHODS: Records of the Hogan Eye Pathology Laboratory were reviewed to determine the incidence of PKP performed for HSK from 1972 through 2001. Archived corneal tissue with the diagnosis of HSK was evaluated for herpes simplex virus (HSV) DNA by polymerase chain reaction (PCR) based assays. RESULTS: The number of corneal buttons submitted with the clinical diagnosis of HSK decreased from 1972 to 2001, while the overall number of PKPs performed did not. The percentage of corneal buttons with a clinical diagnosis of HSK that contained detectable HSV DNA did not change over the course of the study period. CONCLUSION: HSK declined as an indication for PKP from 1972 to 2001 at UCSF. It is unlikely that this decline was the result of improved diagnostic accuracy since detection of HSV DNA in corneal buttons with a clinical diagnosis of HSK was similar at the beginning and end of the study period.

Polymerase chain reaction based detection of fungi in infected corneas.

AIMS: To evaluate a polymerase chain reaction (PCR) based assay to detect fungi in scrapings from infected corneas. METHODS: A PCR assay was developed to amplify a portion of the fungal 18S ribosome gene. Corneal scrapings from 30 patients with presumed infectious keratitis were evaluated using this assay, as well as by standard microbiological techniques, and the results were compared. Conjunctival swabs from each patient's healthy, fellow eye were also evaluated by PCR. RESULTS: PCR and fungal culture results matched (were both positive or both negative for fungi) in 22 (74%) of 30 scrapings from infected corneas. Three (10%) of 30 samples were PCR positive but fungal culture negative; two of these appeared clinically to represent fungal infections, and the third was clinically indeterminate. Four (13%) scrapings were positive by PCR but also by bacterial and not fungal culture. One specimen (3%) was PCR negative but fungal culture positive. Of the conjunctival swabs from each patient's healthy fellow eye, five (17%) of 30 were positive by PCR, and the opposite, infected eye of all five of these harboured a fungal infection. CONCLUSIONS: PCR is promising as a means to diagnose fungal keratitis and offers some advantages over culture methods, including rapid analysis and the ability to analyse specimens far from where they are collected.

Utility of a polymerase chain reaction diagnostic system in a study of the epidemiology of shigellosis among dysentery patients, family contacts, and well controls living in a shigellosis-endemic area.

Polymerase chain reaction (PCR) diagnostic methods have rarely been used in epidemiologic studies of Shigella and enteroinvasive Escherichia coli (EIEC) infections. In this study, amplification of the invasion plasmid antigen H (ipaH) gene by PCR and standard culture methods was used to identify Shigella species or EIEC among 154 patients with dysentery, 154 age-matched controls, and family contacts in Thailand. The ipaH PCR system increased the detection of Shigella species and EIEC from 58% to 79% among patients with dysentery and from 6% to 22% among 527 family contacts; 75% of infections in family members were asymptomatic. Detection of the ipaH gene was statistically associated with dysentery. Household contacts of patients with shigellosis diagnosed only by PCR had significantly higher rates of shigellosis than household contacts of patients who did not have Shigella or EIEC infections. Detection of the ipaH gene by PCR is far more sensitive than detection by standard culture and is highly correlated with evidence of Shigella transmission among family contacts.