Israel Medical Association Journal

Background: The rate of infection with Clostridium difficile colitis and its associated mortality have been increasing in the last decade. The molecular epidemiology of C. difficile in Israel has as yet not been studied.

Objectives: To screen for the existence of the 027 and 078 ribotypes and determine the longitudinal molecular epidemiology of the circulating clinical C. difficile isolates in a large hospital in central Israel.

Methods: Polymerase chain reaction (PCR) ribotyping was performed on C. difficile isolates obtained from hospitalized patients from November 2003 to May 2004 (first study period) and September 2009 (second study period). Isolates with PCR[1] ribotype patterns, unlike those of the available reference strains (078 and 027), were labeled with letters. Forty-six isolates from the first study period and 20 from the second were analyzed.

Results: PCR strain typing of C. difficile isolates yielded approximately 26 unique ribotypes. During the first study period, ribotype A and B accounted for 30% and 28%, respectively, whereas ribotype E and K accounted for 6.5% for each. During the second study period, ribotypes A, E and K disappeared, and the incidence of ribotype B decreased from 28% to 15%. One isolate (1/20, 5%) emerged during the second period and was identified as ribotype 027. Moxifloxacin resistance was found in 93% of ribotype A isolates, 81% of the ribotype B group, and in 44% of other ribotypes.

Conclusions: The predominant ribotypes circulating in our institution were diverse and changing. This is the first report on the emergence of the 027 ribotype in Israel.

Background: Poliovirus rapidly evolves by nucleic acid substitutions and genetic recombination with other polioviruses and non-polio enteroviruses. Evolving oral poliovirus (Sabin strains) can rapidly revert to neurovirulence and undergo antigenic alterations.

Objectives: To evaluate the threat of vaccine-derived poliovirus (1–15% divergence from the respective Sabin strain) for a poliomyelitis-free population in a country with a long-standing routine vaccination program.

Methods: We characterized genetic and antigenic changes in OPV[1] strains isolated from sewage in Israel and evaluated intestinal immunity by measuring fecal excretion after OPV challenge of vaccinated children.

Results: Characterization of poliovirus from sewage revealed eight type 2 and three type 3 vaccine polioviruses that had replicated and started to evolve (vaccine that replicated and diverged by 0.5 to ≤ 1.0%) and nine highly diverged type 2 vaccine-derived polioviruses (1–15% divergence from the respective Sabin strain) with 8–14% divergence between the years 1998 and 2005. Six of the eleven VRPV[2] uniquely recombined with OPV and/or NPEV[3]. The nine VDPV[4] were epidemically related, genotypically neurovirulent, and had 10–15 amino acid substitutions in antigenic sites altering their antigenicity, but shared a single recombination. Type 2 OPV was excreted by 23% and 17% of infants challenged with OPV 3 months after partial immunization (two doses each of OPV and enhanced inactivated poliovirus) or full immunization (three doses of each) respectively, despite high humoral antibody titers.

Conclusions: Our findings, which show that OPV is excreted for a significant period by children with high humoral immunity, emphasize the long-term potential threat from VDPV in highly vaccinated populations. An adequate immunization program, combined with environmental surveillance, is necessary to prevent poliomyelitis and community transmission of poliovirus.