Enhanced Molecular Typing of Treponema pallidum subspecies pallidum Strains From 4 Italian Hospitals Shows Geographical Differences in Strain Type Heterogeneity, Widespread Resistance to Macrolides, and Lack of Mutations Associated With Doxycycline Resistance

Sex Transm Dis. 2018 Apr;45(4):237-242. doi: 10.1097/OLQ.0000000000000741.


Background: Although syphilis rates have been relatively high in Italy for more than 15 years, no data on the molecular types of Treponema pallidum subspecies pallidum circulating in this country are yet available. Likewise, no data on how widespread is resistance to macrolide or tetracycline antibiotics in these strains exist. Such data would, however, promote comprehensive studies on the molecular epidemiology of syphilis infections in Italy and inform future interventions aiming at syphilis control in this and other European countries.

Goals and study design: Swabs from oral, genital, cutaneous, or anal lesions were obtained from 60 syphilis patients attending dermatology clinics in Milan, Turin, Genoa, and Bologna. Molecular typing of T. pallidum DNA was performed to provide a snapshot of the genetic diversity of strains circulating in Northern Italy. Samples were also screened for mutations conferring resistance to macrolides and tetracyclines.

Results: T. pallidum DNA was detected in 88.3% (53/60) of the specimens analyzed. Complete and partial T. pallidum typing data were obtained for 77.3% (41/53) and 15.0% (8/53) of samples, respectively, whereas 4 samples could not be typed despite T. pallidum DNA being detected. The highest strain type heterogeneity was seen in samples from Bologna and Milan, followed by Genoa. Minimal diversity was detected in samples from Turin, despite the highest number of typeable samples collected there. Resistance to macrolides was detected in 94.3% (50/53) of the strains, but no known mutations associated with tetracycline resistance were found.

Conclusions: Genetic diversity among T. pallidum strains circulating in Northern Italy varies significantly among geographical areas regardless of physical distance. Resistance to macrolides is widespread.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Anal Canal / microbiology
  • Anal Canal / pathology
  • Anti-Bacterial Agents / therapeutic use*
  • DNA, Bacterial / genetics
  • Doxycycline / therapeutic use*
  • Drug Resistance, Multiple, Bacterial / genetics*
  • Female
  • Genotype
  • Hospitals / statistics & numerical data
  • Humans
  • Italy / epidemiology
  • Macrolides / therapeutic use*
  • Male
  • Middle Aged
  • Molecular Typing
  • Point Mutation
  • Skin / microbiology
  • Skin / pathology
  • Syphilis / drug therapy
  • Syphilis / epidemiology*
  • Syphilis / microbiology
  • Treponema pallidum / classification*
  • Treponema pallidum / isolation & purification
  • Young Adult


  • Anti-Bacterial Agents
  • DNA, Bacterial
  • Macrolides
  • Doxycycline