Publicação
Clostridium difficile infection: molecular and epidemiology study
| Resumo: | Clostridium difficile is the leading cause of antibiotic-associated diarrhea in developed countries. Elderly hospitalized patients taking antibiotics are the main group at risk of infection. Since 2000, several countries have reported an increased incidence and severity of CDI associated with the emergence of the epidemic RT027. This clone produces Toxin A (TcdA), Toxin B (TcdB) and an additional binary toxin, Clostridium difficile transferase (CDT), has a deletion at position 117 in the tcdC gene (negative regulator of toxin production) and is highly resistant to fluoroquinolones. However, CDI epidemiology is highly variable, as other hypervirulent RTs have also started to emerge, and is still largely unknown in our country. In the present study, 286 C. difficile strains sent from 22 Portuguese hospitals were characterized regarding PCR ribotype, toxin profile, tcdC mutations, antimicrobial susceptibility to MXF, VAN, MTZ, IMP, RIF and TGC, and mechanisms of antimicrobial resistance. Most patients (73.4%) were aged ≥65 years and at least 54.9% had taken antibiotics in the previous months; 76.5% of the cases were healthcare facility-associated (HCFA) and 12.6% were community-associated (CA). Among the 84 distinct RTs found, RT027 was the most frequent (22%), followed by RT014 (8%), RT020 (5%), RT203 (5%), RT017 (4%), RT078 (3%) and RT126 (3%). RT027 was also predominant in the HCFA cases (26%), while RT014 was the most common in CA cases (16.7%). Most strains (96.1%) were toxinogenic, 31.8% were cdtA/cdtB+ and 29% had an extensively truncated TcdC, either due to the deletion Δ117A (23.1%) or the substitution 184C→T (5.9%) in tcdC. Twenty strains were tcdA-/tcdB+. In total, 11 were non-toxinogenic. MXF-resistance was observed in 95 (33.8%) strains, mainly from RT027 (62/95) and RT017 (9/95) but also from common RTs (RT014, RT020) and other non-RT027 cdtA/cdtB+ strains. Most MXF-resistant strains had mutations in GyrA, one of which, D-81→N, not previously described. RIF-resistance was found in 6.7% of the strains, most from RT017, and all exhibited previously described mutations in RpoB. Low level MTZ-resistance was found in 13 (4.6%) strains and RT027 exhibited reduced susceptibility to MTZ when compared to other RTs (geometric mean MIC of 0.79 mg/L vs 0.16 mg/L; t test, p<0.01). Two strains were low-level VAN-resistant and all were TGC-susceptible. The ermB and tetM genes were present in 37 (12.9%) and 43 (15.0%) strains, respectively, being that 26 (9.1%) contained both genes and most RT027 strains (60/63) were ermB-/tetM-. All strains were catD-. The IMP-resistance rate was 19.3% and seven mutations (not previously described) were identified near the conserved motifs of PBP1 in five IMP-resistant strains. These results raise awareness for the high frequency of RT027 but also for the emergence of other hypervirulent RTs, such as RT078 and RT126 that exhibited a truncated TcdC, as well as for the circulation of MXF-resistant strains. Antimicrobial resistance was also observed in other RTs, particularly the multidrug resistant TcdA-/TcdB+ RT017. |
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| Autores principais: | Isidro, Joana Vanessa Duarte |
| Assunto: | Infeção por Clostridium difficile Epidemiologia Ribotipo 027 Suscetibilidade aos antimicrobianos Mecanismos de resistência Teses de mestrado - 2015 |
| Ano: | 2015 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Clostridium difficile is the leading cause of antibiotic-associated diarrhea in developed countries. Elderly hospitalized patients taking antibiotics are the main group at risk of infection. Since 2000, several countries have reported an increased incidence and severity of CDI associated with the emergence of the epidemic RT027. This clone produces Toxin A (TcdA), Toxin B (TcdB) and an additional binary toxin, Clostridium difficile transferase (CDT), has a deletion at position 117 in the tcdC gene (negative regulator of toxin production) and is highly resistant to fluoroquinolones. However, CDI epidemiology is highly variable, as other hypervirulent RTs have also started to emerge, and is still largely unknown in our country. In the present study, 286 C. difficile strains sent from 22 Portuguese hospitals were characterized regarding PCR ribotype, toxin profile, tcdC mutations, antimicrobial susceptibility to MXF, VAN, MTZ, IMP, RIF and TGC, and mechanisms of antimicrobial resistance. Most patients (73.4%) were aged ≥65 years and at least 54.9% had taken antibiotics in the previous months; 76.5% of the cases were healthcare facility-associated (HCFA) and 12.6% were community-associated (CA). Among the 84 distinct RTs found, RT027 was the most frequent (22%), followed by RT014 (8%), RT020 (5%), RT203 (5%), RT017 (4%), RT078 (3%) and RT126 (3%). RT027 was also predominant in the HCFA cases (26%), while RT014 was the most common in CA cases (16.7%). Most strains (96.1%) were toxinogenic, 31.8% were cdtA/cdtB+ and 29% had an extensively truncated TcdC, either due to the deletion Δ117A (23.1%) or the substitution 184C→T (5.9%) in tcdC. Twenty strains were tcdA-/tcdB+. In total, 11 were non-toxinogenic. MXF-resistance was observed in 95 (33.8%) strains, mainly from RT027 (62/95) and RT017 (9/95) but also from common RTs (RT014, RT020) and other non-RT027 cdtA/cdtB+ strains. Most MXF-resistant strains had mutations in GyrA, one of which, D-81→N, not previously described. RIF-resistance was found in 6.7% of the strains, most from RT017, and all exhibited previously described mutations in RpoB. Low level MTZ-resistance was found in 13 (4.6%) strains and RT027 exhibited reduced susceptibility to MTZ when compared to other RTs (geometric mean MIC of 0.79 mg/L vs 0.16 mg/L; t test, p<0.01). Two strains were low-level VAN-resistant and all were TGC-susceptible. The ermB and tetM genes were present in 37 (12.9%) and 43 (15.0%) strains, respectively, being that 26 (9.1%) contained both genes and most RT027 strains (60/63) were ermB-/tetM-. All strains were catD-. The IMP-resistance rate was 19.3% and seven mutations (not previously described) were identified near the conserved motifs of PBP1 in five IMP-resistant strains. These results raise awareness for the high frequency of RT027 but also for the emergence of other hypervirulent RTs, such as RT078 and RT126 that exhibited a truncated TcdC, as well as for the circulation of MXF-resistant strains. Antimicrobial resistance was also observed in other RTs, particularly the multidrug resistant TcdA-/TcdB+ RT017. |
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