Beyond CC398: Characterisation of Other Tetracycline and Methicillin-Resistant Staphylococcus aureus Genetic Lineages Circulating in Spanish Hospitals

Abstract

Tetracycline resistance (Tet^R) has been evidenced as a good phenotypic marker for detection of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) isolates of the clonal complex CC398. The aim of this study was to characterise a collection of 95 Tet^R-MRSA isolates, not belonging to the lineage CC398, that were obtained in a previous multicentre study, to detect other MRSA clonal complexes that could be associated with this phenotypic Tet^R marker. The Tet^R-MRSA isolates were recovered from 20 Spanish hospitals during 2016 and they were characterised to determine their antimicrobial resistance and virulence phenotypes/genotypes as well as the presence of the immune evasion cluster (IEC). A high proportion of isolates belonging to the CC1 lineage (46%) were observed, as well as to the CC5, CC8 and CC45 lineages (11% each one). Thirty-two different spa-types were identified, being predominantly CC1-t127 (40%) and CC45-t1081 (11%). The IEC system (with the gene scn as marker) was present in 73% of isolates and 16% produced the Panton Valentine leucocidin (PVL). A high proportion of MRSA-CC1 isolates were scn-negative (38.6%) and 52.9% of them were blaZ-negative. A multidrug resistance (MDR) phenotype was identified in 86% of MRSA isolates. The knowledge of other Tet^R-MRSA genetic lineages, in addition to CC398, is highly relevant, since most of them were MDR and some of them presented important virulence factors. Strains potentially associated with livestock (as the subpopulation CC1-t127-scn-negative) or with humans (as the CC45 lineage or the subpopulation CC1-scn-positive) have been found in this study. The use of tetracycline-resistance for detection, not only of CC398 but also of other LA-MRSA lineages should be tracked in the future.

Keywords: CC1; CC398; MRSA; multicentre study; t127; tetracycline resistance.

Figure 1

Presence of immune evasion cluster (IEC) among Tet^R-MRSA non-CC398 isolates: (A) Presence or absence of IEC according to the clonal complexes (CCs) of the isolates; (B) Presence or absence of the IEC in PVL-positive isolates according to their clonal complexes (CCs).

Figure 2

Statistically significant differences found in the characterisation of our Tet^R-MRSA non-CC398 isolates. (A) Absence of scn in CC1 and non-CC1 isolates; (B) MDR detection in clinical and epidemiological surveillance samples; (C) Detection of the ermB gene in erythromycin-clindamycin constitutive resistant (ERY^R-cCLI^R) and erythromycin-clindamycin (ERY^R-iCLI^R) inducible resistant isolates. * p ≤ 0.05.

Figure 3

Antimicrobial resistance phenotype and genotype detected among Tet^R-MRSA non-CC398 isolates. (A) Antimicrobial resistance phenotype (ERY, erythromycin; CLI, clindamycin; CIP, ciprofloxacin; FUS, fusidic acid; MUP, mupirocin); (B) Antimicrobial resistance genotype.

Figure 4

Presence or absence of the resistance blaZ gene in CC1 and non-CC1 tetracycline-resistant MRSA isolates according to the presence or absence of the IEC (scn gene).