Thursday, 23 December 2010

Spain: MRSA st398 in pigs and people

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This report confirms the dangers of MRSA st398 to pig farmers and workers. It also underlines the risks to the immunocompromised when it gets into the hospitals.

Governments must take immediate action to get reliable test results for the pigs and get the veterinarians with their wild prescribing habits under tight external supervision.

That includes Britain, where the pigs have been known to be ill for the past decade, but where the usage of antibiotics in pigs and the incidence of MRSA st398 still seems to be a state secret.

Full report here

Volume 17, Number 1–January 2011

Letter

Empyema caused by MRSA ST398 with Atypical Resistance Profile, Spain


Carmen Lozano, Carmen Aspiroz, Ana Isabel Ezpeleta, Elena Gómez-Sanz, Myriam Zarazaga, and Carmen Torres

To the Editor: We report a case of empyema caused by methicillin-resistant Staphylococcus aureus (MRSA) sequence type ST398 in a 79-year-old man in Spain who had severe chronic obstructive pulmonary disease. In 2009, the patient was hospitalized in the intensive care unit because of decompensation of his chronic obstructive pulmonary disease, profound iliofemoral venous thrombosis, right pneumothorax, and lung carcinoma. Thoracic drainage, support measures, and intravenous levofloxacin were initiated, but no clinical improvement was seen. Purulent exudates from the thoracic drainage tube and of a tracheal aspirate were cultured. MRSA was isolated from both samples and from a nasal swab. Antimicrobial drug therapy was changed from levofloxacin to intravenous linezolid, but the patient's clinical situation rapidly worsened, and he died of multiorgan failure...

...The patient lived with his wife and 2 sons near a pig farm. Both sons worked on the farm; the patient, but not his wife, helped sporadically on the farm. Nasal samples from the 3 family members indicated MRSA carriage in 1 son but not in the other son or the patient's wife. The characteristics of the nasal MRSA strain recovered from the son were identical to those previously detected in MRSA strains from the patient (Table). In addition, nasal swabs from 18 pigs on the farm were randomly taken, and MRSA isolates were detected in 9 (50%) pigs; 1 MRSA isolate per animal was further characterized. Eight isolates were typed as ST398/t011/SCCmecV/agrI, and the remaining one as ST398/t1451/SCCmecV/agrI. All animal isolates had the same resistance phenotype and genotype as the MRSA isolates from the patient and son. None harbored the studied virulence factors (Table). All isolates had an unusual clindamycin-resistance/erythromycin-susceptibility phenotype and harbored the vga(A) gene...

...Other studies have suggested clonal spread and transmission of MRSA ST398 between pigs and persons who work with them (4,5). This microorganism has been generally associated with skin and soft tissue infections in humans (6). Nevertheless, severe infections by ST398 also have been sporadically described, and the report of 7 pneumonia cases associated with mechanical ventilation in central Europe is relevant (7). In general, ST398 isolates have fewer virulence factors than do other clones of MRSA (2); nonetheless, human infections from Panton-Valentine leukocidin–positive ST398 isolates have been reported (8). The immunocompromised status of patients in intensive care units could favor dissemination of ST398 in this environment....

...In conclusion, we report potential pig-to-human transmission of MRSA ST398. MRSA ST398 can be associated with severe respiratory pathology in immunocompromised patients, and these microorganisms could also be resistant to other first-line antimicrobial agents, such as fluoroquinolones, used to treat these infections. Moreover, the unusual clindamycin-resistance/erythromycin-susceptibility phenotype might be a key marker (in addition to tetracycline resistance) for the possible presence of livestock-associated MRSA...