Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 15, Number 5—May 2009
Letter

Community-acquired Methicillin-Resistant Staphylococcus aureus ST398 Infection, Italy

Cite This Article

To the Editor: Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has been identified in livestock animals (particularly pigs), veterinarians, and animal farm workers (1,2). CA-MRSA strains from pigs have been classified most frequently within the multilocus sequence type (ST) 398 (1) and have been rarely identified as a cause of invasive infection in humans (1,3,4). We report a case of invasive infection in a pig-farm worker in Cremona, Italy, an intensive animal farming area; the infection was caused by MRSA of swine origin, ST398.

The case-patient was a 58-year-old man admitted to a surgical department in Cremona, Italy, on July 30, 2007, because of a 1-week history of fever and intense pain in his right buttock. He worked on a pig farm, was obese, consumed high volumes of wine (1.5 L/day), was taking medication for hypertension, and had not had recent (<5 years) contact with the healthcare system. At the time of hospital admission, he was moderately ill, oriented, and cooperative. His right buttock was extremely painful. He reported neither recent trauma nor anything that would explain infection. Laboratory examination showed increased C-reactive protein (298 mg/L) and leukocytosis (28,000 cells/mm3) with neutrophilia (80%). Empiric treatment with intravenous ampicillin-sulbactam was started.

Based on clinical and magnetic resonance imaging data, the diagnosis was cellulitis, pyomyositis, and pelvic multiloculated abscess of the buttock. A needle aspiration of the abscess, guided by computed tomography, was performed. Because of persistent fever (38.5°C), oral ciprofloxacin was added to the patient’s treatment regimen on day 3. Blood and abscess cultures yielded MRSA that was sensitive to glycopeptides, rifampin, linezolid, gentamicin, and mupirocin and resistant to co-trimoxazole, macrolides, clindamycin, and fluoroquinolones. After treatment was switched to vancomycin plus rifampin, the patient’s general condition improved; he was discharged from the hospital after 24 days.

An epidemiologic investigation of the patient’s family and 3 fellow workers and their families was performed; nasal and inguinal swabs were obtained from these 11 persons. Two fellow workers were colonized with S. aureus, 1 with methicillin-sensitive S. aureus (MSSA) and the other with MRSA. The pig farm, a farrow-to-finish production farm with 3,500 pigs, was screened for MRSA according to guidelines of the European Food Safety Authority (5). Dust swabs were taken from 5 areas of the farm; 7 MRSA isolates were detected.

S. aureus species identification was confirmed by PCR (6). Staphylococcal chromosomal cassette mec type (SCCmec) was identified by multiplex PCR testing (7,8). Panton-Valentine leukocidin (PVL) gene detection and spa and ST typing were performed as previously described (9).

The isolate from the patient belonged to spa type t899, was ST398, carried an SCCmec type IVa cassette, and was PVL negative. The isolate from the MRSA-colonized worker was a t108 strain carrying SCCmec type V. The isolate from the MSSA-colonized worker was identified as t899. The dust swabs yielded 7 isolates: 2 belonged to t899 and carryied SCCmec IVa; 5 belonged to t108 and carryied SCCmec V. The isolates obtained from the patient, farrowing area 7, and gestation area 1 were indistinguishable (i.e., same spa type, SCCmec type, and ST profile; Table), thus confirming the animal origin of transmission.

This case highlights other considerations. First, although the isolate, as expected, was PVL negative, its aggressiveness resembled that of PVL-positive strains. Second, all S. aureus isolates identified, MRSA and MSSA, belonged to t899 or t108, within the ST398 group, in agreement with the observation of van Dujkeren et al. (9) that ST398 MSSA, a possibly virulent strain (10), may acquire different SCCmec cassettes relatively easily. Third, ST398 carriage was high (75%) among workers; 2 of 4 were carriers of MRSA ST398 and 1 was a carrier of MSSA ST398. This strain may be a hazard to the health of pig farmers and a possible cause of zoonotic infection. When treating pig farmers for possible staphylococcal infection, healthcare workers should consider using antimicrobial drugs effective against MRSA and should consider the aggressive resistance pattern observed in this case, which was more similar to hospital-acquired strains than to classic CA-MRSA.

The identification of a case of ST398 endocarditis (4) and of a nosocomial outbreak of ST398 in the Netherlands (3) may support the hypothesis that the scarce number of infections reported so far may be due to the still-limited spread of ST398 among critically ill patients; emergence among pigs is thought to be recent. As observed by Wulf and Voss, the pathogenicity, aggressiveness, or potential spread of ST398 among humans remains to be ascertained (1).

In conclusion, attention should be given to the emergence of MRSA strains among animals, and continuous surveillance in humans should monitor the extent of disease from MRSA ST398, especially in areas of intensive animal farming. Collaboration between infectious disease specialists, microbiologists, and epidemiologists, on both the human and the veterinary sides, should be strengthened and readied for appropriate action whenever complex, zoonotic, public health issues occur.

Top

Angelo PanComments to Author , Antonio Battisti, Alessia Zoncada, Francesco Bernieri, Massimo Boldini, Alessia Franco, Maurilio Giorgi, Manuela Iurescia, Silvia Lorenzotti, Mario Martinotti, Monica Monaci, and Annalisa Pantosti
Author affiliations: Istituti Ospitalieri di Cremona, Cremona, Italy (A. Pan, A. Zoncada, F. Bernieri, S. Lorenzotti, M. Martinotti); Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Rome, Italy (A. Battisti, A. Franco, M. Iurescia); Istituto Zooprofilattico Sperimentale delle Regioni Lombardia ed Emilia-Romagna, Cremona (M. Boldini); Azienda Sanitaria Locale di Cremona, Cremona (M. Giorgi); Istituto Superiore di Sanità, Rome (M. Monaci, A. Pantosti)

Top

References

  1. Wulf  M, Voss  A. MRSA in livestock animals—an epidemic waiting to happen? Clin Microbiol Infect. 2008;14:51921. DOIPubMedGoogle Scholar
  2. Wulf  MW, Sørum  M, van Nes  A, Skov  R, Melchers  WJ, Klaassen  CH, Prevalence of methicillin-resistant Staphylococcus aureus among veterinarians: an international study. Clin Microbiol Infect. 2008;14:2934. DOIPubMedGoogle Scholar
  3. Wulf  MW, Markestein  A, van der Linden  FT, Voss  A, Klaassen  C, Verduin  CM. First outbreak of methicillin-resistant Staphylococcus aureus ST398 in a Dutch hospital, June 2007. Euro Surveill. 2008;13:pii 8051.
  4. Ekkelenkamp  MB, Sekkat  A, Carpaij  N, Troelstra  A, Bonten  MJM. Endocarditis due to meticillin-resistant Staphylococcus aureus originating from pigs [in Dutch]. Ned Tijdschr Geneeskd. 2006;150:24427.PubMedGoogle Scholar
  5. Report of the Task Force on Zoonoses. Data collection on a proposal for technical specifications for a baseline survey on the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in breeding pigs. European Food Safety Authority Jounral. 2007;129:114.
  6. Baron  F, Cochet  MF, Pellerin  JL, Ben Zakour  N, Lebon  A, Navarro  A, Development of a PCR test to differentiate between Staphylococcus aureus and Staphylococcus intermedius. J Food Prot. 2004;67:23025.PubMedGoogle Scholar
  7. Boye  K, Bartels  MD, Andersen  IS, Møller  JA, Westh  H. A new multiplex PCR for easy screening of methicillin-resistant Staphylococcus aureus SCCmec types I–V. Clin Microbiol Infect. 2007;13:7257. DOIPubMedGoogle Scholar
  8. Zhang  K, McClure  JA, Elsayed  S, Louie  T, Conly  JM. Novel multiplex PCR assay for characterization and concomitant subtyping of staphylococcal cassette chromosome mec types I to V in methicillin-resistant Staphylococcus aureus. J Clin Microbiol. 2005;43:502633. DOIPubMedGoogle Scholar
  9. van Duijkeren  E, Ikawaty  R, Broekhuizen-Stins  MJ, Jansen  MD, Spalburg  EC, de Neeling  AJ, Transmission of methicillin-resistant Staphylococcus aureus strains between different kinds of pig farms. Vet Microbiol. 2008;126:3839. DOIPubMedGoogle Scholar
  10. Monaco  M, Antonucci  R, Palange  P, Venditti  M, Pantosti  A. Methicillin-resistant Staphylococcus aureus necrotizing pneumonia. Emerg Infect Dis. 2005;11:16478.PubMedGoogle Scholar

Top

Table

Top

Cite This Article

DOI: 10.3201/eid1505.081417

Related Links

Top

Table of Contents – Volume 15, Number 5—May 2009

EID Search Options
presentation_01 Advanced Article Search – Search articles by author and/or keyword.
presentation_01 Articles by Country Search – Search articles by the topic country.
presentation_01 Article Type Search – Search articles by article type and issue.

Top

Comments

Please use the form below to submit correspondence to the authors or contact them at the following address:

Angelo Pan, Divisione di Malattie Infettive, Istituti Ospitalieri di Cremona, Largo Priori 1, 26100 Cremona, Italy

Send To

10000 character(s) remaining.

Top

Page created: December 16, 2010
Page updated: December 16, 2010
Page reviewed: December 16, 2010
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
file_external