Noella Gardella

Community-associated methicillin-resistant Staphylococcus aureus, eastern Argentina

Sixty-nine community-associated methicillin-resistant Staphylococcus aureus recovered in 6 healthcare centers from northeastern and eastern Argentina were genotyped by pulsed-field gel electrophoresis. The predominant pulsotype was widely distributed harbored SCCmec type IV and Panton-Valentine leukocidin genes. Representative isolates were characterized by multilocus sequence typing and spa typing, demonstrating that this clone belonged to ST5 and spa type 311.

Prevalence and characterization of methicillin-resistant Staphylococcus aureus among healthy children in a city of Argentina

Community acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is a major global problem. Healthy carriers of S. aureus strains have an important role in the dissemination of this bacterium. The aim of this study was to estimate the prevalence of S. aureus and methicillin-resistant S. aureus (MRSA) carriage among healthy children in a city of Buenos Aires province, Argentina, and to determine the potential risk factors for its acquisition. We also described the molecular features of MRSA strains circulating in this population. S. aureus carriage was investigated in all children attending the last year of kindergarten during the 2008 school- year period. Household contacts of MRSA carriers were also screened. Of 316 healthy children, 98 (31.0%) carried S. aureus, including 14 MRSA carriers (4.4%) and 84 methicillin susceptible S. aureus (MSSA) carriers (26.6%). All MRSA isolates carried the SCCmec type IV cassette. Eight of the fourteen isolates were closely related to the clone responsible for most severe community-acquired MRSA infections caused in our country (CAA: PFGE A, SCCmec IV, spa t311, ST5). Two subtypes (A(1) and A(2)) were distinguished in this group by PFGE. Both had agr type II and presented the same virulence determinants, except for PVL coding genes and sea that were only harbored by subtype A(1). Our results, based on the analysis of MRSA isolates recovered in the screening of healthy children, provide evidence of a community reservoir of the major CA-MRSA clone described in Argentina.

Methicillin-resistant Staphylococcus aureus in community-acquired meningitis

Historically, infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have been associated with healthcare settings. However, since the 1990s, community-acquired MRSA (CA-MRSA) infections have been increasingly recognized [1]. The microorganisms involved differ from those related to nosocomial infections in the presence of type IV staphylococcal cassette chromosome (SCC) mec elements, virulence genes encoding a toxin called Panton–Valentine leukocidin (PVL), which is not found in HA-MRSA isolates [2], and in the lack of the typical multiresistance pattern present in nosocomial staphylococci. Even though most infections caused by CA-MRSA in the community involve skin and soft tissues, and invasive CA-MRSA infections have been reported infrequently until now, their incidence is increasing [3]. Among the life-threatening community-acquired staphylococcal infections, meningitis has fortunately been reported only sporadically, accounting for less than 3% of cases diagnosed as bacterial in origin [4, 5]. Considering the rarity of staphylococcal meningitis cases, it is not surprising that the role of CA-MRSA remains obscure, at least in our region, since almost no data is available on the prevalence of these strains. Nevertheless, hospital-acquired MRSA infections progressing to meningitis or cerebral abscesses are significant [6, 7]. The lack of accompanying resistance in a large series of CNS infections reported by Jones et al. [7] is noteworthy and may suggest the introduction and dissemination of CA-MRSA in the participating hospitals. Here, we report on two children with acute bacterial meningitis due to community-acquired MRSA who were admitted to the Pediatric Hospital of Posadas, a 100-bed tertiary-care hospital located in a region of about 1.5-million inhabitants in northeastern Argentina. As a reference, MRSA accounted for one-third of SA isolates during 2004, and most of them did not exhibit the typical antimicrobial resistance profile associated with nosocomial MRSA. In December 2004 a 5-year-old girl was admitted with a 5-day history of sacral and lumbar pain, fever and a cough, which were being treated with amoxicillin-clavulanic acid. Diagnosis at admission was meningeal syndrome. Cerebrospinal fluid was purulent and direct Gram stain showed gram-positive cocci. Blood counts showed 15,400 leukocytes/mm and a hematocrit level of 29%. Her C-reactive protein level was 768 mg/l, and she was hematuric. A combined cefotaxime-vancomycin antibiotic treatment was administered immediately. Upon characterization of MRSA without any accompanying resistance, cefotaxime was replaced by rifampin. After treatment for 21 days, clinical evolution was excellent and there was no evidence of neurologic sequelae. In January 2005, a 6-year-old boy from Posadas City was brought to the hospital with fever and a diffuse petechial rash; the rash had been present for 48 h and he had a 24-h history of headache and urinary incontinence. The severity of symptoms led to an initial diagnosis of anaphylactic shock, and he was admitted directly to the emergency room; he was then transferred to the intensive care unit, where he was treated with diphenhydramine, noradrenaline and corticoids. After medical reanimation was required, the clinical diagnosis was changed to septic shock and meningitis, and he was treated with cefotaxime and acyclovir. Cerebrospinal fluid analysis showed a leukocyte count of 528/mm, a glucose level of 0.51 (serum glucose 0.86), and a protein level of 0.31 g/l. Blood analysis showed definite leukopenia (leukocyte count about 3,100/mm). From day 3 after admission, when cultures of both blood and cerebrospinal fluid grew MRSA M. von Specht . P. Tagliaferri Hospital Público Provincial de Pediatría de Autogestión, Avenida Mariano Moreno 110, 3300-Posadas, Provincia de Misiones, Argentina

Methicillin-resistant Staphylococcus aureus ST30-SCCmec IVc clone as the major cause of community-acquired invasive infections in Argentina

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have become a major concern worldwide. We conducted a prospective multicenter study of invasive CA-MRSA to evaluate clinical features and genotype of strains causing invasive infections in Argentina. A total of 55 patients with invasive CA-MRSA infections were included. Most patients (60%) had bloodstream infections, 42% required admission to intensive care unit and 16% died. No CA-MRSA isolates were multiresistant (resistant ⩾3 classes of antibiotics). All isolates carried Panton-Valentine leukocidin (PVL) genes and staphylococcal cassette chromosome (SCCmec) type IV. The majority CA-MRSA strains belonged to ST30 and had identical pulsed-field gel electrophoresis (PFGE) patterns, qualifying as a clonal dissemination of a highly transmissible strain. The main clone recovered from patients with CA-MRSA invasive infections was genotyped as pulsed-field gel electrophoresis type C-ST30, SCCmec type IVc-spa type 019, PVL positive. It has become predominant and replaced the previously described CA-MRSA clone (PFGE type A, ST5, SCCmec type IV, spa type 311).

The length of the Staphylococcus aureus protein A polymorphic region regulates inflammation: impact on acute and chronic infection.

Staphylococcus aureus protein A (SpA) plays a critical role in the induction of inflammation. This study was aimed to determine whether the number of short sequence repeats (SSRs) present in the polymorphic region modulates the inflammatory response induced by SpA. We demonstrated that there is a dose-response effect in the activation of interferon (IFN)-β signaling in airway epithelial and immune cells, depending on the number of SSRs, which leads to differences in neutrophil recruitment. We also determined that a significant proportion of isolates from patients with chronic infections such as osteomyelitis and cystic fibrosis carry fewer SSRs than do isolates from patients with acute infections or healthy carriers and that there was an inverse correlation between the number of SSRs and the length of disease course. Given the importance of IFN signaling in eradication of S. aureus, loss of SSRs may represent an advantageous mechanism to adapt to and persist in the host.

Characteristics of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains isolated from skin and soft-tissue infections in Uruguay.

We analyzed 90 nonduplicates community-associated methicillin-resistant S. aureus (CA-MRSA) strains isolated from skin and soft-tissue infections. All strains were mecA positive. Twenty-four of the 90 strains showed inducible macrolide-lincosamide-streptogramin B resistance. All strains produced α-toxin; 96% and 100% of them displayed positive results for lukS-F and cna genes, respectively. Eigthy-five strains expressed capsular polysaccharide serotype 8. Six different pulsotypes were discriminated by pulsed-field gel electrophoresis (PFGE) and three predominant groups of CA-MRSA strains (1, 2, and 4) were identified, in agreement with phenotypic and genotypic characteristics. Strains of group 1 (pulsotype A, CP8+, and Panton-Valentine leukocidin (PVL)+) were the most frequently recovered and exhibited a PFGE band pattern identical to other CA-MRSA strains previously isolated in Uruguay and Brazil. Three years after the first local CA-MRSA report, these strains are still producing skin and soft-tissue infections demonstrating the stability over time of this community-associated emerging pathogen.

Prospective Multicenter Study of Community-Associated Skin and Skin Structure Infections due to Methicillin-Resistant Staphylococcus aureus in Buenos Aires, Argentina

Background Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is now the most common cause of skin and skin structure infections (SSSI) in several world regions. In Argentina prospective, multicenter clinical studies have only been conducted in pediatric populations. Objective Primary: describe the prevalence, clinical and demographic characteristics of adult patients with community acquired SSSI due to MRSA; secondary: molecular evaluation of CA-MRSA strains. Patients with MRSA were compared to those without MRSA. Materials and Methods Prospective, observational, multicenter, epidemiologic study, with molecular analysis, conducted at 19 sites in Argentina (18 in Buenos Aires) between March 2010 and October 2011. Patients were included if they were ≥14 years, were diagnosed with SSSI, a culture was obtained, and there had no significant healthcare contact identified. A logistic regression model was used to identify factors associated with CA-MRSA. Pulse field types, SCCmec, and PVL status were also determined. Results A total of 311 patients were included. CA-MRSA was isolated in 70% (218/311) of patients. Clinical variables independently associated with CA-MRSA were: presence of purulent lesion (OR 3.29; 95%CI 1.67, 6.49) and age <50 years (OR 2.39; 95%CI 1.22, 4.70). The vast majority of CA-MRSA strains causing SSSI carried PVL genes (95%) and were SCCmec type IV. The sequence type CA-MRSA ST30 spa t019 was the predominant clone. Conclusions CA-MRSA is now the most common cause of SSSI in our adult patients without healthcare contact. ST30, SCCmec IV, PVL+, spa t019 is the predominant clone in Buenos Aires, Argentina.

Estudio comparativo de clones de aislamientos de Staphylococcus Aureus resistentes a meticilina prevalentes en la Argentina

Fil: Gardella, Noella. Universidad de Buenos Aires. Facultad de Farmacia y Bioquimica; Argentina

Application of Molecular Typing Methods to the Study of Medically Relevant Gram-Positive Cocci

Strain typing is an integral part of epidemiological investigations of bacterial infections. Typing methods fall into two broad categories: phenotypic and genotypic methods. Phenotypic methods are those that characterize the products of gene expression in order to differentiate strains. Properties such as biochemical profiles, antimicrobial susceptibility profiles, bacteriophage types, and antigens present on the cell surface are examples of phenotypic methods that can be used for typing isolates. Since they involve gene expressions, these properties have a tendency to vary, based on changes in growth conditions and growth phase, being often difficult to detect.