Nosocomial bloodstream infections in a nationwide study: comparison between solid organ transplant patients and the general population.

BACKGROUND: The incidence of bloodstream infection (BSI) varies according to the transplanted organ. Mortality can be as high as 24%, with a significant impact on graft survival. Transplantation is a risk factor for multidrug-resistant (MDR) organisms, but comparison with a non-transplanted population in a single large cohort has not been described. METHODS: This is a prospective nationwide study (16 centers) reporting data on 2364 monomicrobial nosocomial BSIs, comparing 83 episodes in solid organ transplant patients with 2447 BSIs occurring in the general hospital population. RESULTS: The prevalence of groups of infecting organisms (gram-positive, gram-negative, and fungi) was similar between transplant patients and the general population and a similar crude mortality rate was observed (34.9% in transplant vs. 43.3% in non-transplant patients). Staphylococcus aureus was the single most frequently isolated organism in both groups, and Acinetobacter species was more frequently isolated in the general population. Regarding MDR organisms, Klebsiella species, and Enterobacter species resistant to cefepime, as well as Acinetobacter species resistant to meropenem, were significantly more frequent in transplant patients. CONCLUSION: Antimicrobial resistance is higher, particularly among gram-negative bacteria in the transplant population, although the overall mortality rate between transplant and non-transplant patients with nosocomial BSI is similar.

Oxacilin-resistant Coagulase-negative staphylococci (CoNS) bacteremia in a general hospital at São Paulo city, Brasil.

In the last decades, coagulase-negative staphylococci (CoNS), especially Staphylococcus epidermidis have become an important cause of bloodstream infections. In addition, rates of methicillin-resistance among CoNS have increased substantially, leading to the use of glicopeptides for therapy. The objective of this study was to evaluate eleven consecutives clinically relevant cases of oxacillin-resistant CoNS bacteremia in a general hospital localized in São Paulo city, Brazil. Five different species were identified by different phenotypic methods, including S. epidermidis (5), S. haemolyticus (3), S. hominis (1), S. warneri (1) and S. cohnii subsp urealyticus (1). A variety of Pulsed Field Gel Electrophoresis profiles was observed by macrorestriction DNA analysis in S. epidermidis isolates, but two of three S. haemolyticus isolates presented the same profile. These data indicated the heterogeneity of the CoNS isolates, suggesting that horizontal dissemination of these microorganisms in the investigated hospital was not frequent. One S. epidermidis and one S. haemolyticus isolates were resistant to teicoplanin and susceptible to vancomycin. The selective pressure due to the use of teicoplanin in this hospital is relevant.

An outbreak of catalase-negative methicillin-resistant Staphylococcus aureus.

The wide dissemination of a major epidemic methicillin-resistant Staphylococcus aureus (MRSA) clone in Brazilian hospitals (Brazilian clone) limits the value of molecular typing techniques such as pulsed-field gel electrophoresis (PFGE) for outbreak investigation. We report the first outbreak of a catalase-negative strain of MRSA, which was initially detected by the unusual result of this phenotypical test. The outbreak occurred in the Hospital Sanatorinhos de Carapicuíba, a 237-bed secondary hospital located in São Paulo, Brazil. From May to August 2002, a total of 11 MRSA isolates were recovered from four patients in the intensive care unit. All the isolates were catalase negative and susceptible only to vancomycin and linezolid. Three of the four patients eventually died. Molecular typing demonstrated an indistinguishable PFGE pattern among the 11 isolates, with similarities to the Brazilian clone and the hospital's usual MRSA strain. This report emphasizes the importance of an uncommon phenotypical result as a marker for initiating an outbreak investigation and should encourage clinical laboratories to recognize and report such isolates.

Detection of colonization by carbapenem-resistant organisms by real-time polymerase chain reaction from rectal swabs in patients with chronic renal disease.

BACKGROUND: Carbapenem-resistant organism (CRO) colonization is a serious problem that increases the risk of infection and contributes to dissemination of antimicrobial resistance in healthcare-associated environments. The risk of acquisition and dissemination of CRO is high in chronic renal failure patients and the surveillance culture is recommended as a component of infection control programmes. AIM: To assess colonization by CRO, comparing phenotypic and molecular-based methods of diagnostics, in rectal swabs in a large population of chronic renal failure patients. METHODS: A total of 1092 rectal swabs (ESwab™) were collected at two different times from 546 chronic kidney disease (CKD) patients from a specialized tertiary care university centre. They were divided into three groups: conservative treatment (N = 129), dialysis (N = 217), and transplanted patients (N = 200). A chromogenic (CHROMagar™) KPC agar and the multiplex real-time polymerase chain reaction (qPCR) targeting carbapenemase-encoding genes were tested as phenotypic and molecular screening for carbapenemase production. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and conventional PCR were also performed on the isolates grown on chromogenic agar. FINDINGS: Among the 1092 samples, 150 (13.7%) were identified as CRO producers according to chromogenic agar. Only 26 (2.4%) were confirmed as KPC by conventional PCR. According to qPCR direct from swab, 31 (2.8%) were positive for KPC, 39 (3.6%) for GES, and three (0.3%) for SPM with kappa index of 0.256. CONCLUSION: The qPCR technique provides faster results when compared to culture method and enables rapid implementation of control measures and interventions to reduce the spread of CRO in healthcare settings, especially among CKD patients.

Unusual association of NDM-1 with KPC-2 and armA among Brazilian Enterobacteriaceae isolates.

We report the microbiological characterization of four New Delhi metallo-ß-lactamase-1 (blaNDM-1)-producing Enterobacteriaceae isolated in Rio de Janeiro, Brazil. blaNDM-1 was located on a conjugative plasmid and was associated with Klebsiella pneumoniae carbapenemase-2 (blaKPC-2) or aminoglycoside-resistance methylase (armA), a 16S rRNA methylase not previously reported in Brazil, in two distinct strains of Enterobacter cloacae. Our results suggested that the introduction of blaNDM-1 in Brazil has been accompanied by rapid spread, since our isolates showed no genetic relationship.

Phagocytosis and killing of epidemic methicillin-resistant Staphylococcus aureus by human neutrophils and monocytes.

Staphylococcus aureus is a pathogen that has been associated with nosocomial infections since the preantibiotic era. Since the introduction of antibiotics in medical practice in the 1940 s, methicillin-resistant S. aureus (MRSA) strains have been emerging in various parts of the world. In view of the important role of the phagocytic system in the defense against this bacteria, we decided to study phagocytosis by neutrophils and monocytes of an epidemic MRSA strain in São Paulo, Brazil, in comparison with methicillin-sensitive strains. Complement system opsonins are fundamental for efficient ingestion of the resistant and sensitive strains by both types of phagocytes. We found no association of the opsonic requirement of the MRSA strain with the multiresistance phenotype. On the other hand, the MRSA strain was found to be more resistant to the effector mechanisms of neutrophils than both sensitive strains when opsonized with fresh serum, despite the phagocytosis results. This fact suggests that the intracellular killing of S. aureus is an additional parameter of bacterial virulence, but new approaches must be implemented to study the interactions of this MRSA strain with phagocytes in order to investigate the possible factors involved in its behavior in response to neutrophil effector mechanisms.

Mycobacterium tuberculosis bacteremia diagnosed in an HIV-negative patient in Brazil: a rare or an under-reported event?

A case of Mycobacterium tuberculosis bacteremia in an HIV negative immunodepressed patient was described using the BACTEC 460 TB system. This bacterium should be investigated in the blood of immunodepressed non-HIV infected patients with prolonged fever.

Characterization of bacteriophages infecting clinical isolates of Pseudomonas aeruginosa stored in a culture collection.

Some clinical isolates of Pseudomonas aeruginosa stored in our culture collection did not grow or grew poorly and showed lysis on the culture plates when removed from the collection and inoculated on MacConkey agar. One hypothesis was that bacteriophages had infected and killed those clinical isolates. To check the best storage conditions to maintain viable P. aeruginosa for a longer time, clinical isolates were stored at various temperatures and were grown monthly. We investigated the presence of phage in 10 clinical isolates of P. aeruginosa stored in our culture collection. Four strains of P. aeruginosa were infected by phages that were characterized by electron microscopy and isolated to assess their ability to infect. The best condition to maintain the viability of the strains during storage was in water at room temperature. Three Siphoviridae and two Myoviridae phages were visualized and characterized by morphology. We confirmed the presence of bacteriophages infecting clinical isolates, and their ability to infect and lyse alternative hosts. Strain PAO1, however, did not show lysis to any phage. Mucoid and multidrug resistant strains of P. aeruginosa showed lysis to 50% of the phages tested.

Microbial profile and antibiotic susceptibility of culture-positive bacterial endophthalmitis.

PURPOSE: To assess the distribution of microorganisms isolated from patients with bacterial endophthalmitis and their antimicrobial susceptibility. METHODS: Retrospective analysis of medical and microbiological records of patients with suspected diagnosis of endophthalmitis. The following information was assessed: number of presumed and culture-positive endophthalmitis cases, source of infection, microbiological result (aqueous and/or vitreous culture and Gram staining), microbial characterization and distribution, and antimicrobial susceptibility. RESULTS: A total of 107 (46%) of 231 patients with bacterial endophthalmitis showed positive results by gram stain or culture. Of these, 97 (42%) patients were positive for culture only. Most of them (62%) were secondary to a surgical procedure (postoperative), 12% were posttraumatic and 26% were secondary to an unknown source or the data were unavailable. A total of 100 microorganisms were isolated (38 aqueous and 67 vitreous samples) from the 97 culture-positive cases (91% were gram-positive and 9% were gram-negative). Coagulase-negative Staphylococcus(CoNS) (48%) were the most frequently isolated, followed by Stretococcus viridans(18%), and Staphylococcus aureus(13%). The antimicrobial susceptibility for CoNS was as follows: amikacin-91.6%, cephalothin-97.9%, ceftriaxone-50%, ciprofloxacin-62.5%, chloramphenicol-91.8%, gatifloxacin-79.5%, gentamicin-72.9%, moxifloxacin-89.5%, ofloxacin-70.8%, oxacillin-58.3%, penicillin-33.3%, tobramycin-85.4%, and vancomycin-100%. CONCLUSION: Gram-positive bacteria were the major causes of infectious endophthalmitis in this large series, usually following surgery. CoNS was the most common isolate. Of interest, susceptibility to oxacillin and fourth-generation quinolones was lower than previously published.

New multilocus sequence typing of MRSA in São Paulo, Brazil.

An increased incidence of nosocomial and community-acquired infections caused by methicillin-resistant Staphylococcus aureus (MRSA) has been observed worldwide. The molecular characterization of MRSA has played an important role in demonstrating the existence of internationally disseminated clones. The use of molecular biology methods in the surveillance programs has enabled the tracking of MRSA spread within and among hospitals. These data are useful to alert nosocomial infection control programs about the potential introduction of these epidemic clones in their areas. Four MRSA blood culture isolates from patients hospitalized at two hospitals in the city of São Paulo, Brazil, were analyzed; one of them was community acquired. The isolates were characterized as SCCmec, mecA and PVL by PCR, pulsed-field gel electrophoresis (PFGE) profile and molecular sequence typing (MLST) genotyping. The isolates presented type IV SCCmec, and none proved to be positive for PVL. The isolates showed a PFGE profile similar to the pediatric clone. MLST genotyping demonstrated that the isolates belonged to clonal complex 5 (CC5), showing a new yqiL allele gene, resulting in a new sequence typing (ST) (1176). Our results showed that strains of MRSA carrying a new ST are emerging in community and nosocomial infections, including bacteremia, in São Paulo, Brazil.

Characterization of bacteriophages infecting clinical isolates of Pseudomonas aeruginosa stored in a culture collection

Some clinical isolates of Pseudomonas aeruginosa stored in our culture collection did not grow or grew poorly and showed lysis on the culture plates when removed from the collection and inoculated on MacConkey agar. One hypothesis was that bacteriophages had infected and killed those clinical isolates. To check the best storage conditions to maintain viable P. aeruginosa for a longer time, clinical isolates were stored at various temperatures and were grown monthly. We investigated the presence of phage in 10 clinical isolates of P. aeruginosa stored in our culture collection. Four strains of P. aeruginosa were infected by phages that were characterized by electron microscopy and isolated to assess their ability to infect. The best condition to maintain the viability of the strains during storage was in water at room temperature. Three Siphoviridae and two Myoviridae phages were visualized and characterized by morphology. We confirmed the presence of bacteriophages infecting clinical isolates, and their ability to infect and lyse alternative hosts. Strain PAO1, however, did not show lysis to any phage. Mucoid and multidrug resistant strains of P. aeruginosa showed lysis to 50% of the phages tested.

Acute endophthalmitis following intravitreal bevacizumab (Avastin) injection.

PURPOSE: To report two cases of acute endophthalmitis following intravitreal bevacizumab injection. METHODS: Two patients with exudative age-related macular degeneration were treated sequentially with an intravitreal injection of bevacizumab and developed signs of severe but painless infectious endophthalmitis 2 days later. Vitreous samples were obtained, followed by the injection of vancomycin 1 mg/0.1 ml and ceftazidime 2.25 mg/0.1 ml. Pulsed-field gel electrophoresis (PFGE) was used to determine whether the isolated microorganisms were the same. RESULTS: Coagulase-negative staphylococci were identified and isolated from the vitreous specimen of both patients. PFGE revealed different patterns of banding, excluding that interpatient contamination occured. CONCLUSIONS: Infectious endophthalmitis is a potential complication of intravitreal bevacizumab injection.

New multilocus sequence typing of MRSA in São Paulo, Brazil

An increased incidence of nosocomial and community-acquired infections caused by methicillin-resistant Staphylococcus aureus (MRSA) has been observed worldwide. The molecular characterization of MRSA has played an important role in demonstrating the existence of internationally disseminated clones. The use of molecular biology methods in the surveillance programs has enabled the tracking of MRSA spread within and among hospitals. These data are useful to alert nosocomial infection control programs about the potential introduction of these epidemic clones in their areas. Four MRSA blood culture isolates from patients hospitalized at two hospitals in the city of São Paulo, Brazil, were analyzed; one of them was community acquired. The isolates were characterized as SCCmec, mecA and PVL by PCR, pulsed-field gel electrophoresis (PFGE) profile and molecular sequence typing (MLST) genotyping. The isolates presented type IV SCCmec, and none proved to be positive for PVL. The isolates showed a PFGE profile similar to the pediatric clone. MLST genotyping demonstrated that the isolates belonged to clonal complex 5 (CC5), showing a new yqiL allele gene, resulting in a new sequence typing (ST) (1176). Our results showed that strains of MRSA carrying a new ST are emerging in community and nosocomial infections, including bacteremia, in São Paulo, Brazil.

Lesões cervicais e infecção pelo papilomavirus humano no sistema prisional da cidade de São Paulo, Brasil / Cervical lesions and human papillomavirus infection in women at a prisional system in São Paulo city, Brazil

A relação entre o câncer cervical e a infecção pelo Papilomavírus Humano (HPV) está bem estabelecida. Múltiplos parceiros e múltiplas práticas sexuais são os fatores de risco associados à infecção pelo HPV. Existe uma grande probabilidade em que as mulheres internas em presídios tenham uma maior suscetibilidade de adquirir a infecção genital. A avaliação de alterações celulares, pelo exame de Papanicolaou, e identificação molecular de DNA-HPV de alto risco são utilizadas para a detecção e prevenção do câncer cervical. Quatrocentas e nove amostras cervicais de mulheres internas, nopresídio feminino da cidade de São Paulo, com idade entre 18 e 60 anos, foram analisadas, em 2006. Os achados celulares foram classificados com base no Sistema Bethesda (2001). O DNA-HPV foi identificado pelo PCR convencional, empregando os primersuniversais MY09/11, e os tipos identificados por PCR/RFLP, utilizando enzimas de restrição. Vinte e sete (6,60%) dos 409 esfregaços das internas do sistema penal revelaramLesões Escamosas Intraepiteliais de Baixo Grau (LSIL), 3 (11,11%) mostram alterações compatíveis com Lesões Escamosas Intraepiteliais de Alto Grau (HSIL), 5 (18,53%) exibiram Atipias Escamosas de Significado Indeterminado (ASC-US), 1 (3,70%) mostrou Células Glandulares Atípicas (CGA) e 1 (3,70%) revelou Carcinoma de Células Escamosas. DNA-HPV de alto risco foi identificado em 12 (44,43%) amostras (HPV 16, 18, 31, 33, 34, 39 e 61). Oito (29,62%) amostras revelaram infecção por HPV de baixo risco (HPV 6b). O presente estudo detectou uma alta prevalência de LSIL e HSIL associada à presença de DNA-HPV de alto risco, nas mulheres internas no sistema prisional.

The association between cervical cancer and Human PapillomavirusInfection (HPV) has been determinated. Multiple partners andmultiple sexual practices are risk factors associated with HPVinfection. There is a high probability that women resident in prisionscould be more susceptible to acquire genital HPV infection. Thescreening of cellular changes by pap-smear and the molecularidentification of high risk DNA-HPV is usefull for the detection andprevention of cervical cancer. Four hundred nine samples of cervicalsmear from women resident in a prisional system in São Paulo,between 18 to 60 years old were analyzed in 2006. The cellularresults were reported according to the Bethesda System Terminology,2001. The DNA-HPV detection was made by Conventional PCR usingConsensus Primers MY 09/11 and the HPV types were identify byPCR-RFLP using restriction endonuclease enzymes.Twenty seven(6,60%) out of 409 pap-smears samples showed pre malignant lesion.Seventeen (62,96%) out of these 27 samples revealed Low Squamous Intraepitheal Lesion (LSIL), 3 (11,11%) showed changessuggestive of High Squamous Intraepithelial Lesion (HSIL), 5(18,53%) samples presented Atypical Squamous Cells ofUndetermined Significance (ASC-US), 1 (3,70%) sample had AtypicalGlandular Cells (AGC), and 1 (3,70%) sample showed CervicalSquamous Carcinoma. High Risk DNA-HPV was identified in 12(44,43%) (HPV 16, 18, 31, 33, 34, 39 and 61). Eight (29,62%) samplesrevealed the low risk for neoplasic lesion subtype HPV-6b. Thepresent study reveal a high prevalence of LSIL and HSIL associatedwith the presence of High-risk DNA-HPV in women resident in aprisional system.

Detection and typing of human papillomavirus in cutaneous warts of patients infected with human immunodeficiency virus type 1.

BACKGROUND: Cutaneous warts are caused by human papillomavirus (HPV). To date, more than 120 different types of HPV are known, of which 80 have been completely characterized. Prevalence studies on types of HPV present in cutaneous warts have been carried out in immunocompetent individuals and immunosuppressed organ allograft recipients, but not in human immunodeficiency virus (HIV)-positive patients. OBJECTIVES: To determine the HPV types present in cutaneous warts of HIV-infected patients. METHODS: Twenty-five biopsies of cutaneous warts from HIV-infected patients and 14 samples from control non-HIV-infected patients were studied. HPV detection was performed by polymerase chain reaction using two sets of primers: MY09/MY11 and RK91. The type of HPV was determined by restriction fragment length polymorphism analysis and direct sequencing of the amplified products. RESULTS: HPV DNA was detected in 64% of cutaneous warts from HIV-infected patients and in 79% of samples from the control group. The HPV types identified in HIV-infected patients were: HPV 2 (38%), 57 (31%), 27 (12%), 6 (12%) and 7 (6%). HPV 2/27/57 predominated in both groups, being present in 81% of lesions from HIV-infected patients and 82% of samples from non-HIV-infected patients. HPV 6, a genital HPV type rarely found in cutaneous lesions, was detected in two warts from HIV-infected patients and in one lesion of the immunocompetent group. HPV 7, characteristically associated with butcher's warts, and recently detected in oral and perioral lesions of HIV-infected patients, was found for the first time in a non-facial lesion of an HIV-infected patient. CONCLUSIONS: This is the first study evaluating the prevalence of HPV types in cutaneous warts of HIV-infected patients and immunocompetent individuals in Brazil.

Mycobacteraemia among HIV-1-infected patients in São Paulo, Brazil: 1995 to 1998.

From July 1995 to August 1998, mycobacterial blood cultures were obtained from 1032 HIV-infected patients seen at the Centro de Referência e Treinamento de AIDS (CRTA), Hospital São Paulo (HSP), and Centro de Referência de AIDS de Santos (CRAS). Overall, 179 episodes of mycobacteraemia were detected: 111 (62.0%) at CRTA, 50 (27.9%) at HSP, and 18 (10.1%) at CRAS. The frequency of positive cultures declined sharply from 22.6% in 1995 to 6.9% in 1998, consistent with the decrease in opportunistic infections following the publicly funded distribution of highly active antiretroviral therapy. In 1995, mycobacteraemia was more frequently due to Mycobacterium avium complex (59.2%) than Mycobacterium tuberculosis (28.6%), whereas in 1998 the relative frequencies were reversed (28.6 vs. 64.3% respectively), probably justified by the increased virulence of M. tuberculosis and the greater risk of invasive infection in less-immunocompromised patients, including patients unaware they are infected with HIV.

Oxacilin-resistant Coagulase-negative staphylococci (CoNS) bacteremia in a general hospital at São Paulo city, Brasil / Bacteremias por Staphylococcus coagulase negativos oxacilina resistentes em um hospital na cidade de São Paulo, Brasil

In the last decades, coagulase-negative staphylococci (CoNS), especially Staphylococcus epidermidis have become an important cause of bloodstream infections. In addition, rates of methicillin-resistance among CoNS have increased substantially, leading to the use of glicopeptides for therapy. The objective of this study was to evaluate eleven consecutives clinically relevant cases of oxacillin-resistant CoNS bacteremia in a general hospital localized in São Paulo city, Brazil. Five different species were identified by different phenotypic methods, including S. epidermidis (5), S. haemolyticus (3), S. hominis (1), S. warneri (1) and S. cohnii subsp urealyticus (1). A variety of Pulsed Field Gel Electrophoresis profiles was observed by macrorestriction DNA analysis in S. epidermidis isolates, but two of three S. haemolyticus isolates presented the same profile. These data indicated the heterogeneity of the CoNS isolates, suggesting that horizontal dissemination of these microorganisms in the investigated hospital was not frequent. One S. epidermidis and one S. haemolyticus isolates were resistant to teicoplanin and susceptible to vancomycin. The selective pressure due to the use of teicoplanin in this hospital is relevant.

Staphylococcus coagulase negativos (SCoN), especialmente Staphylococcus epidermidis tem se tornado causa importante de infecções da corrente circulatória nas últimas décadas. Além disso, percentuais de resistência a meticilina entre os SCoN têm aumentado significativamente, levando ao uso de glicopeptídeos nestes pacientes. O objetivo deste estudo foi avaliar onze casos consecutivos de bacteremia clinicamente relevantes por SCoN oxacilina resistentes em um hospital localizado na cidade de São Paulo, Brasil. Cinco diferentes espécies foram identificadas por diferentes métodos fenotípicos, incluindo S. epidermidis (5), S. haemolyticus (3), S. hominis (1), S. warneri (1) e S. cohnii subsp urealyticus (1). Diferentes perfis eletroforéticos obtidos pela técnica de "Pulsed Field Gel Electrophoresis" foram observados na análise da macrorestrição do DNA nos isolados de S. epidermidis, mas dois dos três isolados de S. haemolyticus apresentaram o mesmo perfil. Esses dados indicam uma heterogeneidade nos isolados SCoN, sugerindo que a disseminação horizontal no hospital investigado não é freqüente. Um isolado de S. epidermidis e um de S. haemolyticus foram resistentes à teicoplanina e sensíveis à vancomicina. Observa-se a relevância da pressão seletiva pelo uso de teicoplanina nos pacientes deste hospital.

Typing of Enterococcus faecium by polymerase chain reaction and pulsed field gel electrophoresis

Polymerase chain reaction (PCR) with JB1 or REP consensus oligonucleotides and pulsed field gel electrophoresis (PFGE) were used to study genomic DNA extracted from 31 strains of enterococci. Eleven ATCC strains, representative of 11 species of Enterococcus, were initially tested by JB1-PCR, revealing that Enterococcus malodoratus and Enterococcus hirae presented identical banding patterns. Eight Enterococcus faecium isolates from Stanford University and 12 from Sao Paulo Hospital were studied by JB1-PCR, REP-PCR 1/2R and PFGE. Among the isolates from Stanford University, 5 genotypes were defined by JB1-PCR, 7 by REP-PCR 1/2R and 4 by PFGE. Among the isolates from Sao Paulo Hospital, 9 genotypes were identified by JB1-PCR, 6 by REP-PCR and 5 by PFGE. The three methods identified identical genotypes, but there was not complete agreement among them

Phagocytosis and killing of epidemic methicillin-resistant Staphylococcus aureus by human neutrophils and monocytes

Staphylococcus aureus is a pathogen that has been associated with nosocomial infections since the preantibiotic era. Since the introduction of antibiotics in medical practice in the 1940 s, methicillin-resistant S. aureus (MRSA) strains have been emerging in various parts of the world. In view of the important role of the phagocytic system in the defense against this bacteria, we decided to study phagocytosis by neutrophils and monocytes of an epidemic MRSA strain in São Paulo, Brazil, in comparison with methicillin-sensitive strains. Complement system opsonins are fundamental for efficient ingestion of the resistant and sensitive strains by both types of phagocytes. We found no association of the opsonic requirement of the MRSA strain with the multiresistance phenotype. On the other hand, the MRSA strain was found to be more resistant to the effector mechanisms of neutrophils than both sensitive strains when opsonized with fresh serum, despite the phagocytosis results. This fact suggests that the intracellular killing of S. aureus is an additional parameter of bacterial virulence, but new approaches must be implemented to study the interactions of this MRSA strain with phagocytes in order to investigate the possible factors involved in its behavior in response to neutrophil effector mechanisms.