Carbapenem-resistant Pseudomonas aeruginosa: association with virulence genes and biofilm formation

Abstract Pseudomonas aeruginosa is an opportunistic pathogen that causes frequently nosocomial infections, currently becoming more difficult to treat due to the various resistance mechanisms and different virulence factors. The purpose of this study was to determine the risk factors independently associated with the development of bacteremia by carbapenem-resistant P. aeruginosa, the frequency of virulence genes in metallo-β-lactamases producers and to evaluate their ability to produce biofilm. We conducted a case–control study in the Uberlândia Federal University – Hospital Clinic, Brazil. Polymerase Chain Reaction was performed for metallo-β-lactamases and virulence genes. Adhesion and biofilm assays were done by quantitative tests. Among the 157 strains analyzed, 73.9% were multidrug-resistant, 43.9% were resistant to carbapenems, 16.1% were phenotypically positive for metallo-β-lactamases, and of these, 10.7% were positive for blaSPM gene and 5.3% positive for blaVIM. The multivariable analysis showed that mechanical ventilation, enteral/nasogastric tubes, primary bacteremia with unknown focus, and inappropriate therapy were independent risk factors associated with bacteremia. All tested strains were characterized as strongly biofilm producers. A higher mortality was found among patients with bacteremia by carbapenem-resistant P. aeruginosa strains, associated independently with extrinsic risk factors, however it was not evident the association with the presence of virulence and metallo-β-lactamases genes.

Factors influencing survival in patients with multidrug-resistant Acinetobacter baumannii infection

Multidrug-resistant (MDR) Acinetobacter baumannii (Acb) is a rapidly emerging pathogen in healthcare settings. The aim of this study was to evaluate the predictors of poor outcome in patients with MDR Acb. This is the first report documenting factors influencing survival in patients with MDR Acb in this tertiary hospital. This study is a prospective of the hospital epidemiology database. A total of 73 patients with 84 Acb isolates were obtained between August 2009 and October 2010 in this hospital. In the present study, the 30-day mortality rate was 39.7%. Of 84 Acb isolates, 50 (59%) were MDR, nine (11%) were pan-resistant, and 25 (30%) were non-MDR. The non-MDR isolates were used as the control group. The factors significantly associated with multidrug resistance included previous surgeries, presence of comorbidity (renal disease), use of more than two devices, parenteral nutrition, and inappropriate antimicrobial therapy. Significant predictors of 30-day mortality in the univariate analysis included pneumonia, diabetes mellitus, renal disease, use of more than two devices, and inappropriate antimicrobial therapy administered within two days of the onset of infection. The factors associated with mortality in patients with MDR Acb infection in this study were: age > 60 years, pneumonia, diabetes mellitus, renal disease, use of more than two invasive procedures, and inappropriate antimicrobial therapy. Vigilance is needed to prevent outbreaks of this opportunistic and deadly pathogen.

Methicillin-resistant Staphylococcus aureus bloodstream infection: risk factors and clinical outcome in non-intensive-care units / Infecção de corrente sanguínea por Staphylococcus aureus resistente à meticilina: fatores de risco e evolução clínica em unidades não críticas

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) is spread out in hospitals across different regions of the world and is regarded as the major agent of nosocomial infections, causing infections such as skin and soft tissue pneumonia and sepsis. The aim of this study was to identify risk factors for methicillin-resistance in Staphylococcus aureus bloodstream infection (BSI) and the predictive factors for death. METHODS: A retrospective cohort of fifty-one patients presenting bacteraemia due to S. aureus between September 2006 and September 2008 was analysed. Staphylococcu aureus samples were obtained from blood cultures performed by clinical hospital microbiology laboratory from the Uberlândia Federal University. Methicillinresistance was determined by growth on oxacillin screen agar and antimicrobial susceptibility by means of the disk diffusion method. RESULTS: We found similar numbers of MRSA (56.8%) and methicillin-susceptible Staphylococcus aureus (MSSA) (43.2%) infections, and the overall hospital mortality ratio was 47%, predominantly in MRSA group (70.8% vs. 29.2%) (p=0.05). Age (p=0.02) was significantly higher in MRSA patients as also was the use of central venous catheter (p=0.02). The use of two or more antimicrobial agents (p=0.03) and the length of hospital stay prior to bacteraemia superior to seven days (p=0.006) were associated with mortality. High odds ratio value was observed in cardiopathy as comorbidity. CONCLUSIONS: Despite several risk factors associated with MRSA and MSSA infection, the use of two or more antimicrobial agents was the unique independent variable associated with mortality.

INTRODUÇÃO: Methicillin-resistant Staphylococcus aureus (MRSA), se disseminou nos hospitais em diferentes regiões do globo, e é atualmente o principal agente de infecções hospitalares causando infecções de pele, tecidos moles, pneumonia e sepse. O objetivo deste estudo foi identificar fatores de risco para resistência à meticilina em infecções de corrente sanguínea por Staphylococcus aureus e fatores preditivos de mortalidade. MÉTODOS: Uma coorte de 51 pacientes apresentando bacteremia por S. aureus, entre setembro de 2006 a setembro de 2008 foi analisada. Amostras de S. aureus foram obtidas a partir de hemoculturas realizadas pelo laboratório de microbiologia do hospital de clínicas da Universidade Federal de Uberlândia. A resistência à meticilina foi determinada pelo crescimento no agar triagem para oxacilina e a sensibilidade aos antimicrobianos pelo método de difusão em agar. RESULTADOS: Infecções por MRSA (56,8%) e methicillin-susceptible Staphylococcus aureus (MSSA) (43,2%) foram similares e a taxa de mortalidade hospitalar foi de 47%, predominantemente no grupo infectado por MRSA (70,8% vs. 29,2%) (p=0,05). Idade (p=0,02) e a presença de cateter vascular central (p=0,02) foram significantes no grupo de infectados por MRSA. A evolução demonstrou que o uso de dois ou mais agentes antimicrobianos (p=0,03) e tempo de internação prévio à bacteremia superior a sete dias (p=0,006) foram associados à morte. Altos valores de odds ratio foram observados para cardiopatia como comorbidade. CONCLUSÕES: Embora vários fatores de risco tenham sido associados a infecções por MRSA e MSSA e mortalidade o uso de dois ou mais agentes antimicrobianos foi a única variável independente para mortalidade.