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

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.(AU)

Prior oropharyngeal colonization and ventilator-associated pneumonia

This study evaluated the relationship between previous colonization of the oropharynx and development of ventilator-associated pneumonia through the classification of genomic fingerprint pattern by pulsed-field gel electrophoresis of both oxacillin-resistant and oxacillin-susceptible Staphylococcus aureus isolates obtained from hospitalized patients in an intensive care unit.

Experimental model in the qualitative and quantitative assessment of non-Helicobacter gastric microflora under proton pump inhibitors action / Modelo experimental na avaliação qualitativa e quantitativa da microflora gástrica não-Helicobacter sob ação de inibidores de bomba de próton

PURPOSE: To evaluate models of gastric material collection from Wistar rats with and without using proton pump inhibitors(PPIs). METHODS: Twenty-four rats underwent intraperitoneal omeprazol treatment, and other 12 received similar treatment with 0.9 percent saline. All animals underwent collection of gastric material samples, after stomach removal, by either biopsies, or aspirates, or swabs. Samples were bacteriologically processed in order to identify species and strains. Values are described as natural logarithm of colony former units per mL [Ln(CFU/mL)]. Kruskal-Wallis and Mann-Whitney non-parametric tests were used, and p<0.05 was set as statistically significant. RESULTS: Significant difference was not seen for Ln (UFC/mL) values among the three methods of collection irrespective of using or not omeprazol. Also, significant difference was not seen in Ln (UFC/mL) values when comparing a method with each others, either using omeprazol or placebo. A significant increase of bacteria strains occurred when PPI was used, and this was seen on the three ways of collection, mainly in biopsy and swab. CONCLUSION: No difference occurred among the three methods of collecting bacteria samples from stomachs of rats, either when using placebo or omeprazol. A remarkable change is seen on animals bacterial microflora when PPIs are used, and bacteria are better identified when swab and biopsy are used.(AU)

OBJETIVO: Avaliar modelos de coleta de material gástrico de ratos da linhagem Wistar, com e sem o uso de inibidores de bomba de próton (IBPs). MÉTODOS: 24 ratos foram submetidos a tratamento com omeprazol intraperitoneal e 12 outros ratos receberam tratamento semelhante com solução salina a 0,9 por cento. Os animais foram submetidos a coleta de amostras de material gástrico, após retirada do estômago, utilizando-se de biópsias, aspirados ou swabs. Os materiais obtidos foram processados bacteriologicamente para identificação de espécimes quanto ao gênero. Os valores são descritos em logaritmo natural das unidades formadoras de colônias por mL [Ln(UFC/mL)]. Utilizou-se os testes não-paramétricos de Kruskal-Wallis e Mann-Whitney, considerando-se p<0,05 como estatisticamente significativo. RESULTADOS: Não se observou diferença significativa da quantidade de Ln(UFC/mL) entre os três métodos de coleta, independente do uso de omeprazol. Também não se observou diferença significativa de Ln(UFC/mL) ao comparar-se os métodos individualmente entre si nas condições de uso de omeprazol ou placebo. Houve aumento significativo da variedade de gêneros de bactérias com o uso de IBP, nos 3 métodos de coleta, sendo isto mais perceptível na biópsia e swab. CONCLUSÃO: Não houve diferença entre os três métodos de coleta de amostras bacterianas de estômago de ratos, tanto em uso de placebo quanto em uso de omeprazol. Nota-se uma mudança evidente da microflora bacteriana nos animais em uso de IBPs, sendo melhor identificado pelos métodos de swab e biópsia.(AU)

Conventional versus molecular tests (Multiplex PCR and PCR mecA gene) for detection of methicillin resistant Staphylococcus aureus

In this study, for detection of methicillin-resistant S. aureus (MRSA), a mecA multiplex PCR-based amplification was compared with the 1 µg oxacillin disk diffusion test, detection of minimal inhibitory concentration (MIC), and screening in agar with 4% NaCl and 6 µg/mL oxacillin. Among 24 isolates obtained from blood, mecA gene was detected in only 16 (66.7%) isolates by multiplex PCR. The MIC test showed a range of resistance to oxacillin from 0.19 to 512 µg/mL, among these isolates. Data obtained by screening and dilution tests showed that sensitivity to methicillin was 80.0% and 72.8%, respectively, when compared with the presence of mecA gene (multiplex). All isolates, including the negatives, when revaluated for mecA gene by PCR were positive. beta-lactamase production was positive for 20/25 isolates (80.0%). About » of patients died dispite most of them (83.3%) were adequately treated. The simultaneous identification of the bacteria and determination of this susceptibility to antibiotics are necessary for the choice of empiric antibiotic therapy in suspected staphylococcal sepse, but is important to considering the sensibility, specificity and validation of the available kits.

Nesse estudo, para detecção de S. aureus resistente à meticilina (MRSA), a amplificação do gene mecA baseada no multiplex PCR foi comparada com os testes de difusão com disco para 1 µg/mL de oxacilina, detecção da concentração inibitória mínima (CIM), meio de triagem com 4% de NaCl e 6 µg/mL de oxacilina. Na investigação de 24 isolados obtidos de sangue, o genótipo mecA foi detectado em apenas 16 (66,7%) dos isolados pelo multiplex PCR. A CIM apresentou valores variando de 0,19 a 512 µg/mL entre os isolados de MRSA. Os dados obtidos pelos testes de triagem e diluição em ágar apresentaram sensibilidades de 80,0% e 72,8% respectivamente, quando comparados com a presença do gene mecA (multiplex). Todos os isolados, incluindo os negativos, quando reavaliados com a técnica de PCR exclusivo para este gene, o resultado foi positivo. A produção de beta-lactamase foi positiva em 20/25 (80,0%) dos isolados. Cerca de » dos pacientes evoluiu para óbito apesar da maioria (83,3%) ter sido tratada adequadamente. A identificação simultânea da bactéria e sua susceptibilidade aos antibióticos é necessária para a escolha de uma terapia adequada para casos de sepse estafilocócica, mas é importante considerar a sensibilidade, especificidade e validação dos kits disponíveis.

Nosocomial outbreaks due to Pseudomonas aeruginosa and Acinetobacter baumannii in a Neonatal Intensive Care Unit (NICU) of the Uberlândia Federal University Hospital

The study documents the occurrence of two subsequent outbreaks in the NICU of HC-UFU, caused by epidemic strains of multiresistant Pseudomonas aeruginosa and Acinetobacter baumannii, that occurred between March/01 and September and between October/01 and March/02, respectively. The P. aeruginosa outbreak included seven neonates with conjunctivitis and three with bacteremia. A case-control study was conducted for the A. baumannii outbreak, with 11 and 22 neonates, respectively. The isolates of A. baumannii were resistant to gentamacin and ciprofloxacin. P. aeruginosa isolates were resistant to ampicillin/sulbactam gentamicin and ciprofloxacin. The hands of healthcare workers and environmental cultures were negative. The outbreak of P. aeruginosa resulted in the increase of use of imipenem, which could have favoured the emergence of a A. baumannii epidemic strain, despite of its susceptibility to this antibiotic. The risk factors for A. baumannii infection were: weight 1500g, age 7 days, hospitalization > 7 days and use of carbapenems. Containment of the two outbreaks was achieved by introduction of strict hygiene measures and careful nursing care of the infected infants. The reservatory and the route of transmission were not found.

O objetivo foi relatar a ocorrência de dois surtos subseqüentes na UTIN do HC-UFU, por amostras epidêmicas de P. aeruginosa e A. baumannii multirresistentes nos períodos de Mar - Set/01 e Out - Mar/02, respectivamente. O surto por P. aeruginosa incluiu sete neonatos com conjuntivite e três com bacteremia e um estudo caso-controle foi realizado no surto por A. baumannii com 11 e 22 neonatos respectivamente. Os isolados de A. baumannii foram resistentes a gentamicina e ciprofloxacina e os de P. aeruginosa a ampicilina/sulbactam além de gentamicina e ciprofloxacina. As culturas ambientais e das mãos dos profissionais de saúde foram negativas. O surto por P. aeruginosa resultou no aumento do uso de imipenem o que pode ter favorecido a emergência do surto por A. baumannii que embora suscetível a este beta-lactâmico apresentou uma multiresistência importante. A análise univariada relacionou os fatores de risco predisponentes para infecção por A. baumannii: peso 1500g, idade 7 dias, hospitalização > 7 dias e uso de carbapenema. O término dos surtos foi alcançado através medidas de controle de infecção e isolamento de coorte dos neonatos infectados, não sendo possível definir o reservatório e a via de transmissão.