Estudo clínico-epidemiológico das infecções da corrente sanguínea hospitalares por estafilococos coagulase-negativos e dos fatores de risco associados a letalidade
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Data
1997
Autores
Carneiro, Irna Carla do Rosario Souza [UNIFESP]
Orientadores
Pignatari, Antonio Carlos Campos [UNIFESP]
Tipo
Dissertação de mestrado
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Nos ultimos dez a quinze anos, os estafilococos coagulase-negativos (ECN), antes considerados apenas microrganismos avirulentos, comensais da pele humana, passaram a ter seu papel patogenico reconhecido como agentes de infeccoes no ambiente hospitalar. Atualmente, assumem importancia nas infeccoes da corrente sanguinea (ICS) nosocomiais e infectam uma variedade de dispositivos medicos proteticos. As ICS por este agente estao geralmente associadas ao uso de dispositivos intravasculares, ocorrendo preferencialmente em pacientes imunodeprimidos e neonatos prematuros internados em unidades de terapia intensiva, idosos e pacientes portadores de neoplasia, correlacionando-se com taxas consideraveis de letalidade. Entretanto, representam uma causa frequente de contaminacao de culturas, constituindo-se, em muitas situacoes, um dilema para o clinico a diferenciacao entre bacteremia verdadeira e um episodio contaminante. O objetivo deste trabalho foi analisar os aspectos clinico-epidemiologicos das ICS por ECN, procurando determinar os fatores de risco associados a aquisicao das ICS e sua diferenciacao dos episodios contaminantes, assim como aqueles relacionados a letalidade. O trabalho foi realizado no Hospital Universitario da UNIFESP-Escola Paulista de Medicina (Hospital São Paulo), no periodo de 01 de janeiro de 1995 a 31 de dezembro de 1996, onde foram estudados 146 episodios de bacteremia hospitalar por ECN em 143 pacientes, sendo 63,3% (93) ICS e 36,4% (53) considerados como contaminacao. Os episodios de ICS foram mais frequentes em pacientes com idade igual ou superior a 40 anos, sendo 33,3% dos pacientes encontravam-se com 60 anos ou mais. Predominaram os grupos de doencas de base nao fatais ou ausentes e de doencas potencialmente fatais (88,2%). As doencas neoplasicas, neurologicas, cardiovasculares e pulmonares foram as enfermidades mais frequentemente diagnosticadas entre os pacientes com ICS. As enfermarias clinicas foram o principal local de ocorrencia das ICS (45,2%), seguidas das unidades de terapia intensiva (adulto, pediatrica e neonatal) (35,5%). O tempo de internacao dos pacientes com ICS foi longo, em media 48,3 dias, sendo significantemente maior do que no grupo com contaminacao, 32,6 dias. As ICS ocorreram mais tardiamente no curso de internacao dos pacientes, 26,7 dias em media , sendo significante se comparado a 12,8 dias entre os episodios contaminantes. A principal fonte de bacteremia foi primaria, sendo indeterminada em 47,3% e tendo como foco o dispositivo intravascular em 17,2%. A fonte pulmonar foi a segunda mais frequente, identificada em 22,6% dos casos. A presenca de dispositivo intravascular, cateter venoso central, ventilacao mecanica, sondagem vesical e o tempo de aparecimento da bacteremia ( apos sete dias de internacao) representaram os fatores de risco relacionados a aquisicao de ICS hospitalar por ECN. A terapia antimicrobiana foi considerada adequada em 76,3% dos episodios, corrigida em 15,1% e inadequada em 8,6%. As especies mais isoladas nas ICS e no grupo de contaminantes foram S. epidermidis e S. haemolyticus. Predominaram as cepas hospitalares resistentes a oxacilina, identificadas em 76,3% dos casos de infeccao verdadeira e 86,8% nos episodios de contaminacao. As variaveis que se associaram independentemente a ocorrencia de ICS, pelo modelo de regressao logistica multipla foram: ventilacao mecanica (OR=7,3), presenca de cateter venoso central (OR=2,86) e tempo de aparecimento da bacteremia (> sete dias de internacao) (OR=2,43). Atraves deste modelo, foi possivel predizer que a probabilidade de um episodio de bacteremia por ECN, que ocorra ate o setimo dia de internacao em um paciente sem cateter venoso central implantado e sem ventilacao mecanica, ser contaminacao e de 68%. Por outro lado, um paciente em uso de cateter venoso central e submetido a ventilacao mecanica, apresentando bacteremia por ECN apos sete dias de internacao, tem 4% de probabilidade de ter feito um episodio de contaminacao. A mortalidade geral dos pacientes com ICS foi elevada, 54,8%. Considerando a evolucao para o obito ate o 14o apos a bacteremia, a letalidade foi de 36,6%. Analisando-se a presenca das variaveis ate o 14o dia, observou-se que a media de idade dos pacientes que morreram, 50,5 anos, foi significantemente maior do que os doentes que apresentaram boa evolucao, 34,6 anos. O obito ocorreu em 51,6% dos pacientes com idade igual ou superior a 60 anos, sendo significante se comparado aqueles situados em faixa etaria inferior a esta. A ventilacao mecanica foi um fator de risco para letalidade nos pacientes estudados. A evolucao para choque septico, assim como o uso previo de antimicrobianos se associaram ao obito nos pacientes estudados. O isolamento de cepas resistentes a oxacilina contribuiu significantemente com a evolucao desfavoravel das ICS. As variaveis que se associaram independentemente com maior letalidade, na regressao logitica multipla foram: choque septico (OR=4,98), antibioticoterapia previa (OR=4,35), resistencia a oxacilina (OR=3,76) idade avancada (igual ou superior a 60 anos) (OR=2,95). O modelo criado demonstrou que um paciente com idade igual ou superior a 60 anos, fazendo uso de algum antimicrobiano previo, ao apresentar um episodio de ICS por ECN resistente a oxacilina e evolui com choque septico, tem uma probabilidade de 89% de morrer em consequencia da bacteremia. Entretanto, a ocorrencia de ICS por ECN sensivel a oxacilina, em paciente internado com menos de 60 anos, que nao esta fazendo uso de antibiotico previamente a bacteremia e nao apresenta choque no curso da ICS, tem uma probabilidade de morte de apenas 3%
During the past 10-15 years, coagulase-negative staphylococci (CNS), previously regarded as avirulent, harmless comensal organisms of human skin, have been recognized, for its pathogenic role, as agents of infections in the hospital environment. Currently, they gain importance in nosocomial bloodstream infections (BSI) and can infect a wide variety of prosthetic medical devices. The BSI caused by this microorganism are usually associated with intravascular devices, preying, particulary on inmunocompromised patients and premature neonates in intensive care units, ederly and oncologic patients, and related with considerable morbidity rates. However, these microorganisms represent a frequent cause of contaminants cultures, and in many clinical situations, it’s a dilema how to diferentiate a true bacteremia from a contaminant episode. The objective of this study was to analyze the clinical and epidemiological aspects of CNS BSI, aiming to determine the risk factors associated with BSI, as well as the mortality related factors. The study was conduced at University Hospital of UNIFESP-EPM (Hospital São Paulo), from january 1st, 1995 to december 31st, 1996. We evaluated 146 patients, where 63.3%(93) were considered BSI and 36.4% (53) contamination. The episodes of BSI ocurred more frequently in 40-years-old patients or older, and about 33,3% were 60 years of age or older. Non fatal or no underlying diseases and potential fatal diseases groups predominated (88.2%) among patients with BSI. Malignant neoplasias, neurologic, cardiovascular and pulmonary diseases were the most frequently diagnosticated conditions. Medical wards were the principal place of ocurrence of BSI (45.2%), followed by the intensive care units (of adults, pediatric and neonatal) (35.5%). The hospital stay of patients with BSI was 48.3 days in median, significantly longer than the contaminant group. BSI ocurred lately during the hospitalization period, 26.7 days in median, and it was significant when compared with 12.8 days in the contaminant episodes. The most frequently bacteremia was of primary origin, where 47.3% were indeterminated and 16.1% had the intravascular devices as the focus of infection. Pulmonary source was the second most frequently one, identified in 22.6% of cases. Intravascular catheter was present in most of patients with true bacteremia (95.7%). The presence of intravascular devices, central venous catheter, mecanic ventilation, vesical catheter and the time of development of bacteremia (after seven days of hospitalization) represented the risk factors related to nosocomial CNS-BSI. Antimicrobial therapy was considered suitable in 76.3% of the episodes, corrected in 15.1% and unsuitable in 8.6%. The most frequently isolated CNS species were S.epidermidis and S.haemolyticus. Oxacilin-resistant hospital strains predominated, and were present in 76.3% of true bacteremia cases and in 86.8% of contaminant episodes. The variables independently associated to BSI, through the multiple logistic regression, were: mecanic ventilation (OR=7.3), central venous catheter (OR=2.86) and time of development of bacteremia during hospitalization (OR=2.43). Based on this model, it was possible to predict that the probability of an episode of CNS bacteremia being contamination is 68%, when it ocurs until the 7st day of hospital stay, in a patient without central venous catheter and not ventilated mecanically. However, if a patient in use of central venous catheter and mecanic ventilation, develops a CNS bacteremia after seven days of hospitalization, the probabilility that this episode was contaminant is 4%. The crude mortality of paients with BSI was high, 54.8%. Considering the evolution to death a until the 14 day following bacteremia, the mortality rate was 36.6%. Analyzing variables until the 14 day following bactemia, it was noticed that median age of patients who died, 50.5 years, was significantly higher than patients with good outcome, 34.6 years. Death ocurred in 51.6% of 60-years-old patients or older, and it was significant when compared with patients under this age. Mecanic ventilation was a risk factor related to death, as well as the previous use of antimicrobial agents. Isolation of oxacilin-resistant strains contributed significantly with unfavorable outcome of nosocomial BSI. Variables which were independently associated with higher mortality, in the model of multiple logistic regression were : septic shock (OR=4.98), use of antimicrobial agents previous to BSI (OR=4.35), oxacilin-resistant CNS strains (OR=2,95) and ederly (60-years-old patients or older) (OR=2,95). This created model showed that a 60-years-old patient or older, using an antibiotic previously to bacteremia, develops an oxacilin-resistant CNS BSI with septic shock, has a high probability (89%) of dying because of bacteremia. By the other hand, an oxacilin-sensitive CNS BSI, in a patient under 60 years of age, not using an antimicrobial agent previously and not developing septic shock during the course of infection, results in only 3% of probability of dying in consequence of bacteremia.
During the past 10-15 years, coagulase-negative staphylococci (CNS), previously regarded as avirulent, harmless comensal organisms of human skin, have been recognized, for its pathogenic role, as agents of infections in the hospital environment. Currently, they gain importance in nosocomial bloodstream infections (BSI) and can infect a wide variety of prosthetic medical devices. The BSI caused by this microorganism are usually associated with intravascular devices, preying, particulary on inmunocompromised patients and premature neonates in intensive care units, ederly and oncologic patients, and related with considerable morbidity rates. However, these microorganisms represent a frequent cause of contaminants cultures, and in many clinical situations, it’s a dilema how to diferentiate a true bacteremia from a contaminant episode. The objective of this study was to analyze the clinical and epidemiological aspects of CNS BSI, aiming to determine the risk factors associated with BSI, as well as the mortality related factors. The study was conduced at University Hospital of UNIFESP-EPM (Hospital São Paulo), from january 1st, 1995 to december 31st, 1996. We evaluated 146 patients, where 63.3%(93) were considered BSI and 36.4% (53) contamination. The episodes of BSI ocurred more frequently in 40-years-old patients or older, and about 33,3% were 60 years of age or older. Non fatal or no underlying diseases and potential fatal diseases groups predominated (88.2%) among patients with BSI. Malignant neoplasias, neurologic, cardiovascular and pulmonary diseases were the most frequently diagnosticated conditions. Medical wards were the principal place of ocurrence of BSI (45.2%), followed by the intensive care units (of adults, pediatric and neonatal) (35.5%). The hospital stay of patients with BSI was 48.3 days in median, significantly longer than the contaminant group. BSI ocurred lately during the hospitalization period, 26.7 days in median, and it was significant when compared with 12.8 days in the contaminant episodes. The most frequently bacteremia was of primary origin, where 47.3% were indeterminated and 16.1% had the intravascular devices as the focus of infection. Pulmonary source was the second most frequently one, identified in 22.6% of cases. Intravascular catheter was present in most of patients with true bacteremia (95.7%). The presence of intravascular devices, central venous catheter, mecanic ventilation, vesical catheter and the time of development of bacteremia (after seven days of hospitalization) represented the risk factors related to nosocomial CNS-BSI. Antimicrobial therapy was considered suitable in 76.3% of the episodes, corrected in 15.1% and unsuitable in 8.6%. The most frequently isolated CNS species were S.epidermidis and S.haemolyticus. Oxacilin-resistant hospital strains predominated, and were present in 76.3% of true bacteremia cases and in 86.8% of contaminant episodes. The variables independently associated to BSI, through the multiple logistic regression, were: mecanic ventilation (OR=7.3), central venous catheter (OR=2.86) and time of development of bacteremia during hospitalization (OR=2.43). Based on this model, it was possible to predict that the probability of an episode of CNS bacteremia being contamination is 68%, when it ocurs until the 7st day of hospital stay, in a patient without central venous catheter and not ventilated mecanically. However, if a patient in use of central venous catheter and mecanic ventilation, develops a CNS bacteremia after seven days of hospitalization, the probabilility that this episode was contaminant is 4%. The crude mortality of paients with BSI was high, 54.8%. Considering the evolution to death a until the 14 day following bacteremia, the mortality rate was 36.6%. Analyzing variables until the 14 day following bactemia, it was noticed that median age of patients who died, 50.5 years, was significantly higher than patients with good outcome, 34.6 years. Death ocurred in 51.6% of 60-years-old patients or older, and it was significant when compared with patients under this age. Mecanic ventilation was a risk factor related to death, as well as the previous use of antimicrobial agents. Isolation of oxacilin-resistant strains contributed significantly with unfavorable outcome of nosocomial BSI. Variables which were independently associated with higher mortality, in the model of multiple logistic regression were : septic shock (OR=4.98), use of antimicrobial agents previous to BSI (OR=4.35), oxacilin-resistant CNS strains (OR=2,95) and ederly (60-years-old patients or older) (OR=2,95). This created model showed that a 60-years-old patient or older, using an antibiotic previously to bacteremia, develops an oxacilin-resistant CNS BSI with septic shock, has a high probability (89%) of dying because of bacteremia. By the other hand, an oxacilin-sensitive CNS BSI, in a patient under 60 years of age, not using an antimicrobial agent previously and not developing septic shock during the course of infection, results in only 3% of probability of dying in consequence of bacteremia.
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CARNEIRO, Irna Carla do Rosario Souza. Estudo clínico-epidemiológico das infecções da corrente sanguínea hospitalares por estafilococos coagulase-negativos e dos fatores de risco associados a letalidade. 1997. Dissertação (Mestrado em Ciências) - Escola Paulista de Medicina, Universidade Federal de São Paulo (UNIFESP), São Paulo, 1997.