Colonización por Staphylococcus aureus resistente a la meticilina en una unidad de cuidados intensivos de adultos de un hospital colombiano: caracterización fenotípica y molecular con detección de un clon de circulación en la comunidad

Prevalence of the cefazolin inoculum effect (CzIE) in nasal colonizing methicillin-susceptible Staphylococcus aureus in patients from intensive care units in Colombia and use of a modified rapid nitrocefin test for detection

The cefazolin inoculum effect (CzIE) has been associated with poor clinical outcomes in patients with methicillin-susceptible Staphylococcus aureus (MSSA) infections. We aimed to investigate the point prevalence of the CzIE among nasal colonizing MSSA isolates from ICU patients in a multicenter study in Colombia (2019-2023). Patients underwent nasal swabs to assess for S. aureus colonization on admission to the ICU, and some individuals had follow-up swabs. We performed cefazolin MIC by broth microdilution using standard and high inoculum and developed a modified nitrocefin-based rapid test to detect the CzIE. Whole-genome sequencing was carried out to characterize BlaZ types and allotypes, phylogenomics, and Agr-typing. A total of 352 patients were included; 46/352 (13%) patients were colonized with S. aureus and 22% (10/46) and 78% (36/46) with MRSA and MSSA, respectively. Among 36 patients who contributed with 43 MSSA colonizing isolates, 21/36 (58%) had MSSA exhibiting the CzIE. BlaZ type A and BlaZ-2 were the predominant type and allotype in 56% and 52%, respectively. MSSA belonging to CC30 were highly associated with the CzIE, and single-nucleotide polymorphism (SNP) analyses supported possible transmission of MSSA exhibiting the CzIE among some patients of the same unit. The modified nitrocefin rapid test had 100%, 94.4%, and 97.7% sensitivity, specificity, and accuracy, respectively. We found a high point prevalence of the CzIE in MSSA colonizing the nares of critically ill patients in Colombia. A modified rapid test was highly accurate in detecting the CzIE in this patient population.

Prevalence of the Cefazolin Inoculum Effect (CzIE) in Nasal Colonizing Methicillin-Susceptible Staphylococcus aureus in Patients from Intensive Care Units in Colombia and Use of a Modified Rapid Nitrocefin Test for Detection

The cefazolin inoculum effect (CzIE) has been associated with poor clinical outcomes in patients with MSSA infections. We aimed to investigate the point prevalence of the CzIE among nasal colonizing MSSA isolates from ICU patients in a multicenter study in Colombia (2019-2023). Patients underwent nasal swabs to assess for S. aureus colonization on admission to the ICU and some individuals had follow-up swabs. We performed cefazolin MIC by broth-microdilution using standard and high-inoculum and developed a modified nitrocefin-based rapid test to detect the CzIE. Whole genome sequencing was carried out to characterize BlaZ types and allotypes, phylogenomics and Agr-typing. All swabs were subjected to 16S-rRNA metabarcoding sequencing to evaluate microbiome characteristics associated with the CzIE. A total of 352 patients were included; 46/352 (13%) patients were colonized with S. aureus; 22% (10/46) and 78% (36/46) with MRSA and MSSA, respectively. Among 36 patients that contributed with 43 MSSA colonizing isolates, 21/36 (58%) had MSSA exhibiting the CzIE. BlaZ type A and BlaZ-2 were the predominant type and allotype in 56% and 52%, respectively. MSSA belonging to CC30 were highly associated with the CzIE and SNP analyses supported transmission of MSSA exhibiting the CzIE among some patients of the same unit. The modified nitrocefin rapid test had 100%, 94.4% and 97.7% sensitivity, specificity and accuracy, respectively. We found a high prevalence point prevalence of the CzIE in MSSA colonizing the nares of critically-ill patients in Colombia. A modified rapid test was highly accurate in detecting the CzIE in this patient population.

Using Positive Deviance in the prevention and control of MRSA infections in a Colombian hospital: a time-series analysis

Positive Deviance (PD) is a process to achieve a social and cultural change. This strategy has been used for the control of methicillin-resistant Staphylococcus aureus (MRSA) infection in some health institutions in the United States, but has rarely been adopted in institutions from developing countries where resources are limited. We describe our experience of PD in the control of healthcare-associated infections (HAIs) due to MRSA in a Colombian hospital with the aim of reducing HAI rates through a cultural change in processes. A time-series study was conducted based on the MRSA-HAI rate and the number of months with zero MRSA infections before and after application of PD (2001-2012). On comparing the pre-intervention and intervention periods, the mean overall rates of MRSA-HAI was 0·62 and 0·36, respectively (P = 0·0005); the number of months with zero MRSA-HAIs were 3/70 and 12/74 (odds ratio 0·264, 95% confidence interval 0·078-0·897); the percentage of MRSA-HAIs was 53·2% and 41·0%. These results are consistent with other published data. Implementation of PD was associated with a significant reduction of MRSA-HAIs, it did not involve high costs and the changes have been lasting.

[Risk factors for methicillin-resistant Staphylococcus aureus bacteremia: A multicenter matched case-control study]

INTRODUCTION

Methicillin-resistant Staphylococcus aureus is a frequent pathogen at critical care services. Its presence leads to increased hospital stays and mortality risk in patients with bacteremia. However, the etiology of this resistance marker has not been fully studied.

OBJECTIVE

To identify risk factors associated with the emergence of methicillin-resistant S. aureus bacteremia in critically ill patients treated at intensive care units in Bogotá, Colombia.

MATERIALS AND METHODS

We conducted a retrospective paired case-control study, nested in a cohort of patients diagnosed with S. aureus bacteremia and treated at intensive care units between 2006 and 2008 in Bogotá. Cases were patients with positive blood culture to methicillin resistance, matched in a 1:1 ratio with methicillin-sensitive controls isolated from the same institution and hospitalization year. We used conditional logistic regression to analyze the risk factors associated with the presence of resistance, with emphasis on prior antibiotic therapy.

RESULTS

We included 372 patients with S. aureus bacteremia. Factors such as the use of pre-hospital devices: vascular (OR=1.986, 95% CI 1.038 to 3.801) and urinary (OR=2.559, 95% CI: 1.170 to 5.596), along with the number of previously used antibiotics, were associated with the emergence of resistance. The number of antibiotics used previously was determined to have a gradient effect, particularly carbapenems.

CONCLUSIONS

The rational use of antibiotics and surveillance of exposure to surgical procedures or use of invasive devices are interventions that could diminish the emergence of methicillin-resistant S. aureus bacteremia causes.

Multicenter study in Colombia: Impact of a multidimensional International Nosocomial Infection Control Consortium (INICC) approach on central line-associated bloodstream infection rates

BACKGROUND

The objective of this study was to analyze the impact of a multidimensional infection control approach and the use of the International Nosocomial Infection Control Consortium (INICC) Surveillance Online System on central line-associated bloodstream infection (CLABSI) rates from June 2003-April 2010.

METHODS

We conducted a prospective, before-after surveillance study of 2,564 patients hospitalized in 4 adult intensive care units (ICUs) and 424 patients in 2 pediatric ICUs of 4 hospitals in 2 cities of Colombia. During baseline, we performed outcome surveillance of CLABSI applying the Centers for Disease Control and Prevention's National Healthcare Safety Network definitions. During intervention, we implemented the INICC multidimensional approach and the ISOS, which included a bundle of infection prevention practice interventions, education, outcome surveillance, process surveillance, feedback on CLABSI rates and consequences, and performance feedback of process surveillance. Bivariate and multivariate regression analyses were performed using a logistic regression model to estimate the effect of the intervention on the CLABSI rate.

RESULTS

The baseline rate of 12.9 CLABSIs per 1,000 central line (CL) days, with 3,032 CL days and 39 CLABSIs, was reduced to 3.5 CLABSIs per 1,000 CL days, with 3,686 CL days and 13 CLABSIs, accounting for a 73% CLABSI rate reduction (relative risk, 0.27; 95% confidence interval, 0.14-0.52; P=.002).

CONCLUSIONS

Implementing the INICC multidimensional infection control approach for CLABSI prevention was associated with a significant reduction in the CLABSI rate of ICUs of Colombia.

Factores relacionados con la colonización por Staphylococcus aureus

Staphylococcus aureus tiene gran capacidad para colonizar la piel y las mucosas de los seres humanos y de diferentes animales. Varios estudios evidencian el papel de dicha colonización en la patogénesis y la epidemiología de las infecciones causadas por S. aureus. Se ha demostrado que los portadores nasales constituyen una fuente importante de propagación de la bacteria; una amplia proporción de las infecciones estafilocócicas invasivas asociadas al cuidado de la salud son de origen endógeno, y la colonización por cepas de S. aureus resistentes a meticilina (SARM), aún mal entendida, origina mayores complicaciones. La importancia de la colonización se ha definido con más profundidad en ambientes hospitalarios, pero recientemente se han hecho estudios en la comunidad con resultados contradictorios sobre la relación colonización-infección. En esta revisión se presentan algunas características relevantes del proceso de colonización por S. aureus, incluyendo las cepas de SARM, y se consideran los factores humanos y del microorganismo que influyen en él. Asimismo, se hace una revisión de los estudios colombianos al respecto.