PREVALENCE OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS IN SPINAL SURGERY PATIENTS

PREVALÊNCIA DE STAPHYLOCOCCUS AUREUS METICILINA RESISTENTE EM PACIENTES DE CIRURGIA DE COLUNA

PREVALENCIA DE STAPHYLOCOCCUS AUREUS RESISTENTE A METICILINA EN PACIENTES DE CIRUGIA DE COLUMNA

ABSTRACT

Objective

The objective of this study was to determine the prevalence of patients with colonization of methicillin-resistant Staphylococcus aureus (MRSA) in the nasal mucosa, who underwent elective spinal procedures.

Methods

Retrospective study of the medical records of all patients submitted to elective procedures, totaling 125 individuals in the period of 2015 and 2017, performed by two spinal surgeons of the Orthopedics and Traumatology Service of Hospital Mater Dei, Belo Horizonte, Minas Gerais. The pre-operative investigation of MRSA consisted of the collection of a nasal swab for microbiological culture.

Results

Of the 125 patients evaluated, three (2.4%) showed positive results for MRSA nasal colonization. This prevalence is consistent with the international literature, that ranges from 1.5 to 5.9%. Of these patients none had infection of the surgical wound, probably due to the preoperative prophylactic measures.

Conclusions

Despite the limitations of the study, we found that the prevalence of carriers of this nasal MRSA population is similar to that of populations worldwide . Level of evidence III; Retrospective Study.

Staphylococcus Aureus; Prevalence; Spine

RESUMO

Objetivo

O objetivo desse trabalho foi determinar a prevalência dos pacientes submetidos a procedimentos eletivos de coluna com mucosa nasal colonizada por Staphylococcus aureus Meticilina Resistente (MRSA).

Métodos

Foi realizado estudo retrospectivo dos prontuários de todos os pacientes submetidos a procedimentos eletivos, totalizando 125, entre 2015 e 2017, por dois cirurgiões de coluna do serviço de Ortopedia e Traumatologia do Hospital Mater Dei, de Belo Horizonte, Minas Gerais. A investigação pré-operatória para MRSA consistiu em swab nasal submetido à cultura microbiológica.

Resultados

Dos 125 pacientes avaliados, três (2,4%) apresentaram resultado positivo para colonização nasal por MRSA. Essa prevalência está de acordo com a literatura estrangeira, que varia de 1,5 a 5,9%. Desses pacientes, nenhum apresentou infecção da ferida operatória, provavelmente devido às medidas de profilaxia instituídas.

Conclusão

Apesar das limitações do estudo, constatamos que a população estudada apresenta prevalência de carreamento nasal de MRSA similar às populações estrangeiras. Nível de evidência III; Estudo Retrospectivo.

Staphylococcus Aureus; Prevalência; Coluna Vertebral

RESUMEN

El objetivo de este estudio fue determinar la prevalencia de pacientes con colonización de Staphylococcus aureus resistente a la meticilina (SARM) en la mucosa nasal que se sometieron a procedimientos electivos de columna vertebral.

Métodos

Estudio retrospectivo de los registros médicos de todos los pacientes sometidos a procedimientos electivos, con un total de 125 individuos en el período de 2015 a 2017, realizado por dos cirujanos de columna vertebral del Servicio de Ortopedia y Traumatología del Hospital Mater Dei, de Belo Horizonte, Minas Gerais. La investigación preoperatoria de SARM consistió en la recolección de un hisopo nasal para cultivo microbiológico.

Resultados

De los 125 pacientes evaluados, tres (2,4%) tuvieron resultados positivos para la colonización nasal por SARM. Esta prevalencia está de acuerdo con la literatura internacional, que varía de 1,5% a 5,9%. De estos pacientes, ninguno tuvo infección de la herida quirúrgica, probablemente debido a las medidas profilácticas preoperatorias.

Conclusiones

A pesar de las limitaciones del estudio, encontramos que la prevalencia de portadores de SARM nasal de esta población es similar a la de poblaciones de todo el mundo. Nivel de Evidencia III; Estudio retrospectivo.

Staphylococcus Aureus; Prevalencia; Columna Vertebral

INTRODUCTION

Staphylococcus aureus is a facultative anaerobic bacterium described for the first time in 1880 by Alexander Ogston. ¹ It is an immobile, Gram positive, non-sporulated, coagulase positive coccus without a capsule or with a limited capsule. It is found in the external environment and is part of the normal human microbiota. Thus, under normal conditions it is not pathogenic, but when there is a break in the cutaneous barrier or a reduction in immunity it can cause infections and complications that range from cellulitis to sepsis. ²

Among these conditions, we highlight early infection of the surgical wound as an important cause of complications in orthopedic surgeries. Such intercurrences are typically caused by Gram-positive germs, ³ and among them Staphylococcus aureus is the most common pathogen. ³ , ⁴ ,

The prevalence of individuals colonized by these pathogens varies in the literature and depends on the population studied, the anatomical site where the collection is taken, and the number of locations collected. ⁵ American studies cite prevalence of nasal colonization by Staphylococcus aureus as varying between 20 and 30%. ⁶ - ⁸ In a World Health Organization study, the rate of nasal colonization by Methicillin-Resistant Staphylococcus aureus (MRSA) in patients awaiting surgery was 1.8%. ⁹ Sporer et al. ¹⁰ screened 9825 patients for Staphylococcus colonization prior to knee and hip prosthesis surgery and found 2.9% of the patients positive for MRSA and 25.1% positive for Methicillin-Sensitive Staphylococcus aureus (MSSA).

However, there are a few studies on the prevalence of colonization by these bacteria in the healthy Brazilian population. Most of the studies found in Portuguese deal with patients in intensive care units with nosocomial infections or immunocompromised, ¹¹ - ¹³ since these individuals are more susceptible to this infection.

The patients colonized with these bacteria have a significantly higher rate of surgical wound infections following orthopedic surgery, ¹⁴ among which spinal surgery and hip and knee replacement surgeries stand out. ¹⁰ Studies show that this risk is also valid for cardiac and vascular surgeries. ¹⁵ In addition, infections by both Methicillin-Resistant and Methicillin-Sensitive Staphylococcus aureus are associated with higher potential morbidity and mortality when compared to infections by other bacteria of the human flora. ¹⁶

OBJECTIVE

The objective of this study was to determine the prevalence of mucous membranes colonized by MRSA among patients who underwent elective spinal procedures.

METHODS

In this retrospective study, we reviewed the medical records of all patients who underwent elective procedures, a total of 125 from 2015 to 2017, performed by two spine surgeons of the Orthopedics and Traumatology Service of the Hospital Mater Dei, in Belo Horizonte, Minas Gerais.

The preoperative investigation for colonization by MRSA in our service consists of a swab of both nostrils that is submitted to the standard microbiological culture methods. The test was performed no more than 30 days prior to the surgical procedure and the patients returned to the surgeon responsible for the surgery for a preoperative visit and evaluation of the results.

Patients who had undergone a surgical procedure or who had been hospitalized for any reason less than 30 days prior to the examination were excluded.

The Epidemiological Study of Colonization by Staphylococcus aureus and the Correlation with Surgical Site Infection project was received for ethics analysis by the Hospital Mater Dei IRB as protocol number CAAE: 87466518.5.0000.5128

All the patients signed the Informed Consent Form.

RESULTS

Of the 125 patients who met the study inclusion criteria, of whom 52% (65 patients) were female and 48% (60) were male, 2.4% (three patients) had positive results for nasal colonization by Methicillin-Resistant Staphylococcus aureus .

DISCUSSION

Surgical wound infections are important complications of surgical procedures, which increase morbidity and mortality and burden the system. The rate of this serious condition following spinal surgery reported in the literature ranges from 0.7% to 12%. ¹⁷ , ¹⁸ Risk factors that predispose patients to developing postoperative infection are classified as non-modifiable, such as age and primary or revision surgery, or modifiable, such as obesity, tobacco use, and Staphylococcus colonization. The identification of these modifiable factors is important because from it strategies can be designed to optimize progress following surgery.

Thus, this study focused on the prevalence of nasal colonization by Methicillin-Resistant Staphylococcus aureus among the healthy patients who underwent spinal surgical procedures between 2015 and 2017 in two large hospitals. The most common reservoir site for S. aureus is the nostrils, followed by the groin, armpits, and perianal region. ⁵ We used a swab of the nostrils as the screening method, since it is the most widely used in the literature, ¹⁹ - ²¹ has greater sensitivity, and does not embarrass the patients.

This swab can be submitted to two types of analysis to identify MRSA: the polymerase chain reaction (PCR) and seeding microbiological culture medium. The sensitivity and specificity of PCR are 100% and 98%, respectively, while for culture are 90% and 100%, respectively. ²² The advantage of PCR is that the results are available in 24 hours as opposed to the culture, which may take from 3 to 7 days depending on the laboratory. Thus, the first form of analysis is more useful for the hospitalized patient because it permits real-time identification of nasal MRSA colonization, provides an opportunity for early eradication of the pathogen, and prevents transmission to other patients. ³ However, the PCR kits cost more than twice what is spent on growing the cultures. ²³ So, since there was no need for such rapid turnaround of the swab results and so as to not burden the system more than necessary, we opted for culturing the samples collected from the patients.

Once the carriers of these bacteria have been identified, measures should be introduced in the pre- and intraoperative periods directed at minimizing the chances of complications. In our service, we advised all the patients, regardless of the microbiological results, to wash with 2% chlorhexidine the night before and on the day of surgery. We also performed antibiotic prophylaxis with cefazolin 2 g one hour before the skin incision. However, for the patients who screened positive for MRSA, daily washing with 2% chlorhexidine was initiated 5 days prior to surgery. In addition, nasal decolonization was performed with 2% mupirocin, twice daily, for five days and vancomycin 1g was added to the antibiotic prophylaxis.

Mupirocin is a naturally occurring antibiotic, also called pesudomonic acid, as it is derived from the fermentation of Pseudomonas fluorescens . ²⁴ Its action mechanism is the inhibition of protein synthesis, preventing the incorporation of isoleucine into the protein. ²⁵ Thus, it is very effective against aerobic Gram-negative cocci ( S. aureus , S. epidermidis, and B-hemolytic Streptococcus ) and some Gram-negative cocci, but spares most of the normal flora. ²⁶ When used intranasally for 5 days, mupirocin eradicates 78% of the strains of Staphylococcus aureus and reduces the carrying of the bacteria in the nose and on the hands for up to a year. ²⁷ Adverse effects are rare, occurring in less than 1.5% of patients, and include a burning sensation, itching, redness, and contact dermatitis. ²⁶ None of the patients who used this antibiotic in our service had adverse reactions.

Of the 125 patients who were screened for MRSA, 2.4% had positive swab results and were given pre- and transoperative prophylaxis. This prevalence in our study agreed with the foreign literature, where it ranges from 1.5 to 5.9%. ⁹ , ²⁰ , ²¹ , ²⁸ None of our patients had infections of the surgical wound.

The patient sample in our study was small and thus may not be representative of the real prevalence in the healthy Brazilian population.

CONCLUSION

In spite of the study limitations, we found that the population studied had a prevalence of nasal MRSA similar to that of foreign populations. None of the patients carrying the bacteria in the nasal cavity presented infection of the surgical wound, which corroborates the benefits and cost effectiveness of continued screening and the introduction of prophylactic measures when these individuals are identified.

New studies are required to determine whether this prevalence would persist in a larger population and whether there are factors that predispose these patients to be carriers of Methicillin-Resistant Staphylococcus aureus .

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• This study was conducted at the Hospital Mater Dei, Belo Horizonte, MG, Brazil.

Publication Dates

• Publication in this collection
  02 Sept 2019
• Date of issue
  Jul-Sep 2019

History

• Received
  30 Apr 2018
• Accepted
  16 Oct 2018