CHAPTER 14: PEDIATRIC MICROBIOLOGY

LEARNING OBJECTIVES

INTRODUCTION

In many ways, the practice of diagnosing infectious diseases in children is very similar to that in adults. The pathogens are largely the same and the methods used to identify them do not typically differ because they originated from a child. Also, inoculum greatly impacts on the sensitivity of the diagnostic method used. However, there are some important areas where diagnosing disease differs in children. While a comprehensive review of all microbiology is outside the scope of this chapter, the focus will instead be on specific areas where working with children requires a unique approach. Complete information regarding all areas of clinical microbiology can be found in many texts. Two of the more commonly used references include the Manual of Clinical Microbiology (ASM Press) as well as Koneman's Color Atlas and Textbook of Diagnostic Microbiology (Lippincott Williams & Wilkins).^1,2

This chapter will be divided into two general sections. The first will provide a discussion of laboratory methods that should be known to all microbiologists working with pediatric specimens. The second section is organized by clinical presentation. Within each clinical condition discussed will be sections that briefly introduce the disease and the relevant pathogens, pediatric considerations in specimen collection, laboratory diagnosis, treatment, and antimicrobial susceptibility testing. Of note, this chapter will only address the microorganisms that are relevant to each clinical condition and will not include an exhaustive list of all bacterial, viral, fungal, and parasitic infections. Where applicable, important basic considerations in organism identification will be addressed but in-depth discussions about biochemical profiles and antimicrobial resistance mechanisms is outside the scope of this chapter.

THE INDIGENOUS MICROFLORA OF CHILDREN

Proper interpretation of microbiology culture results requires in-depth knowledge of the specimen type and the spectrum of diseases that may be considered when a given specimen is submitted for microbial testing. Knowledge of a patient's medical history, age, gender, and past culture results inform the work-up of specimen. With respect to specimen type, there are generally two main categories: sterile and non-sterile. Sterile site specimens are of utmost importance because they may represent life threatening, invasive infections, but culture interpretation is simpler because in most cases, any organism recovered is considered significant. However, microbiological testing results from specimens from non-sterile sites (eg, respiratory tract, genitourinary tract, gastrointestinal tract, etc.) can be more challenging to interpret. These cultures are complicated by the presence of indigenous microbiota otherwise referred to as normal flora, which can exist as harmless colonizers but can also cause infection. ...