CHAPTER ONE
Infections of the lower respiratory tract, a region from the trachea to the alveoli include pneumonia, emphysema, lung abscess, bronchiolitis, bronchitis, bronchiectasis, lung abscess, and pleural effusion. Acute forms of these infections are among the commonest human infectious diseases globally. Human of all age-groups are affected with associated significant morbidity and mortality [1, 2]. They are a significant contributor to out-patient consultation (6%) and all hospital admission (4.4%). Among adults up to 60 years, lower respiratory tract infections (LRTIs) account for 3%-5% of mortality [3]. Globally, it is estimated that about 4.2 million deaths from acute LRTIs occur among all age groups annually. However, the burden of the diseases is higher in developing countries, where pneumonia is among the most common cause of hospital attendance among adults [4]. The morbidity and mortality arising from these infections varies depending on the underlying etiological agents and their virulence [5]. The incidence and associated mortality due to LRTI can be influenced by several factors including characteristics of the population at risk, standard of the healthcare facilities available, use of immunosuppressive drugs, inappropriate antibiotic therapy, distribution of causative agents, and prevalence of antimicrobial resistance [6].
Each of the different types of LRTIs presents with different epidemiology, clinical presentation, pathogenesis, and outcome [1,4]. Also, the etiology, pathogenesis, clinical presentation and prognosis of each of LRTIs vary with age, sex, season, the type of population at risk and various other factors [7].
The commonly isolated bacteria from various cases of LRTIs include the Gram-positive-bacteria such as Staphylococcus aureus, Streptococcus pneumoniae, and the Gram-negative bacteria including Klebsiellaspecies, Pseudomonas species, Escherichia coli, Acinetobacterspecies, and other non-fermentative Gram-negative bacilli (NFGNB) [1,7]. These causative agents of LRTIs vary from one region to another, and also from time to time. Also, the antibiogram of isolated bacteria varies both geographically and from time to time [5].
The emergence of resistance of these bacteria especially the Gram negative isolates to a wide range of commonly prescribed antibiotics has posed a big challenge to the management of LRTIs in our various health facilities with attendant limitation of therapeutic options when faced with such pathogen. This might be connected to the usual initiation of ‘inappropriate’ antibiotic therapy for suspected cases of LRTIs even before result of culture and antibiotic susceptibility pattern is out. This definitely will increase associated morbidity, duration of treatment, cost of treatment and mortality from these infections.
