The Indian Journal of Pediatrics | 2019
Identifying Etiological Agent for Childhood Pneumonia: An Ongoing Need
Abstract
Acute lower respiratory tract infection (ALRTI) in infants is a broad classification which includes a variety of clinical diseases including pneumonia, bronchiolitis, and wheeze associated with viral respiratory tract infection. Pneumonia contributes to 22% of deaths in under 5 y children in Southeast Asia region [1]. Identification of etiological agent for ALRTI is desirable to differentiate bacterial vs. viral illnesses, to define the need and choice of antibiotics or antiviral agents, and other supportive care as per the infectious agent. Knowledge of etiological agents is also important for public health interventions like type of vaccine (e.g., influenza, pneumococcus vaccine) needed, personal prophylactic measures etc. As etiological agents are likely to change from place to place and over time, studies on prevalence of various etiological agents in specific area is an ongoing need. A study in this issue of the journal by Sonawane et al. from Maharashtra, Western India, evaluated etiology of ALRTI in 100 infants from 1 mo to 1 y of age using nasaopharyngeal swabs with multiplex real time polymerase chain reaction (PCR) for 18 viruses and 3 bacteria [Hemophilus influenzae type b, Chlamydia pneumoniae (C. pneumoniae) and Mycoplasma pneumoniae (M. pneumoniae)] [2]. They could detect atleast one infectious agent in 82 (82%) children, commonest being respiratory syncytial viral (RSV, 35.4%), human rhinovirus (HRV, 25.6%) and adenovirus (ADV, 22%). Among bacterial agents, H. influenzae type b, C. pneumoniae andM. pneumoniae were detected in 5 (6.1%), 2 (2.4%) and 2 (2.4%) patients respectively where only C. pneumoniae was detected as a single agent while other two had co-detection of viruses [2]. A study by Kabra et al. from India evaluated etiology of severe ALRTI (cough with or without fever and tachypnea with lower chest retractions) in 95 children below 5 y of age using virus isolation by culture for four viruses, blood culture for bacteria, and serology for mycoplasma and chlamydia and found organisms in 94% cases (viruses 38%, bacteria 16%,mycoplasma 24%, chlamydia 11%, andmixed in 8%) [3]. Mathew et al. from northern India evaluated etiology of community acquired pneumonia (defined by tachypnea as per WHO definition) in 2345 children of 1–12 y of age using nasopharyngeal aspirate (NPA) (culture and PCR; in 20% samples multiplex PCR), blood culture for bacteria, and serology for mycoplasma and chlamydia and found positive bacterial culture in 15.8% (Streptococcus pneumoniae 79.1%, H. influenzae 9.6%, and Staphylococcus aureus in 6.8%), mycoplasma in 4.3% and chlamydia in 1.1% [4]. The multiplex PCR in 428 NPA samples identified organisms in 98.6% samples where 82.2% had multiple organisms and 16.4% had a single organism [4]. In another study from India, etiology of 18 episodes of ALRTI (defined as tachypnea) in a birth cohort was evaluated using multiplex PCR, blood and NPA culture and serology for chlamydia and mycoplasma and found viruses in 66.7% episodes, bacteria in 94.4% episodes and mixed bacteria and viruses in 44.4% episodes [5]. It is difficult to compare results from different studies because of difference in inclusion criteria, different samples evaluated, and variable methods of organism detection. The inclusion criteria for the current study are not clear because there is ambiguity in number of clinical feature/s considered for inclusion out of eight features (cough, fever, tachypnea, wheeze, stridor, retraction, cyanosis and apnea) mentioned [2]. All children in this study had nasal symptoms with rhinorrhea, hence pre-test probability of viral infection was high [2]. The correlation of clinical phenotype (bronchiolitis, pneumonia, wheeze etc) with etiological agent might have improvised the study results. Detectionmethod applied by the author (nasopharyngeal swab PCR) is good for detecting * Kana Ram Jat [email protected]