The rise in multidrug resistance is a growing public health concern among agents of respiratory tract which is responsible for morbidity, mortality and costs (Uskudar et al., 2021), this make management of respiratory tract infections a great challenge in Africa due to the socioeconomic burden and limited access to good healthcare facilities and indiscriminate use of antibiotics (Serges et al., 2019). The overall incidence of bacterial pathogens of LRTIs recorded in this study was 31%. This finding is slightly higher than those of earlier studies recorded at National Hospital Abuja (14.5%), Ilorin (15.53%), Benin (18.91%), Kano (21.5%) and Nepal (24.6%) (Abdullahi and Iregbu, 2018; Kalgo et al., 2016; Christopher et al., 2011; Taura et al., 2013; Rakshya et al., 2018). Higher prevalence were reported in Bangladesh (64%) and some European countries (59%) (Borkot et al., 2016; Leven et al., 2018), this variation of incidence may be due to differences in geographical location.
Table 1 shows that Staphylococcus aureus (31.1%) was the most predominant bacteria isolated in this location followed by Klebsieella pneumoniae (22.2%), Klebsiella oxytoca (13.9%), Escherichia coli (11.1%), Pseudomanas aeruginosa (5.6%), Aeromonas hydrophila (5.6%), Acinetobacter baumannii (4.6%), B. pseudomallei (2.8%) and Proteus spp (2.8%) in order of ranking. The distribution of aetiology of lower respiratory tract as recorded in this study is similar to the previous study at National Hospital Abuja (Abdullahi and Iregbu, 2018), study in Shanghai, China from 2013 to 2015 (Pengcheng et al., 2018), a multicenter Analysis from Turkey (Guclu et al., 2021) and Ethiopia (Dessie et al., 2021) except that, in addition, the current study isolated Aeromonas hydrophila and B. pseudomallei. Some studies from neighbouring countries such as Yaoundé, Cameroon (Tchatchouang et al., 2019) and other studies in some part of Europe (Leven et al., 2018) documented S. pneumoniae as the leading pathogen of LRTIs followed by H. influenzae which contradict the current findings where Staphylococcus aureus were the most prevalence bacteria isolated followed by Klebsiella spp, this is similar to the findings in Bangladesh as reported by Borkot et al., (2016) and some studies from southern Ethiopia (Gebre et al., 2021)
Table 2 indicated that, LRTIs were more common in males (53.7%) than that of females (46.3%). This finding is similar to the work conducted in Kano by Taura et al., (2013), India (Shah et al., 2010), Abeokuta, Ogun State, Nigeria (Akingbade et al. 2012) and Bangladesh (Borkot et al., 2016) but however, these results contradicts the data obtained by El- Mahmood et al., (2010), in which in a similar study, out of 232 total isolates, 114 (49.1%) were from males while 118 (50.9%) from females. This also contradicts previous findings in 11 European countries (Belgium, Spain, Poland, Slovakia, UK, Slovenia, Sweden, Italy, France, Germany, and Netherland) where 60% of the female were reported with LRTIs (Ieven et al., 2018). Male prevalence of LRTI may be due to their exposure to different group of population and also to some associated risk factors of respiratory tract infection such as smoking, alcohol consumption and COPD (Panda et al., 2012; Borkot et al., 2016).
Table 3 demonstrated that, most of pathogens were isolated among patients in age range 20–39 years with the percentage occurrence of 43.5%, closely followed by age range 40–59 years with 36.1%, the lowest rate was recorded in age range 0–19 and 60–79 years with 10.2% each. From our study, it was observed that, the young adults and the elderly were most at risk of a severe respiratory condition. This finding tally with the work of Taura et al., (2013) in Kano, Nigeria and some works conducted in Bangladesh (Borkot et al., 2016), India (Akansha et al., 2017) and northwest Ethiopia (Tomasz et al., 2013). In contrast to the current study as reported by Dessie et al., (2021) in Ethiopia, aging is a risk factor for bacterial pneumonia. In their study, the age group > 64 years was 2.4 times more likely to have bacterial pneumonia compared to the age group of 5–15 years (Almirall et al., 2017). Similar findings were reported from Spain (Prina et al., 2015; Rivero-Calle et al., 2016), Pakistan (Ahmad et al., 2017), Japan (Morimoto et al., 2015), and the USA (Quartin et al., 2013)
Table 4 revealed that, most of the isolates were susceptible to piperacilin ((51%), trimetprin sulphamethoxazole (61%), Azithromycin (70%), Ciprofloxacin (71%) and Gentamycin (74%), in order of ranking, these are supported by the findings of El-Mahmood et al., (2010), Taura et al., (2013) and a study in Kathmandu, Nepal (Rakshya et al., 2018). High resistance were recorded in almost all the βeta-lactam antibiotics tested such as Ceftriaxone (63%), Cefuroxime (70%), Cefotaxime (71%), Ceftazidine (75%), Oxacillin (87%) and Amoxicillin (93%). High resistance were also recorded among macrolide (Erythromycin) and Glycopeptide (Vancomycin). This findings correlate with the work carried out by Barkot et al., (2016) in Bangladesh.
Staphylococcus aureus displayed wide range of resistance among βeta-lactam antibiotics tested such as Amoxicillin, cloxacillin, cefuroxime, ceftazidine, cetriaxone, cefixime, cefotaxime except piperacillin in which 50% of the isolates were susceptible, 24% were intermediately resistance and 26% were resistance. Moderately resistance were found associated with erythromycin and Vancomycin among Staphylococcus aureus isolates in this study. Gentamycin and trimtophrim sulphamethoxazole remain the drug of choice in the treatment of LRTI caused by Staphylococcus aureus in this location followed by Azithromycin and ciprofloxacin. The resistance pattern of Staphylococcus aureus is Similar to the work of Garba et al., (2017) in Zaria among Staphylococcus aureus isolated from different clinical samples.
Klebsiella pneumoniae is the second most predominant bacteria isolated from patients with clinical evidence of LRTI in this location followed by Klebsiella oxytoca. They demonstrated an alarming resistance among βeta-lactam antibiotics such as cefuroxime, ceftazidine, ceftriaxone, cefixime, cefotaxime except piperacillin. While Ciprofloxacin and gentamycin demonstrated high activity among Klebsiella pneumoniae and Klebsiella oxytoca isolates followed by Azithromycin and trimethoprim sulphamethaxazole, this finding is similar to the work of Rakshya et al., (2018) in Nepal and Abayomi et al., (2020) in Ogbomoso, Nigeria.
The activity of βeta-lactam antibiotics on Eschericia coli was moderate except that high resistance were recorded on cefuroxime, this finding correlates with the work in Ogbomoso, Nigeria (Abayomi et al., 2020) Most of the Escherichia coli isolates were susceptible to gentamycin and trimethoprim sulphamethoxazole followed by Azithromycin and Ciprofloxacin.
Pseudomonas aeruginosa demonstrated 100% resistance to all βeta-lactam antibiotic tested except piperacillin and good activity were also documented on Ciprofloaxacin, Gentamycin and Azithromycin. The resistance to all antibiotics tested by Pseudomonas aeruginosa as presented in this study is of public health concern with associated treatment failure. P. aeruginosa is a common pathogen in the lungs of those with cystic fibrosis (CF) and is associated with frequent pulmonary exacerbations and high morbidity and mortality (Sriramulu, 2013). The lungs of patients with CF can harbor this organism for decades. With increasing levels of P. aeruginosa drug resistance, treatment of pulmonary exacerbations can be increasingly difficult over time (Atkin et al., 2018).
Burkholderia pseudomallei demonstrated 100% resistance to all the antibiotics tested except that, one of the isolate was susceptible to gentamycin and two isolates were susceptible to ciprofloxacin. Burkholderia pseudomallei is the causative agent for melioidosis, an often fatal disease with a predicted global burden of 165,000 cases per year and 89,000 deaths worldwide (Limmathurotsakul et al., 2016). Regions of melioidosis endemicity, including Southeast Asia and northern Australia, account for up to 40% (Limmathurotsakul et al., 2010) and 10% (Currie et al., 2010) case fatality rates, respectively. Transmission routes include percutaneous inoculation, inhalation, and ingestion of contaminated soil and water (Limmathurotsakul et al., 2013). B. pseudomallei is intrinsically resistant to many antibiotics, including penicillin, ampicillin, and first- and second-generation cephalosporins (Wiersinga et al., 2018).
Aeromona hydrophila also shows resistance to almost all the antibiotics tested except Gentamycin and Azithromycin, this is consisted with the findings in Taiwan (Chao et al., 2013). This study also found out that, approximately 67% of the patients with Aeromonas infection had various underlying diseases, such as diabetes mellitus and hypertension. Similar findings have been reported in a number of case reports, Nagata et al., (2011) described a case of A. hydrophila pneumonia in a 75-year-old woman with colon cancer who died of the disease, Ye et al., (2010) reported on a patient with severe pneumonia due to drug-resistant A. caviae, and Murata et al., (2001) reported on a case of fulminant A. hydrophila pneumonia in a patient with chronic renal failure and liver cirrhosis. The morbidity and mortality rates associated with Aeromonas pneumonia were relatively high (Chao et al., 2013). Therefore, physicians should be aware that immunocompromised patients of advanced age are at risk of developing Aeromonas pneumonia.