Klebsiella pneumoniae has been implicated as one of the main human pathogens causing nosocomial and community acquired infections over a long period of time. Due to antimicrobial resistance, treatment of K. pneumoniae infections has become exceedingly complicated (Moradigaravand et al., 2017). Furthermore, the situation is worsened when antimicrobial resistance is acquired by highly pathogenic strains. Most importantly, resistance to carbapenems of carbapenemase in Klebsiella pneumoniae epitomizes a great threat to the delivery of health services worldwide. To decipher the state of affairs in Uganda, we investigated the prevalence of carbapenem resistant pathogenic K. pneumoniae in Uganda. Findings from this study exhibited that 56.4% of the MDR K. pneumoniae isolates were recovered from urine, 21.2% from pus swab and 10.1% from blood. Indeed, previous studies implicated K. pneumoniae as one of the predominant causes of urinary tract infections, surgical wound infections and bacteriemia [21, 22].
The study screened 227 MDR K. pneumoniae isolates obtained from four tertiary hospitals located in different regions for carbapenem resistance. High overall phenotypic carbapenem resistance prevalence of 23.3% was detected. This is in agreement with other studies in Uganda and Tanzania that reported phenotypic carbapenem resistance prevalence among Enterobacteriaceae of 22.4% [23] and 24% [24] respectively. However, a similar study at MBRRH detected lower phenotypic prevalence of 12.6% [25]. Contrary to this, studies in North Africa and West Africa reported remarkably higher phenotypic resistance of > 50% and K. pneumoniae were the most prevalent isolates [26–29]. Furthermore, in a larger study which covered Gauteng, KwaZulu-Natal, Western Cape and Free State provinces in South Africa documented overwhelming phenotypic resistance of between 47–50% to Imipenem, Meropenem and Doripenem, 84% and 89% to Ertapenem [30, 31]. In comparison with previous studies at MNRH [23] and MBRRH [25] this study shows that the prevalence of carbapenem resistance in Uganda is on the rise and this is terrifying as recent meta-analyses revealed a substantial correlation between carbapenem resistant infections and increased risk of death [32].
Through molecular characterization, we detected carbapenem genotypic resistance frequency ranging from 32.4% at KIU-TH to 70.8% at MRRH and overall genotypic resistance prevalence of 43.2% in Uganda. In contrast, the overall genotypic prevalence was lower than that reported in Tunisia (86.3%) [33], Egypt (56%) [27], South Africa (86.0%), [31], India (76.3%) [34]. Among the five genes which were detected by multiplex PCR, the most encountered gene was OXA-48-like at a genotypic frequency of 36.4%. This corroborates well with recent studies which documented OXA-48-like gene and its variants as the most prevalent genes [27, 31, 33, 35]. OXA-48. OXA-48 was first detected in K. pneumoniae isolate in Turkey 2003. OXA-48 producers spread sporadically to the neighboring countries located in the southern and eastern part of the Mediterranean Sea, and north Africa [36]. This provides an insight why the occurrence of OXA-48 is predominantly high in Egypt and Tunisia [27, 33]. Previous studies reported NDM as the most dominant gene in South Africa [30, 37], VIM and IMP as the most prevalent genes in East Africa [23–25, 38] in contrast with the results of this study. This trend of events clearly shows that OXA-48 producing E. coli and K. pneumoniae have invaded sub-Saharan Africa through immigration of individuals from the endemic region.
The overall phenotypic resistance registered by this study was lower than the genotypic resistance. For example, all isolates which harbored VIM expressed phenotypic resistance to Ertapenem. Whereas OXA-48 provided protection in only 38.3% of the isolates that sheltered it in disc diffusion assays. Oxacillinases encoded for by OXA-48 and its variant genes have been reported to possess low carbapenems hydrolyzing activity [36, 39, 40]. This enlighten why 61.7% of the isolates that housed OXA-48-like genes were sensitive to carbapenems. Furthermore, results of this study outlines that not all isolates that harbored carbapenemase genes were carbapenem insusceptible. This agrees with [40] findings who reported that modification and down regulation of outer membrane proteins through which drugs diffuse to reach their targets complements gene products and among the carbapenems, Ertapenem is affected most by this scenario. This elucidates why resistance to ertapenem was significantly high. Thus, presence of a carbapenemase encoding genes alone does not guarantee resistance.
The capsule is one of the major factors that influence virulence in K. pneumoniae. Several studies have documented how capsular types influence pathogenicity of K. pneumoniae associated infections[8, 41]. Previous studies unraveled the structures of the gene cluster in Klebsiella spp responsible for capsular polysaccharide synthesis (CPS) in some types [42, 43]. The genetic structure is composed of a cluster of six highly conserved genes among different capsule types namely galF, cpsACP, wzi, wza, wzb and wzc that encodes for proteins that play a role in CPS translocation and processing at the bacterial surface and are located at the 5′ end of the cps regions and genes encoding glucose-6-phosphate dehydrogenase (gnd) and UDP-glucose dehydrogenase (ugd) found at the 3′ end. In the middle of the CPS loci lies a variable region that contains certain genes (Wzy and Wzx) that transcribe proteins accountable for polymerization and putting together of the specific CPS subunits. Thus, the great sequence variation of the wzy gene among the different capsular types is the basis of PCR capsular typing assays [43–45]. In light of this, we exploited the Wzy gene to characterize the most clinically important K. pneumoniae capsular serotypes isolated from different tertiary hospitals in Uganda.
Capsular typing by heptaplex PCR revealed that K1, K2, WzyK3, K5 and K20 accounted 46.7% (106/227) of the K. pneumoniae clinical isolates. K54 and K57 were not detected in any of the isolates. Klebsiella pneumoniae K1 and K2 have been reported as the most virulent capsular types causing septicemia and liver abscess [41, 43]. However, other capsular serotypes are equally important as K5.and K20 are also associated with community acquired ailments whereas K3 causes chronic granulomatous infection of the nasal cavity and in some patients, the infection advance and lead to severe respiratory impairment [10, 13]. Thus, the high prevalence of pathogenic capsular serotypes isolated from clinical specimens is a great threat to the healthcare system. There is no data about incidence of K. pneumoniae K types within the sub-Saharan region for comparison. However, results of this study are in line with Lin et al., [46] who reported K1, K2, K3, K5 and K20 as the most prevalent capsular types in Taiwan. Furthermore, out of the 106 klebsiella pneumoniae capsular types, 37 exhibited resistance to carbapenems yet carbapenems are regarded as the drugs of choice for treatment of MDR Gram-Negative HAI when the first line drugs have failed [47]. Acquisition of carbapenem resistance in pathogenic bacteria correlates with treatment failure in addition to increased morbidity and mortality [21]. Investigations elsewhere which looked clinical samples, associated coexistence of capsular and other virulent factors such as rmpA and aerobactin genes with hypervirulent or hypermucoviscous K. pneumoniae variant (hvKP) [48, 49]. Despite the fact that this study did not attempt to detect other virulence factors, high occurrence of carbapenem resistance in capsular serotypes detected in study suggests possible existence carbapenem resistant hypervirulent K. pneumoniae (CR-HvKP) in Ugandan clinical settings. Indeed, this has been case in clinical settings with substantial carbapenem resistance [50–52].