*4.4.5* Enterobacter

*Pathogenic Bacteria*

implemented.

*4.4.3* Klebsiella

*K. pneumoniae* infections [87].

*4.4.4* Escherichia

*4.4.2* Pseudomonas

The pathogenicity, epidemiology, and virulence factors of *Staphylococcus* have been comprehensively reviewed [72]. It was highlighted that colonization is aided by biofilm formation that is housed in extracellular polymeric substance (EPS) found in many bacteria and that virulence factors are expressed with accessory gene regulator (agr) system in response to cell density [73]. To avoid formation of biofilms and EPS in the sachet water-producing environment, adequate personnel hygiene and good manufacturing practices that meet food safety standards must be

The genus *Pseudomonas* especially *P. aeruginosa* is known globally as endemic [74] and an opportunistic pathogen that causes several infections [75]. They are often isolated in clinics [76], and other sources may include residential, recreational, or surface water [77]. The colonies are usually heavily mucoid on solid media. It has been reported that mechanisms of antimicrobial resistance in *Pseudomonas* strains and most bacteria include multidrug efflux pumps and downregulation of outer membrane porins, whereas virulence may include secretion of toxins and the ability to form biofilms [78, 79]. A natural property of *Pseudomonas* is the possession of multiple mechanisms for different forms of antibiotic resistance [80], and this may have facilitated its occurrence in boreholes and sachet water.

*Klebsiella* causes many infections, which includes urinary tract infections, pneumonia, bacteremia, and liver abscesses [81]. The genus is associated with water, and this may be why it has been isolated in both borehole and sachet water. The organism is found in drinking water [82], rivers [83], and sewage water [84], which may encourage environmental spread. It has been reported that the organism has a variety of virulence and immune evasive factors, which contribute to uptake of genes associated with antimicrobial resistance and pathogenicity [85]. A report [86] suggested that the species *K. pneumoniae* acquired antimicrobial resistance genes independently and their population is highly diverse. An analysis of strains from human and animal isolates spanning four continents has shown convergence of virulence and resistance genes, which may lead to untreatable invasive

The most studied species of the *Escherichia* genus is *E. coli*, a coliform bacteria used to verify hygiene status in food and water. Usually, the presence of various strains of pathogenic or nonpathogenic *E. coli* in food or water samples indicates fecal contamination [88]. It has been reported that [89] a comparative analysis show that avian and human *E. coli* isolates contain similar sets of genes encoding virulence factors and that they belong to the same phylogenetic groups, which may

A study of the prevalence of *E. coli* strain O157:H7 in England and Scotland showed that it has a seasonal dependency, with greater fecal shedding of the organism in the warmer months together with increased reporting of *E. coli* O157:H7 infection among hospitalized patients [90]. This finding is very worrying because it suggests that there could be high prevalence when applied to Nigeria because the country has a warm climate all year round. However, good manufacturing practices irrespective of the climate appear to be the key factor in producing packaged

indicate the zoonotic origin of extraintestinal pathogenic *E. coli*.

**222**

The genus *Enterobacter* consists of coliforms that are known to be of non-fecal origin. It is believed [92] that many *Enterobacter* species, which could act as pathogens, are widely encountered in nature but are most frequently isolated in human clinical specimens possibly because phenotypic identification of all species belonging to this taxon is usually difficult and not always reliable. Therefore, the identification of this genus in borehole and sachet water may need a revisit since molecular methods were not used. The organism is known as a ubiquitous and persistent Gram-negative bacterium in drinking water [17], but there are few studies of its occurrence or prevalence in borehole and sachet water or other water sources in Nigeria.

To understand the carbapenemase-producing *Enterobacter* spp. and the development of molecular diagnostics, Chavda et al. [93] used genomic analysis of 447 sequenced strains to establish diverse mechanisms underlying the molecular evolutionary trajectory of drug-resistant *Enterobacter* spp. Their findings showed the acquisition of an antibiotic resistance plasmid, followed by clonal spread and horizontal transfer of *blaKPC*-harboring plasmids between different phylogenomic groups. The report also showed repeated transposition of the *blaKPC* gene among different plasmid backbones.
