In the present study, the Odds of death among neonates with positive cultures was 2.7 folds higher than those with a negative cultures (relative risk = 2.7, CI= 1.45-5.02, p= 0.002). The case fatality rate among neonates with positive and negative cultures was 49.4% and 28%, respectively. In a similar study, it was reported that the case fatality rate increased in neonates who had signs of infection with positive culture results compared to those with negative culture results (28.5% and 8.6%, respectively) [11]. Another study done by Mohaddesi et al, reported that the most common risk factor for neonatal deaths was sepsis, which raised the risk of death to 6.42 times compared to other causes [12]. The association between positive neonatal cultures and mortality might reflect a higher microbial load among neonates with positive cultures and thus a higher mortality rate. Neonates with clinical signs of infection and yet a negative culture might have had other non-culturable causes of sepsis (e.g: viral infections), or might have had a lower microbial load which was undetectable by conventional culture methods. Regarding the microbial profile of the neonatal infections, gram negative bacteria were the most prevalent microorganisms (47.4%) and were comprised mainly of K.pneumoniae (32.6%) and Acinetobacter spp. (11.6%). Gram positive bacteria were prevalent in 24.2% of positive neonatal 182 samples, and were mainly comprised of MRSA (11.6%). Candida spp. were isolated in 28.4% of positive neonatal samples. In a recent previous study in the same NICU, closely related results were reported, where the positive neonatal samples comprised mainly of K. pneumoniae (29.2%), C. albicans (20.8%), A. baumannii and S. aureus (12.5% each) and P. aeruginosa (8.3%) [13]. This consistent predominance of K. pneumoniae, Acinetobacter spp. and Candida spp. in both studies emphasizes the importance of tracing the reservoirs of such pathogens in this particular NICU and the implementation of proper infection control measures. Similarly, Gadallah et al. reported Klebsiella spp. as the predominant pathogen isolated from HCAIs [14]. However, contrasting results were reported in other studies. In Egypt, a study by Hassan et al, reported that among their positive cultures of neonates in NICU, gram positive bacteria were predominant [15]. Also, a study in Nigeria reported a predominance of gram positive bacteria among their positive culture results [16]. Another study in China reported that S. aureus, was the commonest microorganism isolated from their positive cases (37.5%) [17]. This difference may be due to variations in population characteristics and predisposing factors.
It was also noticed that Gentamycin and Cefoperazone which are routinely used in the protocol of this NICU department were not effective against K. pneumoniae, Acinetobacter and MRSA isolates and their use should be reconsidered. Physicians, nurses and workers at the NICU can serve as reservoirs and vehicles for the spread of pathogens from different hospital wards to NICUs. HCWs hands are a source of transmission of HCA pathogens. Bacterial contamination is often acquired after direct contact with patients, body fluid secretions, or indirectly after touching contaminated environmental surfaces. In the current study, 21 HCWs (8 physicians and 13 nurses) had their fingerprints cultured. The following pathogenic microorganisms were isolated from the hands of 19% of HCWs: MRSA (12.5%), K. pneumoniae (7.7%) and A. junii (12.5%). Sixteen (76%) of HCWs had CoNS on their hands. Sepehri et al. reported lower rates, where nearly 40% of HCWs’ hands had bacterial isolation with S.epidermidis, while contamination with HCAI pathogens was observed among 6% only of HCWs’ hands [18]. Contamination of the NICU environment plays an important role in the acquisition of HCA pathogens by both patients and HCWs. The rate of positive cultures of environmental surfaces in the current study was 23%.The most frequently pathogen contaminated samples came from sinks, as 60% of the samples from sinks were contaminated by different microorganisms (E. faecalis 7.5%, K. pneumoniae 6.25%, Acinetobacter spp. 3.75% and P. aeruginosa 3.75%). In a study of Tarabay et al, sinks were related to a P. auroginosa infection outbreak in a NICU, where exposure occurred through bathing of neonates, or healthcare staff using contaminated sinks for hand washing [19]. In the current study, 21.7% of crash carts samples were contaminated by E. faecalis, K. pneumoniae and P. aeruginosa. These carts are very important since they are used for neonatal drug preparations and are frequently touched by nurses. Incubators were contaminated (28.8%) with different microorganisms, which comprised mainly of CoNS (84.75%), E. faecalis (7.5%), K. pneumoniae (6.25%), Acinetobacter spp. (3.75%) and MRSA (2.5%). In a study by Gray et al., bacteria were isolated from 30% of incubators in a NICU which was close to the current study [20]. The role of the environment in transmitting infections to neonates has been a subject of debate, with conflicting results between studies. In the present study, the same microorganisms were isolated from incubators, weight balance and crash carts denoting possible role of environment in transmitting these pathogens to neonates. Sequencing showed that 3 Candida isolates from different neonates were identified as C. tropicalis, two of which were homologous, suggesting transmission among neonates, either directly or indirectly. The second Candida cluster was composed of one C. glabrata environmental strain (isolated from a crash cart) and another homologous neonatal strain, denoting a possible source of infection including environmental surfaces. An isolate of K.pneumoniae from the CSF showed homology with another isolate from a portal incubator. Similarly, another K.pneumoniae strain was detected in both a neonatal blood sample and an examining bed. There was also another common strain of K. pneumoniae isolated from different sources (CSF and HCWs finger printing). Similarly, Malik et al reported that K. pneumoniae environmental strains were the source of nosocomial infections [21]. In contrast, a study by Gramatniece et al, reported that they failed to identify the source of A.baumannii outbreak after taking almost 300 environmental samples from different sites in the NICU [22].
In the present study, all homologous strains of K. pneumoniae (from all sources) were also multi-drug resistant. This denotes the perpetuation of such MDR pathogens between different reservoirs in the NICU, and necessitating their tracing and eradication.
Despite the various spectrum of pathogens isolated in the present study, it was noted that only Klebsiella spp. and Candida spp. showed homology between isolates from different sources. Their easy transmissibility between reservoirs in the NICU reflects high virulence and the need for more diligent infection control measures and antimicrobial stewardship.
Although the most highly contaminated environmental surface in this study were sinks (60% of them were contaminated), however, none of their strains were identical to any of those from neonates. On the other hand, environmental strains with shared homology to neonatal ones came from: crash carts, examining beds and portal incubators. These sites therefore pose higher risk as surfaces of greater risk of infection transmission to neonates. We recommend that these sites should be addressed vigorously by the infection control team in this NICU with more frequent disinfection.
Limitations of the study
More environmental swab samples might have revealed more identical isolates shared between neonates, environment and HCWs. Differences in environmental surveillance cultures between studies might contribute to the discrepancy in the reported magnitude of the problem. The unequal number of environmental samples in our study should be reconsidered in future work, with more focus on the more highly contaminated surfaces.
Another limitation of our work was that antifungal susceptibility testing was not done for Candida spp. isolates.