Due to different empirical uses of antibiotics and implementation of preventive measures, the bacterial spectrum may vary geographically and temporally (9). In this multicenter retrospective study, we highlight Klebsiella pneumoniae, Escherichia coli and GBS as the leading causes of EOS, HALOS and CALOS, respectively. This study was conducted in China, a lower-middle income country with paucity of high-quality data. HALOS caused by K pneumonia predominated in our study and was associated with a high degree of AMR and adverse outcomes. The result would be important for clinicians in Chinese NICUs to guide optimal clinical prevention strategies and for consideration of empirical antibiotic treatment during clinical management.
Nosocomial infection is a major health problem particularly in NICUs in developing countries (20). In current study, about two thirds of pathogens identified were responsible for HALOS. Approximately 60% of HALOS were due to GNB which was similar to the results from previous Chinese studies (21, 22). A review of 11,471 bloodstream samples indicated that GNB was detected from no less than 60% of positive blood cultures in all the developing settings of the world (23). Similar to that reported from South Asia (3) and Egypt (7), Klebsiella pneumonia was the most common GNB causing LOS. By contrast, Coagulase negative staphylococcus (CoNS) was significantly predominant in western countries for LOS, such as 40% in Switzerland (10). The preponderance of CoNS might indicate the developed regions’ adoption of neonates with lower gestational age and lower birth weight and prolonged use of central catheters which are risk factors for CoNS infection (24). The predominance of GNB in our developing counties may largely be attributed to the lack of standard infection-control practices. Insufficient hand hygiene, lack of essential equipment and supplies including sinks, running water and disposables, overcrowding and understaffing are described to be key contributions to nosocomial infection caused by GNPs (25). We find that HALOS frequently correlated with low gestational age, low birth weight and comorbidities which were also mentioned in another recent prospective population-based cohort study (10). Therefore, implementation of these basic hygiene practices should be emphasized more in Chinese NICUs to minimize the hazards of the high incidence of HALOS caused by GNB. Also, empiric antibiotics selected to treat suspected HALOS in Chinese NICUs need to effectively treat GNP, especially Klebsiella pneumonia.
Another remarkable finding in the Chinese NICUs was the relatively high percentage of fungi in HALOS. Nearly all the identified fungi infections were responsible for HALOS, which was paralleled with other Chinese studies (21, 22). Similarly, recent studies have also reported outbreaks of fungal nosocomial infection in Chinese NICUs which alerted clinicians (26, 27). Prolonged antibiotic therapy, broad spectrum antibiotic exposure may be the connection to high prevalence of fungi nosocomial infections (28). This highlights the need to develop new and more effective approaches to prevent HALOS.
A strength of this study was that all 25 hospitals have their own maternity/obstetric ward and almost all neonates were born onsite with only a few transferred. This makes the pathogens in EOS more precise and representable. In the current study, Escherichia coli was the most common pathogen in EOS, followed by GBS. Similarly, the latest surveillance from a national neonatal research network in US demonstrated the shift from GBS to E. coli as the predominant pathogen and the increase in Escherichia coli infections among very low-birth-weight infants (29). Escherichia coli predominated among preterm infants in current study which was similar to those reported in most developed countries (6, 10, 29). Previously, GBS was reported to be a rare cause of EOS and was documented in only few reports from China and other Asian countries (7, 30). Reason for the low proportion of GBS in EOS may be partially due to the overuse of antenatal antibiotics in China. However, we did not have the data on antenatal antibiotic use. Escherichia coli was the most common pathogen in EOS and the second common in HALOS. The extraordinary similarity of this spectrum supports the assumption that the cause of EOS may not only be due to vertical transmission from mothers but also can be caused by unsanitary practices in the labour rooms and NICUs. Further investigations are of urgent need to identify the causes of GNP in EOS in China and subsequently develop targeted prevention strategies.
Most CALOS occurred in term or near-term newborns, accounting for a small percentage of BSI. GBS and Staphylococcus aureus were the leading responsible pathogens. Similar to reports in developed counties, infants with CALOS had a higher birth weight and gestational age and fewer adverse outcomes compared to those who developed HALOS (10). The relatively low incidence rate may be related to the lack of strict management of antibiotics in China and relatively easy access. Antibiotics may have been applied before admission resulting in false negative results in blood cultures.
Ampicillin/piperacillin and third-generation cephalosporin are the first choices for empirical treatment to neonatal sepsis in China (31) however ampicillin and gentamicin are commonly recommended in some areas (32). Unfortunately, in our study, GNB from HALOS exhibited a high degree of resistance to first and second line drugs recommended by the World Health Organization, ampicillin (87.5%-100%) and third generation cephalosporins (26%-63.3%), whereas only 6%-20.9% exhibit resistance to gentamicin. Furthermore, a relatively high proportion of GNB was resistant to the WHO classified “watch group” antibiotics, such as meropenem (2.7%-31.3%). Nowadays, multidrug-resistance GNB is of increasing concern in neonates because few therapeutic options are available (33). Klebsiella pneumonia and Escherichia coli received much attention because of their high rates of MDR in HALOS (60.7%) and EOS (40.4%), respectively. Research found that the most frequent mechanism of MDR in GNB was ESBL production (34). Paralleled to the rates of MDR, approximately two thirds of Klebsiella pneumonia in HALOS and half of Escherichia coli in EOS were resistant to third-generation cephalosporins. The increasing resistance to second and third line antibiotic medication is of great concern. When suspecting sepsis in a neonate that might be caused by a GNB, empiric use of the available antibiotic should be more and more tailored to the local antibiogram.
Another issue of equal concern is the high proportion of methicillin-resistant Staphylococcus aureus in LIMCs, especially in south Asia where 56% of S. aureus infections were reported to be methicillin-resistant (23). In our study, more than two thirds of Staphylococcus aureus were methicillin resistant. Fortunately, all of the cases remained susceptible to watch group antibiotics such as vancomycin, which was in agreement with most other studies (7, 16).
Antimicrobial resistance is a rapidly emerging, potentially disastrous problem. Resistance to alternative antibiotics is seriously limiting our antibiotic options. In general, empirical antibiotic treatment should be guided by the antimicrobial resistance patterns of bacterial pathogens commonly detected from local infections. We need more reliable and accurate diagnostic methods to rule out sepsis, thereby preventing abuse of antibiotics in NICUs.
Strengths of this study include its enrollment of pathogens from all neonates admitted to the NICU, distinguishing pathogens and AMR between EOS, HALOS and CALOS, and large sample size. The following limitations should be considered: 1) the choice of a definition on neonatal sepsis is a limitation inherent to many studies. The diagnosis of neonatal sepsis is mainly based on Chinese Consensus formulated by Chinese Pediatric Society which may not have been widely accepted (24). The diagnosis of infection of CONS usually relies on confirmation with second blood culture, but this practice is not routinely followed in LMICs. Therefore we are not certain whether CONS represented true pathogen infections or potential contaminants; 2) antibiotics are usually used in offsite born neonates prior to admission that limit potential pathogens identified for CALOS. 3), we merely collected the data on the proportion of causative pathogens between EOS, HALOS and CALOS, but we were unable to calculate the incidence rates.