While it is reported that COVID-19 patients are more prone to secondary bacterial infections, which are strongly linked to the severity of complications of the disease, bacterial coinfections associated with COVID-19 are not widely studied. This work aimed to investigate the prevalence of bacterial coinfections and associated antibiotic resistance profiles among hospitalised COVID-19 patients. Age, gender, weight, bacterial identities, and antibiotic sensitivity profiles were collected retrospectively for 108 patients admitted to the intensive care unit (ICU) and non-ICU ward of a single center in Saudi Arabia. ICU patients (60%) showed a significantly higher percentage of bacterial coinfections in sputum (74%) and blood (38%) samples, compared to non-ICU. Acinetobacter baumannii (56%) and Klebsiella pneumoniae (56%) were the most prevalent bacterial species from ICU patients, presenting with full resistance to all tested antibiotics except colistin. By contrast, samples of non-ICU patients exhibited infections with Escherichia coli (31%) and Pseudomonas aeruginosa (15%) predominantly, with elevated resistance of E. coli to piperacillin/tazobactam and trimethoprim/sulfamethoxazole. This alarming correlation between multi-drug resistant bacterial coinfection and admission to the ICU requires more attention and precaution with prescribed antibiotics to limit the spread of resistant bacteria and improve therapeutic management.

Infections caused by multi-drug-resistant bacteria in patients with chronic diseases have been associated with high mortality and morbidity. While few reports have evaluated bacterial infections in multiple chronic disease patients, the focus of the current study was to investigate the prevalence of bacterial infections and the susceptibility profiles of causative strains among various groups of patients suffering from chronic diseases. Microbiological reports of patients suffering from cancer, diabetes mellitus, cardiovascular diseases, kidney diseases, and skin burns were retrospectively collected from a tertiary hospital in Saudi Arabia. Approximately 54.2% of recruited patients were males, and positive urine was the most prevalent specimen associated with kidney disease patients (25%). Escherichia coli isolates were predominant among cardiovascular, kidney, and cancer patients. Staphylococcus aureus was commonly detected in diabetics and those with burns. Although resistance patterns varied based on the type of specimens and underlying diseases, Escherichia coli showed limited resistance to colistin, carbapenems, and tigecycline, while S. aureus demonstrated susceptibility to ciprofloxacin, gentamicin, and rifampin. These observations are crucial for clinicians and policymakers to ensure effective treatment plans and improve outcomes in these patients with comorbidity.

Neonatal infections including sepsis and urinary tract infections are considered among the leading causes of mortality in neonatal intensive care units (NICU). Thus, use of empiric antibiotics is very important in infected neonates and the success of this practice is mainly reliant on the availability of an up-to-date antibiogram for currently used antibiotic drugs. In this study, we aim to determine the bacteriological profile and antibiotic susceptibility pattern of bacteria isolated from blood or/and urine cultures belonging to patients at the NICU. A total of 54 urine samples were collected in the period between January 2015 and December 2019. Data of infants with positive urine and blood bacterial isolates were gathered retrospectively. The most commonly isolated bacteria from urine observed were K. pneumoniae (44%) and E. coli (39%), while Acinetobacter baumannii (33%) and K. pneumoniae (22%) predominated in neonatal blood samples. The majority of uropathogens and blood isolates exhibited low resistance to imipenem and tigecycline, respectively. These antibiotics would be recommended for future use as empirical treatment in neonates with urinary tract infections and/or sepsis. This investigation highlights the importance of surveillance studies to manage and ensure the effectiveness of treatment plan for critically ill infants.

Many bacteria produce polysaccharide-based capsules that protect them from environmental insults and play a role in virulence, host invasion, and other functions. Understanding how the polysaccharide components are synthesized could provide new means to combat bacterial infections. We have previously characterized two pairs of homologous enzymes involved in the biosynthesis of capsular sugar precursors GDP-6-deoxy-D-altro-heptose and GDP-6-OMe-L-gluco-heptose in Campylobacter jejuni. However, the substrate specificity and mechanism of action of these enzymes - C3 and/or C5 epimerases DdahB and MlghB and C4 reductases DdahC and MlghC - are unknown. Here, we demonstrate that these enzymes are highly specific for heptose substrates, using mannose substrates inefficiently with the exception of MlghB. We show that DdahB and MlghB feature a jellyroll fold typical of cupins, which possess a range of activities including epimerizations, GDP occupying a similar position as in cupins. DdahC and MlghC contain a Rossman fold, a catalytic triad and a small C-terminal domain typical of short-chain dehydratase reductase enzymes. Integrating structural information with site-directed mutagenesis allowed us to identify features unique to each enzyme and provide mechanistic insight. In the epimerases, mutagenesis of H67, D173, N121, Y134 and Y132 suggested the presence of alternative catalytic residues. We showed that the reductases could reduce GDP-4-keto-6-deoxy-mannulose without prior epimerization though DdahC preferred the pre-epimerized substrate, and identified T110 and H180 as important for substrate specificity and catalytic efficacy. This information can be exploited to identify inhibitors for therapeutic applications or to tailor these enzymes to synthesise novel sugars useful as glycobiology tools.

RNA thermometers (RNATs) trigger bacterial virulence factor expression in response to the temperature shift on entering a warm-blooded host. At lower temperatures these secondary structures sequester ribosome-binding sites (RBSs) to prevent translation initiation, whereas at elevated temperatures they “melt” allowing translation. Campylobacter jejuni is the leading bacterial cause of human gastroenteritis worldwide yet little is known about how it interacts with the host including host induced gene regulation. Here we demonstrate that an RNAT regulates a C. jejuni gene, Cj1163c or czcD, encoding a member of the Cation Diffusion Facilitator family. The czcD upstream untranslated region contains a predicted stem loop within the mRNA that sequesters the RBS to inhibit translation at temperatures below 37°C. Mutations that disrupt or enhance predicted secondary structure have significant and predictable effects on temperature regulation. We also show that in an RNAT independent manner, CzcD expression is induced by Zn(II). Mutants lacking czcD are hypersensitive to Zn(II) and also over-accumulate Zn(II) relative to wild-type, all consistent with CzcD functioning as a Zn(II) exporter. Importantly, we demonstrate that C. jejuni Zn(II)-tolerance at 32°C, a temperature at which the RNAT limits CzcD production, is increased by RNAT disruption. Finally we show that czcD inactivation attenuates larval killing in a Galleria infection model and that at 32°C disrupting RNAT secondary structure to allow CzcD production can enhance killing. We hypothesise that CzcD regulation by metals and temperature provides a mechanism for C. jejuni to overcome innate immune system-mediated Zn(II) toxicity in warm-blooded animal hosts. Sensing the elevated warm-blooded host body temperature through structural changes in so-called RNA thermometers is a recognised virulence strategy in bacterial pathogens and allows appropriate production of virulence factors in the host environment. We demonstrated that this regulatory mechanism is used by Campylobacter jejuni, a globally significant cause of human gastroenteritis, to control production of the CzcD protein that we show acts as a Zn(II) exporter providing tolerance to high levels of Zn(II). From published data, Zn(II) exporters are known to enable bacterial pathogens to overcome host-induced Zn(II) poisoning—a newly discovered innate immune response to infection. Indeed using a simple larval infection model we demonstrated that CzcD enhances larval killing and disrupting the RNA thermometer to allow CzcD production also enhanced killing at lower temperatures. These findings indicate that CzcD temperature regulation enables C. jejuni to overcome host induced Zn(II) toxicity during colonisation of animal hosts including humans. Our results open up a novel area of the host-pathogen interface for investigation in this poorly understood human pathogen. It may also be possible to exploit these findings to develop metal-based intervention strategies to reduce both levels of Campylobacter in the food chain and consequent zoonotic infections.