The emergence of multi-drug-resistant bacteria causing healthcare-associated infections in COVID-19 patients: a retrospective multi-centre study.

INTRODUCTION: We evaluated the prevalence, aetiologies and antibiotic resistance patterns of bacterial infections in hospitalized patients with laboratory-confirmed SARS-CoV-2. We also investigated comorbidities, risk factors and the mortality rate in COVID-19 patients with bacterial infections. METHODS: This retrospective observational study evaluated medical records of 7249 randomly selected patients with COVID-19 admitted to three clinical centres between 1st January 2021 and 16th February 2022. A total of 6478 COVID-19 patients met the eligibility criteria for analysis. RESULTS: The mean age of the patients with SARS-CoV-2 and bacterial infections was 68.6 ± 15.5 years (range: 24-94 years). The majority of patients (68.7%) were older than 65 years. The prevalence of bacterial infections among hospitalized COVID-19 patients was 12.9%, most of them being hospital-acquired (11.5%). Bloodstream (37.7%) and respiratory tract infections (25.6%) were the most common bacterial infections. Klebsiella pneumoniae and Acinetobacter baumannii caused 25.2% and 23.6% of all bacterial infections, respectively. Carbapenem-resistance in Enterobacterales, A. baumannii and Pseudomonas aeruginosa were 71.3%, 93.8% and 69.1%, respectively. Age >60 years and infections caused by ≥3 pathogens were significantly more prevalent among deceased patients compared with survivors (P<0.05). Furthermore, 95% of patients who were intubated developed ventilator-associated pneumonia. The overall in-hospital mortality rate of patients with SARS-CoV-2 and bacterial infections was 51.6%, while 91.7% of patients who required invasive mechanical ventilation died. CONCLUSIONS: Our results reveal a striking association between healthcare-associated bacterial infections as an important complication of COVID-19 and fatal outcomes.

Clinical and molecular characteristics of OXA-72-producing Acinetobacter baumannii ST636 outbreak at a neonatal intensive care unit in Serbia.

AIM: To describe an Acinetobacter baumannii outbreak among preterm neonates in a neonatal intensive care unit (NICU) in Serbia. METHODS: A case-control study was conducted in the NICU at the Institute of Neonatology, Belgrade, Serbia. The case definition of A. baumannii bloodstream infection (BSI) was blood culture confirmation of systemic infection. Isolation, identification and susceptibility testing were performed using conventional methods. Molecular characterization of isolates included resistance gene detection, pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing. Outcomes and clinical and demographic data were obtained from patients' medical records. An infection prevention team was formed and infection control interventions were implemented. FINDINGS: During the outbreak period (May-July 2018), there were 13 cases of A. baumannii BSI among 82 hospitalized neonates. All A. baumannii strains were carbapenem resistant and susceptible to colistin. Molecular characterization of the isolates revealed that they harboured blaOXA66 and blaOXA72 beta-lactamases and belonged to sequence type 636, while the PFGE pattern indicated clonal spread. Lower gestational age, lower Apgar score, vaginal delivery and mechanical ventilation were risk factors for A. baumannii infection. Four patients died, eight patients were treated successfully with colistin, and one patient with sepsis and meningitis on dual ampicillin-sulbactam and colistin therapy recovered with sequelae. The outbreak was eventually controlled by reinforcement of the infection control measures based on a multi-tiered interventional approach. CONCLUSION: This is the first description of an outbreak of BSI among preterm neonates caused by A. baumannii blaOXA66/blaOXA72/ST636 in Serbia.

Trends in macrolide resistance of respiratory tract pathogens in the paediatric population in Serbia from 2004 to 2009.

We report the first study of macrolide resistance in respiratory tract pathogens in a Serbian paediatric population. It included 5293 Streptococcus pneumoniae, 4297 Streptococcus pyogenes, 2568 Moraxella catarrhalis and 1998 Haemophilus influenzae isolates derived from the respiratory tract and 110 invasive isolates from children aged up to 18 years during 2004-2009. Over the 6-year period, a significant increase (P < 0·01) in macrolide resistance was found in both S. pneumoniae and S. pyogenes that reached 45% and 19%, respectively, in 2009. In the same period, consumption of macrolides increased continually from 2·46 to 5·8 defined daily dose/1000 inhabitants per day. The increase in macrolide resistance in S. pyogenes correlated with consumption of total macrolide and long-acting macrolides (r = 0·879, P = 0·05 and r = 0·922, P = 0·026, respectively). A similar trend was observed in pneumoccoci, although it did not reach statistical significance. The growing problem of macrolide resistance in pneumococci and S. pyogenes in Serbia requires further vigilant surveillance.

Typing of macrolide resistant group A streptococci by random amplified polymorphic DNA analysis.

OBJECTIVE: Several studies of group A streptococci (GAS) have revealed that a small number of dominant resistant clones might be responsible for the spread of Streptococcus (S.) pyogenes resistance to macrolides. We aimed to determine the genetic diversity of macrolide resistant group A streptococci (MRGAS), isolated from patients with pharyngitis in Serbia. MATERIALS AND METHODS: The clonal relationships among 76 MRGAS isolates collected during 2008 were studied using two molecular typing methods: emm typing and random amplified polymorphic DNA (RAPD) analysis. Isolates that share the same emm type and RAPD pattern were considered to belong to the same clone. RESULTS: Out of 7 distinct emm types identified, the 3 most frequently occurring overall were emm12, emm75 and emm77 (> 90% of isolates). Although as many as 26 different RAPD patterns were found among the isolates studied, two clones with emm12 and emm77 accounted 32 out of 76 (42%) isolates. CONCLUSIONS: The results indicate a polyclonal spread of erythromycin-resistant Streptococcus pyogenes in our country. Furthermore, predominance of two clones, particularly among emm12 and emm77 strains indicates that erythromycin-resistant GAS of the same clonal origin are widely distributed in Serbia.

Distribution of emm types among group A streptococcal isolates from Serbia.

This is the first study concerning the molecular epidemiology of group A streptococcus in Serbia and includes 145 isolates from patients with various infections during the period 2001-2007. The emm types, superantigen profile and susceptibility pattern were determined. Among 31 emm types identified, the most prevalent were emm 6, emm 12, emm 1, and emm 58. All isolates showed uniform antimicrobial susceptibility to all tested antibiotics, with the exception of tetracycline and erythromycin (41% and 0.7% resistant strains, respectively). Significant heterogeneity of emm types was found, with a high frequency of emm 6 and emm 58, as well as a considerable prevalence of tetracycline resistance, and a low level of macrolide resistance.

Biotypes of group A streptococci from patients with pharyngitis and soft tissue infections.

This study determined the biotypes of group A streptococci (GAS) isolated from 66 pharyngeal and 62 skin and soft-tissue infections. Among all GAS isolates tested, the most common biotypes were 1 and 3, irrespective of the isolation source and the severity of clinical symptoms. However, compared with the pharyngeal group, a more heterogeneous distribution of biotypes was observed among the cutaneous group of isolates, including seven isolates that were non-typeable but had an identical biotype pattern, suggesting that they may represent a new biotype.

Significance of inoculum size in biofilm formation by staphylococci.

In the present study the effect of inoculum size, ranging from 10(6) to 1 cell, in biofilm formation by staphylococci was determined by microtiter plate test. The initial inoculum size had a dramatic effect on the quantity of biofilm formed. A decreased number of bacteria in initial inoculum always resulted in a decreased production of biofilm.

[Streptococcus pneumoniae and beta-lactam antibiotic agents]. / Streptococcus pneumoniae i beta-laktaminski antibiotiski lekovi.

Pneumococcus has been known for over 100 years. Despite an intensive research, the problem of pneumococcal diseases has not yet been solved. During the last few decades, the incidence of pneumococcal pneumonia has declined, but the S. pneumoniae is today the main, or one of the most frequent, causative agents of meningitis, sinusitis, otitis media and conjunctivitis. Besides, cases of pneumococcal appendicitis, tubo-ovarian abscess, haemolytico-uremic syndrome, cellulitis and urinary infections have been described. Therefore, it is very important from medical point of view to follow-up its sensitivity to antibacterial drugs. Unfortunately, during the latest decades, an increase in percentage of resistant clinical isolates has been registered. It is obvious that the investigation of the sensitivity of pneumococci, that is, of their resistance to beta-lactam antibiotics is essential. The examination of the interaction between pneumococci and penicillin has resulted in significant discoveries concerning the mechanism of the effect of penicillin as well as the impact of penicillin-binding proteins, lipoteichoic acid and choline-residues in the cell wall. A particular contribution as regards the effect of penicillin has been achieved by linking murein hydrolases (autolythic enzymes) with the expression of bactericidal effect of penicillin. Besides, the model of pneumococcal resistance to penicillin together with the model of meticillin resistance of staphylococci enabled the perception of the new mechanism of bacteria resistance to beta-lactam antibiotics. Given the pathogenic potential of pneumococci and the increase of clinical isolates resistant to antibiotics, it can be concluded that immunoprophylaxis is of great importance. Although several polyvalent vaccines are being used, there are still unsolved problems whose solution will improve the safety of their application, contribute to a better efficiency and enable a widespread application of antipneumococcal vaccines.

[Is penicillin still the drug of choice in the treatment of diseases caused by beta-hemolytic streptococci?]. / Da li je penicilin jos lek izbora u lecenju oboljenja izazvanih beta-hemolytickim streptokokama?

During the last ten years a new pathomorphosis of streptococci was noticed and described in the USA, Europe and New Zealand. It was expressed by the rise of virulence of beta haemolytic streptococci (BHS) and development of new clinical and epidemiological features. In such circumstances it appears to be very relevant to examine the susceptibility of BHS to penicillin, which is still considered as a drug of choice for the most of streptococcal diseases. Therefore it was decided: 1. to make an analysis of continuous susceptibility testing of BHS to penicillin and 2. to test the possibility of induction and selection of penicillin resistant mutants in vitro. Penicillin susceptibility was examined by broth dilution method Penicillin tolerant strains were separated on the basis of MBC/MIC ratio MBC/MIC > 16 and construction of "killing curves". The possibility of induction and selection of penicillin resistant mutants was tested by subcultivation technique. MIC values for BHS groups: A, B, C and G were: 0.015, 0.060, 0.015 and 0.030 micrograms/ml respectively. The percentage of penicillin tolerant strains was in the range of 3% for group A BHS to 33% for group G BHS. After 60 subcultures in liquid medium containing increasing concentrations of penicillin. MIC values were raised by 2-32 times in comparison with parental strains. As the maximal induced MIC values were 1 and 2 micrograms/ml (one group G and three groups B BHS strains) it can be concluded that BHS at least in vitro expressed penicillin resistance. Although the obtained results are encouraging (there is so far no penicillin resistant clinical isolates), the increasing percent of penicillin tolerant strains and the possibility to induce penicillin resistance in vitro should be considered as a very serious warning. That makes further investigation of the development of penicillin tolerance and resistance mechanisms very current.

[Changes in sensitivity to penicillin and an increase in virulence in beta-hemolytic streptococci followed by changes in the clinical picture of streptococcal syndrome]. / Promena osetljivosti na penicilin i povecanje virulencije beta-hemolitickih streptokoka praceno izmenjenom klinickom slikom streptokoknog sindroma.

According to reports from different geographic areas, the last decade has been characterised with an increasing number of streptococcal diseases. The new streptococcal "pathomorphosis" is presented by alteration of adhesive properties and distribution of various serotypes (domination of M1 and M18 serotypes). It is also expressed by an increased production of pyrogenic exotoxin and necrotic factor. As a consequence, apart from increasing incidence of streptococcal infections, it is observed that the streptococcal syndrome has often grave prognosis followed with a high percentage of mortality. Also a new clinical entity is also described; that of Toxic Shock Like Syndrome. The results of investigation concerning the susceptibility of beta-haemolytic streptococci to penicillin are encouraging. Penicillin resistant strains are not discovered among clinical isolates so far. However, the increased percentage of penicillin tolerant strains, and possibility of induction of penicillin resistance, can be considered as a serious warning. For that reason, further investigation of the mechanisms of developing penicillin tolerance and resistance appears to be highly recommended.