The role of efflux pumps in antibiotic resistance of gram negative rods.

Antibiotic resistance is an important public health problem today, causing increased morbidity and mortality. Resistance to antibiotics in bacteria can develop by various mechanisms such as a change in the target site of the drug, a change in the outer membrane permeability, enzymatic defusing of the drug and efflux of the antimicrobial compound. Some bacteria have the potential to develop resistance to more than one drug by using several mechanisms together. One of the important resistance mechanisms of bacteria is active efflux pumps (EPs). EPs are pump proteins found in all cell types, located in the cell membrane. They are responsible for the excretion of various intracellular and extracellular substances (antibiotics, etc.) out of the cell. There is much research on various antimicrobials that cause antibiotic resistance in Gram negative rods, but studies on EPs are relatively few. Due to the concern that antibiotics will be insufficient in the treatment of diseases, a good understanding of EPs and the discovery of new EP inhibitors will shed light on the future of humanity. In this review, the structure of bacterial EPs in Gram negative bacteria, the role of EPs in multidrug resistance, the importance of EP inhibitors in the fight against antibiotic resistance and the phenotypic and genotypic detection methods of EPs are discussed.

Trends of Antibiotic Resistance in Multidrug-Resistant Pathogens Isolated from Blood Cultures in a Four-Year Period.

BACKGROUND: Multidrug-resistant organisms cause serious infections with significant morbidity and mortality in the worldwide. These organisms have been identified as urgent and serious threats by CDC. The aim of this study was to determine the prevalence and changes of antibiotic resistance of multidrug-resistant pathogens isolated from blood cultures over a four-year period in a tertiary-care hospital. METHODS: Blood cultures were incubated in a blood culture system. Positive signalling blood cultures were subcultured on 5% sheep-blood agar. Identification of isolated bacteria was performed using conventional or automated identification systems. Antibiotic susceptibility tests were performed by disc diffusion and/or gradient test methods, if necessary, by automated systems. The CLSI guidelines were used for interpretation of antibiotic susceptibility testing of bacteria. RESULTS: The most frequently isolated Gram-negative bacteria was Escherichia coli (33.4%) followed by Klebsiella pneumoniae (21.5%). ESBL positivity was 47% for E. coli, 66% for K. pneumoniae. Among E. coli, K. pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii isolates, carbapenem resistance was 4%, 41%, 37%, and 62%, respectively. Carbapenem resistance of K. pneumoniae isolates has increased from 25% to 57% over the years, and the highest rate (57%) occured during the pandemic period. It is noteworthy that the aminoglycoside resistance in E. coli isolates gradually increased from 2017 to 2021. The rate of methicillin-resistant S. aureus (MRSA) was found to be 35.5%. CONCLUSIONS: Increased carbapenem resistance in K. pneumoniae and A. baumannii isolates is noteworthy, but carbapenem resistance in P. aeruginosa decreased. It is of great importance for each hospital to monitor the increase in resistance in clinically important bacteria, especially isolated from invasive samples, in order to take the necessary precautions in a timely manner. Future studies involving clinical data of patients and bacterial resistance genes are warranted.

Efficacy of Ceragenins Alone and in Combinations with Antibiotics Against Multidrug-Resistant Gram Negative Pathogens from Bloodstream Infections.

Ceragenins (CSAs) that mimic the activities of antimicrobial peptides may be new options for the treatment of infections caused by multidrug-resistant pathogens. This study investigated the antibacterial activities of eight different ceragenins against MDR pathogens and the synergistic effects of some ceragenins in combinations with antibiotics (meropenem-MEM, ceftazidime + avibactam-CZA, tigecycline-TIG). A disc diffusion method was used for antibiotic susceptibility tests, a broth microdilution, and checkerboard methods were used to detect minimum inhibitory concentrations (MICs) and the effects of combinations, respectively. While MIC90 values CSA-13, CSA-44, CSA-131 against Klebsiella pneumoniae isolates had similar effect with MEM (8 µg/ml); CSA-13, CSA-44, CSA-131, CSA-138, and CSA-144 had better activity than MEM against Acinetobacter baumannii and Pseudomonas aeruginosa isolates. In particular, CSA-44 and CSA-131 were effective against A. baumannii and P. aeruginosa isolates which resistant to both COL and MEM. CSA-44+MEM and CSA-131+CZA combinations showed synergistic activity against most (70%) of MDR- E. coli isolates. Although TIG is known to have weak activity in nonfermentative bacteria, CSA-44+TIG combination showed synergistic activity against two (17%) of the A. baumanni isolates. In addition, CSA-44+TIG and CSA-131+TIG combinations showed additive effects against all P. aeruginosa isolates. Antagonism was not detected in any of the combinations. CSA-44 and CSA-131 alone/or in combinations with MEM or CZA can be considered as new alternative treatments in serious infections caused by MDR pathogens.

Time kill-assays of antibiotic combinations for multidrug resistant clinical isolates of OXA-48 carbapenemase producing Klebsiella pneumoniae.

Treatment of infections caused by OXA-48 carbapenemase producing multidrug-resistant isolates often necessitates combination therapy. In vitro effect of different antibiotic combinations against multidrug-resistant (MDR) Klebsiella pneumoniae isolates were evaluated in this study.Meropenem-tobramycin (MER+TOB), meropenem-ciprofloxacin (MER+CIP), colistin-meropenem (COL+MER), colistin-ciprofloxacin (COL+CIP) and colistin-tobramycin (COL+TOB) combinations were tested by time kill-assays. Each antibiotic alone and in combination at their Cmax values were tested against 4 clinical K. pneumoniae isolates at 1, 2, 4, 6, 8, 12 and 24 h. Effect of colistin and its associations were also assessed at 30 min. Bactericidal activity was defined as ≥3log10 CFU mL-1 decrease compared with initial inoculum. Synergy was defined as ≥2log10CFU mL-1 decrease by the combination compared with the most active single agent. Presence of blaOXA-48, blaNDM, blaVIM, blaIMP, blaKPC and blaCTX-M-1 genes was screened by PCR using specific primers.The blaOXA-48 gene was identified together with blaCTXM-1 group gene in all isolates. COL+MER demonstrated to be synergistic and bactericidal. MER+TOB showed synergistic and bactericidal effect on two strains although, regrowth was seen on other two strains at 24 h. MER+CIP exhibited indifferent effect on the strains.Combination therapy could be a potential alternative to treat MDR K. pneumoniae infections. This combination might prevent resistance development and secondary effects of colistin monotherapy. MER+TOB and MER+CIP might have an isolate-dependent effect, that may not always result in synergism.

The association of CMV infection with bacterial and fungal infections in hematopoietic stem cell transplant recipients: a retrospective single-center study.

This study aims to evaluate the probable association between CMV infection and bacterial or fungalinfections in 91 consecutive adult patients who underwent autologous or allogeneic HSCT within aperiod of two years.The medical records of the patients were retrospectively reviewed. Blood cultures were evaluatedby an automated blood culture system. A quantitative real-time polymerase chain reaction was performedto detect CMV DNA.CMV infection and CMV disease were detected in 42 (46%) and six (6.6%) patients, respectively. Ofthe 158 microorganisms isolated, 115 (73%) were Gram-positive bacteria. Bacteremia and fungemiadeveloped in 55 (60%) and eight (8%) patients, respectively. Concurrent CMV infection and bacteremiawere detected in 17 (18.7%) patients and concurrent CMV infection and fungal infection weredetected in five (5.5%) patients. Graft versus host disease (GVHD) developed in 15 (50%) allogeneicHSCT recipients and two (2.2%) autologous HSCT recipients. Twenty-one (23%) patients including13 (43%) allogeneic and eight (13%) autologous HSCT recipients died.The most common infection is bacteremia, and it develops concurrently with CMV infection in approximatelyone-fifth of HSCT recipients. Gram-positive bacteria are more common in bacteremia.Further studies on the follow-up and treatment of infections after HSCT will improve post-HSCTsurvival rates.

A Three-Year Analysis of Ocular Infections in a Tertiary Care University Hospital in Turkey.

BACKGROUND: Ocular infections may result in severe vision and eye loss. Especially in keratitis and endophthalmitis, it is essential to identify the causative microorganism and treat it with appropriate antimicrobials. This study aims to investigate microorganisms isolated from various samples in ocular infections and their sensitivity to antibiotics. METHODS: The samples, e.g., abscess, swab, were inoculated to suitable media and at appropriate ambient conditions at 35 - 37°C for 24 - 48 hours. Sterile liquid samples were cultivated in a blood culture bottle. The isolated microorganisms were identified by classical biochemical methods and by using an automatic identification system when necessary. Antibiotic susceptibility tests were performed by the disc diffusion method and interpreted according to CLSI criteria. RESULTS: From a total of 167 ocular samples from 69 patients, 78 (46.7%) microorganisms were isolated. Thirteen (19%) infections were found to be polymicrobial. Three bacteria were isolated from one of them and two bacteria from 12 of them. Twenty-one (30%) of the patients were newborns, and two were children. The average age of adult patients was 55.45 ± 19.7 years. Gram-positive bacteria (n = 46, 59%) were found to be more common than Gram-negative (n = 27, 35%) among all bacteria isolated over three years. Gram-positive bacteria included Staphylococcus aureus (n = 17, 22%), coagulase-negative staphylococci (CNS) (n = 13, 17%), and streptococci (n = 10, 13%). Pseudomonas aeruginosa (n = 8, 10%) was the most common bacterium of the Gram-negative bacteria. Besides, two anaerobic bacteria (2.6%), two fungi (2.6%), and one (1.3%) Nocardia spp. were isolated. It was determined that 35% of S. aureus strains and 46% of CNS strains were resistant to methicillin. CONCLUSIONS: Various and rare microorganisms can be isolated from ocular infections. However, it is still seen that Gram-positive bacteria are more common than Gram-negative. Multi-resistant Gram-negative rods and high rates of methicillin-resistance in staphylococci can affect treatment regimens.

[Serotype distribution and antibiotic resistance of Streptococcus pneumoniae strains isolated from the adult patients in a Turkish üniversity hospital]. / Bir üniversite hastanesinde yetiskin hastalardan izole edilen Streptococcus pneumoniae suslarinin serotip dagilimi ve antibiyotik direnci.

Infections caused by Streptococcus pneumoniae are the most important cause of morbidity and mortality worldwide. S.pneumoniae is the most common cause of community-acquired pneumonia, especially in adults. Invasive pneumococcal disease can usually occur in the elderly, children and immunocompromised individuals. Usage of the vaccines for the protection against S.pneumoniae infections, is an effective method to reduce the burden of disease in both children and adults. Serotypes frequently isolated from purified capsular polysaccharides of S.pneumoniae are used in polyvalent vaccines. Significant differences are observed between countries and regions in serotypes and antibiotic resistance of S.pneumoniae strains. For this reason, each country and region should determine their own serotypes and antibiotic resistance. The aim of this study was to determine serotype distribution, antibiotic resistance and vaccine coverage rates in S.pneumoniae strains isolated from invasive and non-invasive samples of adult patients in our hospital. A total of 100 S.pneumoniae isolates from invasive and non-invasive samples of adult patients between March 2007 and August 2014 were used in this study. S.pneumoniae strains were identified by conventional methods. Serogrouping was performed with the latex particle agglutination and serotyping was made with the conventional Quellung reaction using a commercial type-spesific antisera (Statens Serum Institute, Copenhagen, Denmark). Antibiotic susceptibility testing for penicillin G, cefotaxime and erythromycin was performed by gradient test and evaluated according to the breakpoints of Clinical and Laboratory Standards Institute (CLSI). Sixty four percent of of the S.pneumoniae strains were isolated from non-invasive and 36% were isolated from invasive samples. Serotype 3 (20%), 19F (9%), 8 (7%), 14 (7%), 23F (6%), 6A (6%) were most common determined serotypes among all strains. Among S.pneumoniae strains isolated from invasive samples serotype 3 (22%), 14 (14%), 1 (8%) and in S.pneumoniae strains isolated from non-invasive samples 3 (19%), 19F (11%), 6A (9%), 23F (8%) were the most common serotypes. Among all isolates 2% penicillin and 3% cefotaxime intermediate resistance were detected. Erythromycin resistance was detected in 25% of invasive, 37% of non-invasive strains and a total of 33% in all of the isolates. Vaccine coverage rates were found to be 68% for PCV13 and 78% for PPV23 among all isolates. In our study penicillin resistance was lower compared with the other similar studies in the world, but resistance against erythromycin was almost similar. This study is important to show that serotype 3 predominated in serious pneumococcal infections in the adult population of our hospital. For this reason, administration of routine pneumococcal vaccination program in adults and especially in the elderly is recommended. In conclusion, it is important to know the serotype distribution and antibiotic resistance of S.pneumoniae to monitor the empirical treatment in serious pneumococcal infections.

[Investigation of seropositivity of Bordetella pertussis in adults in a university hospital]. / Bir üniversite hastanesinde yetiskinlerde Bordetella pertussis seropozitifliginin arastirilmasi.

Whooping cough is a vaccine-preventable infectious diseases caused by Bordetella pertussis/parapertussis. Despite of routine immunization programs in the world, pertussis still remains endemic. Recently unvaccinated or partially immunized infants have infected with this pathogen and also increase of incidence was observed in adolescents and adults. The source of pertussis in newborns are attributed to household, especially due to the family members. Theaim of this study was to determine B.pertussis IgG antibody positivity by ELISA method in adults. Eighty-four of the total study population (39.6%) were anti-pertussis IgG positive, 128 (60.4%) were negative. The samples included in the study (n= 212) were divided into three groups according to ages: 19-35 years (Group 1, n= 61), 36-50 years (Group 2, n= 58), 51-65 years (Group 3, n= 93). Anti-pertussis IgG antibody positivity was 26.2% (n= 22) in Group 1, 26.2% (n= 22) in Group 2 and 47.6% (n= 40) in Group 3. According to the anti-pertussis IgG positivity results, no significant difference was observed between genders. The results were obtained as absorbance values by ELISA test, then transformed into semi-quantitative values as NovaTec Test Unit (NTU). NTU positive values were between 11.01-39.4. Ninety four percent of NTU values were in the range of 11.01 to 28.01 and 6% were between 28.01 to 39.4. It was observed that seropositivity rates peaked at ages of 27, 55 and 65. The highest NTU values were observed in the age of 32 in females and in the age of 24 in males. Relatively, low seropositivity values (NT= 15-20) were observed in both females and males to the age of 45 in Group 2. However a slight increase was observed in females after the age of 45. An increase (NTU ≥ 20) was determined in the age of 49 in males. The seropositivity rates were generally low (NT ≤ 20) in females in Group 3, but the highest values (NTU ≥ 30) were observed in 55 and 65 years of age in males in this group. The highest seropositivity (NTI ≥ 30) were in 55 and 65 years of age (NTI ≥ 30) in males and 27 years of age (NTU ≥ 30) in females while in 36-50 age range, it was relatively low (NTI ≤ 20). Routine pertussis vaccination program is not yet implemented for adults in our country. However, the causes more clearly demonstrate the need for adult pertussis vaccination since adults may be incompletely vaccinated or not vaccinated in the childhood, current vaccinations are not available in the childhood of adults, adults become more susceptible to infections as the age increases, life expectancy increases and the likelihood of encountering infections, and childhood vaccination antibodies diminish over time. According to the results of this study, a single dose of pertussis vaccine is recommended to implement for adults in our country.

Effects of tissue plasminogen activator in experimentally induced peritonitis.

BACKGROUND: We aimed to evaluate the microbiological and immunological effects of tissue plasminogen activator (tPA) in a rat model of peritonitis. METHODS: Twenty-four male Wistar albino rats were divided equally into three groups. Peritonitis and thereafter laparotomy and partial omentectomy were performed in all rats. The control group (C) had no further treatment. The antibiotics group (A) received metronidazole and ceftriaxone. The antibiotic and tPA group (A+T) received the same antibiotics as well as tPA. For microbiological and immunological analysis, blood samples were obtained at the 24th hour, and peritoneal fluid samples were obtained at the 24th and 72nd hours. On the fifth day after surgery, all rats were sacrificed, and the macroscopic findings of the peritoneal cavity were recorded. RESULTS: The mean number of intraperitoneal abscesses was significantly higher in the control group and the lowest in the two treatment group (A+T). The levels of cytokines were not significantly different between groups. Giving tPA reduced the number and sizes of the abscesses with no significant difference in inflammatory response. CONCLUSION: In this experimental peritonitis model, it can be postulated that tPA decreased abscess formation without exaggerating the inflammatory response.

The high diversity of MRSA clones detected in a university hospital in istanbul.

BACKGROUND: To characterize the methicillin-resistant Staphylococcus aureus (MRSA) clones present in Istanbul, 102 MRSA isolates collected during a 5-year period at the Istanbul Medical Faculty Hospital were characterized using microarray analysis and phenotypic resistance profiles. METHODS: Resistance to methicillin was detected with a cefoxitin disk diffusion assay and confirmed with a MRSA-agar and MRSA detection kit. Antimicrobial susceptibility testing was performed by a disk diffusion assay and interpreted according to the 2012 guidelines of the Antibiogram Committee of the French Society for Microbiology. Decreased susceptibility to glycopeptides was confirmed using the population analysis profile-area under the curve (PAP-AUC) method. The presence of the mecA gene was detected by polymerase chain reaction. Bacterial DNA was extracted according to the manufacturer's recommended protocol using commercial extraction kits. Strains were extensively characterized using the DNA microarray. RESULTS: Isolates were grouped into six clonal complexes. The most frequently detected clone was the Vienna/Hungarian/Brazilian clone (ST239-MRSA-III), which accounted for 53.9% of the isolates. These isolates were resistant to multiple antibiotics, particularly penicillin, tetracycline, rifampicin, kanamycin, tobramycin, gentamicin, levofloxacin, erythromycin, lincomycin and fosfomycin. Furthermore, three isolates were detected by population analysis profile as heterogeneous vancomycin-intermediate S. aureus (hVISA). The UK-EMRSA-15 clone (ST22-MRSA-IV PVL negative) was detected in 9.8% of the isolates and was mainly susceptible to all anti-staphylococcal antibiotics. Seven isolates (6.9%) were positive for PVL genes and were assigned to the CC80-MRSA-IV clone (European CA-MRSA clone, three isolates), ST8-MRSA-IV clone (USA300 clone, two isolates, one ACME-positive) or ST22-MRSA-IV clone ("Regensburg EMRSA" clone, two isolates). All other clones were detected in one to six isolates and corresponded to well-known clones (e.g., Pediatric clone, Dublin EMRSA clone, WA MRSA-54/63, WA MRSA-1/57). CONCLUSIONS: This work highlighted both the high prevalence of ST239-MRSA-III clone and the large diversity of the other MRSA clones detected in a university hospital in Istanbul.

Computer-assisted flapless implant placement reduces the incidence of surgery-related bacteremia.

OBJECTIVE: Bacteremia--the access of bacterium to the bloodstream--may yield life-threatening complications. The aim of this study was to compare the incidence, duration, and type of bacterium leading to bacteremia with relation to conventional and computer-assisted flapless implant surgery. MATERIAL AND METHODS: A total of 377 implants were placed in 68 edentulous jaws using the conventional (conventional group) or a computer-assisted stereolithographic (SLA) template-guided surgery technique (flapless group). Bacteremia was monitored from pre- and postoperative blood samples. RESULTS: The duration of the surgical intervention was significantly shorter in the flapless group (p = 0.3510). Baseline samples were sterile. Following the 15th minute after the placement of the last implant, bacteria were present in 62 and 12 % of the patients in the conventional and flapless groups, respectively (p < 0.0001; relative risk: 3.05). The differences in the incidence of the bacteremia detected at the baseline and 15 min after the last implant placement were statistically significant in the conventional group (p = 0.0001). However, no such statistical significance was present in the flapless group. Staphylocccus epidermidis, Bifidobacterium spp., Streptococcus viridans, Corynebacterium spp., and Streptococcus sanguinis were the isolated bacterium. CONCLUSIONS: Irrespective of the utilized technique, bacteremia may occur upon the placement of four to eight implants to an edentulous jaw. The probability of bacteremia for the patients operated with the conventional technique is, however, 3.05 greater than those operated with the flapless technique. CLINICAL RELEVANCE: Flapless implant placement reduces the incidence of surgery-related bacteremia and, therefore, may be beneficial to patients at risk.

[Distribution of blaOXA genes in Acinetobacter baumannii strains: a multicenter study]. / Acinetobacter baumannii Izolatlarinda blaOXA Genlerinin Dagilimi: Çok Merkezli Bir Çalisma.

Acinetobacter baumannii is the most important agent of nosocomial infections within the Acinetobacter genus. This gram-negative coccobacillus is intrinsically resistant to many antibiotics used in antimicrobial therapy, and capable of developing resistance including carbapenems. The objective of this study was to develop a multiplex real time polymerase chain reaction (qPCR) kit for OXA subgroups in A.baumannii, and to investigate the distribution of OXA subgroups in A.baumannii strains isolated from geographically different regions of Turkey. A total of 834 A.baumannii clinical isolates collected from different state and university medical centers in 13 provinces (Afyonkarahisar, Ankara, Bolu, Elazig, Erzurum, Isparta, Istanbul, Kahramanmaras, Konya, Sakarya, Van) between 2008-2011, were included in the study. The isolates were identified by conventional methods and automated systems [Vitek2 (bioMerieux, ABD) and Phoenix (BD Diagnostic, MD)]. The susceptibility profiles of the isolates were studied with automated systems and standard disc diffusion method. All samples were subjected to qPCR to detect blaOXA-51-like, blaOXA-23-like and blaOXA-58-like genes. A conventional PCR method was also used to detect blaOXA-24-like gene. The resistance rates observed during the study period were as follows: 96.8% for amoxicillin-clavulanate, 86.8% for ciprofloxacin, 74.7% for gentamicin, 71.7% for amikacin, 73.5% for cefaperozone-sulbactam, 72.1% for imipenem and 73% for meropenem. Six hundred and two (72.2 %) isolates were resistant to both imipenem and meropenem. Colistin was found to be the most effective antibiotic against A.baumannii isolates with 100% susceptibility rate. All isolates were positive for blaOXA-51-like, however blaOXA-24-like gene could not be demonstrated in any isolate. Total positivity rates of blaOXA-23-like and blaOXA-58-like genes were found as 53.7% and 12.5%, respectively, while these rates were 74.4% and 17.3% in carbapenem-resistant isolates, respectively. Twenty-five isolates were positive for both blaOXA-23-like and blaOXA-58-like genes. All of the carbapenem-resistant isolates have OXA type genes with the exception of blaOXA-24-like gene. The positivity rates for blaOXA-23-like and blaOXA-58-like genes varied for each center. In addition, there was a decrease in the frequency of blaOXA-58-like gene, however both blaOXA-23-like gene and carbapenem resistance rates increased during the study period. In conclusion, high rates of resistance to carbapenems were also remarkable but A.baumannii strains keep on sensitivity to colistin. Both blaOXA-23-like and blaOXA-58-like genes were shown to be widespread in carbapenem-resistant A.baumannii clinical isolates. However, blaOXA-23-like gene positive strains were increased throughout the study. Currently, multiplex qPCR is the best way for rapid diagnosis of resistant bacteria for prevention of hospital-acquired infections. The multiplex qPCR kit developed in this study could be useful for rapid diagnosis and identify the frequencies of blaOXA-23-like, blaOXA-51-like and blaOXA-58-like genes in carbapenem-resistant A.baumannii clinical isolates.

Antibacterial activity of Hypericum perforatum L. (St. John's wort) extracts against Gram-positive bacteria and characterisation of its secondary metabolites.

This study aimed to determine the secondary metabolite profiles and antibacterial activity of H. perforatum L extracts against Gram-positive clinical isolates. The plant materials (Sample A and Sample B) were macerated with n-hexane, ethyl acetate and methanol (MeOH). The antibacterial activitiy of plant extracts and routinely used antibiotics were tested against Gram-positive bacteria. The secondary metabolite profiles of Sample A were determined by LC-Q-TOF-MS. The MIC values for n-hexane and ethyl acetate extracts of Sample A were lower than the susceptibility breakpoints of most broad-spectrum antibiotics (e.g. vancomycin, teicoplanin and linezolid) in a certain proportion of Gram-positive bacteria. The n-hexane extract of Sample A showed good antibacterial activity with MICs lower than the susceptibility breakpoint of teicoplanin in 58% of coagulase-negative staphylococci. The n-hexane and ethyl acetate extracts of Sample A had rich phloroglucinol constituents. The n-hexane and ethyl acetate extracts of Sample A could be alternative antibacterial agents against Gram-positive bacteria.

Efficacy of antibiotic combinations in an experimental sepsis model with Pseudomonas aeruginosa.

This study aimed to compare the efficacy of fosfomycin, colistin, tobramycin and their dual combinations in an experimental sepsis model. After sepsis was established with a Pseudomonas aeruginosa isolate (P1), antibiotic-administered rats were divided into six groups: Fosfomycin, tobramycin, colistin and their dual combinations were administered by the intravenous or intraperitoneal route to the groups. The brain, heart, lung, liver, spleen and kidney tissues of rats were cultured to investigate bacterial translocation caused by P1. Given the antibiotics and their combinations, bacterial colony counts in liver tissues were decreased in colistin alone and colistin plus tobramycin groups compared with control group, but there were no significant differences. In addition, a non-statistical decrease was found in the spleen tissues of rats in the colistin plus tobramycin group. There was a > 2 log10 CFU/ml decrease in the number of bacterial colonies in the kidney tissues of the rats in the fosfomycin group alone, but the decrease was not statistically significant. However, there was an increase in the number of bacterial colonies in the spleen and kidney samples in the group treated with colistin as monotherapy compared to the control group. The number of bacterial colonies in the spleen samples in fosfomycin plus tobramycin groups increased compared to the control group. Bacterial colony numbers in all tissue samples in the fosfomycin plus colistin group were found to be close to those in the control group. Colistin plus tobramycin combinations are effective against P. aeruginosa in experimental sepsis, and clinical success may be achieved. New in vivo studies demonstrating the ability of P. aeruginosa to biofilm formation in tissues other than the lung are warranted in future.

Bacteremia following dental implant surgery: preliminary results.

OBJECTIVES: The aims of this study were to investigate the incidence of bacteremia, bacteriology and antibiotic susceptibility against to causative bacteria associated with dental implant installation. STUDY DESIGN: 30 generally healthy patients were enrolled in this study. Blood samples were collected at baseline and at 30 minutes after dental implant installation and 24 hours after dental implant surgery. Blood samples were cultured in a BACTEC system. The isolated bacteria were identified using conventional methods. Antimicrobial sensitivity tests were performed by disc diffusion. RESULTS: No bacteria were isolated at the baseline and 24 hours after surgery, whereas the prevalence of bacteremia at 30 minutes after dental implant installation was 23%. The isolated bacteria species were Staphylococcus epidermidis, Eubacterium spp., Corynebacterium spp. and Streptococcus viridans. The Staphylococcus epidermidis, which was isolated in three patients, was found to be resistant to penicillin which is first choice of many clinicians. CONCLUSION: Our findings suggest that installation of dental implants can produce bacteremia. Within the limitations of this study, it can be speculated that the resistance of antibiotics may compromise the routine prophylaxis against infective endocarditis. Therefore use of blood cultures and antibiograms may be suggested in risky patients. The outcome of the present study should be verified using a larger patient group with varying conditions.

Detection of colistin resistance via four methods in multidrug-resistant Gram-negative rods isolated from blood cultures.

INTRODUCTION: The broth microdilution (BMD) method recommended for the detection of colistin resistance is labor-intensive, time-consuming, and difficult to apply in routine laboratories. Thus, various methods, such as disk elution, commercial microdilution, and rapid polymyxin-NP tests have been developed for the detection of colistin resistance. In this study, a total of 102 multi-resistant Gram-negative bacteria isolated from blood cultures were evaluated by four different methods for the detection of colistin resistance, and compared with the reference method. METHODOLOGY: For the detection of the compatibility of these methods with the reference method, categorical and essential agreements, very major, major, and minor error rates were determined. Colistin-tigecycline and colistin-meropenem combinations were investigated in colistin-resistant isolates. RESULTS: Of the isolates, 15 (15%) [K. pneumoniae (n = 12), A. baumannii (n = 2), E. coli (n = 1)] were resistant to colistin with reference BMD method. MIC50 and MIC90 values of all isolates were ≤ 0.25 µg/mL and 16 µg/mL, respectively. The categorical agreement rates were 100% for commercial microdilution, disk elution, and RPNP test. The essential agreement rates of commercial microdilution, disk elution, and broth macrodilution were 78.4%, 86.3%, and 100%, respectively. Although there were no major errors in these methods, the macrodilution (12%) and commercial microdilution (20.6%) methods showed the most minor errors. Colistin-meropenem combination showed a 100% synergistic effect, but the colistin-tigecycline combination showed an 80% synergistic effect and 20% indifference effect. CONCLUSIONS: Disk elution and RPNP tests are suitable for routine use because they are the most efficient, easiest, low-cost, and good performance tests in detecting colistin resistance.

Serotype distribution of Streptococcus pneumonia in children with invasive disease in Turkey: 2015-2018.

Objectives: To determine the serotype distribution of pneumococcus causing invasive pneumococcal disease (meningitidis, bacteremia and empyema) in children in Turkey, and to observe potential changes in this distribution in time to guide effective vaccine strategies. Methods: We surveyed S. pneumoniae with conventional bacteriological techniques and with real-time polymerase chain reaction (RT-PCR) in samples of cerebrospinal fluid (CSF), blood and pleural fluid. S. pneumoniae strains were isolated from 33 different hospitals in Turkey, which are giving health services to approximately 60% of the Turkish population. Results: A total of 167 cases were diagnosed with invasive pneumococcal disease between 2015 and 2018. We diagnosed 52 (31.1%) patients with meningitis, 104 (62.2%) patients with bacteremia, and 11 (6.6%) patients with empyema. Thirty-three percent of them were less than 2 years old and 56% less than 5 years old. Overall PCV13 serotypes accounted for 56.2% (94/167). The most common serotypes were 19 F (11.9%), 1 (10.7%) and 3 (10.1%). Conclusions: Besides the increasing frequency of non-vaccine serotypes, vaccine serotypes continue to be a problem for Turkey despite routine and high-rate vaccination with PCV13 and significant reduction reported for the incidence of IPD in young children. Since new candidate pneumococcal conjugate vaccines with more serotype antigens are being developed, continuing IPD surveillance is a significant source of information for decision-making processes on pneumococcal vaccination.

[Typing of extended-spectrum beta-lactamases in Escherichia coli and Klebsiella spp. strains and analysis of plasmid profiles]. / Escherichia coli ve Klebsiella spp. suslarinda genilemis spektrumlu beta-laktamazlarin tiplendirilmesi ve plazmid profil analizi.

The aim of this study was to identify the types of extended-spectrum beta-lactamases (ESBL) produced by 12 Escherichia coli and 32 Klebsiella spp. (28 K. pneumoniae, 4 K. oxytoca) strains isolated from various specimens (urine, blood, tracheal aspirate, abscess, throat, drain/catheter tips, pleural/peritoneal fluids, cerebrospinal fluid, eye) of patients hospitalized in different units (intensive care, hematology, oncology neonatology, transplantation, pediatric surgery) of Istanbul Medical Faculty Hospital, Turkey. Antimicrobial susceptibility tests were performed by disc diffusion according to NCCLS (CLSI) guidelines and no resistance to imipenem or meropenem was detected. MICs of cefotaxime and ceftazidime were determined by agar dilution method and MIC50 and MIC90 for cefotaxime were found as 16 microg/ml and 64 microg/ml in both Klebsiella spp. and E. coli strains, respectively. The presence of ESBL was confirmed by double-disc synergy testing and E-test ESBL. All isolates demonstrated an ESBL phenotype by these two methods. Isoelectric focusing (IEF) method demonstrated that the isolates produced 1-4 different beta-lactamases (pls: 5.4-9.0). The rates of TEM, SHV, CTX-M beta-lactamases detected by using specific primers in polymerase chain reaction (PCR), were found as 64.3%, 92.9%, 64.3% for K. pneumoniae and 66.7%, 25%, 83.3%, for E.coli strains, respectively. The profiles generated by randomly amplified polymorphic DNA (RAPD)-PCR using ERIC-2 primer revealed several bands, ranging in size from 170 to 1500 bp. According to RAPD-PCR results, K. pneumoniae, K. oxytoca and E. coli strains were separated to 10, 3 and 6 groups, respectively. In the conjugation experiments, 31 of the isolates (70.4%) transferred their resistance genes to recipient E. coli strain. Plasmid analysis studies showed that resistance genes were carried on a single plasmid (> 48 kb) in 20 transconjugants (64.5%), while the rest of the strains (35.5%) harbored more than one plasmid, with sizes ranging from 10 to 100 kb. These results showed the rapid emergence and high prevalence of CTX-M type enzymes among Klebsiella spp. and E. coli strains in our hospital.

The Impact of Early Postpartum Maternal Pertussis Vaccination on the Protection of Infants: A Randomized Clinical Trial.

BACKGROUND: Despite primary vaccination, infants under six months run a risk of infection with pertussis. OBJECTIVE: To determine the impact of early postpartum maternal pertussis vaccination on protecting infants from the disease. METHODS: All mothers (n=405) who gave birth to healthy term infants were educated on the cocoon strategy. The mothers who consented were immunized with the tetanus-diphtheria-acellular pertussis vaccine within the first three postpartum days. All infants received their pertussis vaccines according to the national schedule. The anti-pertussis IgG titers of infants of thirty vaccinated mothers were compared with those of thirty unvaccinated mothers. RESULTS: The pertussis antibody levels in the infants of vaccinated mothers were significantly higher than those of unvaccinated mothers at the mean infant age of 5.6 ± 1.2 months. Only 6 infants of vaccinated mothers exhibited pertussis-like symptoms, none of whom had positive pertussis PCR. Seventeen infants of unvaccinated mothers had pertussis-like symptoms, and 4 tested positive for pertussis PCR. CONCLUSION: Our results showed that maternal pertussis vaccination, administered within the first three postpartum days, may protect infants against pertussis in their first ten months.