Intestinal Colonization of Preterm Neonates with Carbapenem Resistant Enterobacteria at Hospital Discharge.

Our aim was to investigate gut colonization with carbapenem-resistant Enterobacterales (CRE) in the population of preterm neonates at discharge from a tertiary care center in Serbia. The study included 350 randomly selected neonates/infants discharged in the period April 2018-May 2019. CRE colonization was present in 88/350 (25.1%) of patients. Klebsiella pneumoniae producing KPC and OXA-48 carbapenemase were detected in 45 and 42 subjects, respectively, while NDM producing Escherichia coli was identified in one patient only. All OXA-48 strains harbored blaCTX-M-15, while both blaTEM and blaSHV were present in all but one KPC-producing strain. CRE isolates exhibited a multidrug resistance pattern with uniform fluoroquinolone resistance, universal susceptibility to colistin, and variable susceptibility to aminoglycosides. Administration of carbapenems was common (~50%) and it was strongly associated with colonization, as well as the combinational therapeutic regimens that included meropenem, contrary to ampicillin-sulbactam/colistin therapy and prolonged course of the initial therapy (ampicillin/amikacin ≥ 7 days). Other risk factors for CRE carriage were level of immaturity, admission to neonatal intensive care unit, prolonged hospitalization and invasive procedures. Although the rate of clinically and/or laboratory proven systemic infections was significantly higher among colonized patients, CRE infection was confirmed in one patient only (1.1%) that was colonized with NDM E. coli. Clonal relatedness of CRE isolates was high, with seven and eight clusters detected among KPC (N = 30) and OXA-48 (N = 37) producing strains, respectively. The follow up of the 31 KPC-colonized patients after discharge from hospital revealed common decolonization within one month (~68%). In conclusion, our results demonstrated a high rate of CRE colonization that is most likely related to carbapenem consumption and lack of screening as important infection prevention practice.

Colonization with Multidrug-Resistant Bacteria in the First Week of Life among Hospitalized Preterm Neonates in Serbia: Risk Factors and Outcomes.

The aim of this prospective cohort study was to determine the prevalence of gut colonization with multidrug-resistant (MDR) bacteria, risk factors for colonization, infection risk, and outcomes among preterm neonates hospitalized at a tertiary-care center in Serbia. During the period from December 2017 to April 2018, 103 neonates were screened for rectal carriage at admission and on the seventh day of life. Characterization of MDR strains was done by conventional microbiology and molecular methods. Out of 61 (59.2%) colonized neonates, 12 (11.6%) were found colonized at admission, while 49 (47.6%) became colonized at the study site. Among a total of 72 MDR isolates, extended-spectrum beta-lactamase (ESBL)-producing enterobacteria prevailed (56/72, 77%), followed by Acinetobacter baumannii (14/72, 19%). The majority of ESBL-producing strains carried multiple genes (blaTEM/blaCTX-M-15 or blaTEM/blaSHV). Longer previous hospitalization and delivery by cesarean section were associated with MDR colonization, while mechanical ventilation was a risk factor for colonization at the study site. Infections due to MDR bacteria were more frequent among colonized than non-colonized neonates, but not significantly, and mortality was low (1%) in the studied neonates. These results indicate that hospitalized preterm neonates in Serbia are rapidly colonized with a diversity of MDR species and resistance phenotypes/genotypes.

A Laboratory-Based Surveillance Study of Invasive Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae Diseases in a Serbian Pediatric Population-Implications for Vaccination.

The aim of this study was to present the epidemiology of invasive diseases caused by Neisseria meningitidis and Streptococcus pneumoniae in the pre-vaccine period, and Haemophilus influenzae in the post-vaccine period in a pediatric population from Serbia. Among the meningococci, serogroup B dominated (83%), followed by serogroup C (11.3%). High antigenic diversity was found, with fine type P1.5-1,10-4 being the most frequent. Moderate susceptibility to penicillin was common (55%). Within pneumococci, serotypes 19F, 14, 6B, 6A, 18C, 23F, 3, and 7F prevailed, while 19A was rare (3.6%). The coverages of PCV10 and PCV13 were 68% and 84%, respectively. Major sequence types were ST320, ST15, ST273, ST271, and ST81. Non-susceptibility to penicillin (66.7%), cefotaxime (37%), and macrolides (55%) was predominantly detected in vaccine-related serotypes. Among the 11 invasive H. influenzae isolates collected, there were six Hib, three non-type b, and two non-typeable strains (ntHi) that were antibiotic susceptible. These results imply a potential benefit of future Men-B vaccine implementations. For pneumococci, as PCV10 was recently introduced, a significant reduction of morbidity and antibiotic resistance might be expected. The efficiency of Hib vaccination is evident, but a shift towards non-type b and ntHi strains may be anticipated.

Tigecycline susceptibility of multidrug-resistant Acinetobacter baumannii from intensive care units in the western Balkans.

Tigecycline can be effective to treat infections of carbapenem-resistant Acinetobacter baumannii (CRAB) however, no interpretive criteria have been approved so far. The objectives of this study were to evaluate the proportion of CRAB isolates and to compare gradient test with a broth microdilution (BMD) method for tigecycline susceptibility testing of A. baumannii.This study included 349 multidrug-resistant (MDR) Acinetobacter spp. collected from Serbia, Montenegro, Bosnia and Herzegovina in 2016 and 2017. Antibiotic susceptibility testing was performed by disk diffusion, VITEK2, gradient, ComASP Colistin. Tigecycline susceptibilities were interpreted according to breakpoints of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Food and Drug Administration (FDA).Majority of the tested isolates were CRAB (92.8%). Tigecycline MIC50/MIC90 values were 4/8 µg/mL by BMD and 0.5/4 µg/mL by gradient test. Essential agreement for BMD and gradient test amounted to 65.1%. With EUCAST breakpoints, categorical agreement (CA) was achieved in 38% isolates. Major discordance (MD-false susceptibility/resistance) and minor discordance (mD-false categorization involving intermediate results) were observed in 10% and 57% A. baumannii, respectively. With FDA breakpoints, CA, MD and mD were observed in 44%, 16% and 47% isolates, respectively. Colistin resistance was 2.1%.The study highlights a high proportion of CRAB and several discordances between BMD and gradient test which may lead to inappropriate therapy.

Molecular epidemiology of invasive and non-invasive group B Streptococcus circulating in Serbia.

Streptococcus agalactiae (group B Streptococcus, GBS) remains the leading cause of invasive diseases in neonates and an important cause of infections in the elderly. The aim of this study was to access the prevalence of GBS genito-rectal colonisation of pregnant women and to evaluate the genetic characteristics of invasive and non-invasive GBS isolates recovered throughout Serbia. A total of 432 GBS isolates were tested for antimicrobial susceptibility, capsular polysaccharide (CPS) types and the presence of the hvgA gene. One hundred one randomly selected isolates were further characterized by clustered regularly interspaced short palindromic repeats (CRISPRs) analysis and/or multilocus sequence typing (MLST). The prevalence of GBS colonization in pregnant women was 15%. Overall, six capsular types (Ia, Ib, II to V) were identified, the most common being III (32.2%) and V (25.2%). The hiper-virulent clone type III/ST17 was present in 43.1% and 6.3% (p < 0.05) of paediatric and adults isolates, respectively. Comparative sequence analysis of the CRISPR1 spacers content indicated that a few clones comprised the vast majority of the tested GBS isolates. Thus, it was estimated that dominant clones recovered from infants were CPS III/ST17 in late-onset infections (19/23; 82.6%), and Ia/ST23 in early-onset disease (44.4%). Conversely, genotype CPS V/ST1 was the most prevalent in adults (4/9; 25.4%). All isolates were susceptible to penicillin. Macrolide resistance (23.1%) was strongly associated with the ermB gene and constitutive resistance to clindamycin (63.9%). The majority of strains was resistant to tetracycline (86.6%), mostly mediated by the tetM gene (87.7%). GBS isolates of CPS V/ST1 and CPS III/ST23 were significantly associated with macrolide and tetracycline resistance, respectively. In conclusion, hyper-virulent CPS III/ST17 and V/ST1 were recognized as dominant GBS clones in this study.

Characterization of macrolide-resistant non-invasive pneumococci in the pre-vaccine era in Serbia.

Numerous reports have confirmed that increased macrolide use in the treatment of respiratory tract infection has contributed to the emergence of antibiotic resistance worldwide. Studies have also shown that pneumococcal vaccine can reduce pneumococcal resistance. The aim of this study was to determine the prevalence of co-resistance to penicillin and other antibiotics in macrolide-resistant (MR) non-invasive pneumococcal isolates and to evaluate serotype distribution in resistant strains in the pre-vaccine era in Serbia. About 80% of MR isolates expressed the MLS phenotype with very high resistance to both erythromycin and clindamycin. A total of 132 (84.1%) MR isolates were multiresistant, i.e., they were resistant to erythromycin, penicillin, tetracycline, and trimethoprim-sulfamethoxazole. Among 157 MR pneumococci, 11 different serotypes were found. Four serotypes, 19F, 14, 6B, and 23F, accounted for 77.7% of all MR pneumococcal isolates. Among isolates with the cMLS phenotype, serotypes 19F and 14 were predominant, whereas serotype 6A was the most common among those with the M phenotype, followed by 14. In conclusion, co-resistance to macrolides and penicillin in our non-invasive pneumococcal isolates is high. The majority of tested strains (∼80%) belonged to the four serotypes (19F, 14, 6B, and 23F) that are included in all conjugate vaccine formulations.

Changes in Macrolide Resistance Among Group A Streptococci in Serbia and Clonal Evolution of Resistant Isolates.

In Serbia, the frequency of macrolide-resistant group A streptococci (MRGASs) increased significantly from 2006 to 2009. MRGAS analysis in 2008 revealed the presence of three major clonal lineages: emm75/mefA, emm12/mefA, and emm77/ermTR. The aim of the present study was to determine the prevalence of macrolide resistance and to evaluate variations in the clonal composition of MRGASs. The study included 1,040 pharyngeal group A streptococci collected throughout Serbia, which were tested for antimicrobial susceptibility. MRGAS isolates were further characterized by the presence of resistance determinants, emm typing, and pulsed-field gel electrophoresis analysis. The prevalence of macrolide resistance was 9.6%, showing a slight decrease compared with the rate of 12.5% (2008). Tetracycline resistance was present in 6% of isolates, while norfloxacin nonsusceptibility detected for the first time in Serbia was 9.8%. The M phenotype dominated (84%), followed by the constitutive macrolides, lincosamides, and streptogramin B phenotype (12%). Five emm types were detected: emm75, emm12, emm1, emm28, and emm89. The emm75/mefA (62%), emm12/mefA (14%), and emm12/ermB/tetM (6%) were predominant clones and were found in both the present and the previous study periods at different frequencies. The major change was the loss of emm77/ermTR/tetO, which contributed to 15% of MRGASs in 2008.

MDR1 gene polymorphisms are associated with ulcerative colitis in a cohort of Serbian patients with inflammatory bowel disease.

BACKGROUND: Inflammatory bowel disease (IBD) is a chronic disease of unknown etiology in which genetic factors contribute to development of disease. Single nucleotide polymorphisms (SNPs) in multidrug resistance 1 (MDR1) gene encoding transporter P-glycoprotein have been associated with IBD, but their role in disease susceptibility remains unclear. Therefore, the aim of this study was to investigate the association of three MDR1 polymorphisms, C1236T (rs1128503), G2677T/A (rs2032582) and C3435T (rs1045642), with Serbian IBD patients. METHODS: A total of 206 IBD patients, 107 Crohn's disease (CD) and 99 ulcerative colitis (UC), and 255 healthy controls were included in the study. All subjects were genotyped using TaqMan SNP genotyping assays. Comparisons between the groups were performed using the Pearson Chi-square test. False discovery rate according to Benjamini-Hochberg procedure was applied to adjust for multiple comparisons. RESULTS: Carriers of T allele of all three MDR1 SNPs were more common in UC patients compared to healthy controls, suggesting predisposing role of T allele of these SNPs in UC pathogenesis. Consistently, TT genotype of C1236T and TTT haplotype were also found more frequently in UC patients. On the other hand, C allele and CC genotype of C1236T and C3435T, as well as G allele and GG genotype of G2677T/A were more frequent in healthy subjects, implying protective role of these variants in UC. Likewise, CGC haplotype and CGC/CGC diplotype were more frequent in controls. Contrary to UC, no statistical difference was observed between CD patients and controls in any of the SNPs analyzed. CONCLUSION: MDR1 gene variants and haplotypes were associated with UC in Serbian IBD patients, further supporting their potential role in susceptibility to UC.

Molecular characterization of macrolide resistant Streptococcus pyogenes isolates from pharyngitis patients in Serbia.

A steady increase in macrolide resistance in Streptococcus pyogenes, group A streptococci (GAS) was reported in Serbia during 2004-2009 (9.9%). However, there are no data on the molecular epidemiology of pharyngeal macrolide resistance GAS (MRGAS) isolates. Therefore, the aims of this first nationwide study were to examine the prevalence of macrolide resistance in Serbian GAS and to determine their resistance phenotypes, genotypes and clonal relationships. Overall 3893 non-duplicate pharyngeal S. pyogenes isolates from outpatients with GAS infection were collected throughout country during 2008 and 2009. Among 486 macrolide resistant pharyngeal isolates collected, 103 were further characterized. Macrolide resistance phenotypes and genotypes were determined by double-disk diffusion test and PCR, respectively. Strain relatedness was determined by emm typing, multilocus sequence typing (MLST), multilocus variable tandem repeat analysis (MLVA), phage profiling (PP) and virulence factor profiling (VFP). Overall, macrolide resistance among GAS isolates in Serbia was 12.5%. M phenotype was the most common (71.8%), followed by iMLS (18.4%) and cMLS (9.7%). Three clonal complexes--emm75/mefA/ST49, emm12/mefA/ST36 and emm77/ermA/tetO/ST63 comprised over 90% of the tested strains. Although MLVA, PP and VFP distinguished 10, 20 and 12 different patterns, respectively, cluster analysis disclosed only small differences between strains which belonged to the same emm/ST type. Our data indicate dominance of three major internationally widely disseminated macrolide resistant clones and a high genetic homogeneity among the Serbian MRGAS population. Continued surveillance of macrolide resistance and clonal composition in MRGAS in Serbia in future is necessary to determine stability of MRGAS clones and to guide therapy strategies.

[Invasive isolates of Streptococcus pneumoniae in Serbia: antimicrobial susceptibility and serotypes].

INTRODUCTION: Streptococcus pneumoniae is one of the leading causes of bacterial meningitis and sepsis. Invasive pneumococcal disease is a significant medical problem worldwide, particularly in children, due to a huge increase of pneumococcal resistance to antibiotics. OBJECTIVE: The aim of the study was to investigate the antimicrobial susceptibility pattern of invasive pneumococcal isolates, as well as to determine whether decreased S. pneumoniae susceptibility to antibiotics was related to a particular serotype. METHODS: Antimicrobial susceptibility to 19 antibiotics was determined in 58 invasive pneumococcal strains that were collected from seven regional centers during the period July 2009 to February 2011 in the National Reference Laboratory for streptococci and pneumococci. RESULTS: The overall nonsusceptibility rate to penicillin was detected in 34% of pneumococcal isolates and to erythromycin in 36%. Higher resistance rates were observed among children than among adults. Penicillin resistance rate was 65% in children versus 22% in adults, while erythromycin nonsusceptibility rate was 47% in children versus 32% in adults. Co-resistance to penicillin and erythromycin was detected in 21% strains, mostly isolated from children. Multiresistance was found in one third of isolates. All strains were susceptible to vancomycin, linezolid, fluoroquinolones, telithromycin and rifampicin, while 23 (40%) isolates were susceptible to all tested antibiotics. The most common resistant serotypes were 19F and 14. CONCLUSION: The study has revealed that penicillin and macrolide resistance among invasive pneumococcal isolates is very high in Serbia. This emphasizes the need for continuous monitoring for invasive pneumococcal disease to document the serotype distribution and antimicrobial susceptibility pattern.

[Current knowledge of bacterial vaginosis].

Bacterial vaginosis, earlier termed nonspecific vaginitis (anaerobic vaginosis) because of the absence of recognized pathogens, is most common vaginal syndrome of women of childbearing age affecting 15-30%. This syndrome, whose aetiology and pathogenesis remains unknown, is characterized by significant changes in the vaginal ecosystem. These changes consist of a decrease in the number of lactobacilli and a large increase in the number of anaerobic organisms. The bacteria adhere to desquamated epithelial cells with a distinctive appearance of clue cells The main complaints of women with symptomatic bacterial vaginosis include vaginal discharge and odour. However, a significant number of all women who have bacterial vaginosis deny symptoms. Bacterial vaginosis is associated with a number of gynaecologic and obstetric complications including cervicitis, cervical neoplasia, pelvic inflammatory disease, postoperative infections, and preterm labour.The diagnosis is most frequently made based on vaginal smear stained according to Gram (Nugent scoring method). Metronidazole and clindamycin are the drugs of choice for treatment of women with bacterial vaginosis. Which women should undergo treatment? According to the prevailing attitude, it should include women with symptoms. Symptomatic women with frequent relapses of bacterial vaginosisas, as a rule, have poor response to the applied therapy. To achieve better efficiency in the treatment of such women, it is necessary to have more extensive understanding of all factors in the pathogenesis of the syndrome.

Neonatal cellulitis and sepsis caused by group A streptococcus.

We report a case of late onset neonatal invasive group A streptococcal disease characterized with rapidly progressing cellulitis and development of sepsis. The infection was acquired from benign and mild skin infection of the child's mother. The causative agent was group A streptococcus, belonging to the emm type 53.2, which usually causes mild skin disease.

[Comparison of three diagnostic methods to confirm Helicobacter pylori infection].

INTRODUCTION: Helicobacterpylori induces gastric inflammation in host and such gastritis increases the risk of gastric and duodenal ulceration as well as adenocarcinoma. Because peptic ulcer disease is the major cause of morbidity, accurate diagnosis of H. pylori infection is very important. Unfortunately, there is no gold standard among diagnostic tests for Helicobacter infections. If gastroscopy is performed, histopathology and urease test are the most often used. Still, culturing of this bacterium is essential for drug susceptibility testing and analysis of virulence factors. OBJECTIVE: The aim of this study was to compare three diagnostic procedures--histopathology, urease test and culture, which are used to verify H. pylori infection. METHOD: Three pairs of gastric mucosal biopsy specimens were collected from each of 28 dyspeptic patients undergoing endoscopy. Nineteen patients were not pretreated with antibiotics, while nine had received eradication therapy earlier. One pair of biopsy specimens was used for histopathologic examination, the second for urease test and the third was simultaneously cultured on nonselective and selective solid media. Isolate was identified as H. pylori on the basis of colony morphology, morphological properties and biochemical tests. RESULTS: In 14 out of 28 patients, H. pylori infection was confirmed on the basis of results of all diagnostic procedures. The concordance of these three methods was very good, because the results of histopathology, urease test and culture corresponded in 26 from 28 patients. CONCLUSION: The conclusion of our study is that culture, as the method with high degree of concordance with other two procedures and the only that can give information on drug susceptibility of Helicobacter, is recommended for diagnosis of Helicobacter pylori infection along with histopathology and urease test.

Hydrogen peroxide producing lactobacilli in women with vaginal infections.

OBJECTIVE: Hydrogen peroxide producing lactobacilli are isolated from the vaginas of a majority of healthy reproductive age women. Their toxic and inhibitory effect against the overgrowth of pathogens in the vagina is documented by in vitro studies. Clinical studies concerning the role of hydrogen peroxide producing lactobacilli in vaginal infections are controversial. STUDY DESIGN: The aim of this study was to isolate lactobacilli from women with major vaginal infections: bacterial vaginosis (BV), vulvovaginal candidiasis (VVC) and trichomoniasis (TV), and from women with normal flora (NF), to test their ability to produce hydrogen peroxide, to quantitate lactobacilli and to evaluate factors related to the colonization of vagina with hydrogen peroxide producing lactobacilli. The study group comprised 108 women: 27 with VVC, 26 with BV, 20 with TV and 35 with NF. Data was analysed with Fisher exact test, chi2-test, and ANOVA. RESULTS: Lactobacilli were isolated from 81.5% of women with VVC, 58% of women with BV (p=0019), 55% of women with TV (p=0.015) and from 86% of women with NF. The majority of isolates of lactobacilli from women with VVC, TV and NF produced hydrogen peroxide (77%, 63.5% and 80%, respectively), compared with women with BV where only 26.5% of isolates produced hydrogen peroxide (p=0.01). Quantitative analysis showed that in an overwhelming majority of women colonized with lactobacilli, their count was >10(7) CFU/ml. Upon evaluation of behavioural and demographic characteristics, we found that smokers had a lower incidence of isolation of hydrogen peroxide producing lactobacilli (p=0.018). Our results showed that women with BV lack lactobacilli, especially hydrogen peroxide producing ones. Women with TV had a lower rate of lactobacilli. In women with VVC, there was neither significant difference in the isolation of lactobacilli, nor in their ability to produce hydrogen peroxide, compared to women with NF. CONCLUSION: Our results point out that hydrogen peroxide producing lactobacilli could protect against the development of BV, but not against VVC and TV.

[Importance of microbiologic examination of vaginal secretions in the reproductive period]. / Znacaj mikrobioloskog ispitivanja vaginalnog sekreta u reproductivnom periodu.

Vaginal infections, during reproductive period are frequent and although not life treating, they can affect their normal functions. They can also affect women's fertility as well as the course of pregnancy. The outcome of pregnancy can be endangered due to the possibility of infection of newborn while passing trough birth canal of the infected mother. As statistically shown, bacterial vaginosis is considerably more often found with the patients having precancerous changes on cervix, or diagnosed cancer of cervix, comparing with women with healthy cervix. It can also cause the appearance of postoperative pelvic cellulitis after hysterectomy. On the other side, the presence of S. agalactiae in vaginal secretion may cause very serious and lethal infections of the newborn such as meningitis, pneumonia and sepsis. As for protozoa T. vaginalis it has been shown that it could cause reduced fertility ability and that during pregnancy it could damage fetal membranes and bring to its premature rupture and premature birth. There is also increased risk of cervix cancer. During reproductive period of women especially if risk factors are existing such as hormone therapy, diabetes mellitus type 1 and applications of wide range antibiotics, vaginal fungal infections caused by Candida can frequently appear. These infection apart from the discomfort like itch and affluent secretion they can also mean diagnostic and therapeutical problem. Regular microbiological test of women are highly recommended during reproductive period as standard for bacterial vaginosis, fungal and trichomonas infections. If those results appear negative, further microbiological tests are necessary. Such tests which are more elaborate, more timely and more expensive are referring to tests on chlamydia, microplasma and some viruses that can also be the cause of vaginal secretion disbalance in women during reproductive period.

Epidemiology of diseases caused by Streptococcus pyogenes in Serbia during a nine-year period (1991-1999).

BACKGROUND & OBJECTIVES: Streptococcus pyogenes (group A Streptococcus - GAS) is an important human pathogen which causes a variety of diseases, including tonsillopharyngitis, scarlet fever and rheumatic fever. It is important to understand the changes in epidemiology of the diseases caused by the pathogen for improved control of such infections. Hence, the aim of the present study was to carry out an epidemiological analysis of GAS infections in Serbia in a 9-yr period (1991-1999) and evaluation of susceptibility of GAS isolates obtained during the same period to penicillin and erythromycin. METHODS: Occurrence of tonsillopharyngitis, scarlatina and rheumatic fever was analyzed and GAS carrier status in healthy children was examined over a 9-yr period from 1991 to 1999. Susceptibility to penicillin and erythromycin was determined for 1657 GAS isolates obtained from patients diagnosed with pharyngitis or scarlet fever and 512 isolates from healthy carriers. M-type antigen was also determined in these isolates. RESULTS: The average incidences of tonsillopharyngitis and scarlet fever were 76.2 and 30.8 per cent respectively. A total of 166 cases of rheumatic fever were registered. Per cent of carriers varied from 5.5 to 11.4 per cent over the study period. Predominating M serotypes among GAS isolates tested were M1, M3, M4, M6, M11, M12 and M18, depending on the source of clinical material and period of isolation. Antimicrobial susceptibility testing showed susceptibility to penicillin in all isolates tested and resistance to erythromycin in 2.41 per cent of the isolates. INTERPRETATION & CONCLUSION: Although the fluctuations in incidence were noted during the nine-year period, the incidence of streptococcal tonsillopharyngitis is low but with a steady raise in Serbia. No significant changes in the incidence of scarlet fever and rheumatic fever were noted. Susceptibility to penicillin remained unchanged, but the number or erythromycin resistant strains have increased.

Influence of decreased penicillin susceptibility on growth rate of beta haemolytic streptococci.

BACKGROUND & OBJECTIVES: Beta haemolytic streptococci (BHS), especially group A are still highly susceptible to penicillin. One possible explanation for this could be reduced growth capability in penicillin resistant BHS mutants. The present study was therefore undertaken to analyze the growth rates of BHS with decreased susceptibility to penicillin. METHODS: Serial passages in the medium with subinhibitory concentration of penicillin were done to induce resistance to this antibiotic in 12 clinical isolates of BHS serogroups A, B, C, and G. Both penicillin susceptible (parental) and variants with decreased susceptibility to penicillin (laboratory strains) were grown in three different media and their growth rates were determined by counting the number of bacterial colonies and by measuring optical density of bacterial culture. RESULTS: The lowest increase in minimal inhibitory concentration (MIC) value for penicillin (8-16 times) was obtained in BHS group A isolates, while the increase in MIC values of BHS groups B, C and G strains was higher (64-128 times) and they reached the level of complete resistance. Laboratory variants differed significantly from parental in their morphological and cultural characteristics. There were no statistically significant differences between the growth rates of penicillin susceptible and variants with decreased susceptibility to penicillin, though a delay in multiplication of the laboratory strains during exponential phase of growth was noted. INTERPRETATION & CONCLUSION: Though significant differences in phenotypic characteristics of penicillin susceptible and laboratory variants were noted, the results of this study provides no support to the assumption that variants of BHS with decreased susceptibility to penicillin of BHS were incapable for normal growth. Further studies needs to be done to find out the association between the decreased susceptibility to penicillin in the BHS and decreased growth capability in these bacteria.

[Rapid laboratory diagnosis of tuberculosis in clinical practice]. / Brza bakterioloska dijagnostika tuberkuloze u klinickoj praksi.

The laboratory diagnosis of tuberculosis relies on direct microscopy of smears for acid-fast bacilli and culturing. Microscopy is a rapid, but neither sensitive nor specific diagnostic method. Cultivation on solid media is a time-consuming procedure, and isolation and identification of Mycobacterium tuberculosis takes 3-8 weeks. Introduction of new selective liquid media with a sensitive growth-detection system, dramatically decreased time necessary for isolation and susceptibility testing, so that positive results can be obtained in two weeks. However, wide use of these systems is limited by high cost of instruments and media. Nucleic acid amplification techniques have in recent years been introduced in clinical laboratories for diagnosis of tuberculosis. Amplification techniques are highly sensitive and specific, and positive results are available in a few hours. Nevertheless, molecular methods cannot replace culturing, when drug susceptibility testing is required.