- Volume 32, Issue 2, 1990

Pefloxacin and fleroxacin showed biphasic bactericidal activity against Escherichia coli KL16 in nutrient broth. Bacteriostatic concentrations of chloramphenicol, an inhibitor of protein synthesis, and rifampicin, an inhibitor of RNA synthesis, could not completely abolish the bactericidal activity of either drug. Pefloxacin and fleroxacin were also active against non-dividing E. coli KL16. There fore, pefloxacin and fleroxacin are able to kill bacteria which are not dividing nor actively synthesising protein or RNA.

A micro-enzyme linked immunosorbent assay (micro-ELISA) has been evaluated as a diagnostic test to detect amoebic antigen in polyethylene glycol (PEG) precipitated circulating immune complexes (CIC) in sera from patients with amoebiasis. The immune complexes were captured on rabbit anti-amoebic IgG-coated wells of microtitration plates and the complexed antigen was detected by enzyme linked antihuman immunoglobulins. A titre of > 160 for the immune complexes was considered to be of clinical significance. The immunoassay detected amoebic, antigen-specific CIC in 35 (94·5%) of 37 patients with confirmed amoebic liver abscess. Twenty (55·5%) of 36 clinically suspected cases of amoebic liver abscess had amoebic antigen-specific CIC and responded favourably to anti-amoebic chemotherapy. Only two (20%) of 10 cases of non-dysenteric symptomatic intestinal amoebic infection had amoebic antigen-specific CIC. One (10%) of 10 patients with non-amoebic intestinal disorders also had amoebic antigen in CIC. However, none of 15 cases of non-amoebic hepatic disorders that included hydatid disease, metastatic adenocarcinoma, hepatocellular carcinoma, cholecystitis and choledocal cyst, 13 cases of rheumatoid arthritis and 25 apparently healthy subjects had amoebic antigen in CIC. The levels of the amoebic antigen-specific CIC did not correlate (p>0·05) with either the number of abscess(es) or lobe(s) of the liver involved. However, the levels of antigen-specific CIC were higher (p<0·01) in patients with a liver size of more than 5 cm below the right costal margin. Antigen-specific CIC levels tended to decline or disappear during 3-6 months following completion of therapy. In spite of the limitations for diagnosing symptomatic intestinal amoebic disease, the demonstration of specific CIC is recommended as an immuno-diagnostic procedure for patients with suspected amoebic liver abscess.

Cell-surface hydrophobicity of Helicobacter (formerly Campylobacter) pylori was tested by aqueous two-phase partitioning and hydrophobic interaction chomato-graphy. The hydrophobicity of H. pylori greatly exceeded that of Campylobacter fetus subsp. fetus, C. jejuni and Bacillus subtilis. A partition coefficient (PC) of hydrophobicity in the two-phase system was determined for H. pylori. PC was dependent on pH and the PC value was increased by greater than 20-fold at pH 2.5. Lithium cations increased PC, indicating a net negative surface charge. The presence of urea prevented the relative loss of hydrophobicity at raised pH. Exposure of H. pylori to proteolytic enzymes reduced the ability of the bacteria to adhere to human polymorphonuclear neutrophils (PMN). These findings suggest that H. pylori possesses protein-associated hydrophobic factors that are responsible for the nonopsonic adherence to PMN cell membranes.

Bacteriophages in different stages of maturation were found in thin sections of a clinical isolate of Helicobacter (Campylobacter) pylori. Mature phage heads measured 70 x 60 nm and the tail at least 120 nm. Lysogeny was maintained during subculture on blood agar for more than 3 months after isolation from a gastric biopsy.

An enzyme linked immunosorbent assay (ELISA) with a sonicated suspension of Helicobacter (Campylobacter) pylori as antigen was used to detect anti-H. pylori antibodies in 517 patients without dyspepsia or peptic ulcer symptoms and 401 healthy blood donors. The criterion of seropositivity was determined from a receiver operating curve computed with the values of optical densities of 48 sera from dyspeptic patients with proven helicobacter-associated gastritis and 16 sera from dyspeptic patients with proven helicobacter-associated gastritis and 16 sera from dyspeptic patients with normal antral mucosa and no microbiological or histological evidence of H. pylori infection. The 227 (44%) seropositive persons amongst the patient group appeared to be significantly higher than the 142 (35%) sera with antibodies in the blood donors tested (p<0·03), even when adjustment was made for increasing age. We conclude that the prevalence of antibodies against H. pylori increases with age and that although antibodies are more prevalent in patients attending a hospital than in healthy blood donors, seropositivity suggestive of current or past infection can be found in one third of a randomly chosen population of blood donors.

The increasing incidence of reported scabies in Trinidad, from 24.2/ 100 000 population in 1984 to 59.5/100 000 in 1985, led to a careful monitoring in 1986 of all patients with post-streptococcal acute glomerulonephritis (PSAGN). There were 181 cases of PSAGN; 84 ²-haemolytic streptococcal isolates from 72 patients were sent to the Central Public Health Laboratory, Colindale, for grouping and serotyping. The PSAGN epidemic of 1986 was bimodal. Streptococci of M-type 73 appeared to be associated with the first phase (March-May) and comprised 20% of the isolates serotyped. New to Trinidad, streptococci of M-type 48 (4% of the isolates serotyped) preceded the first phase of the epidemic and were isolated from two patients with PSAGN. Provisional type (PT) 5757, also new to Trinidad, had been previously identified only among serotypes from the United Kingdom and the Federal Republic of Germany. This type was isolated from seven patients, in six from skin lesions and in one from the throat. PT 5757 occurred during the first wave of the epidemic and comprised 14% of the strains serotyped. Thus, the first wave of the bimodal epidemic involved serotypes M73, M48 and PT 5757. The more intense second phase (July-October) was associated with the previously documented nephritogenic M-type 55.

Variation in typing of clinically significant isolates of coagulase-negative staphylococci (CNS) was determined by five typing methods with 143 isolates obtained from 19 patients over periods from 2 days to 1 year. In only one case did all isolates give exactly the same typing pattern by all five tests. No single method, or simple combination, provided a ready means of confirming the relatedness of separate isolates. The most frequently useful tests were antibiotic susceptibility and extrachromosomal DNA banding patterns. However, the results of biotyping, serotyping and phage typing were also helpful in showing the relationship between different isolates from a given patient. In most cases a core pattern varying by the gain or loss of a small number of features, characterised a given patient's isolates. In two cases, apparently radical changes in the infecting organism were observed, and confirmed by restriction endonuclease analysis. Care should be taken when successive isolates of CNS show distinct typing differences in deciding their clinical relevance.

Epidemiological studies require characterisation of pathogenic yeasts at and below the species level. The chromosomes of 130 strains of four pathogenic species of the genus Candida, isolated from clinical material, were separated by pulsed field electrophoresis with the clamped homogeneous electric field (CHEF) technique. Each species was characterised by a distinct electrophoretic karyotype (EK). Furthermore, smaller variations of the EK amongst strains belonging to the same species appeared to offer a useful means of strain differentiation. A karyotyping system is proposed for C. albicans. The EKs were assigned to a code of four numbers which designated the number of bands that could be resolved in each of four sets of chromosomes. Morphotypes of the colonies of C. albicans on malt agar plates, which did not correlate with the EK, could provide a complementary means of strain characterisation in epidemiological studies.

A strain of Klebsiella oxytoca, originally isolated in Liverpool in 1982, has been found to produce a novel transferable β-lactamase, TEM-E2. This enzyme confers resistance to ceftazidime and focused as a doublet band with an iso-electric point (pI) of 5·3. The strain also produced the TEM-1 β-lactamase. Both TEM-1 and TEM-E2 β-lactamases were encoded by a transferable 103 kb plasmid; these two enzymes also had similar molecular weights, were inhibited by clavulanic acid, and hydrolysed ampicillin, carbenicillin and cephaloridine at similar rates. However, unlike the TEM-1 enzyme, the TEM-E2 β-lactamase hydrolysed ceftazidime and cefotaxime with similar efficiency, although it conferred much greater resistance to ceftazidime in the host strain. This is the earliest documented example of a TEM-like enzyme which confers transferable resistance to ceftazidime and related cephalosporins.

A model was developed in mice to study the pathogenesis of urinary tract infections caused by Staphylococcus saprophyticus strains LM-1 and LM-2, Escherichia coli SP444 and S. epidermidis E001. Murine urinary bladders were inoculated with 108 bacteria via a temporary urinary catheter and samples of urine and bladder were removed at days 1, 3, 5 and 10 after inoculation. They were examined both bacteriologically and by electronmicroscopy. Severe disruption of the urothelium was present immediately and the urothelium had become oedematous and ulcerated with increased urothelial exfoliation. Disruption of the urothelium was similar with all the four pathogens studied. The three strains of coagulase-negative staphylococci preferentially attached to the urothelial cell tight junctions and were not associated with polymorphonuclear leucocytes. In comparison, E. coli SP444 was randomly attached over the entire urothelium and was often in association with macrophages. Phagocytosis of E. coli by superficial urothelial cells also occurred.